CN111442809B - Gas-liquid section plug flow online measurement method based on vertical Venturi tube - Google Patents

Gas-liquid section plug flow online measurement method based on vertical Venturi tube Download PDF

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CN111442809B
CN111442809B CN202010327901.7A CN202010327901A CN111442809B CN 111442809 B CN111442809 B CN 111442809B CN 202010327901 A CN202010327901 A CN 202010327901A CN 111442809 B CN111442809 B CN 111442809B
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CN111442809A (en
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贺登辉
赵琳
黄锐
张洁
郭鹏程
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Xian University of Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/76—Devices for measuring mass flow of a fluid or a fluent solid material
    • G01F1/86—Indirect mass flowmeters, e.g. measuring volume flow and density, temperature or pressure
    • G01F1/88—Indirect mass flowmeters, e.g. measuring volume flow and density, temperature or pressure with differential-pressure measurement to determine the volume flow

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Abstract

The invention discloses a gas-liquid slug flow online measurement method based on a vertical Venturi tube, which comprises the following steps that 1, the Venturi tube is vertically arranged, so that gas-liquid slug flow vertically upwards flows through the Venturi tube, and the slug flow pressure at the upstream in the Venturi tube, the slug flow temperature at the downstream and the gas content of the upstream section are measured; step 2, obtaining gas phase and liquid phase density and liquid phase viscosity from slug flow pressure and slug flow temperature; step 3, obtaining the density of the gas-liquid mixture from the gas content of the cross section, the gas phase density and the liquid phase density; step 4, obtaining the apparent flow velocity of the liquid phase according to the relation among the viscosity of the liquid phase, the dimensionless single-phase pressure drop and the Reynolds number of the liquid phase and the relation among the two-phase flow pressure drop multiplier and the section gas fraction, and further obtaining the mass flow of the liquid phase; and 5, obtaining the gas phase apparent flow rate through iteration according to the relation between the liquid phase apparent flow rate, the dimensionless two-phase pressure drop and the gas-liquid phase apparent flow rate, and further obtaining the gas phase mass flow. The invention solves the problem of low accuracy of on-line measurement of the mid-section plug flow in the prior art.

