HK1238324B - Method and apparatus for determining differential density - Google Patents

Description

Method and apparatus for determining density differences

Technical Field

The present invention relates to flow meters and, more particularly, to methods and apparatus for determining fuel quality and system efficiency through density differential measurements.

Background Art

Vibration sensors, such as, for example, vibrating densitometers and Coriolis flowmeters, are well known and are used to measure mass flow and other information related to the material flowing through the conduits in the flowmeter. Exemplary Coriolis flowmeters are disclosed in U.S. Patents 4,109,524, 4,491,025, and Re 31,450, all to J.E. Smith et al. These flowmeters have one or more conduits in straight or curved configurations. For example, each conduit in a Coriolis mass flowmeter is configured with a set of natural vibration modes, which may be simple bends, torsional, or coupled. Each conduit can be driven to oscillate in a preferred mode.

Some types of mass flow meters, particularly Coriolis flow meters, can operate in a manner that performs a direct measurement of density, providing volume information via the quotient of mass over density. See, for example, U.S. Patent No. 4,872,351 to Ruesch for a net oil computer that uses a Coriolis flow meter to measure the density of an unknown multiphase fluid. U.S. Patent No. 5,687,100 to Buttler et al. teaches a Coriolis effect densitometer that corrects density readings for mass flow rate effects in a mass flow meter operating as a vibrating tube densitometer.

Material flows into the flow meter from a connected line on the inlet side of the flow meter, is directed through the conduit(s), and exits the flow meter through the outlet side of the flow meter. The natural vibration modes of the vibrating system are defined in part by the combined mass of the conduits and the material flowing within the conduits.

When there is no flow through the flowmeter, the driving force applied to the conduit(s) causes all points along the conduit(s) to oscillate with the same phase or a small "zero offset" (which is the time delay measured at zero flow). When material begins to flow through the flowmeter, the Coriolis force causes various points along the conduit(s) to have different phases. For example, the phase at the inlet end of the flowmeter lags the phase at the location of the centralized driver, while the phase at the outlet leads the phase at the location of the centralized driver. Sensing elements on the conduit(s) generate sinusoidal signals representing the motion of the conduit(s). The signal output from the sensing elements is processed to determine the time delay between the sensing elements. The time delay between two or more sensing elements is proportional to the mass flow rate of the material flowing through the conduit(s).

Meter electronics connected to the driver generate a drive signal to operate the driver and also determine the mass flow rate and/or other properties of the process material from the signal received from the sensor. The driver can include one of many well-known arrangements; however, a magnet and opposing drive coil have been extremely successful in the flow meter industry. An alternating current is passed to the drive coil to cause the conduit(s) to vibrate at the desired flow tube amplitude and frequency. It is also known in the art to provide the sensor as a magnet and coil arrangement very similar to the driver arrangement. However, while the driver receives a current to induce motion, the sensor uses the motion provided by the driver to induce a voltage. The magnitude of the time delay measured by the sensor is very small; typically measured in nanoseconds. Therefore, it is necessary to make the converter output very accurate.

Generally, a flow meter can be initially calibrated and a flow calibration factor can be generated along with a zero offset. In use, the flow calibration factor can be multiplied by the time delay measured by the sensing element minus the zero offset to generate the mass flow rate. In most cases, a flow meter is typically initially calibrated by the manufacturer and is assumed to provide accurate measurements without the need for subsequent calibration. Furthermore, prior art approaches involve the user zero-calibrating the flow meter after installation by stopping flow, closing valves, and thereby providing the meter with a zero flow rate reference under process conditions.

Vibration sensors, including Coriolis flowmeters, are often used in large engine systems, such as those found in offshore vessels. For such vessels, proper fuel management is critical to efficient engine system operation. Fuel management typically begins with bunkering or fuel loading at the port. At this point, fuel is loaded onto the vessel and the quantity is measured. However, the fuel quality is unknown at this time. Fuel quality is determined by sending samples to a laboratory where viscosity, density, and composition can be determined. Unfortunately, this process often takes several days, so fuel quality issues that arise are typically only revealed after the vessel has left port and has been fully at sea. Furthermore, even if the fuel quality meets a given set of standards, problems within the fuel system can introduce contaminants such as water into the fuel system, which is problematic.

Therefore, what is needed in the art is a method and related apparatus for determining qualitative fuel properties. What is needed is a method and related apparatus for determining the density of fuel before entering an engine and after leaving the engine. What is needed is a method and related apparatus for detecting the potential water content of a fuel. The present invention overcomes these and other problems and achieves an advancement in the art.

Summary of the Invention

According to an embodiment, a method for operating an engine system is provided, the engine system including an engine configured to consume fuel and having at least two flow meters. The embodiment includes the steps of operating the engine disposed between a supply flow meter of the at least two flow meters and a return flow meter of the at least two flow meters; measuring a first fuel density in the supply flow meter and a second fuel density in the return flow meter; comparing the fuel density measurements between the supply flow meter and the return flow meter; determining a density difference measurement value Δρ based on a difference between the second fuel density and the first fuel density; comparing Δρ to a range of theoretical fuel density difference values _Δρt ; and indicating potential fuel contamination if Δρ is outside the range of _Δρt values by a predetermined threshold.

