Aero-engine ground test bed air inlet flow pipe calibration system

Abstract

The invention relates to an aero-engine ground test bed air inlet flow pipe calibration system, and relates to the technical field of air inlet flow pipe calibration, an air extractor is used for supplying set mass flow, a standard air inlet flow pipe is used for measuring and calculating actual mass flow, and then a local actual flow coefficient is obtained through back calculation. A calibration coefficient can be obtained through calculation according to the coefficient and used for calibrating the sonic nozzle, calculating theoretical measurement values of other flowmeters, and comparing the theoretical measurement values with actual values for verification; after the sonic nozzle is calibrated, the standard gas inlet flow pipe can be replaced by the gas inlet flow pipe to be calibrated to be used as a sonic nozzle method gas flow calibration device, and then other gas inlet flow pipes are calibrated. Compared with a traditional mode of using a regulating valve to regulate the flow to measure the flow of the engine, the flow metering error can be corrected to a certain degree, data are more accurate, and the method is reliable, simple, convenient, high in efficiency and safer.

Description

Technical Field

[0001] This invention relates to the field of air intake flow tube calibration technology, and in particular to an air intake flow tube calibration system for an aero-engine ground test bench. Background Technology

[0002] Engine intake airflow is a crucial parameter for evaluating aero-engine performance. Accurate airflow values ​​are essential for evaluating engine performance, safety, and other technical indicators, which directly impact the technical specifications and combat effectiveness of military aircraft. In engine and compressor testing, if the test apparatus draws air directly from the atmosphere, an intake flow meter is typically used to measure the inlet airflow. Total pressure, total temperature, and static pressure are measured at the flow meter's cross-section to calculate the flow rate. When precise measurement of the flow meter's airflow requires considering the influence of the boundary layer on the pipe's inner wall, the outflow coefficient must be obtained, and this coefficient is used to offset the boundary layer's effect on flow measurement. Currently, there are no consistent standards for the design, manufacturing, and use of intake flow meters. The factors affecting the accuracy of flow meter measurements are lacking research and control, resulting in inconsistent flow rate measurements from different flow meters. Therefore, intake flow meters need to be calibrated to determine their accurate outflow coefficient. Summary of the Invention

[0003] To address the shortcomings of related technologies, this invention provides an air intake flow tube calibration system for an aero-engine ground test platform. A predetermined mass flow rate is supplied via an air extraction device, and the actual mass flow rate is measured using a standard air intake flow tube. This result in the local actual flow coefficient. Based on this coefficient, a calibration coefficient is calculated and used to calibrate the sonic nozzle. The theoretical measurements of other flow meters are calculated and compared with the actual values ​​for verification. After the sonic nozzle is calibrated, the standard air intake flow tube can be replaced with the one to be calibrated, serving as a gas flow calibration device for the sonic nozzle method, thereby calibrating other air intake flow tubes. Compared to the traditional method of using regulating valves to adjust flow rate at the engine, this system can correct flow measurement errors to a certain extent, resulting in more accurate data. It is not only reliable, simple, and efficient, but also safer.

[0004] This invention provides an air intake flow pipe calibration system for an aero-engine ground test platform, including an air duct unit and a detection unit; the air duct unit includes: an air intake flow pipe, a buffer chamber, a sonic nozzle, and an air extraction device that are detachably connected in series; the buffer chamber is used to eliminate the direct impact of the airflow from the air intake flow pipe on the airflow inside the sonic nozzle. The detection unit includes: a first pressure component for detecting the stagnation pressure of the gas in the sonic nozzle, a temperature component for detecting the stagnation temperature of the gas in the sonic nozzle, a second pressure component for detecting the static pressure at the outlet of the sonic nozzle, a third pressure component installed on the extraction device for detecting the downstream back pressure of the sonic nozzle, and a data processing module; the data processing module is connected to the first pressure component, the second pressure component, the third pressure component, the temperature component, and the flow calculation module of the inlet flow pipe. After determining that the throat of the sonic nozzle is in a critical flow state based on the detection results of the first, second, and third pressure components, the calibration coefficient of the intake flow pipe to be calibrated is calculated using the formula stored in the data processing module. The formula stored in the data processing module is as follows:

[0005]

[0006] In the formula, The theoretical flow rate of the intake manifold is expressed in kg / s. is the cross-sectional area inside the throat of the sonic nozzle, which is a measured value; The theoretical flow coefficient is a preset value. R is the gas stagnation pressure at the sonic nozzle, Pa, obtained through the first pressure assembly; R is the gas constant, J / (kg×K), obtained through experiments or known data; M is the gas Mach number, obtained through experiments or known data. The stagnation temperature of the gas in the sonic nozzle, K, is obtained through a temperature component. The measured flow rate of the intake flow pipe is kg / s, obtained from the flow calculation module based on the intake flow pipe. This is the calibration coefficient for the intake flow pipe.

