Method for calibrating air inlet flow pipe of aero-engine

Abstract

The invention belongs to the technical field of aero-engines, and particularly relates to an aero-engine air inlet flow pipe calibration method, which comprises the following steps of: measuring internal flow field parameters in a standard flow measurement section through a plurality of sensors, and calculating theoretical air mass flow qm1TH of the standard flow measurement section; the actual air mass flow qm1ACT of the standard flow measuring section is measured through a negative pressure air suction type flow standard device; the outflow coefficient of the standard flow measurement section is calculated; connecting a calibrated engine air inlet flow pipe A2 to the front of the standard flow measuring section, and connecting the engine to the rear of the standard flow measuring section; calculating the actual air mass flow of the standard flow measurement section, and taking the actual air mass flow as the actual air mass flow qm4ACT of the calibrated engine air inlet flow pipe A2; and the outflow coefficient of the calibrated engine air inlet flow pipe A2 is calculated based on the theoretical air mass flow qm4TH and the actual air mass flow qm4ACT of the calibrated engine air inlet flow pipe A2.

Description

Technical Field

[0001] The present application belongs to the technical field of aircraft engines, and in particular relates to a method for calibrating an aircraft engine intake flow tube. Background Art

[0002] The engine intake air flow is an important parameter for evaluating the performance of aircraft engines. Only by obtaining accurate engine air flow values ​​can the performance, safety and other technical indicators of the engine be accurately evaluated. The technical indicators of the engine are directly related to the technical indicators of military aircraft and their combat effectiveness. Generally, in engine whole machine tests and compressor tests, if the tester directly inhales air from the atmosphere, an intake flow tube is often used to measure the inlet air flow. The total pressure, total temperature and static pressure parameters are measured at the flow tube measurement section to calculate the flow. When it is necessary to accurately measure the air flow of the flow tube, the influence of the boundary layer on the inner wall of the pipe must be considered to obtain its outflow coefficient C, so as to use this coefficient to offset the influence of the boundary layer on the flow measurement. At present, the design, manufacture and use of intake flow tubes have not yet formed a consistent specification. There is a lack of research and control on the factors that affect the measurement accuracy of the flow tube, resulting in poor consistency in the flow measurement results of different flow tubes. Therefore, the intake flow tube needs to be calibrated to determine its accurate outflow coefficient.

[0003] The calibration method of the engine intake flow tube currently developed is usually to obtain the outflow coefficient of the flow tube by measuring the boundary layer of the intake flow tube and calculating according to the theoretical model. There is also a method of using the CFD theoretical analysis method to calculate the flow distribution in the flow tube to obtain the outflow coefficient. The most direct and reliable calibration method at present is to calibrate the engine flow tube by experimental means with the help of the engine intake flow real flow calibration device to obtain the accurate outflow coefficient of the flow tube. The current intake flow real flow calibration device is mostly set in the intake section of the engine room test bench or the high-altitude test bench, and the air flow passing through the flow tube is accurately measured by a gas flow meter with known accuracy, so as to realize the real flow comparison calibration. Patent CN109506744B "A method for calibrating the air flow of a venturi nozzle in an aircraft engine whole machine test" discloses a method for calibrating the air flow of a venturi nozzle in an aircraft engine whole machine test. A parallel combination critical flow venturi nozzle group calibration device is installed in the intake pressure stabilizer of the high-altitude platform to complete the real flow calibration of the intake flow tube of the engine whole machine. Summary of the invention

[0004] In order to solve the above problems, the present application provides 1. a method for calibrating an intake flow tube of an aircraft engine, characterized in that:

[0005] Step S1: After the negative pressure suction flow standard device (3) is connected to the standard flow measurement section (1), the engine intake flow pipe A1 (2) is connected before the standard flow measurement section (1);

[0006] Step S2: Measure the internal flow field parameters in the standard flow measurement section (1) through multiple sensors and calculate the theoretical air mass flow rate q of the standard flow measurement section (1). m1TH , and measure the actual air mass flow rate q of the standard flow measurement section (1) through the negative pressure suction type flow standard device (3). m1ACT ;

[0007] Step S3: Calculate the discharge coefficient of the standard flow measurement section (1) based on the theoretical air mass flow rate q m1TH and the actual air mass flow rate q m1ACT of the standard flow measurement section (1).