According to an embodiment, meter electronics for a flow meter is provided, comprising a processing system coupled to a system having an engine. The embodiment is configured to: receive sensor signals from both a supply flow meter and a return flow meter; determine a density difference measurement Δρ between the supply flow meter and the return flow meter based on the received sensor signals; compare Δρ to a range of theoretical fuel density differences _Δρt ; and store the comparison of Δρ to the range of _Δρt values in the meter electronics.

aspect

According to one aspect, a method for operating an engine system is provided, the engine system including an engine configured to consume fuel and having at least two flow meters. The method includes the steps of: operating the engine disposed between a supply flow meter of the at least two flow meters and a return flow meter of the at least two flow meters; measuring a first fuel density in the supply flow meter and a second fuel density in the return flow meter; comparing the fuel density measurements between the supply flow meter and the return flow meter; determining a density difference measurement value Δρ based on a difference between the second fuel density and the first fuel density; comparing Δρ to a range of theoretical fuel density difference values _Δρt ; and indicating potential fuel contamination if Δρ is outside the range of _Δρt values by a predetermined threshold.

Preferably, the method comprises the step of storing Δρ in meter electronics.

Preferably, the step of indicating potential fuel contamination if Δρ lies outside the Δρ _t range by a predetermined threshold comprises indicating water contamination of the fuel if Δρ exceeds the Δρ _t range by a predetermined threshold.

Preferably, the method includes the steps of receiving a temperature sensor signal value from a supply flow meter; receiving a temperature sensor signal value from a return flow meter; and adjusting the first fuel density measurement result and the second fuel density measurement result to compensate for the temperature of the supply flow meter and the return flow meter, respectively.

Preferably, the method includes the steps of receiving temperature sensor signal values from temperature sensors external to the supply flow meter and the return flow meter; and adjusting the first fuel density measurement and the second fuel density measurement to compensate for the temperature sensor signal values.

Preferably, the method comprises the step of triggering an alarm if Δρ lies outside a predetermined threshold within the range _Δρt .

Preferably, the method comprises the steps of measuring fuel flow in a supply flow meter and a fuel flow in a return flow meter while the engine is operating; calculating engine fuel consumption by comparing the fuel flow in the return flow meter with the fuel flow in the supply flow meter; and indicating the fuel consumption measurement results.

According to one aspect, meter electronics for a flow meter is provided, comprising a processing system coupled to a system having an engine. The meter electronics is configured to: receive sensor signals from both a supply flow meter and a return flow meter; determine a density difference measurement Δρ between the supply flow meter and the return flow meter based on the received sensor signals; compare Δρ to a range of theoretical fuel density differences _Δρt ; and store the comparison of Δρ to the range of _Δρt values in the meter electronics.

Preferably, the processing system is configured to indicate potential contamination if Δρ lies outside a range of Δρ _t values by a predetermined threshold.

Preferably, the processing system is configured to indicate potential water contamination if Δρ exceeds a predetermined threshold value within the range of Δρ _t values.

Preferably, the flow meter is in fluid communication with the water emulsification system.

Preferably, the processing system is configured to: determine a temperature of the supply flow meter; determine a temperature of the return flow meter; and output an adjusted fluid consumption measurement corrected for the operating temperature.

Preferably, the processing system is configured to: determine a temperature outside the supply flow meter and the return flow meter; and output an adjusted fluid consumption measurement corrected for the temperature outside the supply flow meter and the return flow meter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 shows a prior art vibration sensor assembly;

FIG2 shows a prior art fuel system;

FIG3 shows meter electronics according to an embodiment of the present invention;

4 is a graph showing measured density of fuel in a fuel system according to an embodiment;

5 is a flowchart describing a method of operating an engine system according to an embodiment;

FIG6 is a flowchart describing another method of operating an engine system according to an embodiment; and

FIG. 7 is a flowchart describing yet another method of operating an engine system according to an embodiment.

DETAILED DESCRIPTION

Figures 1-7 and the following description depict specific examples to teach those skilled in the art how to make and use the best mode of the present invention. For the purpose of teaching the principles of the invention, some conventional aspects have been simplified or omitted. Those skilled in the art will recognize that variations of these examples fall within the scope of the present invention. Those skilled in the art will recognize that the features described below can be combined in various ways to form multiple variations of the present invention. Therefore, the present invention is not limited to the specific examples described below, but is only limited by the claims and their equivalents.

1 shows an example of a flow meter 5 in the form of a Coriolis flow meter that includes a sensor assembly 10 and one or more meter electronics 20. The one or more meter electronics 20 are connected to the sensor assembly 10 to measure characteristics of the flowing material such as, for example, density, mass flow rate, volume flow rate, total mass flow, temperature, and other information.