[0007] In some embodiments, a standard intake flow pipe is selected as the intake flow pipe of the air passage unit. After the sonic nozzle throat reaches the critical flow state, the output result of the flow calculation module of the standard intake flow pipe is used as... Substitute into the following formula to calculate ;

[0008] The theoretical flow rate of the intake manifold is expressed in kg / s. is the cross-sectional area inside the throat of the sonic nozzle, which is a measured value; This is the theoretical flow coefficient; R is the gas stagnation pressure at the sonic nozzle, in Pa, obtained through the first pressure assembly; R is the gas constant, in J / (mol·K), obtained through experiments or known data; M is the gas Mach number, obtained through experiments or known data. The stagnation temperature of the sonic nozzle gas, K, is obtained through a temperature component.

[0009] In some embodiments, before using the aero-engine ground test bench inlet flow pipe calibration system, an airtightness test is performed with the inlet flow pipe removed: after determining that the sonic nozzle throat is in a critical flow state based on the test results of the first pressure component, the second pressure component, and the third pressure component, if the fluctuation range of the first pressure component, the second pressure component, and the third pressure component all meet the preset requirements within a set time period, then the aero-engine ground test bench inlet flow pipe calibration system is qualified for airtightness and can be used to calibrate the inlet flow pipe; otherwise, the aero-engine ground test bench inlet flow pipe calibration system cannot be used to calibrate the inlet flow pipe.

[0010] In some embodiments, the buffer chamber includes: a lower chamber open at the top, a rectifier plate detachably connected to the top surface of the lower chamber, an upper chamber open at both ends detachably connected to the top surface of the rectifier plate, and a sealing cover detachably connected to the top surface of the upper chamber; the rectifier plate is provided with a plurality of air holes communicating with the upper chamber and the lower chamber; an air intake flow pipe is detachably connected to the upper chamber, and a sonic nozzle is detachably connected to the lower chamber.

[0011] In some embodiments, the air tightness test is performed once each in the state of the buffer chamber with the structure intact, in the state of the buffer chamber with the sealing cover removed, and in the state of the buffer chamber with only the lower chamber. If all three air tightness tests are qualified, the air intake flow pipe calibration system of the aero-engine ground test bench can be used to calibrate the air intake flow pipe; otherwise, the air intake flow pipe calibration system of the aero-engine ground test bench cannot be used to calibrate the air intake flow pipe.

[0012] In some embodiments, the first pressure component includes a first pressure sensor and a first pressure calculation module. The first pressure sensor is installed at the inlet of the sonic nozzle and connected to the first pressure calculation module, which is connected to a data processing module. The first pressure calculation module is used to convert the detection result of the first pressure sensor into the sonic nozzle gas stagnation pressure using a pressure conversion formula. The pressure conversion formula is as follows:

[0013] In the formula, The stagnation pressure of the gas in the sonic nozzle. The result is from the detection of the first pressure sensor. Where M is the specific heat ratio of the gas and M is the Mach number of the gas. M is obtained through experiments or publicly available data; The temperature component includes a temperature sensor and a temperature calculation module. The temperature sensor is installed at the inlet of the sonic nozzle and connected to the temperature calculation module, which in turn is connected to the data processing module. The temperature calculation module converts the sensor's readings into the sonic nozzle's gas stagnation temperature using a temperature conversion formula. The temperature conversion formula is as follows:

[0014] In the formula, Let T be the stagnation temperature of the gas at the sonic nozzle, and T be the temperature detected by the temperature sensor. Where M is the specific heat ratio of the gas and M is the Mach number of the gas. M is obtained through experiments or publicly available data.

