CN111307227A - Crescent pore plate gas-liquid two-phase flow measuring device - Google Patents

Abstract

The invention relates to a gas-liquid two-phase flow measurement device of a crescent orifice plate, comprising a crescent orifice plate, a pressure transmitter, a front differential pressure transmitter, a rear differential pressure transmitter, a measurement pipeline and an information processor, wherein , the outer diameter of the crescent orifice plate matches the inner diameter of the measuring pipe, and includes a crescent-shaped notch, which is fixed on the inner wall of the measuring pipe with the notch facing down when in use, and the crescent orifice plate is used as the interface. The measuring pipeline is divided into an upstream pipeline and a downstream pipeline. The first pressure taking place is set in the upstream pipeline, the second pressure taking place and the third pressure taking place are set in the downstream pipeline in sequence, and a pressure taking ring is set at each of the three pressure taking places. The main body of each pressure-taking ring chamber is an annular cavity opened on the pipe wall of the measuring pipeline, a plurality of pressure-taking holes are opened on the inner wall of each pressure-taking ring, and a connection is provided at the upper position of the outer wall of the pressure-taking ring. The pressure-inducing port of the external pressure-inducing tube. The present invention has higher measurement accuracy.

Description

A gas-liquid two-phase flow measurement device for a crescent orifice plate

technical field

The invention relates to the technical field of flow measurement, in particular to a gas-liquid two-phase flow measurement device of a crescent orifice.

Background technique

As a kind of multiphase flow, gas-liquid two-phase flow widely exists in natural gas, petroleum, chemical industry, nuclear energy, aerospace and other fields. Different from single-phase flow, gas-liquid two-phase flow contains both gas and liquid. When they coexist and flow at the same time, due to the large difference in the medium characteristics of the two-phase fluid, the physical properties such as friction coefficient, fluid density and viscosity The parameters are different, and the two-phase fluids interact and influence each other, so that the two-phase flow shows quite complex characteristics compared with the single-phase flow. Many criterion relationships and analysis methods in the single-phase flow cannot be directly Applied to the study of gas-liquid two-phase. At the same time, the detection of gas-liquid two-phase flow parameters is very difficult under the influence of many working conditions such as gravity, temperature, pressure, and phase-splitting flow. In the gas-liquid two-phase flow, different flow rates, pressures, pipe layouts and pipe geometry will cause the shape of the phase interface to be different and form different flow patterns. The gas-liquid two-phase flow patterns in the horizontal circular pipeline include bubble flow, slug flow, plug flow, stratified flow, annular flow, mist flow, etc.

In my country, the vast majority of natural gas wells are low-yield gas wells. Due to the low output, the wellhead flow pattern is mainly stratified flow, and a cheap and economical gas-liquid two-phase flowmeter is required. Flow meters, due to their high price, are mainly used in high-production gas wells.

The existing technology has the following shortcomings: one of the current applications in the industrial field is to use a single-phase flowmeter such as a precession vortex or a turbine and other velocity flowmeters to directly measure two-phase fluids with low liquid content, and the measurement accuracy is obviously affected by the liquid content. Therefore, the measurement accuracy is poor; the other is a gas-liquid two-phase flowmeter based on differential pressure flowmeters such as venturi, orifice, nozzle, etc., all of which are designed for axisymmetric structure. High measurement accuracy can be achieved under the working conditions of low liquid content, but under the working conditions of low production gas wells and high liquid content, this type of gas-liquid two-phase flowmeter will not adapt to the actual pipeline flow field conditions. resulting in low measurement accuracy. This type of gas-liquid two-phase flowmeter is often expensive to manufacture and is not convenient for daily use.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a non-axisymmetric flow-like throttling member structural design according to the law of interaction between gas-liquid two-phase fluids. This throttling member is named as a crescent orifice. On this basis, a gas-liquid two-phase flow measurement device is provided. The present invention can realize accurate measurement without separation of gas-liquid two-phase on-line, and solve the problems of traditional gas-liquid two-phase flowmeter, such as high manufacturing cost, inconvenience for daily use, low measurement accuracy and poor measurement efficiency. The present invention adopts the following technical solutions:

A gas-liquid two-phase flow measurement device with a crescent orifice plate, comprising a crescent orifice plate, a pressure transmitter, a front differential pressure transmitter, a rear differential pressure transmitter, a measurement pipeline and an information processor, wherein the The outer diameter of the crescent orifice matches the inner diameter of the measuring pipe, including a crescent-shaped notch, which is fixed on the inner wall of the measuring pipe with the notch facing downwards. It is divided into upstream pipeline and downstream pipeline. The first pressure taking place is set in the upstream pipeline, the second pressure taking place and the third pressure taking place are set in the downstream pipeline in sequence, and a pressure taking ring chamber is set at each of the three pressure taking places. The main body of each pressure-taking ring chamber is an annular cavity opened on the pipe wall of the measuring pipe, a plurality of pressure-taking holes are opened on the inner wall of each pressure-taking ring, and the outer wall of the pressure-taking ring is provided with a connection to external pressure at the upper position. The pressure-inducing port of the pipe, the lower position of the outer wall of the pressure-taking ring is provided with a sewage outlet that is connected to the external sewage pipe, and a sewage valve is installed at the end of the sewage pipe. The outgoing pressure guiding pipes are respectively connected to the front differential pressure transmitter, the pressure guiding pipes connected to the second pressure taking place and the third pressure taking place are respectively connected to the rear differential pressure transmitter, and the first pressure taking place is connected to the rear differential pressure transmitter respectively. The pressure-inducing pipe connected at the place is connected with the pressure transmitter, and the detection signals of the two differential pressure transmitters and the pressure transmitter are transmitted to the information processor.

Preferably, the throttling height of the crescent orifice plate and the inner radius of the measuring pipe take the same value, and the crescent orifice plate is as thin as possible under the condition that the rigidity requirement is met. The ratio R/h of the outer circle radius R of the crescent-shaped notch part of the crescent orifice plate to the center distance h is between 1.07 and 4.45. The equivalent throttling ratio of the crescent orifice plate is 0.35-0.65. The distance from the first pressure taking place to the upstream end face of the crescent orifice plate is 0.5-1 times the inner diameter of the pipe, the distance from the second pressure taking place to the downstream end face of the crescent orifice plate is 0.5-2 times the inner diameter of the pipe, and the third pressure taking place is 0.5-2 times the inner diameter of the pipe. The distance from the pressure point to the downstream end face of the crescent orifice is 5-10 times the inner diameter of the pipe. A temperature transmitter is fixed on the pipe wall of the measuring pipe, and its measuring signal is sent to the information processor.

The present invention provides a gas-liquid two-phase flow measuring device with a crescent orifice plate, which has the following advantages compared with the prior art:

(1) The present invention utilizes a non-axisymmetric flow-like crescent orifice plate 10 to throttle the gas-phase flow, regulate the liquid-phase flow state by the gas flow, and form a two-phase flow with obvious differences, so that the gas-liquid two-phase has a With better identifiability, it can achieve the purpose of broadening the measurement range of volumetric liquid content.

(2) In the present invention, a first pressure taking place, a second pressure taking place and a third pressure taking place are respectively set in the upstream pipeline and the downstream pipeline where the crescent orifice plate 10 is located, and the first pressure taking place and the second pressure taking place can be passed through The pressure is taken at the third pressure-taking place and the third pressure-taking place respectively, to realize the measurement of two different differential pressure values, the front differential pressure and the rear differential pressure. At the same time, through these two different differential pressure values, and using the relevant algorithm, it is convenient to effectively calculate the gas output. The relevant flow parameters of the gas phase and the liquid phase in the liquid two-phase flow, and the non-axisymmetric structure of the crescent orifice 10 is extremely suitable for the stratified flow in the gas-liquid two-phase flow, which is convenient for effective measurement of stability. , which further ensures the measurement accuracy and measurement efficiency.