Sensor assembly 10 includes a pair of flanges 101 and 101', manifolds 102 and 102', and conduits 103 and 103'. Manifolds 102 and 102' are attached to opposite ends of conduits 103 and 103'. Flanges 101 and 101' of this example are attached to manifolds 102 and 102'. Manifolds 102 and 102' of this example are attached to opposite ends of spacer 106. Spacer 106 maintains spacing between manifolds 102 and 102' in this example to prevent undesirable vibrations in conduits 103 and 103'. Conduits 103 and 103' extend outward from the manifolds in a substantially parallel manner. When sensor assembly 10 is inserted into a piping system (not shown) carrying flowing material, the material enters sensor assembly 10 through flange 101, passes through inlet manifold 102, where the total amount of material is directed into conduits 103 and 103', flows through conduits 103 and 103' and back into outlet manifold 102' where it exits sensor assembly 10 through flange 101'.

Sensor assembly 10 includes a driver 104. Driver 104 is attached to conduits 103 and 103' in a position where driver 104 can vibrate conduits 103, 103' in a drive mode. More specifically, driver 104 includes a first driver component (not shown) attached to conduit 103 and a second driver component (not shown) attached to conduit 103'. Driver 104 can include one of many well-known arrangements, such as, for example, a magnet mounted to conduit 103 and an opposing coil mounted to conduit 103'.

In this example, the drive mode is the first out-of-phase bending mode, and conduits 103 and 103' are selected and appropriately mounted to inlet and outlet manifolds 102, 102' to provide a balanced system having approximately the same mass distribution, moment of inertia, and elastic modulus about bending axes W-W and W'-W', respectively. In this example, where the drive mode is the first out-of-phase bending mode, conduits 103 and 103' are driven by driver 104 in opposite directions about their respective bending axes W-W and W'-W'. A drive signal in the form of an alternating current can be provided by one or more meter electronics 20, such as via passage 110, and passed through a coil to induce oscillation in both conduits 103, 103'. Those skilled in the art will recognize that other drive modes may be used within the scope of the present invention.

The illustrated sensor assembly 10 includes a pair of sensors 105, 105' attached to conduits 103, 103'. More specifically, a first sensor (not shown) is located on conduit 103, and a second sensor (not shown) is located on conduit 103'. In the depicted embodiment, the sensors 105, 105' can be electromagnetic detectors, such as sensor magnets and sensor coils, that generate sensor signals representative of the velocity and position of the conduits 103, 103'. For example, the sensors 105, 105' can supply the sensor signals to one or more meter electronics 20 via passages 111, 111'. Those skilled in the art will recognize that the movement of the conduits 103, 103' is proportional to certain characteristics of the flowing material, such as the mass flow rate and density of the material flowing through the conduits 103, 103'.

It should be appreciated that while the sensor assembly 10 described above includes a dual flow conduit flowmeter, it is well within the scope of the present invention to implement a single conduit flowmeter. Furthermore, while the flow conduits 103, 103' are illustrated as including curved flow conduit configurations, the present invention can be implemented using flowmeters including straight flow conduit configurations. It should also be appreciated that the sensitive elements 105, 105' can include strain gauges, optical sensors, laser sensors, or any other sensor type known in the art. Therefore, the particular embodiment of the sensor assembly 10 described above is merely an example and should in no way limit the scope of the present invention.

In the example shown in FIG1 , one or more meter electronics 20 receive sensor signals from sensors 105 , 105 ′. Path 26 provides input and output devices that allow the one or more meter electronics 20 to interface with an operator. The one or more meter electronics 20 measure characteristics of the flowing material, such as, for example, phase difference, frequency, time delay, density, mass flow rate, volume flow rate, total mass flow, temperature, meter verification, and other information. More specifically, the one or more meter electronics 20 receive one or more signals, such as from sensors 105 , 105 ′ and one or more temperature sensors 107 , such as resistance temperature devices (RTDs), and use this information to measure characteristics of the flowing material. The temperature sensors 107 may be included with the flow meters 214 , 216 or located external to the flow meters 214 , 216 .

The art of measuring characteristics of flowing materials using vibrating sensor assemblies (such as, for example, Coriolis flowmeters or densitometers) is well understood; therefore, for the sake of brevity in this description, a detailed discussion is omitted. However, as a brief overview, the density of an unknown fluid flowing through an oscillating flow tube is proportional to the square of the period during which the tube resonates. In U.S. Patent No. 4,491,009 to Ruesch, a circuit for calculating density using two series-connected integrators is described. A reference voltage is applied to the first integrator. Because the spring constant of each flow tube varies with temperature and thus changes the resonant frequency, the reference voltage appropriately compensates for temperature variations in the tubes. The two integrators operate for a period equal to the square of the resonant period. In this manner, the output signal generated by the analog circuit provides the product of a temperature-dependent function and the square of the value of the resonant period. By appropriately scaling the reference voltage, the output analog signal provides a direct readout of the density measurement (in units of specific gravity) of the unknown fluid flowing through the flow tube. It should be noted that this is merely one example of a prior art density measurement performed with a vibrating meter and is in no way intended to limit the scope of the present invention.

