HK1124113B

HK1124113B - Meter electronics and methods for rapidly determining a mass fraction of a multi-phase from a coriolis flow meter signal

Info

Publication number: HK1124113B
Application number: HK08113385.8A
Authority: HK
Inventors: Mark James Bell; Craig B. Mcanally
Original assignee: Micro Motion, Inc.
Priority date: 2005-05-20
Filing date: 2006-05-19
Publication date: 2010-12-10

Description

Electronic meter and method for rapidly determining mass fraction of multi-phase fluid from coriolis flowmeter signal

Technical Field

The invention relates to an electronic meter and a method of determining a mass fraction of a fluid component in a fluid material flowing through a flow meter.

Background

The use of coriolis mass flowmeters to measure mass flow and other information for materials flowing through a pipeline is known from U.S. patent 4,491,025 issued to j.e. smith et al on 1/1 of 1985 and re.31,450 issued to j.e. smith on 11/2 of 1982. The flow meter has one or more flow tubes of different configurations. Each conduit structure may be considered to have a set of natural vibration modes including, for example, simple bending, torsional, radial, and coupled modes. In a typical coriolis flowmeter mass flow measurement application, a conduit structure is excited in one or more vibration modes as a material flows through the conduit, and motion of the conduit is measured at spaced points along the conduit.

The vibrational modes of the material fill system are defined in part by the combined mass of the flow tube and the material in the flow tube. Material flows to the flow meter from a pipeline connected on the inlet side of the flow meter. The material is then introduced into the flow tube or tubes and flows out of the flow meter into a pipeline connected to the outlet side.

The driver applies a force to the flow tube. The force causes the flow tube to oscillate. When no material flows through the flowmeter, all points along the flow tube oscillate with the same phase. As material begins to flow through the flow tube, coriolis accelerations cause each point along the flow tube to have a different phase relative to other points along the flow tube. The phase on the inlet side of the flow tube lags the driver, while the phase on the outlet side leads the driver. Sensors are placed at different points on the flow tube to generate sinusoidal signals indicative of the motion of the flow tube at the different points. The phase difference between the two sensor signals is proportional to the mass flow rate of material through the flow tube or flow tubes.

One application of the vibrating flow tube apparatus described above is in measuring the mass flow rate of a fluid material. However, in some fluid measurement environments, the fluid material comprises a multiphase flow, i.e., comprising two or more fluid phases, a gas phase and a solid phase. A typical multiphase flow material includes a fluid flow material that includes, for example, entrained gas, such as air.

The prior art flow meters are unable to accurately, quickly, or satisfactorily track or determine the pickoff sensor frequency during a two-phase flow of fluid material. Prior art vibratory flow meters are designed to measure a relatively stable and uniform mass flow of a fluid material. However, since the fluid measurement reflects the mass of the fluid material, a sudden change in mass may cause an erroneous measurement or the mass flow change may not even be tracked by the flow meter. For example, when the fluid material includes entrained air, air bubbles passing through the flow meter may cause spikes in the frequency response of the flow meter. These frequency errors can cause difficulties in determining an accurate mass flow rate, and can be propagated by any subsequent other flow characteristic calculations. As a result, the determination of the phase is also slow and prone to errors, since the prior art technique utilizes a determined pick-up frequency to obtain the phase difference. Thus, any error in the frequency determination is combined into the phase determination. The result is an increased error in the frequency determination and the phase determination, resulting in an increased error in the determination of the mass flow. Furthermore, because the determined frequency values are used to determine mass flow and density values (density is approximately equal to the square of a ratio of frequencies), the error in frequency determination is repeated or combined in the mass flow and density determination.

The prior art methods of metering fluid materials do not satisfactorily measure a single component of a multiphase flow. The prior art frequency determination is relatively slow. The prior art frequency determination typically characterizes the fluid over a time period of at least 1-2 seconds and thus produces an average frequency measurement. The prior art method is satisfactory for single phase flow and slowly and moderately varying fluids. The prior art cannot measure sharp changes. Accurate measurement of individual fluid components cannot be achieved by the prior art. The prior art is not able to accurately determine the mass of a multiphase flow at a point in time. The prior art is unable to determine the mass fraction of a single fluid component of a multiphase flow.

Disclosure of Invention

The above and other problems are solved and an advance in the art is achieved by providing an electronic meter and method of determining the mass fraction of a fluid component in a fluid material flowing through a flow meter.

An electronic meter for determining a mass fraction of a fluid component in a fluid material flowing through a flow meter is provided according to an embodiment of the invention. The electronic meter includes: an interface for receiving a frequency response of a fluid material; and a processing system in communication with the interface. The processing system is configured to receive a frequency response from the interface, and decompose the frequency response into at least a gas frequency component and a fluid frequency component. The processing system is also configured to determine an overall density from the frequency response and determine a gas density from the gas frequency components. The processing system is also configured to determine a void fraction of the gas from the frequency response and the one or more gas frequency components and the fluid frequency component. The processing system is also configured to multiply the gas voidage by a ratio of the gas density to the overall density to determine the mass fraction.

A method of determining a mass fraction of a fluid component in a fluid material flowing through a flow meter is provided according to an embodiment of the invention. The method comprises the following steps: receiving a frequency response of the fluid material; decomposing the frequency response into at least a gas frequency component and a fluid frequency component; determining the overall density from the frequency response; and determining the gas density from the gas frequency component. The method also includes determining a void fraction of the gas from the frequency response and the one or more gas frequency components and the fluid frequency component. The method also includes multiplying the void fraction of the gas by a ratio of the gas density to the overall density to determine the mass fraction.

A method of determining a mass fraction of a fluid component in a fluid material flowing through a flow meter is provided according to an embodiment of the invention. The method comprises the following steps: receiving a frequency response of the fluid material; processing the frequency response through a notch filter that substantially filters one of the gas frequency component and the fluid frequency component; determining the overall density from the frequency response; the gas density is determined from the gas frequency component. The method also includes determining a void fraction of the gas from the frequency response and the one or more gas frequency components and the fluid frequency component. The method also includes multiplying the void fraction of the gas by a ratio of the gas density to the overall density to determine the mass fraction.

A method of determining a mass fraction of a fluid component in a fluid material flowing through a flow meter is provided according to an embodiment of the invention. The method comprises the following steps: receiving a frequency response of the fluid material; filtering the frequency response through a first filter that substantially filters out gas frequency components and substantially passes fluid frequency components, wherein the first filter outputs fluid frequency components; the frequency response is filtered by a second filter that substantially filters out fluid frequency components and substantially passes gas frequency components, wherein the second filter outputs gas frequency components. The method also includes determining an overall density from the frequency response and determining a gas density from the gas frequency component. The method also includes determining a void fraction of the gas from the frequency response and the one or more gas frequency components and the fluid frequency component. The method also includes multiplying the void fraction of the gas by a ratio of the gas density to the overall density to determine the mass fraction.

Inventive aspects

In one aspect of the electronic meter, the gas density comprises an inverse of a square of the gas frequency and the overall density comprises an inverse of the square of the frequency.

In another aspect of the electronic meter, the processing system is further configured to determine a mass flow rate of the fluid material from the frequency response and determine at least one of the first fluid component mass and the second fluid component mass using the mass fraction and the mass flow rate.

In another aspect of the electronic meter, the frequency response includes a first sensor signal and a second sensor signal, and the processing system is further configured to determine a substantially instantaneous frequency and determine a substantially instantaneous phase difference, wherein the mass flow rate is determined using the frequency and the phase difference.

In another aspect of the electronic meter, the frequency response includes a first sensor signal and a second sensor signal, and the processing system is further configured to determine a substantially instantaneous frequency, determine a substantially instantaneous phase difference, divide the phase difference by the frequency to obtain a time delay, and multiply the time delay by a constant to obtain the mass flow rate.

In another aspect of the electronic meter, the frequency response includes a first sensor signal and a second sensor signal, and the processing system is further configured to generate a first 90 degree phase shift from the first sensor signal, calculate the frequency using the first 90 degree phase shift and the first sensor signal, determine a substantially instantaneous phase difference, divide the phase difference by the frequency to obtain a time delay, multiply the time delay by a constant to obtain the mass flow rate.

In another aspect of the electronic meter, the frequency response includes a first sensor signal and a second sensor signal, and the processing system is further configured to generate a first 90 degree phase shift from the first sensor signal, calculate the phase difference using the first 90 degree phase shift, the first sensor signal, and the second sensor signal, determine a substantially instantaneous phase difference, divide the phase difference by the frequency to obtain a time delay, and multiply the time delay by a constant to obtain the mass flow.

In another aspect of the electronic meter, the frequency response includes a first sensor signal and a second sensor signal, and the processing system is further configured to generate a first 90 degree phase shift from the first sensor signal, generate a second 90 degree phase shift from the second sensor signal, calculate the phase difference using the first 90 degree phase shift, the second 90 degree phase shift, the first sensor signal, and the second sensor signal, determine a substantially instantaneous phase difference, divide the phase difference by the frequency to obtain a time delay, and multiply the time delay by a constant to obtain the mass flow.

