阅读说明：本技术 一种管道内两相流空泡份额实时在线测量系统与方法 (Real-time online measurement system and method for vacuole share of two-phase flow in pipeline ) 是由 乔守旭 谭思超 钟文义 于 2020-12-02 设计创作，主要内容包括：本发明是一种水平管道内空泡份额在线测量系统与方法,可实时测量管道内的气液两相泡状流空泡份额值,涉及热工水力、石油开采与输运和蒸汽生产等技术领域。本发明由水平管段、差压测量装置、质量流量计及数据分析系统组成,具体包括水平管段、水平尺、取压孔、导压管、差压变送器、质量流量计、数据传输线路、数据采集系统和数据分析程序组成。本发明借助水平尺保证水平管道安装的水平度,通过差压变送器测量两取压孔之间的压差,通过质量流量计直接测量两相流质量流量、结合在数据分析程序中输入的气液两相物性参数,运用两相流摩擦压降公式即可计算空泡份额数值。(The invention discloses an on-line measurement system and method for vacuole share in a horizontal pipeline, which can measure the vacuole share value of gas-liquid two-phase vacuole flow in the pipeline in real time and relates to the technical fields of thermal engineering waterpower, oil exploitation and transportation, steam production and the like. The invention consists of a horizontal pipe section, a differential pressure measuring device, a mass flowmeter and a data analysis system, and particularly comprises the horizontal pipe section, a level gauge, a pressure taking hole, a pressure guide pipe, a differential pressure transmitter, the mass flowmeter, a data transmission line, a data acquisition system and a data analysis program. The invention ensures the levelness of the installation of a horizontal pipeline by means of a level ruler, measures the pressure difference between two pressure taking holes by a differential pressure transmitter, directly measures the mass flow of two-phase flow by a mass flow meter, combines gas-liquid two-phase physical property parameters input in a data analysis program, and can calculate the void fraction value by using a two-phase flow friction pressure drop formula.)

1. A real-time on-line measurement system for void fraction of two-phase flow in a pipeline is characterized by comprising a horizontal pipe section, a differential pressure measurement device, a mass flowmeter and a data analysis system; two pressure taking holes are formed in the flow direction below the horizontal pipe section, the differential pressure measuring device is connected with the horizontal pipe section through the pressure taking holes, the mass flowmeter is arranged on the horizontal pipe section, the differential pressure measuring device is composed of a pressure guide pipe and a differential pressure transmitter, and the differential pressure transmitter and the mass flowmeter are connected with a data analysis system.

2. The system for real-time on-line measurement of void fraction in two-phase flow in a pipe according to claim 1, wherein the data analysis system comprises a data acquisition system and a data analysis program.

3. The system for real-time on-line measurement of void fraction in two-phase flow in a pipeline according to claim 1, wherein the cross-sectional shape of the horizontal pipeline is determined according to the shape of the pipeline to be measured, the length of the horizontal pipeline is 2-10 times the hydraulic diameter of the pipeline, and flanges or reserved welding ports are arranged at two ends of a pipeline section and are used for connecting a mass flowmeter and other measuring pipelines.

4. The system for real-time on-line measurement of void fraction in two-phase flow in a pipeline according to claim 1, wherein a level bar is installed above the horizontal pipe section for adjusting the horizontal degree of the pipeline.

5. The system for real-time on-line measurement of void fraction in two-phase flow in a pipe according to claim 1, wherein the distance between the two pressure sampling holes is not less than 1 time of the hydraulic diameter of the pipe.

6. The system for real-time on-line measurement of void fraction in two-phase flow according to claim 1, wherein the mass flow meter is located 1-5 times the hydraulic diameter downstream of the second pressure measurement port in the flow direction.

7. A real-time online measurement method for void fraction of two-phase flow in a pipeline is characterized in that a data analysis system collects data and mass flow signals of a dynamic differential pressure transmitter in real time and carries out online processing to obtain a void fraction value, and the void fraction value is calculated according to the following formula:

in the formula: alpha is void fraction, G is mass flow rate, rho is density of gas-liquid two-phase, D is equivalent diameter, delta P_FTwo-phase friction pressure.

Technical Field

The invention relates to the field of gas-liquid two-phase parameter measurement, in particular to a bubble flow void fraction or section gas content measurement system and method in the fields of thermal hydraulic power, oil exploitation and transportation, steam production and scientific experiments.

