A measuring method and device based on critical venturi nozzle parallel effective flow area

Abstract

The application discloses a critical Venturi nozzle based parallel effective flow area measurement method and device, which comprises inputting gas source pressure and predicted effective area of a measured member into a control system, and the control system automatically selects and combines specific branches in a Venturi nozzle array according to input parameters; a pressure regulating valve is adjusted to make the system reach a flow stable state, and whether each branch Venturi nozzle is in a critical state is monitored; inlet total pressure, inlet total temperature and throat flow area of each branch Venturi nozzle in the critical state are collected, and mass flow through the measured workpiece is calculated; pressure difference before and after the measured member and local atmospheric density are collected, and the calculated total mass flow is used to calculate the effective flow area of the measured member; the pipe pressure is changed through the pressure regulating valve, and the average value of the results obtained through multiple measurements is taken as the final measurement result; the application detects effective areas of nozzles and blades of different types of gas turbines, judges nozzle consistency and effective areas of blade cooling channels.

Description

Technical Field

[0001] This invention relates to a method and apparatus for measuring the effective flow area of ​​parallel critical venturi nozzles, belonging to the field of gas turbine nozzle and blade flow technology. Background Technology

[0002] Gas turbine blades and nozzles, as core hot-end components that kineticize high-temperature, high-pressure gas, operate for extended periods in extreme environments involving oxidation, corrosion, and thermal shock coupling, exceeding the material's melting point. Their stable operation directly determines the turbine's power output, thermal efficiency, and safe operating cycle. However, in actual operation, nozzles frequently experience sintering and cooling hole blockage. Inappropriate maintenance strategies or failure to accurately assess the extent of damage can not only lead to a significant decrease in unit efficiency but may also trigger safety accidents. Therefore, developing an efficient and accurate device for detecting the effective flow area of ​​gas turbine blades and nozzles is of immense engineering value and urgent practical importance for ensuring equipment availability, extending the lifespan of hot-end components, and reducing maintenance costs. Summary of the Invention

[0003] The purpose of this invention is to provide a method and device for measuring the effective flow area based on parallel critical Venturi nozzles. By controlling the system to autonomously select the combination of Venturi nozzles, the measurement range can be improved while increasing work efficiency.

[0004] To achieve the above objectives / to solve the above technical problems, the present invention is implemented using the following technical solution: The first aspect discloses a method for measuring the effective flow area of ​​parallel critical Venturi nozzles, including: Step S1: Input the air source pressure and the predicted effective area of ​​the measured object into the control system. The control system automatically selects and combines specific branches in the Venturi nozzle array according to the input parameters. Step S2: Open the solenoid valve of the corresponding branch, adjust the pressure regulating valve to make the system reach a stable flow state, and monitor whether the Venturi nozzles of each branch are in a critical state. Step S3: Collect the total inlet pressure, total inlet temperature, and throat flow area of ​​each branch Venturi nozzle in the critical state, and calculate the mass flow rate through the workpiece being measured. Step S4: Collect the pressure difference before and after the test piece and the local atmospheric density, and combine the calculated total mass flow rate to calculate the effective flow area of ​​the test piece; Step S5: Change the pipeline pressure by adjusting the pressure valve, and take the average value of the results obtained from multiple measurements as the final measurement result.

[0005] Optionally, in step S2, the condition for determining that the Venturi nozzle has reached the critical state is: The ratio of the pressure in each branch pipe after the Venturi nozzle to the air inlet pressure of the Venturi nozzle is measured. If Pb / Px≤0.528, the Venturi nozzle of that branch is determined to be in a critical state. The air inlet pressure of the Venturi nozzle is measured by a pressure sensor, and the pressure of each branch pipeline is measured by a pressure sensor.