In another aspect of the electronic meter, the frequency response includes a first sensor signal and a second sensor signal, and the processing system is further configured to generate a 90 degree phase shift from the first sensor signal, calculate a frequency response using the 90 degree phase shift and the first sensor signal, calculate a phase difference using at least the 90 degree phase shift, the first sensor signal, and the second sensor signal, calculate a time delay using the frequency response and the phase difference, calculate a mass flow rate from the time delay, determine a substantially instantaneous phase difference, divide the phase difference by the frequency to obtain a time delay, and multiply the time delay by a constant to obtain the mass flow rate.

In one aspect of the method, the gas density comprises the inverse of the square of the gas frequency and the overall density comprises the inverse of the square of the frequency.

In another aspect of the method, the method further includes determining a mass flow rate of the fluid material from the frequency response and determining at least one of the first fluid component mass and the second fluid component mass using the mass fraction and the mass flow rate.

In another aspect of the method, determining the mass flow rate includes determining a substantially instantaneous frequency and determining a substantially instantaneous phase difference, wherein the frequency and the phase difference are used to determine the mass flow rate.

In another aspect of the method, the frequency response includes a first sensor signal and a second sensor signal, and determining the mass flow rate includes: determining a substantially instantaneous frequency; determining a substantially instantaneous phase difference; dividing the phase difference by the frequency to obtain a time delay; and multiplying the time delay by a constant to obtain the mass flow.

In another aspect of the method, the frequency response includes a first sensor signal and a second sensor signal, and determining the mass flow rate further includes: generating a first 90 degree phase shift from the first sensor signal; calculating the frequency using the first 90 degree phase shift and the first sensor signal; determining a substantially instantaneous phase difference; dividing the phase difference by the frequency to obtain a time delay; and multiplying the time delay by a constant to obtain the mass flow.

In another aspect of the method, the frequency response includes a first sensor signal and a second sensor signal, and determining the mass flow rate further includes: generating a first 90 degree phase shift from the first sensor signal; calculating the phase difference using the first 90 degree phase shift, the first sensor signal, and the second sensor signal; determining a substantially instantaneous phase difference; dividing the phase difference by the frequency to obtain a time delay; and multiplying the time delay by a constant to obtain the mass flow.

In another aspect of the method, the frequency response includes a first sensor signal and a second sensor signal, and determining the mass flow rate further includes: generating a first 90 degree phase shift from the first sensor signal; generating a second 90 degree phase shift from the second sensor signal; calculating the phase difference using the first 90 degree phase shift, the second 90 degree phase shift, the first sensor signal, and the second sensor signal; determining a substantially instantaneous phase difference; dividing the phase difference by the frequency to obtain a time delay; and multiplying the time delay by a constant to obtain the mass flow.

In another aspect of the method, the frequency response includes a first sensor signal and a second sensor signal, and determining the mass flow rate further includes: generating a first 90 degree phase shift from the first sensor signal; calculating a frequency response using the 90 degree phase shift and the first sensor signal; calculating a phase difference using at least the 90 degree phase shift, the first sensor signal, and the second sensor signal; calculating a time delay using the frequency response and the phase difference; calculating a mass flow from the time delay; determining a substantially instantaneous phase difference; dividing the phase difference by the frequency to obtain a time delay; and multiplying the time delay by a constant to obtain the mass flow.

Drawings

Like reference symbols in the various drawings indicate like elements.

FIG. 1 is a Coriolis flow meter in an embodiment of the present invention;

FIG. 2 illustrates a meter electronics according to an embodiment of the present invention;

fig. 3 is a flow chart of a method of processing sensor signals in a coriolis flow meter according to an embodiment of the invention;

FIG. 4 illustrates a meter electronics according to an embodiment of the present invention;

fig. 5 is a flow chart of a method of processing first and second sensor signals in a coriolis flow meter according to an embodiment of the invention;

FIG. 6 is a block diagram of a portion of a processing system according to an embodiment of the present invention;

FIG. 7 shows Hilbert transform (Hilbert transform) block details according to an embodiment of the invention;

FIGS. 8 and 9 are two separate branch structure diagrams of an analysis block according to an embodiment of the present invention;

FIG. 10 is a graph of power spectral density of a pickoff sensor signal of a flow meter under normal conditions;

fig. 11 shows a hilbert transform block according to a single phase shift embodiment;

FIG. 12 shows an analysis block for a single phase shift embodiment;

FIG. 13 illustrates the sensor process of the present invention compared to the prior art, wherein each time difference (Δ t) value is compared;

FIG. 14 shows an electronic meter according to another embodiment of the invention;

FIG. 15 is a graph of meter frequency response for air, fluid, and a combined air/fluid mixture (i.e., a fluid including entrained air);

FIG. 16 is a flow chart of a method of determining a mass fraction of a fluid component in a fluid material flowing through a flow meter according to an embodiment of the invention;

FIG. 17 is a flow chart of a method of determining a mass fraction of a fluid component in a fluid material flowing through a flow meter according to an embodiment of the invention;

FIG. 18 is a frequency diagram illustrating low pass and high pass filter responses that are decomposed into fluid frequency components and gas frequency components in accordance with an embodiment of the present invention;

FIG. 19 is a flow chart of a method of determining a mass fraction of a fluid component in a fluid material flowing through a flow meter according to an embodiment of the invention;

fig. 20 is a graph of notch filter frequency response.

Detailed Description

Fig. 1-20 and the specific examples detailed below teach those skilled in the art how to make and use the best mode of the invention. Some conventional aspects have been simplified or omitted for the purpose of teaching inventive principles. Those skilled in the art will appreciate variations from these examples that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. Therefore, the present invention is not limited to the specific examples described below, but is defined by the claims and their equivalents.

Fig. 1 shows a coriolis flow meter 5 that includes a metering assembly 10 and an electronic meter 20. The metering assembly 10 is responsive to the mass flow and density of the process material. The meter electronics 20 is connected to the metering assembly 10 by leads 100 to provide density, mass flow and temperature information over the channel 26, as well as information not relevant to the present invention. Although it will be apparent to those skilled in the art that the present invention may be embodied in a vibrating tube densitometer that does not have the additional measurement capability provided by a coriolis mass flow meter, the structure of a coriolis flow meter is described.

The metering assembly 10 includes a pair of manifolds 150 and 150 ', flanges 103 and 103' having flanged necks 110 and 110 ', a pair of parallel flow tubes 130 and 130', a drive mechanism 180, a temperature sensor 190, and a pair of speed sensors 170L and 170R. The flow tubes 130 and 130 'have two substantially straight inlet legs 131 and 131' and outlet legs 134 and 134 ', the inlet legs 131 and 131' and outlet legs 134 and 134 'converging toward each other at the flow tube mounting blocks 120 and 120'. The flow tubes 130 and 130' are bent at two symmetrical positions along their length and are substantially parallel over their entire length. Brace bars 140 and 140 'serve to define axes W and W' about which each flow tube oscillates.

The side branches 131, 131 ' and 134, 134 ' of the flow tubes 130 and 130 ' are fixedly connected to flow tube mounting blocks 120 and 120 ', which in turn are fixedly connected to the branch tubes 150 and 150 '. This provides a continuous closed material path through coriolis flowmeter assembly 10.

When flanges 103 and 103 ' having holes 102 and 102 ' are connected through inlet end 104 and outlet end 104 ' to a process line (not shown) carrying the process material being measured, the flowmeter material inlet end 104 passing through hole 101 in flange 103 is directed through manifold 150 to flow tube mounting block 120 having surface 121. In the branch 150, the material is distributed and introduced into the flow tubes 130 and 130'. Through the existing flow tubes 130 and 130 ', the process material is remixed into the single flow in the branch tube 150 ' and is then led into the outlet end 104 ' which is connected to the process line (not shown) through the flange 103 ' with the threaded hole 102 '.

Flow tubes 130 and 130 'are selected and suitably mounted to flow tube mounting blocks 120 and 120' to have substantially the same mass distribution, moment of inertia (moment of inertia), and Young's modulus (Young's module) about bending axes W-W and W '-W', respectively. These bending axes pass through the struts 140 and 140'. Because the young's modulus of the flow tube changes with temperature and this change affects the flow and density calculations, a temperature resistance probe (RTD)190 is mounted to the flow tube 130' to continuously measure the flow tube temperature. Thus, the temperature of the flow tube and the voltage present at a given current through the RTD are controlled by the temperature of the material flowing through the flow tube. The temperature dependent voltage appearing across the RTD is used by the meter electronics 20 in a known manner to compensate for the change in the spring rate of the flow tubes 130 and 130', which is caused by any change in the temperature of the flow tubes. The RTD is connected to the meter electronics 20 via lead 195.

In the first out of phase bending mode of the flow meter, the two flow tubes 130 and 130 'are driven in opposite directions about their respective bending axes W and W' by the driver 180. The drive mechanism 180 may comprise any known arrangement such as a magnet mounted to the flow tube 130' and an opposing coil mounted to the flow tube 130 and through which an alternating current is passed for oscillating the two flow tubes. With the electronic meter 20, a suitable drive signal is applied to the drive mechanism 180 via the lead 185.

The electronic meter 20 receives the RTD temperature signal on lead 195 and the left and right velocity signals appear on leads 165L and 165R, respectively. The electronic meter 20 generates a driving signal that appears on the lead 185 to drive the member 180 and vibrate the tubes 130 and 130'. The electronic meter 20 processes the left and right velocity signals and the RTD signal to calculate the mass flow rate and density of the material flowing through the metering assembly 10. This information, along with other information, is applied by the meter electronics 20 to the application device 29 via the pathway 26.