[0015] In some embodiments, multiple first pressure sensors are uniformly arranged around the axial direction of the sonic nozzle, and P is the average value of the detection results of all first pressure sensors; multiple temperature sensors are uniformly arranged around the axial direction of the sonic nozzle, and T is the average value of the detection results of all temperature sensors; the second pressure component includes multiple second pressure sensors uniformly arranged around the axial direction of the sonic nozzle, and a second pressure calculation module connecting all second pressure sensors and the data processing module, the second pressure calculation module outputting the average value of the detection results of all second pressure sensors as the static pressure at the outlet of the sonic nozzle to the data processing module; the third pressure component includes multiple third pressure sensors uniformly arranged around the air passage axis of the suction device, and a third pressure calculation module connecting all third pressure sensors and the data processing module, the third pressure calculation module outputting the average value of the detection results of all third pressure sensors as the downstream back pressure of the sonic nozzle to the data processing module.

[0016] In some embodiments, the data processing module stores a critical threshold W. When the ratio of the static pressure at the outlet of the sonic nozzle to the gas stagnation pressure at the sonic nozzle is less than W, and the back pressure downstream of the sonic nozzle is less than the static pressure at the outlet of the sonic nozzle, the data processing module determines that the throat of the sonic nozzle is in a critical flow state. Both the back pressure downstream of the sonic nozzle and the static pressure at the outlet of the sonic nozzle are absolute pressures.

[0017] In the formula, Specific heat ratio of gases, for monatomic gases It is 1.67; for diatomic gases It is 1.4; for polyatomic gases It is 1.3; air It is 1.4.

[0018] In some embodiments, the gas constant R of air is 8.314 J / (mol·K); the gas Mach number M is 1 after the throat of the sonic nozzle is in the critical flow state; the cross-sectional area inside the throat of the sonic nozzle is... The unit is .

[0019] In some embodiments, the air intake flow pipe and the buffer chamber, the buffer chamber and the sonic nozzle, and the sonic nozzle and the extraction device are all connected by flanges and bolts.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention discloses a ground-based test bench air intake flow pipe calibration system. It supplies a predetermined mass flow rate via an air extraction device, calculates the actual mass flow rate using a standard air intake flow pipe, and then calculates the local actual flow coefficient. Based on this coefficient, a calibration coefficient is derived, used to calibrate a sonic nozzle, calculate the theoretical measurement values ​​of other flow meters, and compare and verify them with the actual values. After the sonic nozzle is calibrated, the standard air intake flow pipe can be replaced with the one to be calibrated, serving as a gas flow calibration device for the sonic nozzle method, and subsequently calibrating other air intake flow pipes. Compared to the traditional method of using a regulating valve to adjust the flow rate at the engine, this system can correct flow measurement errors to a certain extent, making the data more accurate. It is not only reliable, simple, and efficient, but also safer. Attached Figure Description

[0021] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the air intake flow pipe calibration system for the ground test bench of an aero-engine according to the present invention.

[0022] In the diagram: 1. Standard inlet flow pipe; 11. Differential pressure transmitter; 2. Buffer chamber; 3. Sonic nozzle; 4. Air extraction device; 5. Computer; 6. First pressure sensor; 7. Second pressure sensor; 8. Third pressure sensor; 9. Temperature sensor; 10. Inlet flow pipe to be calibrated. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] In the description of this invention, it should be understood that the terms "center", "lateral", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this 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. Therefore, they should not be construed as limitations on this invention.

[0025] The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include one or more of that feature.

[0026] The term "sonic nozzle" is also known as a critical flow venturi nozzle.

[0027] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" 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 direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0028] like Figure 1 As shown in an illustrative embodiment of an air intake flow tube calibration system for an aero-engine ground test stand according to the present invention, the air intake flow tube calibration system for an aero-engine ground test stand includes at least: an air duct unit and a detection unit; the air duct unit includes: an air intake flow tube, a buffer chamber 2, a sonic nozzle 3 and an air extraction device 4, which are detachably connected in series; the buffer chamber 2 is used to eliminate the direct impact of the airflow from the air intake flow tube on the airflow inside the sonic nozzle 3. The detection unit includes: a first pressure component for detecting the gas stagnation pressure of the sonic nozzle 3, a temperature component for detecting the gas stagnation temperature of the sonic nozzle 3, a second pressure component for detecting the outlet static pressure of the sonic nozzle 3, a third pressure component installed on the extraction device 4 for detecting the downstream back pressure of the sonic nozzle 3, and a data processing module; the data processing module is connected to the first pressure component, the second pressure component, the third pressure component, the temperature component, and the flow calculation module of the inlet flow pipe; Based on the detection results of the first pressure component, the second pressure component, and the third pressure component, after determining that the throat of the sonic nozzle 3 is in a critical flow state, the calibration coefficient of the intake flow pipe 10 to be calibrated is calculated using the formula stored in the data processing module; the formula stored in the data processing module is as follows:

[0029]

[0030] In the formula, The theoretical flow rate of the intake manifold is expressed in kg / s. is the cross-sectional area inside the throat of the sonic nozzle, which is a measured value; The theoretical flow coefficient is a preset value. R is the gas stagnation pressure at the sonic nozzle, Pa, obtained through the first pressure assembly; R is the gas constant, J / (kg×K), obtained through experiments or known data; M is the gas Mach number, obtained through experiments or known data. The stagnation temperature of the gas in the sonic nozzle, K, is obtained through a temperature component. The measured flow rate of the intake flow pipe is kg / s, obtained from the flow calculation module based on the intake flow pipe. This is the calibration coefficient for the intake flow pipe.

[0031] The inlet flow pipe is a differential pressure flow meter, consisting of a bell-shaped inlet and a straight pipe section. A differential pressure transmitter 11 is installed on the pipe, and the transmitter 11 is connected to the flow calculation module. The flow calculation module calculates Q using the following formula:

[0032] In the formula, Let A be the flow coefficient of the intake flow pipe, and A be the internal cross-sectional area of ​​the straight section of the intake flow pipe. The measured value is from the differential pressure transmitter. A represents the gas density, obtained through experiments or publicly available data. The unit for A is preferably square millimeters.

[0033] The rated flow rate of the sonic nozzle is within the range of the intake flow pipe.

[0034] Calibration of various intake flow rates can be achieved by replacing different intake flow pipes and different sonic nozzles.

[0035] This system can accurately determine the outflow coefficient of the intake flow pipe by calibration. It has a simple structure, is easy to assemble, and has low requirements for the coaxiality of the air passage unit, which helps to improve its assembly and calibration efficiency.

[0036] In some embodiments, a standard intake flow pipe 1 is selected as the intake flow pipe of the airway unit. After the throat of the sonic nozzle 3 is in a critical flow state, the output result of the flow calculation module of the standard intake flow pipe 1 is used as... Substitute into the following formula to calculate ;

[0037] The theoretical flow rate of the intake manifold is expressed in kg / s. is the cross-sectional area inside the throat of the sonic nozzle, which is a measured value; This is the theoretical flow coefficient; R is the gas stagnation pressure at the sonic nozzle, in Pa, obtained through the first pressure assembly; R is the gas constant, in J / (mol·K), obtained through experiments or known data; M is the gas Mach number, obtained through experiments or known data. The stagnation temperature of the sonic nozzle gas, K, is obtained through a temperature component.

[0038] In some embodiments, before using the aero-engine ground test bench inlet flow pipe calibration system, an airtightness test is performed with the inlet flow pipe removed: based on the test results of the first pressure component, the second pressure component, and the third pressure component, after determining that the throat of the sonic nozzle 3 is in a critical flow state, if the fluctuation range of the first pressure component, the second pressure component, and the third pressure component within a set time period all meet the preset requirements, then the aero-engine ground test bench inlet flow pipe calibration system is qualified for airtightness and can be used to calibrate the inlet flow pipe; otherwise, the aero-engine ground test bench inlet flow pipe calibration system cannot be used to calibrate the inlet flow pipe.

[0039] In some embodiments, the buffer chamber 2 includes: a lower chamber open at the top, a rectifier plate detachably connected to the top surface of the lower chamber, an upper chamber open at both ends detachably connected to the top surface of the rectifier plate, and a sealing cover detachably connected to the top surface of the upper chamber; the rectifier plate is provided with a plurality of air holes communicating with the upper chamber and the lower chamber; an air intake flow pipe is detachably connected to the upper chamber, and a sonic nozzle 3 is detachably connected to the lower chamber.

[0040] In some embodiments, the air tightness test is performed once each in the state of the buffer chamber 2 with the structure intact, in the state of the buffer chamber 2 with the sealing cover removed, and in the state of the buffer chamber 2 with only the lower chamber. If all three air tightness tests are qualified, the air intake flow pipe calibration system of the aero-engine ground test bench can be used to calibrate the air intake flow pipe; otherwise, the air intake flow pipe calibration system of the aero-engine ground test bench cannot be used to calibrate the air intake flow pipe.