[0006] Optionally, in step S3, the mass flow rate calculation formula for the Venturi nozzles of each branch pipe is as follows: ; in, w The mass flow rate through the workpiece being measured; K The constant is for air ( k =1.4R=287.06J / (kgK)). K =0.0404; P t The measured total pressure at the venturi tube inlet; T t The measured total temperature at the venturi tube inlet; A The throat flow area is obtained from calibration. q (λ) It is a dimensionless dense flow, in the critical state q (λ) =1.

[0007] Optionally, in step S4, the formula for calculating the effective flow area of ​​the tested component is as follows: ; in: AC d The effective area of ​​the measured part; w The total mass flow rate measured; DP The pressure difference before and after the test piece; r air This refers to the local atmospheric density.

[0008] Second aspect: A measuring apparatus for implementing the method described in the first aspect is disclosed, characterized in that it comprises: The air supply unit includes a compressor and an air filter assembly; the air outlet of the compressor is connected in series with the air filter assembly through a pipeline, and an inlet pressure sensor and an inlet temperature sensor are installed on the filtered gas pipeline to monitor the state of the gas in the main pipe. The flow control and regulation unit includes a pressure regulating valve, multiple parallel branches, and each branch is sequentially equipped with a branch pressure sensor, a branch temperature sensor, a solenoid valve, a venturi nozzle, a nozzle post-pressure sensor, a nozzle post-temperature sensor, and an emergency pressure relief valve. The test unit for the test device includes a pressure sensor before the test device, a temperature sensor before the test device, the test device, a pressure sensor after the test device, and a temperature sensor after the test device. The control system is used to connect all the aforementioned sensors and actuators and to process the data.

[0009] Optionally, the Venturi nozzle array includes a set of independent critical Venturi nozzles with nominal flow rates of Q, 1.5Q, 2Q, 2.5Q, 3Q, and 3Q, respectively, and the throat area of ​​each Venturi nozzle is fixed.

[0010] Optionally, the installation position of the measuring point of the measuring device satisfies: The distance between the intake pressure sensor and the air source is greater than or equal to 10 times the pipe diameter; The installation distance between the nozzle and the pressure measuring point after the test piece should be greater than or equal to 3 to 5 times the pipe diameter.

[0011] Optionally, the emergency pressure relief valve is configured to automatically open and relieve pressure when the pipeline pressure exceeds a set value, in order to prevent the risk of overpressure caused by the failure of the pressure regulating valve.

[0012] Optionally, the device includes six parallel measurement branches, and the internal components of each branch are connected in series according to the airflow direction, with the specific connection order as follows: The first branch: It is led out from the main branch pipe and connected in sequence to the branch pressure sensor, the branch temperature sensor, the solenoid valve, the Venturi nozzle, the pressure sensor after the nozzle and the temperature sensor after the nozzle. An emergency pressure relief valve is connected in parallel before and after the Venturi nozzle or at an appropriate position in this branch. The second branch: It is led out from the main branch pipe and connected in sequence to the branch pressure sensor, branch temperature sensor, solenoid valve, venturi nozzle, nozzle post-pressure sensor and nozzle post-temperature sensor, and is equipped with an emergency pressure relief valve. The third branch: It is led out from the main branch pipe and connected in sequence to the branch pressure sensor, branch temperature sensor, solenoid valve, venturi nozzle, nozzle post-pressure sensor and nozzle post-temperature sensor, and is equipped with an emergency pressure relief valve. The fourth branch: It is led out from the main branch pipe and connected in sequence to the branch pressure sensor, branch temperature sensor, solenoid valve, venturi nozzle, nozzle post-pressure sensor and nozzle post-temperature sensor, and is equipped with an emergency pressure relief valve. The fifth branch: It is led out from the main branch pipe and connected in sequence to the branch pressure sensor, branch temperature sensor, solenoid valve, venturi nozzle, nozzle post-pressure sensor and nozzle post-temperature sensor, and is equipped with an emergency pressure relief valve. The sixth branch: It is led out from the main branch pipe and connected in sequence to the branch pressure sensor, branch temperature sensor, solenoid valve, venturi nozzle, nozzle post-pressure sensor and nozzle post-temperature sensor, and is equipped with an emergency pressure relief valve.