(3) The present invention can realize accurate metering without separation of gas-liquid two-phase online, which is of great significance for optimizing production process technology, reducing production and development costs and improving control and management level.

Description of drawings

Figure 1 is a schematic diagram of the overall structure of a crescent orifice gas-liquid two-phase flow measurement device;

Fig. 2 is the overall left side view of the gas-liquid two-phase flow measuring device of the crescent orifice plate;

Figure 3 is a detailed view of the crescent orifice in the gas-liquid two-phase flow measurement device of the crescent orifice;

Figure 4 is a structural diagram of a crescent orifice;

FIG. 5 is a B-B cross-sectional view of the third pressure-taking ring chamber 15 in FIG. 1;

Figure 6 is a structural diagram of a circular cutout orifice plate throttle;

Fig. 7 is a schematic diagram of the principle of throttling gas-liquid two-phase fluid by a crescent orifice plate;

Fig. 8 is the flow state diagram of gas-liquid two-phase fluid before and after passing through the crescent orifice;

9 is a comparison diagram of the gas-liquid two-phase measurement results (front differential pressure ΔP ₁ ) of the crescent orifice plate and the circular orifice plate of the present invention;

10 is a comparison diagram of the gas-liquid two-phase measurement results (rear differential pressure ΔP ₂ ) of the crescent orifice plate and the circular orifice plate of the present invention;

11 is a comparison diagram of the gas-liquid two-phase measurement results (K value) between the crescent orifice gas-liquid two-phase flow measurement device of the present invention and the Venturi two-phase flowmeter.

Description of the labels in the figure: 1 pressure transmitter; 2 front differential pressure transmitter; 3 rear differential pressure transmitter;

4 temperature transmitter; 5 three valve group; 6 first pressure taking ring chamber; 7 pressure suction pipe; 8 blowdown pipe; 9 blowdown valve; 10 crescent orifice; 11 measuring pipe; 12 pressure hole; 13 information processing The second pressure-taking ring chamber 15 of the device 14 is the third pressure-taking ring chamber;

t Thickness of crescent orifice plate; R Radius of outer circle of crescent orifice plate; r Internal radius of measuring pipe; h distance from center of circle; a Throttle height of crescent orifice plate;

ΔP ₁ front differential pressure; ΔP ₂ rear differential pressure; K front differential pressure/rear differential pressure;

A gas flow area; B liquid flow area.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

As shown in Figures 1-5, the present invention provides a structural design and a corresponding technical solution: a gas-liquid two-phase flow measurement device for a crescent orifice plate, comprising a crescent orifice plate 10, a pressure transmitter 1, a front differential Pressure transmitter 2, rear differential pressure transmitter 3, measurement pipeline 11 and information processor 13, a temperature transmitter 4 is installed at the lower end of the information processor 13, and the upstream pipeline of the crescent orifice 10 is provided with the first A pressure-taking place, the pipeline downstream of the crescent orifice 10 is sequentially set with a second pressure-taking place and a third pressure-taking place, and the pressure-inducing pipes 7 connected from the first pressure-taking place and the second pressure-taking place are respectively connected to To the front differential pressure transmitter 2, the pressure guiding pipes 7 connected from the second pressure taking place and the third pressure taking place are respectively connected to the rear differential pressure transmitter 3, and the ends of the pressure guiding pipes 7 are installed There are three valve groups 5 , and the high pressure end of the front differential pressure transmitter 2 is connected to the pressure transmitter 1 .