[0041] In some embodiments, the first pressure component includes a first pressure sensor 6 and a first pressure calculation module. The first pressure sensor 6 is installed at the inlet of the sonic nozzle 3 and connected to the first pressure calculation module, which is connected to a data processing module. The first pressure calculation module is used to convert the detection result of the first pressure sensor 6 into the gas stagnation pressure of the sonic nozzle 3 using a pressure conversion formula. The pressure conversion formula is as follows:

[0042] In the formula, The stagnation pressure of the gas in the sonic nozzle. The result is from the detection of the first pressure sensor. Where M is the specific heat ratio of the gas and M is the Mach number of the gas. M is obtained through experiments or publicly available data; The temperature component includes a temperature sensor 9 and a temperature calculation module. The temperature sensor 9 is installed at the inlet of the sonic nozzle 3 and connected to the temperature calculation module, which is connected to the data processing module. The temperature calculation module converts the detection result of the temperature sensor 9 into the gas stagnation temperature of the sonic nozzle 3 using a temperature conversion formula. The temperature conversion formula is as follows:

[0043] In the formula, Let T be the stagnation temperature of the gas at the sonic nozzle, and T be the temperature detected by the temperature sensor. Where M is the specific heat ratio of the gas and M is the Mach number of the gas. M is obtained through experiments or publicly available data.

[0044] In some embodiments, multiple first pressure sensors 6 are uniformly arranged around the axial direction of the sonic nozzle 3, and P is the average value of the detection results of all first pressure sensors 6; multiple temperature sensors 9 are uniformly arranged around the axial direction of the sonic nozzle 3, and T is the average value of the detection results of all temperature sensors 9; the second pressure assembly includes multiple second pressure sensors 7 uniformly arranged around the axial direction of the sonic nozzle 3, and a second pressure calculation module connecting all second pressure sensors 7 and the data processing module. The second pressure calculation module outputs the average value of the detection results of all second pressure sensors 7 as the static pressure at the outlet of the sonic nozzle 3 to the data processing module; the third pressure assembly includes multiple third pressure sensors 8 uniformly arranged around the air passage axis of the suction device 4, and a third pressure calculation module connecting all third pressure sensors 8 and the data processing module. The third pressure calculation module outputs the average value of the detection results of all third pressure sensors 8 as the downstream back pressure of the sonic nozzle 3 to the data processing module.

[0045] The flow calculation module, the first pressure calculation module, the second pressure calculation module, the third pressure calculation module, the temperature calculation module, and the data processing module are all mounted on the same computer.

[0046] The above steps reduce the impact of airway pressure and temperature gradients on the accuracy of test results and improve calibration precision.

[0047] In some embodiments, the data processing module stores a critical threshold W. When the ratio of the static pressure at the outlet of the sonic nozzle 3 to the gas stagnation pressure at the outlet of the sonic nozzle 3 is less than W, and the back pressure downstream of the sonic nozzle 3 is less than the static pressure at the outlet of the sonic nozzle 3, the data processing module determines that the throat of the sonic nozzle 3 is in a critical flow state. Both the back pressure downstream of the sonic nozzle 3 and the static pressure at the outlet of the sonic nozzle 3 are absolute pressures.

[0048] In the formula, Specific heat ratio of gases, for monatomic gases It is 1.67; for diatomic gases It is 1.4; for polyatomic gases It is 1.3; air It is 1.4.

[0049] In some embodiments, the gas constant R of air is 8.314 J / (mol·K); the gas Mach number M is 1 after the throat of the sonic nozzle is in the critical flow state; the cross-sectional area inside the throat of the sonic nozzle is... The unit is .