FIG2 illustrates a fuel system 200 according to an embodiment. System 200 is shown as a typical marine fuel system. Fuel is stored in main tanks 202 and 204. In one example embodiment, heavy fuel oil (HFO) is stored in a first main tank 202, and marine diesel oil (MDO) is stored in a second main tank 204. Main tanks 202 and 204 are fed into a day tank 206 via fuel lines 203 and 205, respectively. This is merely an example, and it should be understood that there may be more than two main tanks, or only one. Furthermore, HFO and MDO are merely examples of usable fuels, and any fuel is contemplated to be within the scope of the embodiment. Day tank 206 is typically sized to store a limited amount of fuel for safety and pollution prevention purposes. Day tank 206 prevents excessive fuel storage in areas such as a vessel's engine room, minimizing the risk of fire or explosion. If a fire occurs, limited fuel availability helps reduce the severity of fire-related incidents. Additionally, day tank 206 receives fuel that is given to engine 208 but is not used thereby, so return fuel is sent back to day tank 206 via return fuel line 207. In some systems 200, a water emulsification system 224 may be provided to introduce water into the fuel for the purpose of reducing emissions.

During operation, fuel is typically recirculated from the day tank 206 to the engine 208 or other fuel-consuming device, and any fuel not consumed flows back to the day tank 206 in a closed loop circuit 218. If the day tank 206 becomes low on fuel, fuel from the main tanks 202, 204 refills the day tank 206. A pump 210 provides the necessary motion to pump fuel from the day tank 206 to the engine 208 and back. An online preheater 212 heats the fuel to a temperature ideal for utilization by the engine 208. For example, the operating temperature of HFO is generally between approximately 120°C and 150°C, while MDO is ideally between approximately 30°C and 50°C. The appropriate temperature for a particular fuel allows the viscosity of the fuel to be controlled and maintained within a desired range. The kinematic viscosity of a fuel is a measure of its fluidity at a certain temperature. Since the viscosity of fuel decreases with increasing temperature, the viscosity of the fuel at the moment it leaves the engine's fuel injector (not shown) must be within the range specified by the engine manufacturer in order to produce the optimal fuel spray pattern. Viscosities outside of specifications result in substandard combustion, power loss, and potential deposit formation. Preheater 212, when properly set for the particular fuel being used, allows for optimal viscosity to be achieved.

To measure flow parameters such as mass flow rate or density, for example, in an embodiment, a series flow meter is utilized. Supply flow meter 214 is located upstream of engine 208, while return flow meter 216 is located downstream of engine 208. Because, for example, engine 208 does not use all of the fuel supplied to the engine in a common fuel rail system (not shown), excess fuel is recirculated through day tank 206 and closed-loop circuit 218. Therefore, a single flow meter would not provide accurate flow measurements (particularly regarding engine fuel consumption), so both supply flow meter 214 and return flow meter 216 are required (upstream and downstream of engine 208, respectively). The difference in flow rates measured by flow meters 214 and 216 is roughly equal to the flow rate of fuel consumed by engine 208. Therefore, the difference in measured flow rates between flow meters 214 and 216 is the primary value of interest in most applications similar to the configuration shown in FIG. However, it should be noted that the common rail fuel system is used merely as an example and does not limit the scope of the claimed invention. Other fuel systems in which fuel is returned and/or recirculated are contemplated. It should also be appreciated that while the system 200 shows only one fuel outlet 222 and two flow meters 214 , 216 , in some embodiments, there will be multiple fuel outlets and more than two flow meters.

When operating a large engine, knowing the inlet and outlet state of the system is critical for the efficiency and performance of the fuel system 200. Most of these systems 200, such as the fuel system shown in Figure 2, have a fuel conditioning system (comprising preheater 212) that is used for preparing fuel to a specific viscosity, temperature, and consistency before the fuel enters the engine 208. Having the correct fuel state can strongly influence the performance of the engine. The viscometer 213 downstream of the preheater 212 measures fuel viscosity, and in some embodiments can communicate with the preheater 212 to adjust the preheater temperature so that the fuel remains within a predetermined viscosity range. Currently, fuel monitoring systems are almost only present on the inlet side of the engine, and after the fuel passes through the engine, the monitoring of the state of the fuel is done less. Determinedly, the change in the state of the fuel after the engine is an indication of fuel quality or engine performance.

According to an embodiment, the engine status is monitored by checking the density of the fuel before and after the engine 208, as any changes may indicate potential problems in the system, such as those related to fuel quality and engine performance. The supply flow meter 214 measures the density of the fuel before the engine 208, and the return flow meter 216 measures the density of the fuel after the engine 208.

FIG3 illustrates meter electronics 20 according to an embodiment of the present invention. Meter electronics 20 may include an interface 301 and a processing system 303. Processing system 303 may include a storage system 304. Storage system 304 may include internal memory and/or external memory. Meter electronics 20 may generate a drive signal 311 and supply drive signal 311 to driver 104. Furthermore, meter electronics 20 may receive sensor signals 310 from flow meters 214 , 216 , such as pick-off/velocity sensor signals, strain gauge signals, optical signals, temperature signals, or any other signals known in the art. Meter electronics 20 may operate as a density meter or as a mass flow meter, including a Coriolis flow meter. It should be appreciated that meter electronics 20 may also operate as some other type of vibration sensor assembly, and the specific examples provided should not limit the scope of the present invention. Meter electronics 20 may process sensor signals 310 to obtain flow characteristics of the material flowing through flow conduits 103 , 103 ′. In some embodiments, for example, the meter electronics 20 may receive a temperature signal 312 from one or more RTD sensors or other temperature sensors 107 .