Fig. 2 shows an electronic meter 20 according to an embodiment of the invention. The meter electronics 20 may include an interface 201 and a processing system 203. The meter electronics 20 receives first and second sensor signals, such as pick-up/speed sensor signals, from the metering assembly 10. The meter electronics 20 processes the first and second sensor signals to obtain a flow characteristic of the fluid material flowing through the metering assembly 10. For example, the meter electronics 20 may determine from the sensor signals, for example, one or more of phase difference, frequency, time difference (Δ t), density, mass flow rate, and volumetric flow rate. In addition, other flow characteristics may be determined in accordance with the present invention. These determinations are discussed below.

The phase difference determination and the frequency determination are much faster and more accurate and reliable than these determinations of the prior art. In a particular embodiment, the phase difference determination and the frequency determination may be obtained directly from the phase shift of only one sensor signal without any frequency reference signal. This advantageously reduces the processing time required to calculate the flow characteristic. In another specific embodiment, the phase difference is obtained from the phase shift of two sensor signals, while the frequency is obtained from only one phase shifted signal. This increases the accuracy of the two flow characteristics and allows them to be determined more quickly than in the prior art.

The prior art frequency determination methods typically take 1-2 seconds to perform. In contrast, frequency determination according to the present invention may be performed in as little as 50 milliseconds (ms). Depending on the type and configuration of the processing system, the sampling rate of the vibrational response, filter size, decimation rate, etc., even faster frequency determination may be expected. At a frequency determination rate of 50ms, the meter electronics 20 according to the present invention may be approximately 40 times faster than the prior art.

The interface 201 receives a sensor signal from one of the speed sensors 170L and 170R via the conductor 100 of fig. 1. The interface 201 may perform any needed or desired signal conditioning, such as any manner of formatting, amplifying, buffering, etc. Optionally, some or all of the signal conditioning may be performed in the processing system 203.

Further, the interface 201 may enable communication between the electronic meter 20 and an external device. The interface 201 may communicate electronically, optically, or wirelessly in any manner.

The interface 201 in one particular embodiment is coupled to a digitizer 202, wherein the sensor signal comprises an analog sensor signal. Digitizer 202 samples and digitizes the analog sensor signal and generates a digital sensor signal. The digitizer 202 may also perform any required decimation, wherein the digital sensor signal may be decimated to reduce the amount of signal that needs to be processed and to reduce processing time. This extraction will be discussed in more detail below.

The processing system 203 manages the operation of the meter electronics 20 and processes fluid measurements from the fluid metering assembly 10. The processing system 203 executes one or more processing routines and thus processes the fluid measurements to generate one or more flow characteristics.

The processing system 203 may comprise a general purpose computer, a microprocessor system, logic circuitry, or some other general purpose and custom processing device. The processing system 203 may be distributed among a plurality of processing devices. Processing system 203 may include any type of integrated or stand-alone electronic storage medium such as storage system 204.

The processing system 203 processes the sensor signal 210 to determine one or more flow characteristics from the sensor signal 210. For example, the one or more flow characteristics may include phase difference, frequency, time difference (Δ t), mass flow rate, and/or density of the fluid material.

In the particular embodiment shown, the processing system 203 determines the flow characteristic from the two sensor signals 210 and 211 and the single sensor signal phase shift 213. The processing system 203 may determine at least a phase difference and a frequency from the two sensor signals 210 and 211 and the single sensor signal phase shift 213. Thus, the first or second phase shift sensor signal (e.g., an upstream or downstream pickoff signal) may be processed by the processing system 203 according to the present invention to determine phase difference, frequency, time difference (Δ t), and/or mass flow rate of the fluid material.

The storage system 204 may store flow meter parameters and data, software programs, constant values, and variable values. In a particular embodiment, the storage system 204 includes programs that are executed by the processing system 203. In one embodiment, the memory system 204 stores a phase shift routine 212, a phase difference routine 215, a frequency routine 216, a time difference (Δ t) routine 217, and a flow characteristic routine 218.

In a particular embodiment, the memory system 204 stores variables used to operate the coriolis flow meter 5. The memory system 204 in one particular embodiment stores variables, such as a first sensor signal 210 and a second sensor signal 211, that are received from the speed/pickup sensors 170L and 170R. In addition, the storage system 204 may store the resulting 90 degree phase shift 213 to determine flow characteristics.

In a particular embodiment, the storage system 204 stores one or more flow characteristics obtained from the fluid measurements. The storage system 204 in one embodiment stores flow characteristics, such as phase difference 220, frequency 221, time difference (Δ t)222, mass flow 223, density 224, and volume flow 225, which are determined from the sensor signal 210.

The phase shift routine 212 performs a 90 degree phase shift on the input signal, i.e., the sensor signal 210. In one embodiment, the phase shift routine 212 performs a Hilbert transform (discussed below).

The phase difference routine 215 uses a single 90 degree phase shift 213 to determine the phase difference. Additional information may also be used to calculate the phase difference. In a particular embodiment, the phase difference is calculated from the first sensor signal 210, the second sensor signal 211, and the 90 degree phase shift 213. The determined phase difference may be stored in the phase difference 220 of the storage system 204. When the phase difference is determined from the 90 degree phase shift 213, the phase difference can be calculated and obtained more quickly than in the prior art. This can provide a critical difference in flowmeter applications with high flow rates or in applications where multi-phase flow occurs. Furthermore, the phase difference may be determined independently of the frequency of the sensor signal 210 or 211. Furthermore, since the phase difference is independent of the frequency determination, the error component in the phase difference does not include the error component of the frequency determination, i.e. there is no mixing error in the phase difference measurement. Therefore, the phase difference error is reduced on the basis of the phase difference of the prior art.

The frequency routine 216 determines the frequency (e.g., as represented by the first sensor signal 210 or the second sensor signal 211) from the 90 degree phase shift 213. The determined frequency may be stored in the frequency 221 of the storage system 204. When the frequency is determined from a single 90 degree phase shift 213, the frequency can be calculated and obtained more quickly than in the prior art. This can provide a critical difference in flowmeter applications with high flow rates or in applications where multi-phase flow occurs.

The time difference (Δ t) routine 217 determines the time difference (Δ t) between the first sensor signal 210 and the second sensor signal 211. The time difference (Δ t) may be stored in the time difference (Δ t)222 of the storage system 204. The time difference (Δ t) essentially comprises the determined phase divided by the determined frequency and is thus used for determining the mass flow.

The flow characteristics program 218 may determine one or more flow characteristics. For example, the flow characteristic routine 218 may use the determined phase difference 220 and the determined frequency 221 to accomplish these additional flow characteristics. It will be appreciated that additional information, such as mass flow or density, is required for these determinations. The flow characteristic routine 218 can determine the mass flow rate from the time difference (Δ t)222 and thus from the phase difference 220 and the frequency 221. The formula for determining mass flow is given in U.S. patent 5,027,662 to Titlow et al, which is incorporated herein by reference. The mass flow rate is related to the mass flow rate of the fluid material in the metering assembly 10. Likewise, the flow characteristics routine 218 may also determine the density 224 and/or the volumetric flow rate 225. The determined mass flow, density, and volume flow may be stored in mass flow 223, density 224, and volume 225, respectively, of storage system 204. In addition, the flow characteristics may be communicated to an external device by the meter electronics 20.

Fig. 3 is a flow chart 300 of a method of processing sensor signals in a coriolis flow meter according to an embodiment of the invention. In step 301, first and second sensor signals are received. The first sensor signal may comprise an upstream or downstream pickoff sensor signal.

In step 302, the sensor signals may be adjusted. In a particular embodiment, the conditioning may include filtering to remove noise and undesired signals. In one particular embodiment, the filtering may include band pass filtering centered around a desired fundamental frequency of coriolis flow meter 5. In addition, other adjustment operations may also be performed, such as amplification, buffering, and so forth. If the sensor signal comprises an analog signal, this step may also include any type of sampling, digitizing, and decimation that are performed to produce a digital sensor signal.

In step 303, a single 90 degree phase shift is generated. The 90 degree phase shift comprises a 90 degree phase shift of the sensor signal. The 90 degree phase shift may be performed by any type of phase shift mechanism or operation. In a specific embodiment, the 90 degree phase shift is performed using a hilbert transform operating on digital sensor signals.

In step 304, the phase difference is calculated using a single 90 degree phase shift. Additional information may also be used to calculate the phase difference. In a specific embodiment, the phase difference is determined from the first sensor signal, the second sensor signal and a single 90 degree phase shift. This phase difference comprises a phase difference in the response signal, i.e., in the pickoff sensors, as may be appreciated due to the coriolis effect in the vibrating meter assembly 10.

The final phase difference is determined without any frequency values being required in the calculation. This final phase difference can be obtained more quickly than the phase difference calculated using the frequency. This final phase difference has a higher accuracy than the phase difference calculated using the frequency.

In step 305, a frequency is calculated. The frequency according to the invention is advantageously calculated from the 90 degree phase shift. The frequency in one particular embodiment utilizes a 90 degree phase shift and a corresponding sensor signal, the 90 degree phase shift being derived from the corresponding sensor signal. The frequency is a vibrational response frequency of one of the first sensor signal and the second sensor signal (the frequencies of the two sensor signals are substantially equal in operation). The frequency comprises the vibration frequency of the flow tube or tubes in response to vibrations generated by driver 180.