[0050] In some embodiments, the air intake flow pipe and the buffer chamber 2, the buffer chamber 2 and the sonic nozzle 3, and the sonic nozzle 3 and the extraction device 4 are all connected by a flange and a plurality of bolts distributed around the flange axis. Through the description of several embodiments of the air intake flow pipe calibration system for an aero-engine ground test stand according to the present invention, it can be seen that the embodiments of the air intake flow pipe calibration system for an aero-engine ground test stand according to the present invention have at least the following advantages: This invention discloses a ground-based test bench air intake flow pipe calibration system. It supplies a predetermined mass flow rate via an air extraction device, calculates the actual mass flow rate using a standard air intake flow pipe, and then calculates the local actual flow coefficient. Based on this coefficient, a calibration coefficient is derived, used to calibrate a sonic nozzle, calculate the theoretical measurement values ​​of other flow meters, and compare and verify them with the actual values. After the sonic nozzle is calibrated, the standard air intake flow pipe can be replaced with the one to be calibrated, serving as a gas flow calibration device for the sonic nozzle method, and subsequently calibrating other air intake flow pipes. Compared to the traditional method of using a regulating valve to adjust the flow rate at the engine, this system can correct flow measurement errors to a certain extent, making the data more accurate. It is not only reliable, simple, and efficient, but also safer.

[0051] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0052] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A calibration system for the air intake flow pipe of an aero-engine ground test stand, characterized in that, It includes an airway unit and a detection unit; the airway unit includes: an intake flow pipe, a buffer chamber, a sonic nozzle and an air extraction device that are detachably connected in series; the buffer chamber is used to eliminate the direct impact of the airflow from the intake flow pipe on the airflow inside the sonic nozzle. The detection unit includes: a first pressure component for detecting the stagnation pressure of the gas in the sonic nozzle, a temperature component for detecting the stagnation temperature of the gas in the sonic nozzle, a second pressure component for detecting the static pressure at the outlet of the sonic nozzle, a third pressure component installed on the extraction device for detecting the downstream back pressure of the sonic nozzle, and a data processing module; the data processing module is connected to the first pressure component, the second pressure component, the third pressure component, the temperature component, and the flow calculation module of the inlet flow pipe. After determining that the throat of the sonic nozzle is in a critical flow state based on the detection results of the first, second, and third pressure components, the calibration coefficient of the intake flow pipe to be calibrated is calculated using the formula stored in the data processing module. The formula stored in the data processing module is as follows: In the formula, The theoretical flow rate of the intake manifold is expressed in kg / s. is the cross-sectional area inside the throat of the sonic nozzle, which is a measured value; The theoretical flow coefficient is a preset value. R is the gas stagnation pressure at the sonic nozzle, Pa, obtained through the first pressure assembly; R is the gas constant, J / (kg×K), obtained through experiments or known data; M is the gas Mach number, obtained through experiments or known data. The stagnation temperature of the gas in the sonic nozzle, K, is obtained through a temperature component. The measured flow rate of the intake flow pipe is kg / s, obtained from the flow calculation module based on the intake flow pipe. This is the calibration coefficient for the intake flow pipe.

2. The aero-engine ground test bench inlet flow pipe calibration system according to claim 1, characterized in that, A standard intake flow pipe is selected as the intake flow pipe for the airway unit. After the sonic nozzle throat reaches the critical flow state, the output result of the flow calculation module of the standard intake flow pipe is used as... Substitute into the following formula to calculate ; The theoretical flow rate of the intake manifold is expressed in kg / s. is the cross-sectional area inside the throat of the sonic nozzle, which is a measured value; This is the theoretical flow coefficient; R is the gas stagnation pressure at the sonic nozzle, in Pa, obtained through the first pressure assembly; R is the gas constant, in J / (mol·K), obtained through experiments or known data; M is the gas Mach number, obtained through experiments or known data. The stagnation temperature of the sonic nozzle gas, K, is obtained through a temperature component.

3. The aero-engine ground test stand inlet flow pipe calibration system according to claim 1, characterized in that, Before using the aero-engine ground test bench inlet flow pipe calibration system, an airtightness test is performed with the inlet flow pipe removed. Based on the test results of the first, second, and third pressure components, after determining that the sonic nozzle throat is in a critical flow state, if the fluctuation range of the first, second, and third pressure components within the set time period meets the preset requirements, then the aero-engine ground test bench inlet flow pipe calibration system is qualified for airtightness and can be used to calibrate the inlet flow pipe; otherwise, the aero-engine ground test bench inlet flow pipe calibration system cannot be used to calibrate the inlet flow pipe.

4. The aero-engine ground test bench inlet flow pipe calibration system according to claim 3, characterized in that, The buffer chamber includes: a lower air chamber with an open top, a rectifier plate detachably connected to the top surface of the lower air chamber, an upper air chamber with an open top and bottom detachably connected to the top surface of the rectifier plate, and a sealing cover detachably connected to the top surface of the upper air chamber; the rectifier plate is provided with multiple air holes connecting the upper air chamber and the lower air chamber; an air intake flow pipe is detachably connected to the upper air chamber, and a sonic nozzle is detachably connected to the lower air chamber.