Background

The bubble flow of gas-liquid two-phase is one of the most important and common flow patterns in engineering, and is widely used in petrochemical industry, steam manufacturing, nuclear reactor thermal and hydraulic industry and other industrial fields. The void fraction (also called section gas content) represents the percentage of gas in a gas-liquid two-phase mixture, the parameter directly influences the heat and mass transfer characteristics of two-phase flow, is an important parameter influencing the operation and performance of a two-phase flow system, and has important significance for real-time measurement of the two-phase flow. Various measurement methods with different characteristics are currently developed, including contact and non-contact methods. The probe and silk screen measurement technology belongs to contact measurement, measurement equipment is high in cost and needs to be calibrated, and operation is complex. The visualization measurement technology based on high-speed photography needs to arrange a transparent measurement window, has certain limitation on adaptability, and has lower measurement precision when bubbles are overlapped. The principle of the quick-closing valve measuring method is mature, but sampling is needed in measurement, so that part of measuring equipment is large in size, and certain lag exists in measurement. The measurement method based on capacitance or resistance tomography has great difficulty in the aspect of insulation treatment. The above method has a limitation in measurement under high temperature and high pressure. Radiographic-based measurement techniques have a certain radioactivity, and are also high in cost and operational complexity.

Disclosure of Invention

The invention provides a system and a method for measuring the void fraction in a horizontal pipeline, which can be used for measuring the void fraction of the bubble flow in the pipeline under different working conditions including high temperature and high pressure in real time on line.

The purpose of the invention is realized as follows:

a real-time on-line measurement system for void fraction of two-phase flow in a pipeline comprises a horizontal pipe section, a differential pressure measurement device, a mass flowmeter and a data analysis system; two pressure taking holes are formed in the flow direction below the horizontal pipe section, the differential pressure measuring device is connected with the horizontal pipe section through the pressure taking holes, the mass flowmeter is arranged on the horizontal pipe section, the differential pressure measuring device is composed of a pressure guide pipe and a differential pressure transmitter, and the differential pressure transmitter and the mass flowmeter are connected with a data analysis system.

The invention also includes such features:

the data analysis system comprises a data acquisition system and a data analysis program;

the cross section shape of the horizontal pipeline is determined according to the shape of the pipeline to be measured, the length of the horizontal pipeline is 2-10 times of the hydraulic diameter of the pipeline, and flanges or reserved welding ports are arranged at two ends of a pipeline section and used for connecting a mass flowmeter and other measuring pipelines;

a horizontal ruler is arranged above the horizontal pipe section and used for adjusting the horizontal degree of the pipeline;

the distance between the two pressure taking holes is not less than 1 time of the hydraulic diameter of the pipeline;

and the mass flow meter is positioned at the position 1-5 times of the hydraulic diameter at the downstream of the second pressure measuring port in the flow direction.

A real-time online measurement method for void fraction of two-phase flow in a pipeline is characterized in that a data analysis system collects data and mass flow signals of a dynamic differential pressure transmitter in real time and carries out online processing to obtain a void fraction value, and the void fraction value is calculated according to the following formula:

in the formula: alpha is void fraction, G is mass flow rate, rho is density of gas-liquid two-phase, D is equivalent diameter, delta P_FTwo-phase friction pressure.

Compared with the prior art, the invention has the beneficial effects that:

the method can be used for measuring the bubble portion of the bubble flow under the high-temperature and high-pressure working condition;

the invention can carry out real-time on-line measurement and can be used for measuring the bubble portion of the bubble flow under steady-state and unsteady-state working conditions.

Drawings

FIG. 1 is a schematic view of a system for measuring void fraction in a horizontal pipe according to the present invention;

in the figure, 1-horizontal pipe section, 2-level bar, 3 mass flowmeter, 4-pressure taking hole, 5-first pressure guide pipe, 6-second pressure guide pipe, 7-differential pressure transmitter, 8-data transmission line and 9-data analysis system.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

A real-time on-line measurement system for void fraction of two-phase flow in a pipeline consists of a horizontal pipe section, a differential pressure measurement device, a mass flowmeter and a data analysis system;

the horizontal pipe section consists of pipe sections with the same cross section shape as the measuring pipeline, and high-low pressure taking holes are arranged at the bottommost part of the horizontal pipe section along the flow direction and used for connecting a differential pressure measuring device;

the differential pressure measuring device is composed of a pressure guide pipe and a differential pressure transmitter, wherein the high and low pressure sides of the differential pressure transmitter are respectively connected with a pressure taking hole of the horizontal pipe section and used for measuring two-phase pressure drop values of the pipe section;

the mass flowmeter is specifically a Coriolis mass flowmeter and can directly measure the mass flow of the two-phase flow under the high-temperature and high-pressure environment.