Interface 301 can receive sensor signals 310 from driver 104 or sensors 105, 105' via leads 110, 111, 111', respectively. Interface 301 can perform any necessary or desired signal conditioning, such as formatting, amplification, buffering, etc. Alternatively, some or all of the signal conditioning can be performed in processing system 303. Furthermore, interface 301 can enable communication between meter electronics 20 and external devices. Interface 301 can be configured with any form of electronic, optical, or wireless communication.

In one embodiment, the interface 301 may include a digitizer 302, wherein the sensor signal includes an analog sensor signal. The digitizer 302 may sample and digitize the analog sensor signal and generate a digital sensor signal. The digitizer 302 may also perform any necessary sampling, wherein the digital sensor signal is sampled to reduce the amount of signal processing required and to reduce processing time.

The processing system 303 may perform operations of the meter electronics 20 and process flow measurements from the sensor assembly 10. The processing system 303 may execute one or more processing routines, such as a density difference routine 313, a zero difference routine 314, an overall operation routine 315, and a fuel type signal routine 316, and thereby process the flow measurements to produce one or more flow measurements that are ultimately used to calculate fuel consumption of the fuel system 200 and calculate a density difference measurement value 319 and any other related calculations.

According to an embodiment, meter electronics 20 may be configured to measure flow through supply flow meter 214 and return flow meter 216 as part of density difference routine 313. According to an embodiment, meter electronics 20 may also measure temperature signal 312 and correlate the temperature to the flow rate captured at a given temperature.

As an example of density difference routine 313, system 200 may include a supply flow meter 214 and a return flow meter 216 that both have (or share) meter electronics 20. If not shared, the meter electronics may communicate with each other via interconnect 220. Supply flow meter 214 and return flow meter 216 may each generate a density 317. A density difference measurement Δρ, 319 is calculated using the density 317 from supply flow meter 214 and return flow meter 216 as part of density difference routine 313. Mass flow rate 318 or density 317 may be calculated, for example, as part of operating routine 315. In one embodiment of operating routine 315, the return flow rate is subtracted from the supply flow rate, thereby providing a fuel consumption measurement. Meter electronics 20 subtracts the two absolute flow signals to produce a difference output and additionally accounts for any signal processing delays between the meters.

In an embodiment, the temperature signal 312 is read, and the zero flow rate consumption difference between the return flow meter 216 and the supply flow meter 214 is also saved and calculated as part of the zero difference routine 314. The zero difference improves the flow difference calculation performed between the two meters because it mitigates the temperature effects between the meters. This eliminates the need to perform a zeroing procedure before operation. In a working example, if the engine is shut down, there is still flow (e.g., 1000 kg/hr) through both flow meters 214, 216. The meters will most likely not both read exactly 1000 kg/hr. Instead, one may read 999 kg/hr and the other 1001 kg/hr, so the user will see a consumption (or production) measurement of 2 kg/hr when the engine is shut down. Over a long operating period, this error of 2 kg/hr will equate to a large difference. Therefore, at a specific temperature, the zero difference of 2 kg/hr is used in the overall operation routine 315 as a correction for any flow meter measurement.

Processing system 303 may include a general-purpose computer, a microprocessor system, a logic circuit, or some other general-purpose or custom processing device. Processing system 303 may be distributed among multiple processing devices. Processing system 303 may include any form of integrated or independent electronic storage media, such as storage system 304.

The processing system 303 processes, among other things, the sensor signal 310 to generate a drive signal 311. The drive signal 311 is supplied to the driver 104 to vibrate the associated flow tube(s), such as the flow tubes 103, 103' of FIG.

It should be understood that the meter electronics 20 may include various other components and functions well known in the art. These additional features are omitted from the description and drawings for the sake of brevity. Therefore, the present invention should not be limited to the specific embodiments shown and discussed.

FIG4 is a graph depicting density difference measurement results. Detecting water contamination in a fuel system is an example (but not limiting) use of the embodiments presented herein. In addition to overall measurements of fuel quality, the unexpected presence of water in the fuel supply is a qualitative indicator of a potential problem. In one embodiment, by examining the density difference measurement results (inlet density versus outlet density), it is possible to determine the potential water content of the fuel entering engine 208. The density of the fuel can be measured by supply flow meter 214, and a first fuel density is calculated. Once the fuel not consumed by engine 208 passes through return flow meter 216, a second density is calculated by return flow meter 216. As a non-limiting example, the temperature of the fuel at the engine inlet (and supply flow meter 214) can be 20°C cooler than the temperature measured by return flow meter 216. Since the density of fuel decreases with increasing temperature, a lower density measurement would be expected in return flow meter 216. However, if the density measurement of return flow meter 216 is the same as or higher than that of supply flow meter 214, this indirectly suggests water contamination of the fuel. 4 shows the measured inlet density 400 and outlet density 402 as measured by supply flow meter 214 and return flow meter 216, respectively, over time 404. Region A indicates the fuel flowing in the closed loop 218 of fuel system 200 when engine 208 is shut down. As is apparent, once engine 208 is running (region B), the temperature of the outlet will rise. This is shown in the graph at the point where it begins by the dotted vertical line labeled "consumption event increases outlet temperature." In the example provided by the graph, the density measured at inlet 400 remains stable, even when engine 208 is running. However, outlet density 402 increases over time after engine 208 is started. This indicates the potential presence of water in the fuel.