Description

Gas-liquid section plug flow online measurement method based on vertical Venturi tube
Technical Field
The invention belongs to the technical field of multiphase flow measurement, and relates to an online gas-liquid slug flow measurement method based on a vertical venturi tube.
Background
Slug flow is a typical flow pattern that exists during hydrocarbon production and transport. For example, in wet natural gas pipelines and gas-liquid mixed pipelines containing low liquid content, the phenomenon of gas-liquid two-phase slug flow is very easy to occur in the pipelines under the influence of factors such as topographic relief effect and the like. The diameter of bubbles in the slug flow is close to the pipe diameter, the slug flow is a flowing structure of one section of liquid and one section of gas, the slug flow has the characteristics of intermittence and instability, the strong pressure and liquid holdup fluctuation of a pipeline is often caused, the normal conveying of fluid and the stability of downstream processing equipment are influenced, and the risks of mechanical damage and erosion corrosion of the pipeline are aggravated. The existence of slug flow is not only unfavorable for the normal operation of the system, but also restricts the improvement of the oil gas metering precision, and seriously influences the exploitation of offshore oil gas resources. The traditional slug flow measurement method adopts a gas-liquid separator to separate and then separately measure the flow of gas and liquid phases, and the existing multiphase flow measurement method is difficult to realize the online accurate measurement of the slug flow and lacks a method specially for measuring the slug flow. The on-line measurement of slug flow has become a difficult problem in the field of multiphase flow measurement.
Disclosure of Invention
The invention aims to provide a gas-liquid slug flow online measurement method based on a vertical Venturi tube, and solves the problem that the slug flow online measurement precision is low in the prior art.
The technical scheme adopted by the invention is that,
the on-line measuring method of the gas-liquid slug flow based on the vertical Venturi tube is characterized by comprising the following specific steps:
step 1, vertically arranging a Venturi tube to enable gas-liquid slug flow to vertically flow upwards through the Venturi tube, and measuring slug flow pressure P at one end of the inner upstream of the Venturi tubeTPDownstream end slug temperature TTPAnd the gas content alpha of the section of the slug flow at the upstream endG；
Step 2, the slug flow pressure PTPSlug flow temperature TTPCalculating to obtain the gas density rhoGDensity of liquid ρLAnd viscosity of liquid phase muL；
Step 3, according to the gas content alpha of the slug flow cross sectionGGas density ρGAnd density of the liquid ρLObtaining the density rho of the gas-liquid mixtureTP；
Step 4, according to the viscosity mu of the liquid phaseLThe relation between dimensionless single-phase pressure drop P and liquid phase Reynolds number Re, two-phase flow pressure drop multiplier
Figure BDA0002463871450000021
And cross-sectional gas content alphaGObtaining the liquid phase apparent flow velocity USLFurther obtaining the mass flow m of the liquid phaseL；
Step 5, according to the liquid phase apparent flow velocity USLDimensionless two-phase pressure drop
Figure BDA0002463871450000022
Ratio U to the gas-liquid phase apparent flow velocity*By iteratively obtaining the gas phase superficial flow velocity USGFurther obtaining the gas phase mass flow mG。
The present invention is also characterized in that,
gas-liquid mixture density ρ in step 3TPThe calculation formula of (2) is as follows:
ρTP＝ρGαG+ρL(1-αG) (1)
the relation between the dimensionless single-phase pressure drop P and the Reynolds number Re of the liquid phase in the step 4 is as follows:
Figure BDA0002463871450000031
in the formula,. DELTA.PL0Is the pressure drop of the liquid phase flowing through the venturi tube alone; u shapeSLIs the liquid phase apparent flow rate; a is1And b1All are constant, and Reynolds number Re of liquid phase is defined as Re ═ rhoLUSLD/μLWherein D is the inner diameter of the pipeline;
wherein the two-phase flow pressure drop multiplier
Figure BDA0002463871450000032
And cross-sectional gas content alphaGThe relationship of (1):
Figure BDA0002463871450000033
in the formula,. DELTA.PTPThe pressure drop when gas-liquid two-phase flows through the Venturi tube; a is2And b2Are all constants;
the apparent flow velocity U of the liquid phase can be obtained by solving the simultaneous formulas (2) and (3)SLFurther, the liquid phase mass flow rate m can be obtained by the formula (4)L：
mL＝πD2ρLUSL/4 (4)
Dimensionless two-phase pressure drop in step 5
Figure BDA0002463871450000034
Ratio U to the gas-liquid phase apparent flow velocity*The relationship of (1) is:
Figure BDA0002463871450000035
in the formula of USGIs the gas phase apparent flow rate; u shape*Is the ratio of the apparent flow rates of the gas and liquid phases, U*＝USG/USL；a3And b3Are all constants;
the apparent flow velocity U of the liquid phase obtained in the step 4SLSubstituting the obtained product into formula (5), and obtaining the gas phase apparent flow velocity U through iterationSGFurther, the gas phase mass flow m is obtained by the formula (6)G：
mG＝πD2ρGUSG/4 (6)
The invention has the advantages that
Firstly, the invention acquires the pressure, temperature and differential pressure of slug flow flowing through the venturi tube by vertically arranging the venturi tube, and calculates the gas-liquid two-phase flow of the slug flow by combining the section gas content obtained by the section gas content measuring device.
The method can directly obtain the liquid phase flow through equation simultaneous connection without iteration and coupled solution with a gas phase equation, avoids the increase of solution errors and the situation that multiple solutions have no solution caused by error transfer, and has the advantages of simple and convenient calculation, good real-time performance, high precision, simple system and the like.
Drawings
FIG. 1 is a flow chart of an online gas-liquid slug flow measuring method based on a vertical venturi tube;