The frequency thus derived is obtained without any separate frequency reference signal. In faster operation than the prior art, the frequency is obtained from a single 90 degree phase shift. The resulting frequency has a higher accuracy than the frequency calculated in the prior art.

In step 306, the mass flow rate of the fluid material is calculated. The mass flow is calculated from the final phase difference and the final frequency calculated in steps 304 and 305. Further, the mass flow calculation may calculate a time difference (Δ t) from the phase difference and the frequency, and finally calculate the mass flow using the time difference (Δ t).

In step 307, the density is optionally determined. The density may be determined as a flow characteristic and may be determined, for example, from the frequency.

In step 308, the volumetric flow rate is optionally determined. The volumetric flow rate may be determined as a flow characteristic and may be determined, for example, from mass flow rate and density.

Fig. 4 illustrates a meter electronics 20 according to a particular embodiment of the present invention. The same components as in fig. 2 are denoted by the same reference numerals.

The meter electronics 20 in this particular embodiment includes a first sensor signal 210 and a second sensor signal 211. The processing system 203 processes the first and second (digital) sensor signals 210 and 211 to determine one or more flow characteristics from the signals. As previously described, the one or more flow characteristics may include phase difference, frequency, time difference (Δ t), mass flow rate, density, and/or volumetric flow rate of the fluid material.

In the particular embodiment shown, the processing system 203 determines the flow characteristics from only the two sensor signals 210 and 211 without any external frequency measurements and without an external frequency reference signal. The processing system 203 may determine at least a phase difference and a frequency from the two sensor signals 210 and 211.

As previously described, the memory system 204 stores a phase shift routine 212, a phase difference routine 215, a frequency routine 216, a time difference (Δ t) routine 217, and a flow characteristic routine 218. The storage system 204 stores a first sensor signal 210 and a second sensor signal 211. The storage system 204 also stores a first 90 degree phase shift 213 and a second 90 degree phase shift 213 generated from the sensor signals to determine the flow characteristic. As previously described, the storage system 204 stores the phase difference 220, the frequency 221, the time difference (Δ t)222, the mass flow 223, the density 224, and the volume flow 225.

The phase shift routine 212 performs a 90 degree phase shift on the input signal, including on the first sensor signal 210 and on the second sensor signal 211. The phase shift routine 212 in one embodiment performs a hubert transform (discussed below).

The phase difference routine 215 determines the phase difference using the first 90 degree phase shift 213 and the second 90 degree phase shift 214. Additional information may also be used to calculate the phase difference. In a particular embodiment, the phase difference is calculated from the first sensor signal 210, the second sensor signal 211, the first 90 degree phase shift 212, and the second 90 degree phase shift 213. As previously described, the determined phase difference may be stored in the phase difference 220 of the storage system 204. When the phase difference is determined using the first and second 90 degree phase shifts, the phase difference can be calculated and obtained more quickly than in the prior art. This can provide a critical difference in flowmeter applications with high flow rates or in applications where multi-phase flow occurs. Furthermore, the phase difference may be determined independently of the frequency of the sensor signals 210 and 211. Furthermore, since the phase difference is independent of the frequency determination, the error component in the phase difference is not affected by the error component of the frequency determination, i.e. there is no mixing error in the phase difference measurement. Therefore, the phase difference error is reduced on the basis of the phase difference of the prior art.

The frequency routine 216 determines a frequency (e.g., as represented by the first sensor signal 210 or the second sensor signal 211) from the first 90 degree phase shift 213 and the second 90 degree phase shift 214. As previously described, this determined frequency may be stored in the frequency 221 of the storage system 204. When determining the frequency from the first and second 90 degree phase shifts, the frequency can be calculated and obtained more quickly than in the prior art. This can provide a critical difference in flowmeter applications with high flow rates or in applications where multi-phase flow occurs.

The time difference (Δ t) routine 217 determines the time difference (Δ t) between the first sensor signal 210 and the second sensor signal 211. As previously described, the time difference (Δ t) may be stored in the time difference (Δ t)222 of the storage system 204. The time difference (Δ t) essentially comprises the determined phase divided by the determined frequency and is thus used for determining the mass flow.

As previously described, the flow characteristics routine 218 may determine one or more of mass flow, density, and/or volumetric flow.

Fig. 5 is a flow chart 500 of a method of processing first and second sensor signals in a coriolis flow meter according to an embodiment of the invention. In step 501, a first sensor signal is received. In a particular embodiment, the first sensor signal comprises an upstream or downstream pickoff sensor signal.

In step 502, a second sensor signal is received. In a particular embodiment, the second sensor signal comprises a downstream or upstream pickoff sensor signal (i.e., as opposed to the first sensor signal).

In step 503, the sensor signals may be adjusted. In a particular embodiment, the conditioning may include filtering to remove noise and undesired signals. In one particular embodiment, the filtering may include bandpass filtering, as previously described. In addition, other adjustment operations may also be performed, such as amplification, buffering, and so forth. If the sensor signal comprises an analog signal, this step may also include any type of sampling, digitizing, and decimation that are performed to produce a digital sensor signal.

In step 504, a first 90 degree phase shift is generated. The first 90 degree phase shift comprises a 90 degree phase shift of the first sensor signal. The 90 degree phase shift may be performed by any type of mechanism or operation. In a specific embodiment, the 90 degree phase shift is performed using a hilbert transform operating on digital sensor signals.

In step 505, a second 90 degree phase shift is generated. The second 90 degree phase shift comprises a 90 degree phase shift of the second sensor signal. Like the first 90 degree phase shift, the 90 degree phase shift may be performed by any type of mechanism or operation.

In step 506, a phase difference between the first sensor signal and the second sensor signal is calculated using the first 90 degree phase shift and the second 90 degree phase shift. Additional information may also be used to calculate the phase difference. In a specific embodiment, the phase difference is determined from the first sensor signal, the second sensor signal, the first 90 degree phase shift and the second 90 degree phase shift. This phase difference comprises a phase difference in the response signals, i.e., in both pickup sensors, as can be appreciated due to the coriolis effect in the vibrating meter assembly 10.

The final phase difference is determined without any frequency values being required in the calculation. This final phase difference can be obtained faster than the phase difference calculated using the frequency. This final phase difference has a higher accuracy than the phase difference calculated using the frequency.

In step 507, a frequency is calculated. The frequency according to the invention is advantageously calculated from a first 90 degree phase shift and a second 90 degree phase shift. The frequency in one particular embodiment is obtained using the 90 degree phase shifts and the corresponding sensor signals from which the 90 degree phase shifts are obtained. The frequency is a vibrational response frequency of one of the first sensor signal and the second sensor signal (the frequencies of the two sensor signals are substantially equal in operation). The frequency comprises the vibration frequency of the flow tube or tubes in response to vibrations generated by driver 180.

The frequency thus obtained is obtained without any separate frequency reference signal. In faster operation than the prior art, the frequency is obtained from these 90 degree phase shifts. The resulting frequency has a higher accuracy than the frequency calculated in the prior art.

In step 508, the mass flow rate of the fluid material is calculated. The mass flow is calculated from the final phase difference and the final frequency calculated in steps 506 and 507. Further, the mass flow calculation may calculate a time difference (Δ t) from the phase difference and the frequency, and finally calculate the mass flow using the time difference (Δ t).

In step 509, the density is optionally determined as previously described.

In step 510, the volumetric flow rate is optionally determined, as previously described.

Fig. 6 is a block diagram of a portion of a processing system 203 in accordance with a specific embodiment of the present invention. In the figure, the blocks represent processing circuits or processing actions/procedures. The block diagram 600 comprises a filter block 601 of order 1, a filter block 602 of order 2, a hilbert transform block 603 and an analysis block 604. The LPO and RPO inputs include a left pickoff signal input and a right pickoff signal input. The LPO or RPO may include a first sensor signal.

In a particular embodiment, the order 1 filter block 601 and the order 2 filter block 602 comprise digital finite impulse response (RIR) polyphase decimation filters implemented in the processing system 203. These filters provide an optimal method of filtering and decimating one or both sensor signals, the filtering and decimation being performed at the same timing and at the same decimation rate. Alternatively, the order 1 filter block 601 and the order 2 filter block 602 may include finite impulse response (IIR) filters or other suitable digital filters or filter processes. However, it is understood that other filtering processes and/or embodiments of filtering are contemplated within the scope of the description and claims.

Fig. 7 shows details of the hilbert transform block 603 according to a specific embodiment of the present invention. In the particular embodiment shown, the hilbert transform block 603 comprises an LPO branch 700 and an RPO branch 710. The LPO branch 700 includes an LPO delay block 701 connected in parallel with an LPO filter block 702. Likewise, the RPO branch comprises an RPO delay block 711 in parallel with an RPO filter block 712. The LPO delay block 701 and RPO delay block 711 guide the sampling delay. Thus, the LPO delay block 701 and the RPO delay block 711 select LPO and RPO digital signal samples that are later in timing than the LPO and RPO digital signal samples filtered by the LPO filter block 702 and the RPO filter block 712. The LPO filter block 702 and the RPO filter block 712 phase shift the input digital signal samples by 90 degrees.