[0013] Optionally, the outlet ends of the six parallel measurement branches converge into a main manifold leading to the test unit of the device under test.

[0014] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: This invention discloses a method and apparatus for measuring the effective flow area of ​​gas turbine nozzles and blades. Based on the critical Venturi nozzle principle, this method enables accurate measurement of the flow rate consistency of nozzles from different gas turbine models and the effective flow area of ​​blade cooling holes. Compared with existing technologies, this invention not only solves the problem of low measurement accuracy of traditional flowmeters but also avoids the operational complexity caused by frequently changing flowmeters with different ranges due to different turbine models. It significantly improves the versatility and convenience of measurement, thus providing a reliable guarantee for the safe and stable operation of gas turbines. Attached Figure Description

[0015] Figure 1 The diagram shown is a schematic of the measuring device of the present invention.

[0016] In the diagram: 1 is the air source, 2-3 are the air filter assembly, 4 is the pressure sensor, 5 is the temperature sensor, 6 is the pressure regulating valve, 7-12 are the pressure sensors, 13-18 are the temperature sensors, 19-24 are the solenoid valves, 25-30 are the Venturi nozzles, 31-36 are the pressure sensors, 37-42 are the temperature sensors, 43-48 are the emergency pressure relief valves, 49 is the temperature sensor, 50 is the pressure sensor, 51 is the device under test, 52 is the temperature sensor, 53 is the pressure sensor, and 54 is the control system. Detailed Implementation

[0017] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0018] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0019] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0020] Example 1 discloses a method for measuring the effective flow area based on parallel critical Venturi nozzles, including: Step S1: Input the air source pressure and the predicted effective area of ​​the measured component 51 into the control system 54. The control system 54 automatically selects and combines specific branches in the Venturi nozzle array according to the input parameters. Step S2: Open the solenoid valves 19-24 of the corresponding branch, adjust the pressure regulating valve 6 to make the system reach a stable flow state, and monitor whether the Venturi nozzles of each branch are in a critical state. Step S3: Collect the total inlet pressure, total inlet temperature, and throat flow area of ​​each branch Venturi nozzle in the critical state, and calculate the mass flow rate through the workpiece being measured. Step S4: Collect the pressure difference before and after the test piece 51 and the local atmospheric density, and combine the calculated total mass flow rate to calculate the effective flow area of ​​the test piece 51. Step S5: Change the pipeline pressure through the pressure regulating valve 6, and take the average value of the results obtained from multiple measurements as the final measurement result.

[0021] In this embodiment, during the specific implementation process, the condition for determining that the Venturi nozzle has reached the critical state in step S2 is as follows: The ratio of the pressure in each branch pipe after the Venturi nozzle to the air inlet pressure of the Venturi nozzle is measured. If Pb / Px≤0.528, the Venturi nozzle of that branch is determined to be in a critical state. The air inlet pressure of the Venturi nozzle is measured by pressure sensor 7-12, and the pressure of each branch pipeline is measured by pressure sensor 31-36.

[0022] In this embodiment, during the specific implementation process, the formula for calculating the mass flow rate of the Venturi nozzles in each branch pipe in step S3 is as follows: ; in, w The mass flow rate through the workpiece being measured; K It is a constant for air k =1.4R=287.06J / kgK, K=0.0404; P t The measured total pressure at the venturi tube inlet; T t The measured total temperature at the venturi tube inlet; A The throat flow area is obtained from calibration. qλ It is a dimensionless dense flow, in the critical state qλ =1.

[0023] In this embodiment, during the specific implementation process, the formula for calculating the effective flow area of ​​the measured component in step S4 is as follows: ; in: AC d The effective area of ​​the measured part; w The total mass flow rate measured; DP The pressure difference before and after the test piece; r air This refers to the local atmospheric density.