The data analysis system is composed of a data acquisition system and a data analysis program and is used for calculating the vacuole quota value by reading the measured value of the differential pressure transmitter, the two-phase mass flow and the gas-liquid two-phase physical property parameters;

the cross section shape of the horizontal pipeline is determined according to the shape of the pipeline to be measured, the length of the horizontal pipeline is 2-10 times of the hydraulic diameter of the pipeline, and flanges or reserved welding ports are arranged at two ends of a pipeline section and used for connecting a mass flowmeter and other measuring pipelines;

a horizontal ruler is arranged above the horizontal pipe section and used for adjusting the horizontal degree of the pipeline;

the pressure measuring holes are positioned at the lowest part of the horizontal pipeline, and the distance between the pressure measuring holes is not less than 1 time of the hydraulic diameter of the pipeline;

the pressure tapping pipe is vertically and horizontally arranged, and two ends of the pressure guiding pipe are respectively connected with a pressure tapping hole and a differential pressure transmitter measuring interface;

the mass flow meter is positioned at the downstream of the second pressure measuring port by 1-5 times of the hydraulic diameter in the flowing direction, so that the influence on the pressure drop measurement of the horizontal section is avoided.

The data analysis system can acquire data and mass flow signals of the dynamic differential pressure transmitter in real time and perform online processing to obtain a cavitation fraction value;

the pressure drop delta P measured by the differential pressure transmitter in the differential pressure measuring device is reduced from the weight position pressure drop delta P_GAccelerated pressure drop Δ P_AAnd the friction pressure drop Δ P_FThe composition is shown as a formula (1).

ΔP＝ΔP_G+ΔP_A+ΔP_F (1)

For the differential pressure measuring device, the pressure drop of the heavy position is zero due to the horizontal arrangement of the measuring pipeline; because the cross-sectional area of the measuring pipeline is unchanged and the length of the measuring pipeline is short, the change value of the void fraction is small, and the change of the accelerated pressure drop is negligible. Therefore, the two-phase pressure drop of the horizontal pipeline measured by the differential pressure transmitter in the measuring device is mainly two-phase friction pressure drop, namely:

the two-phase friction pressure drop is calculated by the Lockhart-Martinelli method, which introduces a liquid-separating phase conversion parameter (two-phase friction factor), as shown in equation (3).

In the formula (3), the reaction mixture is,is a two-phase friction factor, X is a Matim parameter, which can be calculated by the formulas (4) and (5) respectively; c is a dimensionless parameter, and the value is related to the flow state of each phase.

In the formulae (4) and (5),in order to be a two-phase frictional pressure drop,respectively representLiquid and gas friction pressure drops.

The two-phase friction pressure drop obtained according to equation (4) is shown in equation (6). Wherein, Δ P_FlCan be calculated by darcy equation (7).

In the formula (7), f_k、ρ_k、j_kRespectively representing k-phase friction resistance coefficient, fluid density and converted flow rate; d is the equivalent diameter.

The coefficient of friction resistance f is turbulent for most two-phase flows in the industrial field_kCalculated by the Brachiis formula (8). Wherein, Re_k、μ_kRespectively, k-phase Reynolds number and kinetic viscosity.

The apparent flow rate j can be converted into an actual flow rate v by equation (9), which can be further converted into a mass flow rate G and a void fraction α by equation (10).

j_g＝αv_g,j_l＝(1-α)v_l (9)

In the formula, rho, j and v are density, apparent flow velocity and actual flow velocity of gas-liquid two phases respectively, the mass flow velocity G is obtained by converting total mass flow measured by a mass flowmeter, x is mass gas content, and A is the cross section area of a flow passage.

In the formula (10), the mass air content x has the following relationship with the void fraction α and the slip ratio S.

By substituting formula (4) to formula (11) into formula (3), it is possible to obtain:

for common bubble flow in the industry, the speed slippage between two phases is small, and the slip speed ratio S is approximately equal to 1; under turbulent conditions, the dimensionless parameter C takes the kirschham recommended value C-20. By substituting the above value into formula (12), an implicit expression (13) of the void fraction α can be obtained:

in the formula (13), only the void fraction α is an unknown quantity to be determined, and other parameters can be obtained through experimental measurement or conversion. For non-bubble flow conditions, the void fraction can be measured using equation (12) using the S value of the calibration pair.