The hilbert transform block 603 is the first step to provide a phase measurement. The hilbert transform block 603 receives the filtered, decimated LPO and RPO signals and performs a hilbert transform. The hilbert transform produces 90 degree phase shifted versions of the LPO and RPO signals, i.e., it produces a 90 phase shifted (Q) component of the original, in-phase (I) signal component. Thus, along with the original in-phase (I) signal components LPO I and RPO I, the output of the hilbert transform block 603 provides new 90-degree phase shifted (Q) components LPO Q and RPO Q.

The input to the hilbert transform block 603 may be expressed as:

LPO＝A_lpo cos(ωt) (2)

RPO＝A_rpo cos(ωt+φ) (3)

by the hilbert transform, its output becomes:

LPO_hilbert＝A_lpo sin(ωt) (4)

RPO_hilbert＝A_rpo sin(ωt+φ) (5)

combining the original term with the output of the hilbert transform yields:

LPO＝A_lpo[cos(ωt)+isin(ωt)]＝A_lpo e^j(ωt) (6)

RPO＝A_rpo[cos(ωt+φ)isin(ωt+φ)]＝A_rpo e^j(ωt+φ) (7)

fig. 8 and 9 are block diagrams of two separate branches of analysis block 604, in accordance with a specific embodiment of the present invention. The analysis block 604 is the final order frequency, differential phase and delta T (at) measurements. Fig. 8 is a phase section 604 comprising a first branch determining the phase difference from the in-phase (I) and 90 degree phase shift (Q) components. Fig. 9 is a frequency portion 604b, the frequency portion 604b determining the frequency from the in-phase (I) and 90 degree phase shift (Q) components of a single sensor signal. The single sensor signal may comprise an LPO signal, as shown, or alternatively an RPO signal.

In the particular embodiment of fig. 8, phase portion 604a of analysis block 604 includes connection blocks 801a and 801b, a conjugate block 802, a complex multiplication block 803, a filter block 804, and a phase angle block 805.

Connection blocks 801a and 801b receive and pass the in-phase (I) and 90 degree phase shift (Q) components of the sensor signal. The conjugate block 802 complex conjugates the sensor signal (here the LPO signal) and forms a negative imaginary signal. The complex multiplication block 803 multiplies the RPO signal and the LPO signal, performing the following equation (8). The filter block 804 performs digital filtering, such as FIR filtering as previously described. The filter block 804 may include polyphase decimation filtering, which is utilized to remove harmonic components from the in-phase (I) and 90 degree phase shift (Q) components of the sensor signal and decimate the signal. The filter coefficients may be selected to provide decimation of the input signal, for example by a decimation factor of 10. The phase angle block 805 determines the phase angle from the in-phase (I) and 90 degree phase shift (Q) components of the LPO and RPO signals. The phase angle block 805 performs equation (11) shown below.

The phase section 604a shown in fig. 8 performs the following equation:

LPO×RPO＝A_lpoe^-j(ωt)×A_Rpoe^j(ωt+φ)＝A_lpo×A_Rpoe^{j(-ωt+ωt+φ)} (8)

where LPO is the complex conjugate of LPO, assuming:

A_Rpo＝A_Lpo＝A (9)

then:

LPO×RPO＝A²e^j(φ)＝A²[cos(φ)+isin(φ)] (10)

the final differential phase angle is:

fig. 9 is a block diagram of the frequency portion 604b of the analysis block 604 according to the present invention. The frequency portion 604b may operate on either the left or right pickoff signals (LPO or RPO). The frequency portion 604b in the particular embodiment shown comprises a connection block 901, a complex conjugate block 902, a sample block 903, a complex multiplication block 904, a filter block 905, a phase angle block 906, a constant block 907 and a division block 908.

As previously described, connection block 901 receives the in-phase (I) and 90 degree phase shift (Q) of the sensor signal) Components and passes them on. The conjugate block 902 complex conjugates the sensor signal, here the LPO signal, and forms a negative imaginary signal. Delay block 903 introduces a sample delay to frequency portion 604b, thus selecting the digital signal sample that is chronologically older. The chronologically older digital signal samples are multiplied by the current digital signal in the complex multiplication block 904. The complex multiplication block 904 multiplies the LPO signal by the LPO conjugate signal, and performs the following equation (12). The filter block 905 performs digital filtering, such as the FIR filtering described above. The filter block 905 may include polyphase decimation filtering, which is utilized to remove harmonic components from the in-phase (I) and 90 degree phase shift (Q) components of the sensor signal and decimate the signal. The filter coefficients may be selected to provide decimation of the input signal, for example by a decimation factor of 10. The phase angle block 906 determines the phase angle from the in-phase (I) and 90 degree phase shifted (Q) components of the LPO signal. The phase angle block 906 performs a portion of equation (13) below. The constant block 907 provides factors, including the sampling rate F, as shown in equation (14)_sDivided by twice pi. The division block 908 performs the division operation of equation (14).

The frequency section 604b performs the following equation:

thus, the angle between two consecutive samples is:

it is the angular frequency picked up on the left, converted to hertz:

wherein, F_sIs the rate of the hilbert transform block 603. In the foregoing example, "Fs" is about 2 kHz.

FIG. 10 is a plot of power spectral density of a flow meter pickoff sensor signal under typical conditions. The fundamental frequency of the meter is the highest peak of the plot and is located at about 135 Hz. The figure also shows several other large peaks in the spectrum (the first non-fundamental mode is a twisted mode with a frequency about 1.5 times the fundamental mode frequency). These peaks include the harmonic frequencies of the flow meter and also include other, undesirable sensor modes (i.e., a twist mode, a second bending mode, etc.).

Fig. 11 shows an alternative hilbert transform block 603' according to a single phase shift specific embodiment. The hilbert transform block 603' in this particular embodiment comprises an LPO branch 1100 and an RPO branch 1110. The LPO branch 1100 comprises a delay block 701 connected in parallel with a filter block 702. The RPO branch 1110 in this particular embodiment includes only a delay block 701. As previously described, the delay block 701 introduces a sampling delay. As previously described, the filter block 702 phase shifts the input digital signal samples by 90 degrees. It will be appreciated that the alternative hilbert transform block 603' may just phase shift the RPO signal.

This processing embodiment utilizes the hubert transform/phase shift of only one sensor signal to obtain the frequency and phase difference (see fig. 2-3). This greatly reduces the number of calculations required to make the phase measurements and greatly reduces the number of calculations required to obtain mass flow.

In this embodiment, the output of the hilbert transform block 603' will provide a 90 degree phase shifted (Q) component of either the left or right sensor signal, but not both. In the following example, the LPO signal is phase shifted.

LPO＝A_lpo cos(ωt)

(26)

RPO＝A_rpo cos(ωt+φ)

(27)

Using the hilbert transform, the output becomes:

LPO_hilbert＝A_lposin(ωt)

(28)

RPO＝A_rpo cos(ωt+φ)

(29)

combining the LPO original term with the output of the hilbert transform (i.e., by 90 degree phase shift) yields:

LPO＝A_lpo[cos(ωt)+isin(ωt)]＝A_lpoe^j(ωt) (30)

while RPO remains the same:

fig. 12 shows analysis block 604 a' of a single phase shift embodiment. The analysis block 604 a' in this particular embodiment comprises a connection block 801, a complex multiplication block 803, a low pass filter block 1201 and a phase angle block 805. The analysis block 604 a' in this particular embodiment performs the following equation:

(32)

the low-pass filter block 1201 includes a low-pass filter that removes high-frequency components generated by the complex multiplication block 803. The low pass filter block 1201 may perform any type of low pass filtering operation. The result of the multiplication operation produces two terms. Since the (- ω t) and (ω t) terms can cancel each other, the terms (- ω t + ω t + φ) combine and simplify to the phase φ only term (DC result). At twice the frequency, the (ω t + ω t + φ) term reduces to (2 ω t + φ). Since the result is a result of the sum of two terms, the high frequency term (2 ω t + φ) can be removed. The only signal of interest here is the DC term. The high frequency term (2 ω t + φ) may be filtered from the result using a low pass filter. The cut-off of the low-pass filter can be positioned anywhere between 0 and 2 omega.

After filtering, the result is:

thus, the differential phase angle is:

by performing the hubert transform on one pickoff signal, rather than two pickoff signals, the computational load required to perform phase and frequency estimation in a coriolis mass flowmeter is advantageously reduced. Thus, the phase and frequency can be determined using two sensor signals, but only one 90 degree phase shift.

Fig. 13 shows the sensor process of the present invention compared to the prior art, where each time difference (at) value is compared. The graph shows a fluid material comprising a gas flow (e.g., bubbles). Under this condition, the fluid noise is substantially reduced in the new algorithm because of the phase and frequency calculation rates. As can be seen from the figure, the results obtained by the present invention do not show the large peaks and valleys reflected in the prior art (Δ t) measurements.

The present invention is different from the prior art. First, the prior art typically utilizes a pickup signal and a separate frequency source to determine the pickup frequency, e.g., a driver signal is sent to a driver system to determine the vibration response frequency. In contrast, the present invention determines the frequency by phase shifting one of the two sensor signals. The prior art is unable to determine the vibration response frequency from the phase shift of the sensor signal.