[0008] Step S4: Connect the engine intake flow pipe A2 (4) to be calibrated before the standard flow measurement section (1), and connect the engine after the standard flow measurement section (1).

[0009] Step S5: Test the internal flow field parameters in the standard flow measurement section (1) through multiple sensors, calculate the actual air mass flow rate of the standard flow measurement section (1) based on the discharge coefficient, and use it as the actual air mass flow rate q of the engine intake flow pipe A2 (4) to be calibrated. m4ACT ;

[0010] Step S6: Measure the internal flow field parameters of the engine intake flow pipe A2 (4) to be calibrated through multiple sensors, and calculate the theoretical air mass flow rate q m4TH ;

[0011] Step S7: Calculate the discharge coefficient of the engine intake flow pipe A2 (4) to be calibrated based on the theoretical air mass flow rate q m4TH and the actual air mass flow rate q m4ACT of the engine intake flow pipe A2 (4) to be calibrated.

[0012] Preferably, the standard flow measurement section (1) is axially provided with at least 3 measurement sections, and the measurement sections are circumferentially arranged with total temperature and total pressure parameter measurement probes and wall static pressure measurement points for measuring the internal flow field parameters flowing through the standard flow measurement section (1).

[0013] Preferably, the internal flow field parameters include total pressure, total static pressure difference and total temperature.

[0014] Preferably, the calculation formula for the theoretical air mass flow rate q m is:

[0015]

[0016] where C is the discharge coefficient, dimensionless; d is the diameter of the flow pipe measurement section, in2 ; g c is the gravitational acceleration constant, ft-lbm / lbf-s 2 ; M air is the molar mass of dry air, lbm / lbmol; P t is the total pressure at the measurement section of the flow tube, lbf / in 2 (psi); q m is the air mass flow rate, lbm / s; R is the universal gas constant, lbf-ft / lb-mol-°R; T is the total temperature at the measurement section of the flow tube, °R; ΔP is the total static pressure difference at the measurement section of the flow tube, lbf / in 2 (psi); κ is the specific heat ratio of air, dimensionless.

[0017] Preferably, the standard flow measurement section (1) includes: a cylinder body (1-2), a front mounting flange (1-1) located at the front end of the cylinder body (1-2), a rear mounting flange (1-6) located at the rear end of the cylinder body (1-2), a universal mounting seat (1-3) provided on the cylinder body (1-2) for installing sensors, a circumferential static pressure measurement assembly (1-4) provided on the cylinder body (1-2), a laser velocity measurement observation window (1-5), an axial static pressure measurement assembly (1-7), a total temperature test probe (1-8), and a total static pressure test probe (1-9).

[0018] Preferably, the deviation of the diameter of any cross-section of the cylinder body (1-2) from the average diameter shall not be greater than 0.05%.

[0019] Preferably, the theoretical air mass flow rate q of the standard flow measurement section (1) m1TH The calculation formula further includes: is the air velocity of the 1-standard flow measurement section measured by the laser velocity measurement system (LDV)

[0020] q m1TH = AρV 1 ;

[0021] wherein, A is the cross-sectional area of the standard flow measurement section (1); ρ is the air density; V 1 is the air velocity of the standard flow measurement section measured by the laser velocity measurement system (LDV).

[0022] Preferably, the laser emitted by the laser velocity measurement system passes through the laser velocity measurement observation window (1-5) and then passes through the inside of the standard flow measurement section (1), and then passes through the opposite laser velocity measurement observation window (1-5) and enters the LDV receiver to read the air velocity inside the standard flow measurement section (1).

[0023] Preferably, the installation interfaces of the total temperature test probe (1-8) and the total static pressure test probe (1-9) are kept consistent for interchangeable installation positions.