FIG. 2 is a schematic diagram of an online gas-liquid slug flow measuring system in the online gas-liquid slug flow measuring method based on the vertical venturi tube.
In the figure, 1, a Venturi tube, 2, a section gas content measuring device, 3, a pressure sensor, 4, a high-pressure measuring hole, 5, a temperature sensor, 6, a differential pressure sensor, 7, a low-pressure measuring hole and 8, a signal acquisition and processing device.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
The invention discloses a gas-liquid slug flow online measuring method based on a vertical Venturi tube, which comprises the following specific steps of:
step 1, vertically arranging a Venturi tube 1 to enable gas-liquid slug flow to vertically flow upwards through the Venturi tube 1, and measuring slug flow pressure P at one end of the upstream end in the Venturi tube 1TPDownstream end slug temperature TTPAnd the gas content alpha of the section of the slug flow at the upstream endG；
Step 2, the slug flow pressure PTPSlug flow temperature TTPCalculating to obtain the gas density rhoGDensity of liquid ρLAnd viscosity of liquid phase muL；
Step 3, according to the gas content alpha of the slug flow cross sectionGGas density ρGAnd density of the liquid ρLObtaining the density rho of the gas-liquid mixtureTP(ii) a Density p of gas-liquid mixtureTPThe calculation formula of (2) is as follows:
ρTP＝ρGαG+ρL(1-αG) (1)
step 4, according to the viscosity mu of the liquid phaseLThe relation between dimensionless single-phase pressure drop P and liquid phase Reynolds number Re, two-phase flow pressure drop multiplier
Figure BDA0002463871450000051
And cross-sectional gas content alphaGObtaining the liquid phase apparent flow velocity USLFurther obtaining the mass flow m of the liquid phaseL；
Step 5, according to the liquid phase apparent flow velocity USLDimensionless two-phase pressure drop
Figure BDA0002463871450000052
Ratio U to the gas-liquid phase apparent flow velocity*By iteratively obtaining the gas phase superficial flow velocity USGFurther obtaining the gas phase mass flow mG。
The step 4 specifically comprises the following steps:
wherein the relation between the dimensionless single-phase pressure drop P and the Reynolds number Re of the liquid phase is as follows:
Figure BDA0002463871450000053
in the formula,. DELTA.PL0Is the pressure drop of the liquid phase flowing through the venturi tube alone; u shapeSLIs the liquid phase apparent flow rate; a is1And b1All are constant, and Reynolds number Re of liquid phase is defined as Re ═ rhoLUSLD/μLWherein D is the inner diameter of the pipeline;
wherein the two-phase flow pressure drop multiplier
Figure BDA0002463871450000054
And cross-sectional gas content alphaGThe relationship of (1):
Figure BDA0002463871450000055
in the formula,. DELTA.PTPThe pressure drop when gas-liquid two-phase flows through the Venturi tube; a is2And b2Are all constants;
the apparent flow velocity U of the liquid phase can be obtained by solving the simultaneous formulas (2) and (3)SLFurther, the liquid phase mass flow rate m can be obtained by the formula (4)L：
mL＝πD2ρLUSL/4 (4)
The step 5 specifically comprises the following steps:
dimensionless two-phase pressure drop
Figure BDA0002463871450000061
Ratio U to the gas-liquid phase apparent flow velocity*The relationship of (1) is:
Figure BDA0002463871450000062
in the formula of USGIs the gas phase apparent flow rate; u shape*Is the ratio of the apparent flow rates of the gas phase and the liquid phase, U*＝USG/USL；a3And b3Are all constants;
the apparent flow velocity U of the liquid phase obtained in the step 4SLSubstituting the obtained product into formula (5), and obtaining the gas phase apparent flow velocity U through iterationSGFurther, the gas phase mass flow m is obtained by the formula (6)G：
mG＝πD2ρGUSG/4 (6)
The above constant a1、b1、a2、b2、a3、b3All the parameters are obtained by calibrating a gas-liquid two-phase flow experimental system, the value of the parameter is determined by the structure of a Venturi tube, the working condition of incoming flow and other parameters, if a standard Venturi tube with the throttling ratio of 0.55 and the inner diameter of a pipeline of 32 is adopted for realizing the method, and a is obtained by calibrating the gas-liquid two-phase flow experimental system1＝381.3，b1＝0.51，a2＝1，b2＝0.883，a3＝16.49，b3＝11.504。
The method can be completed through an on-line gas-liquid slug flow measuring system, as shown in fig. 2, the on-line gas-liquid slug flow measuring system comprises a venturi tube 1, a section gas content measuring device 2 is arranged at one end of the upper stream of the venturi tube 1, a pressure sensor 3 is arranged at one end of the lower stream of the venturi tube 1, a differential pressure sensor 6 is arranged between one end of the venturi tube 1 and the minimum section, a temperature sensor 5 is arranged at the other end of the venturi tube 1, and the pressure sensor 3, the differential pressure sensor 6 and the temperature sensor 5 are all connected with a signal collecting and processing device 8; one end of the Venturi tube 1 is provided with a high-pressure measuring hole 4, and the high-pressure measuring hole 4 is connected with the pressure sensor 3; a low-pressure measuring hole 7 is formed in the minimum section of the Venturi tube 1, and the high-pressure end and the low-pressure end of the differential pressure sensor 6 are respectively connected with the high-pressure measuring hole 4 and the low-pressure measuring hole 7;
wherein the pressure sensor 3 is used to measure the slug pressure P at the upstream end of the venturiTPThe temperature sensor 5 is used for measuring the plug flow temperature T of one end section at the downstream of the Venturi tubeTPThe section gas content measuring device 2 is used for measuring the gas content alpha of the plug flow section at one end section at the upstream of the Venturi tubeGDifferential pressure sensor 6 is used to measure the pressure drop of the fluid flowing through the venturi.
In conclusion, the method avoids the increase of the solving error and the situation that multiple solutions have no solution due to error transmission, and has the advantages of simple and convenient calculation, good real-time performance, high precision, simple system and the like.