[0024] This invention is based on the principle of "critical Venturi array". During each measurement, a given airflow rate is used, and the effective flow area is obtained from the pressure difference measured at that time. The flow station includes a set of independent critical Venturi nozzle arrays with flow rates of Q, 1.5Q, 2Q, 2.5Q, 3Q, and 3Q, an air filter, Venturi nozzle control valves, array pressure measuring points, array temperature measuring points, an inlet pressure sensor, an inlet temperature sensor, a pressure measuring point for the tested component, and a temperature measuring point for the tested component. Accurate data during the test is obtained through data acquisition and conversion, atmospheric pressure measuring points, atmospheric temperature measuring points, atmospheric humidity measuring points, and a control system.

[0025] During measurement, the air source pressure and the predicted effective area of ​​the measured object are input to the control system 54. The control system automatically selects and combines the Venturi tube array, and the solenoid valves 18-23 of the corresponding branch open. At this time, each Venturi riser is in a critical state. The air source is provided by compressor 1. 2 and 3 are air filters used to remove impurities and moisture from the air. 4 is a pressure sensor, and 5 is a temperature sensor used to monitor the temperature and pressure of the gas in the main pipe. 6 is a pressure regulating valve used to regulate the main pipe pressure. 7-12 are pressure sensors used to measure the air inlet pressure P of the Venturi nozzle in the branch pipe. x 13-18 are temperature sensors used to measure the air inlet temperature of the Venturi nozzles in the branch pipelines; 19-24 are solenoid valves controlling the opening and closing of each branch; 25-30 are Venturi nozzles, whose throat area is fixed, and after reaching the critical state, the gas flow rate is only related to the upstream stagnation pressure; 31-36 are pressure sensors used to measure the pressure P in each branch pipeline after the Venturi nozzles. b37-42 are temperature sensors used to measure the temperature of each branch pipe after the Venturi nozzle. If P b / P x If the pressure is ≤0.528, the Venturi nozzle is considered to have reached the critical state. P43-48 are emergency pressure relief valves used to prevent pressure regulating valve failure and automatically relieve pressure when the pipeline pressure exceeds the set value. 49 is the temperature sensor of the measured object, and 50 is the pressure sensor of the measured object, used to measure the static pressure and temperature before the measured object. When installing the measuring point, the distance between the pressure sensor 4 and the air source should be ≥10 times the pipe diameter, and the installation distance between the nozzle and the pressure measuring point after the measured object should be ≥3~5 times the pipe diameter.

[0026] Once the system determines that the flow has reached a stable state, the effective flow area of ​​the measured component is calculated using the measured pressure and temperature.

[0027] First, based on the calibrated throat area of ​​the Venturi nozzle, and using the readings of the activated branch pressure sensors 7-12, 13-18, 31-36, and 37-42, the mass flow rate of the Venturi nozzle in each branch is calculated as follows: ; in, w The mass flow rate through the workpiece being measured; K The constant is for air ( k =1.4 R=287.06J / (kgK)), K =0.0404; P t The measured total pressure at the venturi tube inlet; T t The measured total temperature at the venturi tube inlet; A The throat flow area is obtained from calibration. q (λ) It is a dimensionless dense flow, in the critical state q (λ) =1.

[0028] Based on the total mass flow rate calculated above, and the pressure measured by the pressure sensors 50 and 53 before and after the nozzle, the effective flow area of ​​the measured component 51 can be calculated: ; in: AC d The effective area of ​​the measured part; w The total mass flow rate measured; DP The pressure difference before and after the test piece; r air This refers to the local atmospheric density. After recording a single set of data, change the pipeline pressure through pressure regulating valve 6, repeat the above steps twice, and average the results of the three measurements to reduce experimental error.