In one embodiment, the density difference measurement Δρ is calculated according to equation (1):

Δρ=ρ _R -ρ _S (1)

in:

ρ _P = density calculated by the return flow meter; and

ρ _S = density calculated by the supply flow meter.

This is just one example of how to calculate Δρ, and other methods, equations, and algorithms are contemplated.

In one case, if a fuel seller supplies fuel that contains what is considered an unacceptably high amount of water, density measurement can be useful to account for this problem. However, when the density of the fuel will simply be higher than expected for that particular fuel, it is a straightforward single-gauge density calculation. This is the case where water enters the fuel system after fueling, where differential fuel measurement system 200 is particularly advantageous.

In one embodiment, several water-cooled injectors (not shown) can be used to atomize and inject the fuel into the combustion chamber of the engine. Due to the high temperatures found in the combustion chamber, it is often necessary to cool the injector tips that protrude therein. A common solution for achieving this occurs by circulating water through passages within the injectors.

A fuel injector is primarily constructed of a metal (typically steel) body with fuel supply and return passages therein. Fuel is supplied to an end chamber near the tip of the injector, where a valve (such as, but not limited to, a needle valve) allows fuel to be metered into the combustion chamber. The valve opens when the fuel pressure exceeds the force of a biasing member configured to hold the valve closed. Passages in the injector body may also be present for the supply and return of water through the nozzle. This describes a typical common rail fuel injector system as an example and is not intended to limit the present invention to such fuel systems. Furthermore, while water is described, other coolants are also contemplated. If an injector malfunctions, water may enter the fuel supply. For example, the fuel supplied to the injector may be delivered to the injector at a pressure of 15 psi. For example, the water circulating through the injector may be at 30 psi. In the event of an injector malfunction, if a seal degrades or there is a physical breach in the fuel and water conduits, water circulating at a higher pressure than the fuel within the injector will enter the fuel conduit and contaminate the closed-loop circuit 218 of fuel system 200. This can be detected as an increase in density as measured by the return flow meter 216 and using the supply flow meter 214 as a reference.

In a similar example, the cylinder head (not shown) of engine 208 may include water passages to allow water to circulate through the cylinder head for cooling purposes. In some engine designs, fuel passages may also exist within the cylinder head. In the event of a cylinder head casting failure or porosity within the casting, it is possible for water to contaminate the fuel supply. As in the above example, in the event of a cylinder head failure, water may enter the fuel line and contaminate the closed-loop circuit 218 of fuel system 200. Again, this can be detected as an increase in density, as measured by the density difference measurement between return flow meter 216 and supply flow meter 214.

Nitric oxide (NO) and nitrogen dioxide (NO ₂ ) are single nitrogen oxides (collectively "NOx") that are produced by the reaction of nitrogen and oxygen during the combustion reaction (most notably at higher temperatures). The large fuel systems 200 of marine vessels are used to produce large amounts of nitrogen oxides, which are emitted into the atmosphere and are considerable air pollutants. Since the atmosphere is approximately 78% nitrogen and 21% oxygen, NOx gases are formed any time combustion occurs in an engine that draws in atmospheric air. Unfortunately, NOx gases contribute to the formation of ozone, smog, and potential acid rain. Therefore, engines and fuel systems often incorporate methods to reduce NOx formation. Adding water to the combustion chamber of a marine diesel engine is a strategy that can be used to reduce NOx production. This lowers the peak combustion temperature, thereby negatively impacting (i.e., reducing) NOx formation. One way to introduce water into the combustion chamber is through the use of emulsified fuel.

Emulsified fuels are typically made from water and liquid fuel. In the case of fuel systems, the emulsion is a multiphase liquid in which the water and fuel phases are immiscible. Emulsifiers (or surfactants) are often used in emulsification to promote a stable mixture. The typical range of water in the fuel is between 5% and 30% by mass. This range varies based on fuel type, water purity, engine configuration, and other factors beyond the scope of this disclosure. The fuel is often mixed with onboard water before entering the combustion chamber (see, for example, emulsification system 224 in FIG. 2 ). The evaporation of water in the combustion chamber generally cools the cylinder walls and the combustion chamber. Of course, the reduced combustion temperature leads to reduced NOx production. If the percentage of water is too high, engine efficiency is compromised, but if the percentage of water in the emulsion is too low, the reduction of NOx compounds is insufficient. Since the amount of water added to form the water/fuel emulsion is known for a particular engine system, the fuel passing through the return flow meter 216 will have an acceptable density range corresponding to the acceptable volume of water in the emulsion. If the density difference indicates that there is no variation in fuel density across the engine, this may indicate a faulty emulsion system, where not enough water is being added to the fuel. Similarly, if the density difference is greater than would be expected based on the volume of water that should be added to the fuel, this may indicate that too much water is being added to the emulsion.