Claims (2)

1. A gas-liquid slug flow online measurement method based on a vertical Venturi tube is characterized by comprising the following specific steps:
step 1, vertically arranging a Venturi tube (1), enabling gas-liquid slug flow to vertically flow upwards through the Venturi tube (1), and measuring slug flow pressure P at one end of the upstream in the Venturi tube (1)TPDownstream end slug temperature TTPAnd the gas content alpha of the section of the slug flow at the upstream endG；
Step 2, the slug flow pressure PTPSlug flow temperature TTPCalculating to obtain the gas density rhoGDensity of liquid ρLAnd viscosity of liquid phase muL；
Step 3, according to the gas content alpha of the slug flow cross sectionGGas density ρGAnd density of the liquid ρLObtaining the density rho of the gas-liquid mixtureTP；
Step 4, according to the viscosity mu of the liquid phaseLThe relation between dimensionless single-phase pressure drop P and liquid phase Reynolds number Re, two-phase flow pressure drop multiplier
Figure FDA0003123751440000011
And cross-sectional gas content alphaGObtaining the liquid phase apparent flow velocity USLFurther obtaining the mass flow m of the liquid phaseL；
Wherein the relation between the dimensionless single-phase pressure drop P and the Reynolds number Re of the liquid phase is as follows:
Figure FDA0003123751440000012
in the formula,. DELTA.PL0Is the pressure drop of the liquid phase flowing through the venturi tube alone; u shapeSLIs the liquid phase apparent flow rate; a is1And b1All are constant, and Reynolds number Re of liquid phase is defined as Re ═ rhoLUSLD/μLWherein D is the inner diameter of the pipeline;
wherein the two-phase flow pressure drop multiplier
Figure FDA0003123751440000013
And cross-sectional gas content alphaGThe relationship of (1):
Figure FDA0003123751440000014
in the formula,. DELTA.PTPThe pressure drop when gas-liquid two-phase flows through the Venturi tube; a is2And b2Are all constants;
the apparent flow velocity U of the liquid phase can be obtained by solving the simultaneous formulas (2) and (3)SLFurther, the liquid phase mass flow rate m can be obtained by the formula (4)L：
mL＝πD2ρLUSL/4 (4)；
Step 5, according to the liquid phase apparent flow velocity USLDimensionless two-phase pressure drop
Figure FDA0003123751440000021
Ratio U to the gas-liquid phase apparent flow velocity*By iterative process to obtain the gas phase apparent flow velocity USGFurther obtaining the gas phase mass flow mG；
Wherein the pressure drop is dimensionless two-phase
Figure FDA0003123751440000022
Ratio U to the gas-liquid phase apparent flow velocity*Is onThe method comprises the following steps:
Figure FDA0003123751440000023
in the formula of USGIs the gas phase apparent flow rate; u shape*Is the ratio of the apparent flow rates of the gas phase and the liquid phase, U*＝USG/USL；a3And b3Are all constants;
the apparent flow velocity U of the liquid phase obtained in the step 4SLSubstituting the obtained product into formula (5), and obtaining the gas phase apparent flow velocity U through iterationSGFurther, the gas phase mass flow m is obtained by the formula (6)G：
mG＝πD2ρGUSG/4 (6)。
2. The on-line measurement method for the plug flow of the gas-liquid section based on the vertical venturi tube as claimed in claim 1, wherein the density p of the gas-liquid mixture in the step 3 is measuredTPThe calculation formula of (2) is as follows:
ρTP＝ρGαG+ρL(1-αG) (1)。
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CN115307696B (en) * 2022-08-22 2024-09-17 西安交通大学 Device and method for online measurement of slug flow two-phase flow based on multi-sensor fusion
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