The present invention adopts the ring chamber pressure taking method, the upstream pipeline and the downstream pipeline are provided with several groups of pressure taking holes 12, and the several groups of the inner pressure taking holes 12 are respectively connected with the outer peripheral first pressure taking ring chamber 6 and the second pressure taking hole 12. The pressure ring chamber 14 is structurally connected to the third pressure taking ring chamber 15 . Fig. 5 takes the third pressure-taking ring chamber 15 as an example, the pressure-taking holes 12 are provided with four, and the four pressure-taking holes 12 are installed on the same plane perpendicular to the axis at each pressure-taking place of the upstream pipeline and the downstream pipeline On the pipe wall, the measurement efficiency and accuracy are ensured; two pressure-taking holes 12 are provided at each pressure-taking place of the upstream and downstream pipes and the maximum diameter in the horizontal direction of the axis, and each of the upstream and downstream pipes is provided with two pressure-taking holes 12. Two pressure-taking holes 12 are arranged at the maximum diameter of the pressure-taking place and the vertical direction of the axis. Above the vertical axis of the annular chamber are all provided with a pressure-inducing port connected to the external pressure-inducing pipe 7, and below the vertical axis of the annular chamber is provided with a sewage outlet connected to the external sewage pipe 8, and the end of the sewage pipe 8 is opened. A drain valve 9 is installed at the place.

The throttling part of the crescent orifice plate 10 faces downward of the horizontal pipe, and the equivalent throttling ratio of the crescent orifice plate 10 is 0.35-0.7, which improves the throttling efficiency; the distance from the first pressure taking place to the crescent orifice plate is 10. The upstream end face is 0.5-1 times the inner diameter of the pipeline, the downstream end face of the second pressure taking place is 0.5-2 times the inner diameter of the crescent orifice plate 10, and the third pressure taking place is far from the downstream end of the crescent orifice plate 10. The end face is 5-10 times the inner diameter of the pipe, which effectively guarantees the measurement accuracy.

Based on the theoretical analysis of the working principle and pressure taking method of the crescent orifice plate gas-liquid two-phase flow measurement device of the present invention, the computational fluid dynamics (CFD) method is used to study the effect of the cross-sectional shape of the crescent orifice plate 10 on the interior of the measurement pipeline. The influence of flow field and differential pressure signal. As shown in Table 1, taking the equivalent throttling ratio of the crescent orifice plate 10 as 0.55 as an example, different computational fluid dynamics simulation models are obtained by changing the structural parameters of the cross-sectional shape of the crescent orifice plate 10, The flow field simulation was performed on each model, the pressure values at the first and second pressure-taking locations were extracted, and the front differential pressure ΔP ₁ value was calculated. From the comparison of the data in the table, it can be seen that when the throttling height a of the crescent orifice plate and the inner radius r of the measuring pipe take the same value, and the thickness t of the crescent orifice plate takes the smaller value, the flow field inside the measuring pipe is the most stable, resulting in Strong differential pressure signal.

The present invention provides the cross-sectional parameter values of the crescent orifice plate 10 with better measurement performance under DN50 and DN100 pipe diameters, as shown in Table 2. In different measuring pipes, keep the throttling height a of the crescent orifice plate equal to the inner radius r of the measuring pipe, and when the equivalent throttling ratio is between 0.35 and 0.65, the radius R of the outer circle of the crescent orifice plate and the distance between the center of the circle The value of the ratio of h, R/h, is between 1.07 and 4.45, and a good measurement effect can still be achieved.

Since the structural parameters on the cross section of the crescent orifice plate 10, such as the thickness t of the crescent orifice plate, the outer circle radius R of the crescent orifice plate, the inner radius r of the measuring pipe, the distance between the center of the circle h and the throttling height a of the crescent orifice plate, have a The measurement performance of the invention has an impact, and can be adjusted according to the actual working conditions and processing technology level.

Working principle: When in use, the gas and liquid are driven to circulate inside the measuring pipe 11. Under the action of the pressure-inducing pipe 7, the initial pressure value inside the measuring pipe 11 is effectively converted into an electrical signal by the pressure transmitter 1, which is convenient for subsequent detection. The work is carried out efficiently. By setting the crescent orifice 10 in the measuring pipe 11, in actual use, the two sides of the crescent orifice 10 are driven to form different differential pressure values, and then the front differential pressure transmitter 2 and the rear differential pressure are activated. When the pressure transmitter 3 is in use, under the auxiliary action of the pressure-inducing pipe 7, the value is obtained through the two pressure-taking holes 12 at each pressure-taking point of the upstream pipeline and the downstream pipeline and the maximum diameter in the horizontal direction of the axis, and then the upstream pipeline The two pressure-taking holes 12 at each pressure-taking point of the downstream pipeline and the largest diameter in the vertical direction of the axis take the value again, so as to effectively obtain the differential pressure value inside the measuring pipeline 11, and at the same time pass the two different differential pressure values. value, and using the relevant algorithm, through the information processor 13, it is convenient to effectively calculate the relevant flow parameters of the gas phase and the liquid phase in the gas-liquid two-phase flow.