5. The aero-engine ground test bench inlet flow pipe calibration system according to claim 4, characterized in that, The air tightness test is performed once each in the following states: with the buffer chamber structure intact, with the buffer chamber sealed, and with only the lower chamber present. If all three air tightness tests are passed, the air intake flow pipe calibration system of the aero-engine ground test bench can be used to calibrate the air intake flow pipe; otherwise, the air intake flow pipe calibration system of the aero-engine ground test bench cannot be used to calibrate the air intake flow pipe.

6. The aero-engine ground test bench inlet flow pipe calibration system according to claim 1, characterized in that, The first pressure component includes a first pressure sensor and a first pressure calculation module. The first pressure sensor is installed at the inlet of the sonic nozzle and connected to the first pressure calculation module, which is connected to a data processing module. The first pressure calculation module is used to convert the detection result of the first pressure sensor into the gas stagnation pressure of the sonic nozzle using a pressure conversion formula. The pressure conversion formula is as follows: In the formula, The stagnation pressure of the gas in the sonic nozzle. The result is from the detection of the first pressure sensor. Where M is the specific heat ratio of the gas and M is the Mach number of the gas. M is obtained through experiments or publicly available data; The temperature component includes a temperature sensor and a temperature calculation module. The temperature sensor is installed at the inlet of the sonic nozzle and connected to the temperature calculation module, which in turn is connected to the data processing module. The temperature calculation module converts the sensor's readings into the sonic nozzle's gas stagnation temperature using a temperature conversion formula. The temperature conversion formula is as follows: In the formula, Let T be the stagnation temperature of the gas at the sonic nozzle, and T be the temperature detected by the temperature sensor. Where M is the specific heat ratio of the gas and M is the Mach number of the gas. M is obtained through experiments or publicly available data.

7. The aero-engine ground test bench inlet flow pipe calibration system according to claim 6, characterized in that, Multiple first pressure sensors are evenly arranged around the axis of the sonic nozzle, with P being the average value of the detection results of all first pressure sensors; multiple temperature sensors are evenly arranged around the axis of the sonic nozzle, with T being the average value of the detection results of all temperature sensors; the second pressure component includes multiple second pressure sensors evenly arranged around the axis of the sonic nozzle, and a second pressure calculation module connecting all second pressure sensors and the data processing module. The second pressure calculation module outputs the average value of the detection results of all second pressure sensors as the static pressure at the outlet of the sonic nozzle to the data processing module; the third pressure component includes multiple third pressure sensors evenly arranged around the axis of the air passage of the suction device, and a third pressure calculation module connecting all third pressure sensors and the data processing module. The third pressure calculation module outputs the average value of the detection results of all third pressure sensors as the downstream back pressure of the sonic nozzle to the data processing module.

8. A calibration system for the air intake flow pipe of an aero-engine ground test stand according to any one of claims 1-7, characterized in that, The data processing module has a critical threshold W in its memory. When the ratio of the static pressure at the outlet of the sonic nozzle to the gas stagnation pressure at the sonic nozzle is less than W, and the back pressure downstream of the sonic nozzle is less than the static pressure at the outlet of the sonic nozzle, the data processing module determines that the throat of the sonic nozzle is in a critical flow state. Both the back pressure downstream of the sonic nozzle and the static pressure at the outlet of the sonic nozzle are absolute pressures. In the formula, Specific heat ratio of gases, for monatomic gases It is 1.67; for diatomic gases It is 1.4; for polyatomic gases It is 1.3; air It is 1.

4.

9. The aero-engine ground test bench inlet flow pipe calibration system according to claim 8, characterized in that, The gas constant R of air is 8.314 J / (mol·K); the Mach number M of the gas is 1 after the throat of the sonic nozzle reaches the critical flow state; the cross-sectional area inside the throat of the sonic nozzle... The unit is .

10. A calibration system for the air intake flow pipe of an aero-engine ground test stand according to any one of claims 1-7, characterized in that, The air inlet flow pipe and buffer chamber, the buffer chamber and sonic nozzle, and the sonic nozzle and extraction device are all connected by flanges and bolts.

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