阅读说明：本技术 一种基于竖直文丘里管的气液段塞流流量在线测量方法 (Gas-liquid section plug flow online measurement method based on vertical Venturi tube ) 是由 贺登辉 赵琳 黄锐 张洁 郭鹏程 于 2020-04-23 设计创作，主要内容包括：本发明公开一种基于竖直文丘里管的气液段塞流流量在线测量方法,步骤1,竖直设置文丘里管,使气液段塞流竖直向上流经文丘里管,测量文丘里管内上游的段塞流压力、下游的段塞流温度和上游截面含气率；步骤2,由段塞流压力、段塞流温度获得气相和液相密度及液相粘度；步骤3,由截面含气率、气相和液相密度获得气液混合物密度；步骤4,由液相粘度、无量纲单相压降与液相雷诺数的关系、两相流压降乘子与截面含气率的关系得到液相表观流速,进而得到液相质量流量；步骤5,由液相表观流速、无量纲两相压降与气液相表观流速之比的关系,通过迭代获取气相表观流速,进而得到气相质量流量。本发明解决了现有技术中段塞流流量在线测量精度不高的问题。(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.)

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 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 1_TPDownstream end slug temperature T_TPAnd a slug flow cross-sectional void fraction α at the upstream end_G；

Step 2, the slug flow pressure P_TPSlug flow temperature T_TPCalculating to obtain the gas density rho_GDensity of liquid ρ_LAnd viscosity of liquid phase mu_L；

Step 3, according to the gas content of the slug flow section α_GGas density ρ_GAnd density of the liquid ρ_LObtaining the density rho of the gas-liquid mixture_TP；

Step 4, according to the viscosity mu of the liquid phase_LThe relation between dimensionless single-phase pressure drop P and liquid phase Reynolds number Re, two-phase flow pressure drop multiplierAnd section gas content α_GObtaining the liquid phase apparent flow velocity U_SLFurther obtaining the mass flow m of the liquid phase_L；

Step 5, according to the liquid phase apparent flow velocity U_SLDimensionless two-phase pressure dropRatio U to the gas-liquid phase apparent flow velocity^*By iterative process to obtain the gas phase apparent flow velocity U_SGFurther obtaining the gas phase mass flow m_G。

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 measured_TPThe calculation formula of (2) is as follows:

ρ_TP＝ρ_Gα_G+ρ_L(1-α_G) (1)。

3. the method for measuring the gas-liquid slug flow on line based on the vertical venturi tube of claim 1, wherein 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:

in the formula,. DELTA.P_L0Is the pressure drop of the liquid phase flowing through the venturi tube alone; u shape_SLIs the liquid phase apparent flow rate; a is₁And b₁All are constant, and Reynolds number Re of liquid phase is defined as Re ═ rho_LU_SLD/μ_LWherein D is the inner diameter of the pipeline;

wherein the two-phase flow pressure drop multiplierAnd section gas content α_GThe relationship of (1):

in the formula,. DELTA.P_TPThe 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：

m_L＝πD²ρ_LU_SL/4 (4)。

4. The method for measuring the gas-liquid slug flow on line based on the vertical Venturi tube according to claim 1, wherein the step 5 is a dimensionless two-phase pressure dropRatio U to the gas-liquid phase apparent flow velocity^*The relationship of (1) is:

in the formula of U_SGIs 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^*＝U_SG/U_SL；a₃And b₃Are all constants;

the apparent flow velocity U of the liquid phase obtained in the step 4_SLSubstituting the obtained product into formula (5), and obtaining the gas phase apparent flow velocity U through iteration_SGFurther, the gas phase mass flow m is obtained by the formula (6)_G：

m_G＝πD²ρ_GU_SG/4 (6)。

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 tube_TPDownstream end slug temperature T_TPAnd a slug flow cross-sectional void fraction α at the upstream end_G；

Step 2, the slug flow pressure P_TPSlug flow temperature T_TPCalculating to obtain the gas density rho_GSealing of liquidDegree rho_LAnd viscosity of liquid phase mu_L；

Step 3, according to the gas content of the slug flow section α_GGas density ρ_GAnd density of the liquid ρ_LObtaining the density rho of the gas-liquid mixture_TP；

Step 4, according to the viscosity mu of the liquid phase_LThe relation between dimensionless single-phase pressure drop P and liquid phase Reynolds number Re, two-phase flow pressure drop multiplierAnd section gas content α_GObtaining the liquid phase apparent flow velocity U_SLFurther obtaining the mass flow m of the liquid phase_L；

