CN2268923Y - Intellectual steam flowmeter with probing needle - Google Patents

Abstract

An intelligent probe type steam flowmeter is used for flow measurement of high temperature superheated steam. The flowmeter adopts the speed probe and temperature sensor which have been calibrated in advance and can feel the total pressure and static pressure as the sensing parts. The secondary instrument adopts the flow rate which can perform signal conversion processing, calculate according to a certain calculation formula, and directly display the result. Totalizer, its transmission unit adopts piezoelectric conversion pressure and differential pressure transmitter. Compared with the orifice flowmeter, the utility model has wide measurement range, high precision and is not affected by the change of flow rate. No pressure loss, can save a lot of energy. Small size, good reliability, stable operation, convenient installation and maintenance. It can be widely used in the measurement of steam flow in thermal power plants and chemical plants.

Description

Smart Probe Steam Flow Meter

The utility model belongs to a gas flow measuring device and relates to a steam flow meter for measuring high-temperature steam.

In the prior art, although there are many equipment and instruments for the flow measurement of high-temperature steam, such as turbine flowmeter, electromagnetic flowmeter, orifice flowmeter and newly developed vortex flowmeter in recent years, all of them are limited by the operating temperature. Or the accuracy is not enough to be used for accurate measurement of high temperature superheated steam. At present, orifice flowmeters are widely used in most thermal power plants and chemical plants. The reason is that, on the one hand, orifice flowmeters are simple in structure and cheap in price; Components can withstand high temperatures above 500°C. Therefore, the orifice flowmeter is still the first choice for measuring high-temperature steam flow in China. But the orifice flowmeter still has the following deficiencies and defects:

One is that it is greatly affected by the size of the flow. When the flow rate becomes smaller, it will cause a larger measurement error. Experiments have shown that when the flow rate is below 30% of the rated value, the Reynolds number becomes smaller due to the change of the flow pattern, and the constant flow coefficient is used in the flow integration, which causes the flow measurement number to be small and cause errors. When the flow rate is less than 10% of the rated value, the pressure difference can no longer be sensed, and the flow rate is difficult to measure, so it has to be regarded as zero. In the steam supply heating network of thermal power plants, errors are often caused by too small user flow rates, sometimes as high as 15%. , bringing huge losses to thermal power plants. The second is that the energy loss of the orifice flowmeter is relatively large, and after a period of use, measurement errors will be caused by wear and tear, and the steam supply needs to be stopped for maintenance and replacement, so the workload is heavy. The third is that the secondary instruments used in the orifice flowmeter mostly use mechanical force balance pressure and differential pressure gauges, which have poor reliability, easy drift of the zero point, and low measurement accuracy.

In order to overcome the deficiencies and defects of the existing technology, the purpose and task of this utility model is to provide thermal power plants and chemical plants with a small volume, high measurement accuracy, no pressure loss, convenient installation and maintenance, and automatic data processing and results. Smart Probe Steam Flow Meter shown.

The utility model is realized through the following technical solutions: it is mainly composed of a primary instrument, a secondary instrument, and a transmission unit installed between the primary instrument and the secondary instrument, a valve and a pipeline. The primary instrument includes a sensing head and a temperature sensor , the secondary instrument adopts a flow totalizer that can perform signal conversion processing, calculate according to a certain formula, and directly display the result, and the transmission unit adopts a pressure transmitter and a differential pressure transmitter, which is characterized by the above-mentioned feeling The head adopts a speed probe calibrated in advance, which can feel the total pressure and static pressure. The speed probe [1] is a metal tubular probe with two groups of detection holes on it, one group is opened at the end of the probe. , the other group is opened on the side of the outer tube of the probe, distributed symmetrically

Accompanying drawing 1 is the system structural diagram of the present utility model.

Accompanying drawing 2 is the enlarged view of the A-A section of accompanying drawing 1, which is the structure diagram of the velocity probe.