[0029] Example 2 discloses a measuring device for implementing the method described in any one of Examples 1, comprising: The air supply unit includes a compressor 1 and air filter groups 2 and 3. The air outlet of the compressor 1 is connected in series with the air filter groups 2 and 3 through a pipeline. An inlet pressure sensor 4 and an inlet temperature sensor 5 are installed on the filtered gas pipeline to monitor the status of the gas in the main pipe. The flow control and regulation unit includes a pressure regulating valve 6 and multiple parallel branches. Each branch is sequentially equipped with a branch pressure sensor 7-12, a branch temperature sensor 13-18, a solenoid valve 19-24, a venturi nozzle 25-30, a nozzle post-pressure sensor 31-36, a nozzle post-temperature sensor 37-42, and an emergency pressure relief valve 43-48. The test unit includes a test pressure sensor 50 before the test, a test temperature sensor 49 before the test, the test 51, a test pressure sensor 53 after the test, and a test temperature sensor 52 after the test. Before the test 51 is installed, the test temperature sensor 49 and the test pressure sensor 50 are installed in sequence. Gas flows through the test 51. On the outlet pipe of the test 51, the test pressure sensor 53 and the test temperature sensor 52 are installed in sequence. Control system 54 is used to connect all the above-mentioned sensors and actuators and to process data; as the core control and data processing unit, control system 54 is electrically connected to the following components via signal lines: All pressure sensors 4,7-12,31-36,50,53; All temperature sensors 5,13-18,37-42,49,52; All actuators, including pressure regulating valve 6, six solenoid valves 19-24 and six emergency pressure relief valves 43-48; The control system 54 is responsible for collecting data from each sensor, calculating the flow rate and effective area according to a preset algorithm, and sending control commands to open / close specific solenoid valve branches and adjust valve opening.

[0030] In this embodiment, the Venturi nozzle array includes a set of independent critical Venturi nozzles with nominal flow rates of Q, 1.5Q, 2Q, 2.5Q, 3Q, and 3Q, respectively, and the throat area of ​​each Venturi nozzle is fixed.

[0031] The installation position of the measuring point of the measuring device satisfies the following: The distance between the intake pressure sensor 4 and the air source is greater than or equal to 10 times the pipe diameter; The installation distance between the nozzle and the pressure measuring point after the test piece should be greater than or equal to 3 to 5 times the pipe diameter.

[0032] In this embodiment, the emergency pressure relief valves 43-48 are configured to automatically open and relieve pressure when the pipeline pressure exceeds the set value, in order to prevent the risk of overpressure caused by the failure of the pressure regulating valve 6.

[0033] In this embodiment, the device includes six parallel measurement branches. The internal components of each branch are connected in series according to the airflow direction, and the specific connection order is as follows: The first branch line: It extends from the main branch pipe and connects in sequence to the branch pressure sensor 7, the branch temperature sensor 13, the solenoid valve 19, the venturi nozzle 25, the post-nozzle pressure sensor 31, and the post-nozzle temperature sensor 37. An emergency pressure relief valve 43 is connected in parallel before, after, or at an appropriate position on this branch line to the venturi nozzle 25.

[0034] The second branch line: extends from the main branch pipe and connects sequentially to the branch pressure sensor 8, branch temperature sensor 14, solenoid valve 20, venturi nozzle 26, nozzle post-pressure sensor 32, and nozzle post-temperature sensor 38. An emergency pressure relief valve 44 is provided accordingly.

[0035] The third branch line: leads out from the main branch pipe and connects in sequence to the branch pressure sensor 9, the branch temperature sensor 15, the solenoid valve 21, the venturi nozzle 27, the nozzle post-pressure sensor 33, and the nozzle post-temperature sensor 39. An emergency pressure relief valve 45 is provided accordingly.

[0036] The fourth branch line: leads out from the main branch pipe and connects in sequence to the branch pressure sensor 10, the branch temperature sensor 16, the solenoid valve 22, the venturi nozzle 28, the nozzle post-pressure sensor 34, and the nozzle post-temperature sensor 40. An emergency pressure relief valve 46 is correspondingly provided.