The flow-like non-axisymmetric structure of the crescent orifice plate 10 in the present invention is extremely suitable for stratified flow and asymmetric annular flow in gas-liquid two-phase flow, effectively ensuring measurement accuracy and measurement efficiency. As shown in FIG. 7 , the gas-liquid two-phase fluid flows through the pipeline from right to left. Under the determined gas-phase flow rate and pressure, with the difference of the liquid content rate, the gas-liquid two-phase fluid flows upstream of the crescent orifice 10 . The flow pattern is basically stratified flow, the liquid phase is below the pipe, and the gas phase is above the pipe; in the process of passing through the crescent orifice 10, the flow area B of the liquid phase in the gas-liquid two-phase fluid remains unchanged, while the flow of the gas phase remains unchanged. The area A will change significantly. Compared with the throttling effect of the crescent orifice plate 10, the rate of change of A will increase significantly; The gas flow rate will be significantly increased and the pressure will be significantly reduced.

Due to the increase in the flow rate of the gas phase, the gas phase can also regulate the flow state of the liquid phase. The gas will not only enter the liquid, but also entrain the liquid to flow, and the vortex flow of the gas will also have an entrainment effect on the liquid. Downstream, with the different effects of gas on the liquid flow, the gas-liquid two-phase fluid will present a fluid flow pattern with obvious differences, such as bubble flow, annular flow to annular mist flow, etc. As shown in Figure 8, the pressure is 1MPa, the gas flow rate is 71m ³ /h, and the flow state of the gas-liquid two-phase fluid changes significantly before and after passing through the crescent orifice 10 under the condition of different volume liquid content.

The above-mentioned interaction between the gas phase and the liquid phase produced by the throttling of the crescent orifice plate 10 makes the front differential pressure ΔP ₁ increase significantly with the increase of the volumetric liquid content. When the gas-liquid two-phase fluid flows through the crescent orifice 10 and enters the pressure recovery stage, the gas phase and the liquid phase form a deceleration and pressurization process, thereby generating the rear differential pressure ΔP ₂ . This process is carried out in the equal-diameter pipeline without any new resistance. The flow element acts on the fluid, so ΔP ₂ increases gently with the increase of liquid holdup, which is much lower than the change degree of ΔP _1. The experimental data are shown in Table 3.

When the cross-sectional parameters of the crescent orifice plate 10 in the present invention, the outer circle radius R and the center distance h of the crescent orifice plate are infinite values, the throttling member can also be called a circular orifice plate, as shown in FIG. 6 . The circular cutout orifice plate throttle is basically used for single-phase fluid measurement, and is used for two-phase fluid measurement for the first time in the present invention. As shown in Figure 9 and Figure 10, based on the same measuring pipe diameter and the same installation conditions, the gas-liquid two-phase measurement results of the crescent orifice plate and the circular orifice plate under the same working conditions are compared. Under the same gas-phase flow rate, with the change of the volume liquid content, the differential pressure before and after the output of the crescent orifice plate in the present invention has obvious differences and the change trend is more stable, so the measurement of the larger two-phase flow rate The present invention has obvious measurement advantages within the scope, and especially has a great influence on improving the measurement accuracy of low-liquid gas-liquid two-phase flow.