Step 5, according to the liquid phase apparent flow velocity U_SLDimensionless two-phase pressure dropRatio U to the gas-liquid phase apparent flow velocity^*By iteratively obtaining the gas phase superficial flow velocity U_SGFurther obtaining the gas phase mass flow m_G。

The present invention is also characterized in that,

gas-liquid mixture density ρ in step 3_TPThe calculation formula of (2) is as follows:

ρ_TP＝ρ_Gα_G+ρ_L(1-α_G) (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:

in the formula,. DELTA.P_L0Is the pressure drop of the liquid phase flowing through the venturi tube alone; u shape_SLIs the liquid phase apparent flow rate; a is₁And b₁All are constant, and Reynolds number Re of liquid phase is defined as Re ═ rho_LU_SLD/μ_LWherein D is the inner diameter of the pipeline;

wherein the two-phase flow pressure drop multiplierAnd section gas content α_GThe relationship of (1):

in the formula,. DELTA.P_TPThe 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：

m_L＝πD²ρ_LU_SL/4 (4)

Dimensionless two-phase pressure drop in step 5Ratio U to the gas-liquid phase apparent flow velocity^*The relationship of (1) is:

in the formula of U_SGIs the gas phase apparent flow rate; u shape^*Is the ratio of the apparent flow rates of the gas and liquid phases, U^*＝U_SG/U_SL；a₃And b₃Are all constants;

the apparent flow velocity U of the liquid phase obtained in the step 4_SLSubstituting the obtained product into formula (5), and obtaining the gas phase apparent flow velocity U through iteration_SGFurther, the gas phase mass flow m is obtained by the formula (6)_G：

m_G＝πD²ρ_GU_SG/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 1_TPDownstream end slug temperature T_TPAnd a slug flow cross-sectional void fraction α at the upstream end_G；

Step 2, the slug flow pressure P_TPSlug flow temperature T_TPCalculating to obtain the gas density rho_GDensity of liquid ρ_LAnd viscosity of liquid phase mu_L；

Step 3, according to the gas content of the slug flow section α_GGas density ρ_GAnd density of the liquid ρ_LObtaining the density rho of the gas-liquid mixture_TP(ii) a Density p of gas-liquid mixture_TPThe calculation formula of (2) is as follows:

ρ_TP＝ρ_Gα_G+ρ_L(1-α_G) (1)

step 4, according to the viscosity mu of the liquid phase_LThe relation between dimensionless single-phase pressure drop P and liquid phase Reynolds number Re, two-phase flow pressure drop multiplierAnd section gas content α_GObtaining the liquid phase apparent flow velocity U_SLFurther obtaining the mass flow m of the liquid phase_L；

Step 5, according to the liquid phase apparent flow velocity U_SLDimensionless two-phase pressure dropRatio U to the gas-liquid phase apparent flow velocity^*By iteratively obtaining the gas phase superficial flow velocity U_SGFurther obtaining the gas phase mass flow m_G。

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:

in the formula,. DELTA.P_L0Is the pressure drop of the liquid phase flowing through the venturi tube alone; u shape_SLIs the liquid phase apparent flow rate; a is₁And b₁All are constant, and Reynolds number Re of liquid phase is defined as Re ═ rho_LU_SLD/μ_LWherein D is the inner diameter of the pipeline;

wherein the two-phase flow pressure drop multiplierAnd section gas content α_GThe relationship of (1):

in the formula,. DELTA.P_TPThe pressure drop when gas-liquid two-phase flows through the Venturi tube; a is₂And b₂Are all constants;

simultaneous formula of channels(2) And (3) solving to obtain a liquid phase apparent flow velocity U_SLFurther, the liquid phase mass flow rate m can be obtained by the formula (4)_L：

m_L＝πD²ρ_LU_SL/4 (4)

The step 5 specifically comprises the following steps:

dimensionless two-phase pressure dropRatio U to the gas-liquid phase apparent flow velocity^*The relationship of (1) is:

in the formula of U_SGIs 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^*＝U_SG/U_SL；a₃And b₃Are all constants;

the apparent flow velocity U of the liquid phase obtained in the step 4_SLSubstituting the obtained product into formula (5), and obtaining the gas phase apparent flow velocity U through iteration_SGFurther, the gas phase mass flow m is obtained by the formula (6)_G：

m_G＝πD²ρ_GU_SG/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 venturi_TPThe temperature sensor 5 is used for measuring the plug flow temperature T of one end section at the downstream of the Venturi tube_TPThe section gas void measuring device 2 is used for measuring the gas void α of the plug flow section at the upstream end of the Venturi tube_GDifferential 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.