[0037] The fifth branch line: extends from the main branch pipe and connects sequentially to the branch pressure sensor 11, the branch temperature sensor 17, the solenoid valve 23, the venturi nozzle 29, the nozzle post-pressure sensor 35, and the nozzle post-temperature sensor 41. An emergency pressure relief valve 47 is provided accordingly.

[0038] The sixth branch line: extends from the main branch pipe and connects sequentially to the branch pressure sensor 12, the branch temperature sensor 18, the solenoid valve 24, the venturi nozzle 30, the nozzle post-pressure sensor 36, and the nozzle post-temperature sensor 42. An emergency pressure relief valve 48 is also provided.

[0039] The outlets of the six parallel measurement branches converge into a main manifold, which leads to the test unit of the device under test.

[0040] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for measuring the effective flow area of ​​parallel critical Venturi nozzles, characterized in that, include: Step S1: Input the air source pressure and the predicted effective area of ​​the test piece (51) into the control system (54). The control system (54) automatically selects and combines specific branches in the Venturi nozzle array according to the input parameters. Step S2: Open the solenoid valve (19-24) of the corresponding branch, adjust the pressure regulating valve (6) to make the system reach a stable flow state, and monitor whether the Venturi nozzles of each branch are in a critical state. Step S3: Collect the total inlet pressure, total inlet temperature, and throat flow area of ​​each branch Venturi nozzle in the critical state, and calculate the mass flow rate through the workpiece being measured. Step S4: Collect the pressure difference before and after the test piece (51) and the local atmospheric density, and calculate the effective flow area of ​​the test piece (51) in combination with the calculated total mass flow rate; Step S5: Change the pipeline pressure through the pressure regulating valve (6), and take the average value of the results obtained from multiple measurements as the final measurement result.

2. The method for measuring the effective flow area based on parallel critical Venturi nozzles according to claim 1, characterized in that, In step S2, the condition for determining that the Venturi nozzle has reached the critical state is: The ratio of the pressure in each branch pipe after the Venturi nozzle to the air inlet pressure of the Venturi nozzle is measured. If Pb / Px≤0.528, the Venturi nozzle of that branch is determined to be in a critical state. The air inlet pressure of the Venturi nozzle is measured by pressure sensor (7-12), and the pressure of each branch pipeline is measured by pressure sensor (31-36).

3. The method for measuring the effective flow area based on parallel critical Venturi nozzles according to claim 1, characterized in that, In step S3, the formula for calculating the mass flow rate of the Venturi nozzles in each branch pipe is as follows: ;in, w The mass flow rate through the workpiece being measured; K The constant is for air ( k =1.4R=287.06J / (kgK)). K =0.0404; P t The measured total pressure at the venturi tube inlet; T t The measured total temperature at the venturi tube inlet; A The throat flow area is obtained from calibration. q(λ) It is a dimensionless dense flow, in the critical state q(λ) =1.

4. The method for measuring the effective flow area based on parallel critical Venturi nozzles according to claim 1, characterized in that, In step S4, the formula for calculating the effective flow area of ​​the measured component is as follows: ； in: AC d The effective area of ​​the measured part; w The total mass flow rate measured; DP The pressure difference before and after the test piece; r air This refers to the local atmospheric density.

5. A measuring apparatus for implementing the method according to any one of claims 1-4, characterized in that, include: The gas supply unit includes a compressor (1) and an air filter group (2, 3); the outlet of the compressor (1) is connected in series with the air filter group (2, 3) through a pipeline. The gas pipeline after filtration is equipped with an inlet pressure sensor (4) and an inlet temperature sensor (5) to monitor the status of the gas in the main pipe. The flow control and regulation unit includes a pressure regulating valve (6), multiple parallel branches, and each branch is sequentially equipped with a branch pressure sensor (7-12), a branch temperature sensor (13-18), a solenoid valve (19-24), a venturi nozzle (25-30), a nozzle post-pressure sensor (31-36), a nozzle post-temperature sensor (37-42), and an emergency pressure relief valve (43-48). The test unit for the test device includes a front pressure sensor (50) for the test device, a front temperature sensor (49) for the test device, the test device (51), a rear pressure sensor (53) for the test device, and a rear temperature sensor (52) for the test device. The control system (54) is used to connect all the above sensors and actuators and to process the data.