FIG5 illustrates an embodiment of a method for indicating potential fuel contamination. Supply flow meter 214 is located upstream of engine 208, and return flow meter 216 is located downstream of engine 208. In step 500, engine 208, which is positioned between supply flow meter 214 and return flow meter 216, is operated. Any difference in the flow rates measured by flow meters 214 and 216 is approximately equal to the flow rate of fuel consumed by engine 208. In step 502, a first fuel density is measured in supply flow meter 214, and a second fuel density is measured in return flow meter 216. In step 504, these measured fuel density values are then compared. As mentioned above, the density of fuel decreases with temperature, so a lower density measurement would be expected in return flow meter 216. If the density measurement of the return flow meter differs significantly from the density measurement of the supply flow meter, this indirectly suggests fuel contamination. In step 506, the difference Δρ between the fuel density values is determined and then, in step 508, compared to a theoretical difference _Δρt between the fuel density values or a range of _Δρt values. For example, and without limitation, Δρ can be determined using equation (1). However, other equations, algorithms, and methods are also contemplated. In step 510, if Δρ is outside the _Δρt range by a predetermined threshold, potential fuel contamination is indicated. This threshold depends on the engine type, fuel type, temperature, the temperature difference between flow meters 214, 216, the presence or absence of the fuel emulsion system 224, and the like.

As mentioned above, the temperature of the fuel at the engine inlet (and supply flow meter 214) is expected to be cooler than the temperature measured by return flow meter 216 when the engine 208 is operating. Therefore, the density measurement result of return flow meter 216 should theoretically be lower than the density measurement result of supply flow meter 214. If not, this may indicate that the fuel may be contaminated by water. Figure 6 is directed to an embodiment for indicating potential water contamination in fuel system 200. Note that the first five steps shown in Figure 6 are common to the first five steps shown in Figure 5. In step 600, the engine 208 is operated, which is arranged between supply flow meter 214 and return flow meter 216. In step 602, a first fuel density is measured in supply flow meter 214, and a second fuel density is measured in return flow meter 216. In step 604, these measured fuel density values are then compared. If the density measurement result of the return flow meter is significantly different from the density measurement result of the supply flow meter, this indirectly suggests water contamination of the fuel. In step 606, Δρ is determined and then compared to _Δρt or a _Δρt range in step 608. In step 610, if Δρ exceeds a predetermined threshold of _Δρt or a _Δρt range, potential water contamination of the fuel is indicated. As a non-limiting example application, if a water-cooled fuel injector (not shown) is used to atomize and inject fuel into the combustion chamber of an engine, a rupture of the injector's water jacket may introduce water into the fuel system after the supply flow meter 214 but before the return flow meter 216. This will, of course, contaminate the closed-loop circuit 218 of the fuel system 200 with water, which can be detected as an increase in density, as measured by the return flow meter 216 and using the supply flow meter 214 as a reference.

FIG7 illustrates a related embodiment for indicating potential fuel contamination, using the temperature of flow meters 214 and 216. In step 700, engine 208, positioned between supply flow meter 214 and return flow meter 216, is operated. In step 702, a first fuel density is measured in supply flow meter 214, and a second fuel density is measured in return flow meter 216. In step 704, temperature sensor signal values are received from both supply flow meter 214 and return flow meter 216. These values may be stored in meter electronics 20. The temperature may be determined by processing sensor signals, such as those received from temperature sensor 107. For example, the temperature may be determined using an RTD. For example, the temperature may correspond to the flow meter temperature, the flow tube temperature, the flow meter case temperature, the meter electronics temperature, or a temperature external to the supply flow meter 214 or return flow meter 216. In one embodiment, each flow meter 214 and 216 includes a separate temperature sensor. In one embodiment, the temperature sensor is located external to the flow meter 214 and 216. In one embodiment, a separate temperature is determined for each flow meter 214, 216, and the measured individual temperatures are input into meter electronics 20. In another embodiment, in step 706, temperature adjustments are determined for the first and second fuel density measurements to compensate for the temperature of supply flow meter 214 and return flow meter 216, respectively. In another embodiment, the temperature outside of supply flow meter 214 and return flow meter 216 is determined, and the first and second fuel density measurements are adjusted in step 706 to compensate for the measured temperature. In step 708, these temperature-compensated measured fuel density values are then compared. In step 710, Δρ is then determined using the temperature-compensated fuel density values. In step 712, Δρ is compared to the _Δρt range. As shown in step 714, if Δρ is outside the _Δρt range by a predetermined threshold, potential fuel contamination is indicated.

In an embodiment of the method for indicating potential fuel contamination, an alarm may be triggered if Δρ differs from _Δρt by a predetermined threshold or is outside a predetermined threshold range of _Δρt . Furthermore, the method may include measuring fuel flow in a supply flow meter and a return flow meter while the engine is operating, thereby calculating engine fuel consumption by comparing the fuel flow in the return flow meter with the fuel flow in the supply flow meter. The fuel consumption measurement is then indicated.