Second, most prior art flow meters utilize prior art frequency determinations to determine the phase difference between the pickoff signals. Thus, any errors included in the prior art frequency determination are included in the prior art phase difference determination, combining the entire error in the prior art mass flow determination. In contrast, the present invention determines phase difference directly from one or both phase shifted sensor signals without using any frequency determination. Thus, any error term is simply the result of the phase operation and phase measurement in the phase difference determination and is not affected by any frequency determination error.

Third, the prior art utilizes a separately determined external frequency to determine mass flow. Typically, the prior art also makes use of phase differences that have been obtained by independently determined external frequencies. Therefore, in the prior art, the mass flow rate may be affected twice by any error in the frequency determination, and thus the accuracy and reliability are not satisfactory. In contrast, in the present invention, the frequency determination and the phase difference determination are obtained independently. Thus, the frequency determination and phase difference determination of the present invention include a much smaller error component. Thus, with the meter electronics and method of the present invention, the amount of error in mass flow determination is greatly reduced. The density and volume flow according to the invention thus also improve accuracy and reliability.

Fourth, the frequency determination of the prior art takes a relatively long time. Where the fluid material comprises a two-phase or three-phase fluid, such as a fluid comprising entrained solids and/or entrained gases (e.g., bubbles), prior art frequency determinations take 1-2 seconds to provide a stable and relatively accurate frequency measurement. In contrast, the frequency and phase difference determination according to the invention can be obtained very quickly, for example on the order of milliseconds or hundreds of milliseconds. All flow characteristics derived from the frequency and phase difference can also be obtained in less time.

Fig. 14 shows a meter electronics 20 according to another embodiment of the present invention. As previously described, the electronic meter 20 of this particular embodiment may include an interface 201, a digitizer 202, a processing system 203, and a storage system 204. The same reference numerals are used for the same components and/or procedures as in the other embodiments. It will be appreciated that the meter electronics 20 of this figure may include various other components and/or programs, such as the components and/or programs previously described.

In operation, the meter electronics 20 processes the first and second sensor signals from the metering assembly 10 to determine the mass fraction of the flow component in the fluid material flowing through the flow meter 5. The mass fraction is the mass flow ratio between the first fluid component and the second fluid component in the two-phase flow. The mass fraction can be used to determine the mass of various fluid components. For example, the fluid may include a fluid component and a gas component. The total mass flow rate of the fluid material may be multiplied by the mass fraction to obtain one or more fluid component mass flow rates and a gas component mass flow rate. The fluid may comprise any type of fluid and the gas may comprise any type of gas. The gas may, for example, comprise air. The following discussion will focus on air in a fluid, but it will be understood that the invention is applicable to any gas.

The meter electronics 20 receives and processes the frequency response 1410 of the metering assembly 10, e.g., the first sensor signal 1410 and the second sensor signal 1411, from the flow meter. The meter electronics 20 decomposes the frequency response 1410 into a gas frequency component 1412 and a fluid frequency component 1416. The meter electronics 20 determines the overall density (ρ) from the frequency response 1410_mix)1420. Likewise, the gas component density (ρ) is determined from the gas frequency response 1412_gas)1420. The meter electronics 20 utilizes the frequency response 1410 with one or more gas frequency components 1412 and fluid frequency components 1416 to determine the void fraction of gas 1418. The meter electronics 20 also utilizes the void fraction 1418, the overall density 1420, and the gas density 1421 to determine the mass fraction 1419. The mass fraction (mf) is defined as:

in one embodiment, the mass fraction comprises a gas mass fraction (mf)_gas). The gas mass fraction comprises:

it is to be understood, however, that the present invention may alternatively determine the fluid mass fraction (mf) in a fluid material_fluid) (or any other mass fraction). Mass fraction of the fluid (mf)_fluid) Complement including gas mass fraction:

however, for simplicity, the discussion will focus on gas mass flow (mf)_gas)。

The first sensor signal 1410 and the second sensor signal 1411 include time-varying electronic signals that are received and processed substantially continuously by the meter electronics 20, such as signals from the pickoff sensors 170L and 170R. The frequency response 1410 may be determined using the processing blocks described previously (see fig. 6-7 and 9). Advantageously, the present invention can quickly, accurately, and reliably determine the void fraction 1418 of the gas when determined using the aforementioned high speed frequencies.

The processing system 203 in this particular embodiment may include a lacunarity program 1401, a notch filter program 1402, and a quality score program 1405. The processing system 203 may also include one or more filters or filter programs, such as a low pass filter program 1403 and a high pass filter program 1404. Alternatively, the one or more filters or filter routines may include a notch filter structure or other filter structure that filters out narrow band frequencies. The processing system 203 may also include a frequency response 1410, a lacunarity 1418, and a quality score 1419 that may store the frequency response measurement, the lacunarity determination, and the quality score determination, respectively. The processing system 203 may also include a fluid frequency component 1416 and a gas frequency component 1412, which may store operating frequency values for voidage and mass fraction determinations. The processing system 203 may also include an overall density 1420, a gas component density 1421, and a fluid component density 1422, which store operating density values for void fraction and mass fraction determinations.

The frequency response 1410 includes a mixing frequency (f)_mix) Wherein the frequency response 1410 may include a gas frequency component (f)_gas)1412 and a fluid frequency component (f)_fluid)1416. Mixing the frequencies (f)_mix) After decomposing into these frequency components and determining these frequency components, the lacunarity and mass fraction may be determined. At any time, the frequency response 1410 may include any amount of the gas frequency component (f)_gas)1412 (i.e., entrained gas).

Fig. 15 is a graph of meter frequency response for air, fluid, and mixed air/fluid mixtures (i.e., fluids including entrained gas). The gas density in the fluid material flowing through the flow meter is different from the fluid density. Since the density can be derived from the measured frequency, the frequency associated with air is also different from the frequency of the fluid. This is also true for other gases or gas mixtures.

The equation for calculating the frequency is:

where ω is the angular frequency of the coriolis flowmeter. Omega_-1The term represents angular frequency samples from a previous or earlier sampling period. This angular frequency ω is converted to a frequency in hertz (Hz), giving:

the equation assumes that only one frequency is present. If there are two frequencies, when in the case of entrained air (air frequency and frequency of fluid material flow), then the new equation becomes:

wherein f is_mixIs the frequency response of the entire fluid material, including the gas frequency component (f)_gas) And a fluid frequency component (f)_fluid)。

Referring again to fig. 14, a low pass filter routine 1403 performs low pass filtering. The low pass filter passes low frequencies substantially below the low pass cut-off frequency. Therefore, a low pass filter may be used to remove high frequencies.

The high pass filter routine 1404 performs high pass filtering. The high-pass filter passes high frequencies substantially above the high-pass cut-off frequency. Thus, a high pass filter may be used to remove low frequencies.

The notch filter routine 1402 performs notch filtering. The notch filter rejects the narrowband frequency centered at the "notch" of the notch filter frequency response. Only the frequencies in the notch are filtered out by the notch filter. Thus, the notch filter is very useful for removing known, undesired frequencies from the frequency response 1410.

The voidage program 1401 determines voidage (typically gas) in a fluid material. The void fraction can be determined from the density of the fluid component, where the overall density (ρ)_mix) Including gas component density (p)_gas) And fluid component density (p)_fluid) The sum of (1).

The density (p) substantially comprises:

where f is a frequency measurement of the fluid frequency component 1416 (i.e., f)_mix). Fluid component density (ρ) may be calculated using fluid frequency component 1416_fluid)1422. In a particular embodiment, the fluid frequency component 1416 includes an average mixture frequency. The gas component density (gas)1421 may be calculated using the gas frequency component 1412. Therefore, the void fraction 1418 of the gas is calculated as the fluid component density (ρ)_fluid)1422 subtract the entire density (ρ)_mix)1420, divided by the fluid component density (ρ)_fluid)1422 minus the gas component density (ρ)_gas)1421. The voidage calculation has the following form:

the final gas voidage 1418 reflects the gas-liquid ratio in the fluid material.

The quality score program 1405 determines a quality score 1419 from the frequency response 1410. In one particular embodiment, the mass fraction program 1405 utilizes the determined Void Fraction (VF)1418 and the obtained density value to calculate a mass fraction 1419.

The mass (m) and volume (V) are related to the density (p). Thus, the density includes:

thus, the mass fraction (mf) can be simplified to:

(44)

because Voidage (VF) includes volume ratio:

the mass fraction (mf) then includes:

therefore, the porosity (VF) and the gas component density (ρ)_gas)1421 and Total Density (ρ)_mix) The quality score is determined in 1422. Gas component density (p)_gas)1421 and Total Density (ρ)_mix)1422 may be determined from the gas frequency component 1412 and the frequency response 1410, respectively.

It is to be understood that if a gas or fluid is known, only one of the gas frequency component 1412 and the fluid frequency component 1416 is required. For example, if the gas comprises air, then a standard air frequency response (and density) may be assumed. Thus, known gas or fluid frequencies can be filtered out and only one filtering step is required.

The meter electronics 20 may additionally determine other flow characteristics such as total mass flow, component volume, and the like. The meter electronics 20 may be in communication with the metering assembly 10, wherein the metering assembly 10 may comprise any type of flow meter that generates a frequency response. In one particular embodiment, the metering assembly 10 comprises a coriolis flow meter. In another particular embodiment, the metering assembly 10 includes a vibrating densitometer.