A method and system for measuring void fraction in a horizontal pipeline, wherein the void fraction is calculated by a relational expression between the void fraction and two-phase flow pressure drop and slip speed ratio; the measuring system consists of a horizontal pipe section, a differential pressure measuring device, a mass flowmeter and a data analysis system; the cross section shape of the horizontal pipeline is matched with the pipeline to be tested, and the length of the horizontal pipeline is 2-10 times of the hydraulic diameter of the pipeline; flanges or reserved welding ports are arranged at two ends of the horizontal pipeline; a horizontal ruler is arranged above the horizontal pipeline, and two pressure taking holes with the distance not less than 1 time of the hydraulic diameter of the pipeline are arranged at the lowest part of the horizontal pipeline; the differential pressure measuring device consists of a pressure guide pipe 5, a pressure guide pipe 6 and a differential pressure transmitter 7, wherein the high and low pressure sides of the differential pressure transmitter are respectively connected with an upstream and downstream pressure taking hole of the horizontal pipeline; the mass flowmeter is a high-temperature and high-pressure resistant Coriolis force mass flowmeter and is positioned at the position 1-5 times of the hydraulic diameter at the downstream of the second pressure measuring port in the flow direction; the data analysis system consists of a data acquisition system and a data analysis program, and the data acquisition system is connected with the differential pressure transmitter through a data transmission line; the data analysis program can input the component physical properties of different two-phase flows; the system can measure the vacuole volume value of gas-liquid two-phase vacuole flow in the pipeline in real time.

The invention is based on the pressure drop measurement principle, and converts the average volume fraction value of the cross section of two-phase flow in the horizontal pipeline into friction pressure drop for measurement.

As shown in figure 1, the cross section of the horizontal pipeline adopted by the invention is matched with the pipeline to be tested, and the length of the horizontal pipeline is 2-10 times of the hydraulic diameter of the pipeline; flanges or reserved welding ports are arranged at two ends of the pipe section and are used for connecting a measuring pipeline; a horizontal ruler 2 is arranged above the horizontal pipeline and used for adjusting the horizontal position of the pipeline; the interval of the pressure taking holes of the horizontal pipeline is not less than 1 time of the hydraulic diameter of the pipeline, and the pressure taking holes are positioned at the lowest side of the horizontal pipeline, so that bubbles on the wall surface can effectively enter the pressure guide pipe, and the reliability of pressure drop measurement is ensured.

The differential pressure measuring device consists of a pressure guide pipe 5, a pressure guide pipe 6 and a differential pressure transmitter 7, wherein the high and low pressure sides of the differential pressure transmitter are respectively connected with the upstream and downstream static pressure taking holes of the horizontal pipeline, and the two-phase pressure drop between the two pressure taking holes is collected.

The mass flowmeter 3 is a high-temperature and high-pressure resistant Coriolis force mass flowmeter and is arranged at the position 1-5 times of the hydraulic diameter downstream of the second pressure measuring port of the measuring section to directly measure the mass flow of the two phases.

The data acquisition system is connected with the differential pressure transmitter through a data transmission line, and can perform online acquisition on the pressure drop and the mass flow of two phases in real time;

the data analysis program takes a pressure drop numerical value, two-phase mass flow, physical property parameters of each component, geometric dimension of the pipeline and dimensionless parameter C measured by the pressure difference sensor as data input, and solves the equivalent diameter, the mass flow rate and the void fraction in sequence, and finally the measurement system can be suitable for measuring the void fraction of the two-phase bubble flow of different working media.

The above detailed description and embodiments of the present invention are the best mode of the present invention, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention.

In summary, the following steps: the invention discloses an online measurement method and system for vacuole share in a horizontal pipeline, which can measure the vacuole share value of gas-liquid two-phase vacuole flow in the pipeline in real time and relates to the technical fields of thermal engineering waterpower, oil exploitation and transportation, steam production and the like. The invention consists of a horizontal pipe section, a differential pressure measuring device, a mass flowmeter and a data analysis system, and particularly comprises the horizontal pipe section, a level gauge, a pressure taking hole, a pressure guide pipe, a differential pressure transmitter, the mass flowmeter, a data transmission line, a data acquisition system and a data analysis program. The invention is based on the two-phase flow pressure drop measuring principle, and measures the average void fraction of the cross section through the relation between the void fraction and the two-phase friction pressure drop. In the measuring process, the levelness of the installation of the horizontal pipeline is ensured by means of a level ruler, the differential pressure between two pressure taking holes is measured by a differential pressure transmitter, the mass flow of the two-phase flow is directly measured by a mass flow meter, and the cavitation fraction value can be calculated by combining gas-liquid two-phase physical property parameters input in a data analysis program and applying a two-phase flow friction pressure drop formula. The real-time online measurement of the bubble portion of the gas-liquid two-phase bubble flow is realized.