As described above, the present invention provides various systems and methods for determining fuel quality using a vibrating flow meter, such as a Coriolis flow meter. Although the various embodiments described above are directed to flow meters, and particularly Coriolis flow meters, it should be appreciated that the present invention should not be limited to Coriolis flow meters. Rather, the methods described herein can be utilized with respect to other types of flow meters, or other vibrating sensors that lack some of the measurement capabilities of a Coriolis flow meter.

The detailed description of the above embodiments is not an exhaustive description of all embodiments contemplated by the inventors to be within the scope of the present invention. Indeed, those skilled in the art will recognize that certain elements of the above-described embodiments may be variously combined or eliminated to create additional embodiments, and such additional embodiments fall within the scope and teachings of the present invention. It will also be apparent to those skilled in the art that the above-described embodiments may be combined in whole or in part to create additional embodiments within the scope and teachings of the present invention.

Thus, although specific embodiments of the present invention and examples thereof are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the present invention, as will be appreciated by those skilled in the relevant art. The teachings provided herein are applicable to other vibration sensors, and not only to the embodiments described above and shown in the accompanying drawings. Accordingly, the scope of the present invention should be determined from the following claims.

Claims (12)

1. A method for operating an engine system, the engine system comprising an engine configured to consume fuel and having at least two flow meters, the method comprising the steps of: An engine is operated between the supply flow meter and the return flow meter of the at least two flow meters; A first fuel density is measured in the supply flow meter and a second fuel density is measured in the return flow meter; Compare the fuel density measurement results between the supply flow meter and the return flow meter; The density difference measurement value Δρ is determined based on the difference between the second fuel density and the first fuel density; Compare the range of Δρ with the theoretical fuel density difference _Δρt ; and If the Δρ is outside the range of the Δρ _t value at a predetermined threshold, it indicates potential fuel contamination. 2. The method for operating an engine system according to claim 1, characterized in that the method includes the step of storing the Δρ in a metering electronic device. 3. The method for operating an engine system according to claim 1, wherein the step of indicating potential fuel contamination if the Δρ is outside the range of _Δρt by a predetermined threshold includes indicating water contamination of the fuel if the Δρ exceeds the range of _Δρt . 4. The method for operating an engine system according to claim 1, characterized in that the method comprises the following steps: Receive the temperature sensor signal value from the supply flow meter; Receive the temperature sensor signal value from the return flow meter; and The first fuel density measurement result and the second fuel density measurement result are adjusted to compensate for the temperature of the supply flow meter and the return flow meter, respectively. 5. The method for operating an engine system according to claim 1, characterized in that the method comprises the following steps: Receive temperature sensor signal values from temperature sensors outside the supply flow meter and the return flow meter; and The first fuel density measurement result and the second fuel density measurement result are adjusted to compensate for the temperature sensor signal value. 6. The method for operating an engine system according to claim 1, characterized in that the method comprises the following steps: An alarm is triggered if the Δρ is outside the predetermined threshold range of _Δρt . 7. The method for operating an engine system according to claim 1, characterized in that the method comprises the following steps: The fuel flow in the supply flow meter and the fuel flow in the return flow meter are measured simultaneously with the engine operation; Engine fuel consumption is calculated by comparing the fuel flow in the return flow meter with the fuel flow in the supply flow meter; and Indicates fuel consumption measurement results. 8. A metering electronic device (20) for flow meters (214, 216), comprising a processing system (303) connected to a system (200) having a motor (208), configured as follows: Receive sensor signals (310) from both the supply flow meter (214) and the return flow meter (216); The density difference measurement value Δρ between the supply flow meter (214) and the return flow meter (216) is determined based on the received sensor signal (310); Compare the range of Δρ with the theoretical fuel density difference _Δρt ; and The comparison of the range of Δρ and _Δρt values is stored in the metering electronic device (20); and The processing system (303) is configured to indicate potential contamination if the Δρ is outside the range of the Δρ _t value by a predetermined threshold. 9. The metering electronic device (20) for flow meters (214, 216) according to claim 8, characterized in that the processing system (303) is configured to indicate potential water pollution if the Δρ exceeds a predetermined threshold value of the range of _Δρt . 10. The metering electronic device (20) for flow meters (214, 216) according to claim 8, characterized in that the flow meters (214, 216) are in fluid communication with the water emulsification system (224). 11. The metering electronic device (20) for flow meters (214, 216) according to claim 8, characterized in that the processing system (303) is configured as follows: Determine the temperature of the supply flow meter (214); Determine the temperature of the return flow meter (216); and Outputs fluid consumption measurements adjusted for operating temperature correction. 12. The metering electronic device (20) for flow meters (214, 216) according to claim 8, characterized in that the processing system (303) is configured as follows: Determine the temperatures outside the supply flow meter (214) and the return flow meter (216); and Output fluid consumption measurement results with temperature correction adjustments for the supply flow meter (214) and the return flow meter (216).