6. The effective flow area measuring device based on parallel critical Venturi nozzles according to claim 5, characterized in that, The Venturi nozzle array comprises a set of independent critical Venturi nozzles with nominal flow rates of Q, 1.5Q, 2Q, 2.5Q, 3Q, and 3Q, respectively, and the throat area of ​​each Venturi nozzle is fixed.

7. The effective flow area measuring device based on parallel critical Venturi nozzles according to claim 5, characterized in that, The installation position of the measuring point of the measuring device satisfies the following: The distance between the intake pressure sensor (4) and the air source is greater than or equal to 10 times the pipe diameter; The installation distance between the nozzle and the pressure measuring point after the test piece should be greater than or equal to 3 to 5 times the pipe diameter.

8. The effective flow area measuring device based on parallel critical Venturi nozzles according to claim 5, characterized in that, The emergency pressure relief valve (43-48) is configured to automatically open and relieve pressure when the pipeline pressure exceeds the set value, so as to prevent the risk of overpressure caused by the failure of the pressure regulating valve (6).

9. The effective flow area measuring device based on parallel critical Venturi nozzles according to claim 5, characterized in that, The device includes six parallel measurement branches, and the internal components of each branch are connected in series according to the airflow direction, with the specific connection order as follows: The first branch: It is led out from the main branch pipe and connected in sequence to the branch pressure sensor (7), the branch temperature sensor (13), the solenoid valve (19), the Venturi nozzle (25), the nozzle post pressure sensor (31) and the nozzle post temperature sensor (37). An emergency pressure relief valve (43) is connected in parallel before, after or at an appropriate position on the Venturi nozzle (25) of this branch. The second branch: It is led out from the main branch pipe and connected in sequence to the branch pressure sensor (8), the branch temperature sensor (14), the solenoid valve (20), the venturi nozzle (26), the nozzle post pressure sensor (32) and the nozzle post temperature sensor (38), and is equipped with an emergency pressure relief valve (44). The third branch: It is led out from the main branch pipe and connected in sequence to the branch pressure sensor (9), the branch temperature sensor (15), the solenoid valve (21), the venturi nozzle (27), the nozzle post pressure sensor (33) and the nozzle post temperature sensor (39), and is equipped with an emergency pressure relief valve (45). The fourth branch: It is led out from the main branch pipe and connected in sequence to the branch pressure sensor (10), the branch temperature sensor (16), the solenoid valve (22), the venturi nozzle (28), the nozzle post pressure sensor (34) and the nozzle post temperature sensor (40), and is equipped with an emergency pressure relief valve (46). Fifth branch: It is led out from the main branch pipe and connected in sequence to the branch pressure sensor (11), the branch temperature sensor (17), the solenoid valve (23), the venturi nozzle (29), the nozzle post pressure sensor (35) and the nozzle post temperature sensor (41), and is equipped with an emergency pressure relief valve (47). The sixth branch: It is led out from the main branch pipe and connected in sequence to the branch pressure sensor (12), the branch temperature sensor (18), the solenoid valve (24), the venturi nozzle (30), the nozzle post-pressure sensor (36) and the nozzle post-temperature sensor (42), and is equipped with an emergency pressure relief valve (48).

10. The effective flow area measuring device based on parallel critical Venturi nozzles according to claim 9, characterized in that, The outlets of the six parallel measurement branches converge into a main manifold, which leads to the test unit of the device under test.

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