FIG. 16 is a flow chart 1600 of a method for determining a mass fraction of a fluid component in a fluid material flowing through a flow meter, in accordance with a specific embodiment of the present invention. In step 1601, a frequency response is received. For example, the frequency response is received in the meter electronics 20. The frequency response includes a frequency responsive to the vibrating meter assembly 10 with the fluid material.

In step 1602, the frequency response is decomposed into a gas frequency component 1412 and a fluid frequency component 1416. This is possible because the frequency response 1410 includes a gas frequency component related to the flow of gas in the fluid material and a fluid frequency component related to the flow of fluid. As previously described, this decomposition may be performed by one or more filters.

In step 1603, the overall density (ρ) is determined from the frequency response_mix). Overall density (. rho.)_mix) Reflecting the density of the combined fluid and gas fluid components. As mentioned before, the overall density (p)_mix) Essentially comprising one divided by the square of the frequency response (i.e., the inverse of the frequency response).

In step 1604, from the gas frequency component (f)_gas) In determining the gas component density (p)_gas). Gas component density (p)_gas) Which reflects precisely the density of the air flow component.

In step 1605, a void fraction of gas (VF)1418 is determined using the frequency response 1410, the gas frequency component 1412, and the fluid frequency component 1416 as previously described. The final void fraction of gas 1418 may be expressed as a ratio, percentage, or other measure.

In step 1606, the porosity (VF)1418 and the gas density (ρ) are determined from equation 46_gas) And the overall density (p)_min) The ratio determines the mass fraction.

FIG. 17 is a flow chart 1700 of a method for determining a mass fraction of a fluid component in a fluid material flowing through a flow meter in accordance with a specific embodiment of the invention. One method of decomposing the frequency response into fluid and gas frequency components includes performing two filtering operations. The primary filtering operation includes filtering the frequency response using a first filter that substantially filters the gas frequency component and substantially passes the fluid frequency component. The second filtering operation includes filtering the frequency response using a second filter that substantially filters the fluid frequency components and substantially passes the gas frequency components. Thus, the first filter outputs fluid frequency components, while the second filter outputs gas frequency components.

In step 1701, a response signal is received, as previously described.

In step 1702, the frequency response is filtered through a first filter. The first filter substantially filters out gas frequency components and substantially passes fluid frequency components (see fig. 18). In a specific embodiment, the first filter comprises a low-pass filter, wherein a low-pass cut-off frequency of the low-pass filter is substantially above the fluid frequency component. Thus, the low pass filter substantially passes fluid frequency components and substantially rejects gas frequency components.

In step 1703, the frequency response is filtered by a second filter. The second filter substantially filters out fluid frequency components and substantially passes gas frequency components. In a particular embodiment, the second filter comprises a high pass filter, wherein a high pass cutoff frequency of the high pass filter is substantially below the gas frequency component (but above the fluid frequency component). Thus, the high pass filter substantially passes gas frequency components and substantially rejects fluid frequency components.

In step 1704, the overall density (ρ) is determined as previously described_mix)。

In step 1705, the gas density (ρ) is determined as previously described_gas)。

In step 1706, the void fraction 1418 of the gas is determined using the frequency response 1410, the gas frequency component 1412, and the fluid frequency component 1416, as previously described.

In step 1707, a quality score 1419 is determined, as previously described.

FIG. 18 is a frequency graph illustrating low pass and high pass filter responses for decomposition into fluid and gas frequency components in accordance with an embodiment of the present invention. The lower line of the graph represents the meter frequency response including a fluid frequency component lobe and a gas frequency component lobe. The upper line includes a low pass filter response and a high pass filter response along the cutoff frequency. Here, the centers of the cut-off frequencies for the low-pass filter and the high-pass filter are substantially located between the two lobes. The low pass filter and the high pass filter may have a common cutoff frequency or may have different cutoff frequencies depending on the fluid and gas frequency components. It can be seen that the low pass filter will output a fluid frequency component and the high pass filter will output a gas frequency component. Thus, the two filters may decompose the frequency response 1410 into a gas frequency component 1412 and a fluid frequency component 1416.

Another method of resolving the fluid and gas frequency components includes filtering individual, known frequency components and determining fluid and gas component densities using the frequency components passed by the filtering operation. For example, where the gas in the fluid material is air, then the filtering operation may be configured to filter a relatively narrow frequency band centered on a general air frequency response. The overall density derived from the frequency response and the fluid density component derived from the remaining fluid frequency components can then be used to determine the air density term. For example, where the gas is known as air at atmospheric pressure, a filter (e.g., a notch filter) may be used to substantially filter out air frequency components of the frequency response. Thus, the whole density (. rho.)_mix)1420 may be calculated from the frequency response 1410, the fluid component density (ρ)_fluid)1422 may be calculated from the fluid frequency component 1416. Thus, the air component density (ρ)_gas)1421 includes:

ρ_mix＝ρ_fluid(1-VF)+ρ_gas (47)

the equation can be rewritten as:

ρ_mix＝ρ_fluidφ_fluid-ρ_gasφ_gas (48)

alternatively, it will be appreciated that the fluid frequency components may be removed/filtered and the voidage may be determined using the gas frequency components. As previously described, a single frequency removal may be performed where the fluid possesses a known characteristic frequency response and density. Thus, the single frequency removal method can remove either the fluid frequency component or the gas frequency component.

In one particular embodiment, a single frequency component may be removed by one or more filters, while other frequency components may be passed through the filtering operation. One or more of the filters in a particular embodiment comprise a notch filter. The notch filter passes all frequencies except for frequencies within a narrow band (i.e., notches in the frequency response). Alternatively, the one or more filters may include any satisfactory filter or combination of filters.

FIG. 19 is a flow chart 1900 of a method of determining a mass fraction of a fluid component in a fluid material flowing through a flow meter in accordance with a specific embodiment of the invention. In step 1901, a frequency response 1410 is received, as previously described.

In step 1902, the frequency response is processed through a notch filter. The notch filter passes frequencies below or above the notch, for example in this particular embodiment above or below the gas frequency response. Thus, the notch filter substantially filters out the gas frequency component 1412. The notch filter substantially passes the fluid frequency component 1416.

Fig. 20 is a graph of notch filter frequency response. In the example shown, the notch is centered on the gas frequency. The notch filter passes substantially all frequencies above and below the notch and the notch filter rejects substantially only gas frequencies.

Referring again to FIG. 19, in step 1903, the overall density (ρ) is determined as previously described_mix)。

In step 1904, the gas density (ρ) is determined as previously described_gas)。

In step 1905, the void fraction of the gas is determined 1418, as previously described.

In step 1906, a mass score 1419 is determined, as previously described.

If desired, the meter electronics and methods according to the present invention can be implemented in accordance with any of the embodiments to achieve several advantages. The present invention can determine the mass fraction in a two-phase flow. The present invention can determine the mass fraction in a multiphase flow. The present invention can determine the gas mass fraction or the fluid mass fraction. The present invention can determine the mass fraction of air. The present invention can determine the mass of individual fluid components, such as gas fluid component flow and fluid component flow. The invention may provide a quality score determination with better accuracy and reliability. The invention may provide a faster determination of the quality score than the prior art while consuming less processing time.

Claims

1. A meter electronics (20) for determining a mass fraction of a fluid component in a fluid material flowing through a flow meter (5), the meter electronics (20) comprising:

an interface (201) for receiving a frequency response of a fluid material; and

a processing system (203) in communication with the interface (201) and configured to receive the frequency response from the interface (201), decompose the frequency response into at least a gas frequency component and a fluid frequency component, determine an overall density from the frequency response, determine a gas density from the gas frequency component, determine a void fraction of gas from the frequency response and one or more of the gas frequency component and the fluid frequency component, and multiply the void fraction of gas by a ratio of the gas density to the overall density to determine the mass fraction.

2. The meter electronics (20) of claim 1, with the gas density comprising an inverse of the gas frequency squared and the overall density comprising an inverse of the frequency squared.

3. The meter electronics (20) of claim 1, with the processing system (203) being further configured to determine a mass flow rate of the fluid material from the frequency response and to determine at least one of the first fluid component mass and the second fluid component mass using the mass fraction and the mass flow rate.

4. The meter electronics (20) of claim 3, with the frequency response comprising a first sensor signal and a second sensor signal, and with the processing system (203) being further configured to determine a substantially instantaneous frequency of at least one of the first sensor signal and the second sensor signal and to determine a substantially instantaneous phase difference between the first sensor signal and the second sensor signal, with the frequency and the phase difference being used to determine the mass flow rate.

5. The meter electronics (20) of claim 3, wherein the frequency response includes a first sensor signal and a second sensor signal, and the processing system (203) is further configured to determine a substantially instantaneous frequency of at least one of the first sensor signal and the second sensor signal, determine a substantially instantaneous phase difference between the first sensor signal and the second sensor signal, divide the phase difference by the frequency to obtain a time delay between the first sensor signal and the second sensor signal, multiply the time delay by a constant to obtain the mass flow rate.

6. The meter electronics (20) of claim 3, wherein the frequency response includes a first sensor signal and a second sensor signal, and the processing system (203) is further configured to generate a first 90 degree phase shift from the first sensor signal, calculate a frequency of at least one of the first sensor signal and the second sensor signal using the first 90 degree phase shift and the first sensor signal, determine a substantially instantaneous phase difference between the first sensor signal and the second sensor signal, divide the phase difference by the frequency to obtain a time delay between the first sensor signal and the second sensor signal, multiply the time delay by a constant to obtain the mass flow rate.