Describe working principle, structure and specific embodiment of the present utility model in detail below in conjunction with accompanying drawing:

The utility model is mainly composed of a speed probe 1, a temperature sensor 2, a pressure sensor and a transmitter 3, a differential pressure sensor and a transmitter 4, a flow totalizer 5, regulating valves 6, 7, 8 and a pressure equalizing valve 9 composed of. Velocity probe 1 is a small metal tubular probe with two sets of detection holes on it, one group is opened at the end of the probe, which is a single measurement hole 11, facing the airflow, so you can feel the airflow being controlled by the airflow. The total pressure on the measuring position; the other group is opened on the side of the outer tube of the probe, and is several side holes 12 symmetrically distributed around the tube, generally 2-4 are advisable. The static pressure of the airflow can be felt when the airflow flows along the axial direction of the pipe. The pressure felt by the two groups of measuring holes is drawn out through two mutually isolated pipelines inside the probe respectively. That is, the pipeline 13 is a total pressure pipe, and the pipeline 14 is a static pressure pipe. Among them, the static pressure pipe 14 leads to two outlets after passing through the valve 7, one outlet leads to the pressure sensor and the transmitter 3 through the valve 8, and the other outlet leads to the low pressure side of the differential pressure sensor and the transmitter 4; and the total pressure The pipe 13 leads to the high pressure side of the differential pressure sensor and transmitter through the valve 6 . In this way, the differential pressure sensor measures the difference between the total pressure and the static pressure at the location of the speed probe. Due to manufacturing errors, the pressure measured by the probe may have a certain error from the real pressure. Experiments have shown that this error is related to the manufacture of the probe, once the probe is processed, the error is determined. Therefore, this error can be compensated by experimental correction in advance, so as to obtain a correction coefficient.

In the actual measurement, place the probe of the velocity probe in the center of the pipeline to measure the maximum flow velocity Vmax. However, in the actual pipeline flow, the air velocity on a certain section is not uniform, the center is higher and the near wall is lower. According to the basic principles of fluid mechanics, if the average velocity V on a certain section is known, the steam flow rate flowing through this section can be obtained according to G=FγV (where G is the flow rate, F is the interception point of the pipeline, and γ is the air flow density, V is the average velocity). For a specific flow situation, since there is a certain proportional coefficient between the average speed and the maximum speed, this coefficient can also be determined in advance through experiments, so as to obtain another correction coefficient. A total correction coefficient K can be obtained by combining the correction coefficients previously calibrated twice. This leads to a useful formula for calculating the steam flow in a pipe from the measured values: $G=K\left(\frac{{\mathrm{\&pi;<figure-callout\; id="2"\; label="d"\; filenames="Y9521647000061.png"\; state="\{\{state\}\}">d</figure-callout>}}^2}{4}\right)\sqrt{\frac{2g\left(\mathrm{\&Delta;P}\right)}{\frac{(0.00471t+1.286)\&times;100}{P+100}-0.0097+1.32\&times;{10}^{-5}t}}$ (Where P is the total pressure, ΔP is the differential pressure, t is the temperature, and d is the diameter of the pipe to be measured) In the above formula, the pressure P and the differential pressure ΔP can be obtained by the speed probe and the differential pressure values respectively through the pressure sensor 3 and pressure difference sensor 4 into electrical signals; temperature sensor 2 uses thermal resistance thermometers or thermocouples, and also outputs electrical signals. After these signals are converted and processed, the flow rate G is calculated by the flow totalizer according to the above formula, and the results are directly displayed. come out. The pipe diameter d and correction coefficient K are placed in the calculation program as known quantities.

Compared with the existing orifice flowmeter, the utility model has the following advantages and beneficial effects: the steam flowmeter has a wide measurement range, small measurement error, and high measurement accuracy can be obtained at both large and small flow rates. No pressure loss, can save a lot of energy. Small size, good reliability, stable operation, convenient installation and maintenance, can be widely used in the measurement of steam flow in thermal power plants and chemical plants.

Claims (1)

1, a kind of intelligent probe formula steam-flow meter, it is mainly by primary instrument, secondary instrument, and be contained in transducing unit between primary instrument and the secondary instrument, valve and pipeline are formed, primary instrument comprises impression head and temperature sensor, secondary instrument adopts can carry out the signal conversion processing, calculate by certain formula, and the flow integrator that the result is directly shown, transducing unit adopts pressure unit and pressure difference transmitter, it is characterized in that above-mentioned impression head adopt demarcate in advance good, can experience the velocity probe of stagnation pressure and static pressure, this velocity probe [1] is the tubular probe of metal, and two groups of exploration holes are arranged above it, opens in the probe termination for one group, another group is opened in probe outer tube side, is symmetrical distribution.

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