As shown in FIG. 11 , based on the same measuring pipe diameter and the same installation conditions, the measurement results of the present invention and the Venturi two-phase flowmeter in the same gas-liquid two-phase flow rate range are compared. Under the same gas flow rate, the ratio K between the front differential pressure and the rear differential pressure is used to describe the difference between the front differential pressure and the rear differential pressure. There is an obvious inflection point when the liquid content is 5% to 6%, but the measured K value of the present invention has no inflection point and the change trend is more stable, so the present invention has obvious measurement advantages in the larger two-phase flow measurement range, especially It has a great impact on improving the measurement accuracy of high liquid gas-liquid two-phase flow.

Table 1 Simulation models and results of cross-sectional shapes of different crescent orifice plates

Table 2 Parameter values of crescent orifice plate under different pipe diameters

Table 3 Experimental test data under the same gas flow rate of 1MPa and different volumetric liquid contents

Table 4. Calibration data of gas-liquid two-phase flow measuring device with crescent orifice plate in DN50 gas-liquid two-phase

The preferred static test calibration results obtained by the present invention according to the structural parameters of Model 3 are shown in Table 4. In the gas-liquid two-phase flow with the volumetric liquid content in a wide range (0-15%), both the gas phase and the liquid phase can reach Better measurement accuracy, in which the gas flow measurement error is within ±5%, and the liquid flow measurement error is within ±10%.

Claims (6)

1. A gas-liquid two-phase flow measurement device of a crescent orifice plate, comprising a crescent orifice plate, a pressure transmitter, a front differential pressure transmitter, a rear differential pressure transmitter, a measurement pipeline and an information processor, wherein, The outer diameter of the crescent orifice matches the inner diameter of the measuring pipe, and includes a crescent-shaped notch, which is fixed on the inner wall of the measuring pipe with the notch facing down when in use, and the crescent orifice is used as the interface. The pipeline is divided into an upstream pipeline and a downstream pipeline. The first pressure taking place is set in the upstream pipeline, the second pressure taking place and the third pressure taking place are set in the downstream pipeline in sequence, and a pressure taking ring chamber is set at each of the three pressure taking places. , the main body of each pressure-taking ring chamber is an annular cavity opened on the wall of the measuring pipe, a plurality of pressure-taking holes are opened on the inner wall of each pressure-taking ring, and the outer wall of the pressure-taking ring is provided with a connection to the outside The pressure-inducing port of the pressure-inducing pipe, the lower position of the outer wall of the pressure-taking ring is provided with a sewage outlet that is connected to the external sewage pipe, and a sewage valve is installed at the end of the sewage pipe. The pressure-inducing pipes connected to the front differential pressure transmitter are respectively connected to the front differential pressure transmitter, and the pressure-inducing pipes connected to the second and third pressure-taking points are respectively connected to the rear differential pressure transmitter. The pressure-inducing pipe connected from the pressure-taking place is connected with the pressure transmitter, and the detection signals of the two differential pressure transmitters and the pressure transmitter are transmitted to the information processor. 2 . The device according to claim 1 , wherein the throttling height of the crescent orifice plate and the inner radius of the measuring pipe take the same value, and the crescent orifice plate is as thin as possible while meeting the rigidity requirements. 3 . 3 . The device according to claim 1 , wherein the ratio R/h of the outer radius R of the crescent-shaped notch portion of the crescent orifice plate to the center distance h is between 1.07 and 4.45. 4 . 4. The device according to claim 1, wherein the equivalent throttling ratio of the crescent orifice plate is 0.35-0.65. 5 . The device according to claim 1 , wherein the distance from the first pressure taking place to the upstream end face of the crescent orifice plate is 0.5-1 times the inner diameter of the pipe, and the distance from the second pressure taking place to the crescent orifice plate. 6 . The downstream end face is 0.5-2 times the inner diameter of the pipe, and the distance from the third pressure taking place to the downstream end face of the crescent orifice plate is 5-10 times the inner diameter of the pipe. 6. The device according to claim 1, characterized in that, a temperature transmitter is fixed on the pipe wall of the measurement pipe, and the measurement signal thereof is sent to the information processor.

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