7. The meter electronics (20) of claim 3, wherein the frequency response includes a first sensor signal and a second sensor signal, and the processing system (203) is further configured to generate a first 90 degree phase shift from the first sensor signal, calculate a phase difference between the first sensor signal and the second sensor signal using the first 90 degree phase shift, the first sensor signal, and the second sensor signal, divide the phase difference by a frequency of at least one of the first sensor signal and the second sensor signal to obtain a time delay between the first sensor signal and the second sensor signal, and multiply the time delay by a constant to obtain the mass flow rate.

8. The meter electronics (20) of claim 3, wherein the frequency response includes a first sensor signal and a second sensor signal, and the processing system (203) is further configured to generate a first 90 degree phase shift from the first sensor signal, a second 90 degree phase shift from the second sensor signal, calculate a phase difference between the first sensor signal and the second sensor signal using the first 90 degree phase shift, the second 90 degree phase shift, the first sensor signal, and the second sensor signal, divide the phase difference by a frequency of at least one of the first sensor signal and the second sensor signal to obtain a time delay between the first sensor signal and the second sensor signal, and multiply the time delay by a constant to obtain the mass flow rate.

9. The meter electronics (20) of claim 3, wherein the frequency response includes a first sensor signal and a second sensor signal, and the processing system (203) is further configured to generate a 90 degree phase shift from the first sensor signal, calculate a frequency of at least one of the first sensor signal and the second sensor signal using the 90 degree phase shift and the first sensor signal, calculate a phase difference between the first sensor signal and the second sensor signal using at least the 90 degree phase shift, the first sensor signal, and the second sensor signal, divide the phase difference by the frequency to obtain a time delay between the first sensor signal and the second sensor signal, multiply the time delay by a constant to obtain the mass flow rate.

10. A method of determining a mass fraction of a fluid component in a fluid material flowing through a flow meter, the method comprising:

receiving a frequency response of the fluid material;

decomposing the frequency response into at least a gas frequency component and a fluid frequency component;

determining the overall density from the frequency response;

determining a gas density from the gas frequency component;

determining a void fraction of the gas from the frequency response and the one or more gas frequency components and fluid frequency components; and

the void fraction of the gas is multiplied by the ratio of the gas density to the overall density to determine the mass fraction.

11. The method of claim 10, wherein the gas density comprises the inverse of the frequency of the gas squared and the overall density comprises the inverse of the frequency squared.

12. The method of claim 10, further comprising:

determining a mass flow rate of the fluid material from the frequency response; and

at least one of the first fluid component mass and the second fluid component mass is determined using the mass fraction and the mass flow rate.

13. The method of claim 12, wherein the frequency response comprises a first sensor signal and a second sensor signal, and wherein determining the mass flow rate comprises:

determining a substantially instantaneous frequency of at least one of the first sensor signal and the second sensor signal; and

a substantially instantaneous phase difference between the first sensor signal and the second sensor signal is determined, wherein the frequency and the phase difference are used to determine the mass flow rate.

14. The method of claim 12, wherein the frequency response comprises a first sensor signal and a second sensor signal, and determining the mass flow rate comprises:

determining a substantially instantaneous frequency of at least one of the first sensor signal and the second sensor signal;

determining a substantially instantaneous phase difference between the first sensor signal and the second sensor signal;

dividing the phase difference by the frequency to obtain a time delay between the first sensor signal and the second sensor signal; and

the time delay is multiplied by a constant to obtain the mass flow.

15. The method of claim 12, wherein the frequency response comprises a first sensor signal and a second sensor signal, and determining the mass flow rate further comprises:

generating a first 90 degree phase shift from the first sensor signal;

calculating a frequency of at least one of the first sensor signal and the second sensor signal using the first 90 degree phase shift and the first sensor signal;

the time delay is multiplied by a constant to obtain the mass flow.

16. The method of claim 12, wherein the frequency response comprises a first sensor signal and a second sensor signal, and determining the mass flow rate further comprises:

generating a first 90 degree phase shift from the first sensor signal;

calculating a phase difference between the first sensor signal and the second sensor signal using the first 90 degree phase shift, the first sensor signal, and the second sensor signal;

dividing the phase difference by the frequency of at least one of the first and second sensor signals to obtain a time delay between the first and second sensor signals; and

the time delay is multiplied by a constant to obtain the mass flow.

17. The method of claim 12, wherein the frequency response comprises a first sensor signal and a second sensor signal, and determining the mass flow rate further comprises:

generating a first 90 degree phase shift from the first sensor signal;

generating a second 90 degree phase shift from the second sensor signal;

calculating a phase difference between the first sensor signal and the second sensor signal using the first 90 degree phase shift, the second 90 degree phase shift, the first sensor signal, and the second sensor signal;

the time delay is multiplied by a constant to obtain the mass flow.

18. The method of claim 12, wherein the frequency response comprises a first sensor signal and a second sensor signal, and determining the mass flow rate further comprises:

generating a 90 degree phase shift from the first sensor signal;

calculating a frequency of at least one of the first sensor signal and the second sensor signal using the 90 degree phase shift and the first sensor signal;

calculating a phase difference between the first sensor signal and the second sensor signal using at least the 90 degree phase shift, the first sensor signal and the second sensor signal;

the time delay is multiplied by a constant to obtain the mass flow.

19. A method of determining a mass fraction of a fluid component in a fluid material flowing through a flow meter, the method comprising:

receiving a frequency response of the fluid material;

processing the frequency response through a notch filter that substantially filters one of the gas frequency component and the fluid frequency component;

determining the overall density from the frequency response;

determining a gas density from the gas frequency component;

20. The method of claim 19, wherein the gas density comprises the inverse of the frequency of the gas squared and the overall density comprises the inverse of the frequency squared.

21. The method of claim 19, further comprising:

22. The method of claim 21, wherein the frequency response comprises a first sensor signal and a second sensor signal, and wherein determining the mass flow rate comprises:

23. The method of claim 21, wherein the frequency response comprises a first sensor signal and a second sensor signal, and determining the mass flow rate comprises:

the time delay is multiplied by a constant to obtain the mass flow.

24. The method of claim 21, wherein the frequency response comprises a first sensor signal and a second sensor signal, and determining the mass flow rate further comprises:

generating a first 90 degree phase shift from the first sensor signal;

the time delay is multiplied by a constant to obtain the mass flow.

25. The method of claim 21, wherein the frequency response comprises a first sensor signal and a second sensor signal, and determining the mass flow rate further comprises:

generating a first 90 degree phase shift from the first sensor signal;

the time delay is multiplied by a constant to obtain the mass flow.

26. The method of claim 21, wherein the frequency response comprises a first sensor signal and a second sensor signal, and determining the mass flow rate further comprises:

generating a first 90 degree phase shift from the first sensor signal;

generating a second 90 degree phase shift from the second sensor signal;

the time delay is multiplied by a constant to obtain the mass flow.

27. The method of claim 21, wherein the frequency response comprises a first sensor signal and a second sensor signal, and determining the mass flow rate further comprises:

generating a 90 degree phase shift from the first sensor signal;

the time delay is multiplied by a constant to obtain the mass flow.

28. A method of determining a mass fraction of a fluid component in a fluid material flowing through a flow meter, the method comprising:

receiving a frequency response of the fluid material;

filtering the frequency response through a first filter that substantially filters out gas frequency components and substantially passes fluid frequency components, wherein the first filter outputs fluid frequency components;

filtering the frequency response through a second filter that substantially filters out fluid frequency components and substantially passes gas frequency components, wherein the second filter outputs gas frequency components;

determining the overall density from the frequency response;

determining a gas density from the gas frequency component;

29. The method of claim 28, wherein the gas density comprises the inverse of the frequency of the gas squared and the overall density comprises the inverse of the frequency squared.

30. The method of claim 28, further comprising:

31. The method of claim 30, wherein the frequency response comprises a first sensor signal and a second sensor signal, and wherein determining the mass flow rate comprises:

32. The method of claim 30, wherein the frequency response comprises a first sensor signal and a second sensor signal, and determining the mass flow rate comprises:

the time delay is multiplied by a constant to obtain the mass flow.

33. The method of claim 30, wherein the frequency response comprises a first sensor signal and a second sensor signal, and determining the mass flow rate further comprises:

generating a first 90 degree phase shift from the first sensor signal;

the time delay is multiplied by a constant to obtain the mass flow.

34. The method of claim 30, wherein the frequency response comprises a first sensor signal and a second sensor signal, and determining the mass flow rate further comprises:

generating a first 90 degree phase shift from the first sensor signal;

the time delay is multiplied by a constant to obtain the mass flow.

35. The method of claim 30, wherein the frequency response comprises a first sensor signal and a second sensor signal, and determining the mass flow rate further comprises:

generating a first 90 degree phase shift from the first sensor signal;

generating a second 90 degree phase shift from the second sensor signal;

the time delay is multiplied by a constant to obtain the mass flow.

36. The method of claim 30, wherein the frequency response comprises a first sensor signal and a second sensor signal, and determining the mass flow rate further comprises:

generating a 90 degree phase shift from the first sensor signal;

the time delay is multiplied by a constant to obtain the mass flow.