[0024] The advantages of this application include:

[0025] 1) It ensures the consistency between the calibration environment of the intake air flow tube and the actual working environment, eliminating the need for secondary correction and improving the accuracy of the calibration results.

[0026] 2) By means of the actual flow transfer method, it ensures the consistency of the calibration results of the intake air flow tubes of the same type of engine, enabling performance comparison between the intake air flow tubes of the same type of engine.

[0027] 3) The standard flow measurement section can be reused multiple times, is convenient to modify, and saves the cost of batch calibration of the intake air flow tubes of the same type of engine.

[0028] 4) It realizes the direct in-situ calibration of the engine intake air flow tube during the engine whole-machine or component test, shortening the calibration cycle and improving the calibration efficiency. Description of the Drawings

[0029] Figure 1 is the flow chart of the calibration method for the engine intake air flow tube.

[0030] Figure 2 is the lateral schematic diagram of the main components of the standard flow measurement section.

[0031] Figure 3 is the axial schematic diagram of the main components of the standard flow measurement section.

[0032] Figure 4 is the schematic diagram of the layout of the actual flow calibration test for the standard flow measurement section.

[0033] Figure 5 is the schematic diagram of the layout of the actual flow calibration test for flow transfer. Detailed Implementation Manner

[0034] To make the technical solutions and their advantages of this application clearer, the technical solutions of this application will be further described clearly and completely below in conjunction with the drawings. It can be understood that the specific embodiments described here are only partial embodiments of this application, which are only used to explain this application and not to limit this application. It should be noted that for the sake of description, only the parts related to this application are shown in the drawings, and other related parts can refer to the usual design. Without conflict, the embodiments in this application and the technical features in the embodiments can be combined with each other to obtain new embodiments.

[0035] In addition, it should be noted that unless otherwise clearly specified and defined, the similar terms such as "installed", "connected", and "linked" used in the description of this application should be understood in a broad sense. For example, the connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can also be the communication inside two components. Those skilled in the art can understand its specific meaning in this application according to the specific situation.

[0036] As Figures 1-5 shown; the engine intake air flow tube calibration method proposed by the present invention mainly obtains the discharge coefficient of the engine flow tube standard device through a flow actual flow calibration device first, and then conducts a flow actual flow calibration test to perform the comparison and transfer of the flow rate, so as to realize the calibration of the intake air flow tube. The devices involved in the invention mainly include a standard flow measurement section (1), an engine intake air flow tube A1 (2), a negative pressure suction type flow standard device (3), and a to-be-calibrated engine intake air flow tube A2 (4).

[0037] The implementation process of this calibration method is as Figure 1 shown.

[0038] Step 1: Design and manufacture a standard flow measurement section

[0039] The standard flow measurement section is a precision-manufactured circular tube type flow standard device, which is matched and designed according to the calibration target flow tube, and there are at least 3 measurement sections arranged axially thereon. The measurement sections are arranged with total temperature and total pressure parameter measurement probes and wall static pressure measurement points in the circumferential direction for measuring the internal flow field parameters of the flowing-through standard device.

[0040] As follows Figure 2 shown, the main structure includes a front mounting flange 1-1, a cylinder 1-2, a universal mounting seat 1-3, a circumferential static pressure measurement assembly 1-4, a laser velocity measurement observation window 1-5, a rear mounting flange 1-6, an axial static pressure measurement assembly 1-7, a total temperature test probe 1-8, and a total static pressure test probe 1-9.

[0041] The front mounting flange 1-1 is a circular ring type flange, which is mainly used to connect with the intake air flow tube, and the flange interface is consistent with the rear flange of the intake air flow tube.

[0042] The cylinder 1-2 is a circular tube type cylinder, and its inner diameter should be the same as the inner diameter of the to-be-calibrated intake air flow tube. During the manufacturing process, the internal flow path size of the cylinder needs to be strictly controlled. At least 4 sections (including the test section) are selected to measure the inner wall diameter, and at least 8 points are measured at each section, avoiding the opening positions, and accurate to two decimal places. The deviation of the diameter of any section of the standard flow measurement section cylinder from the average diameter shall not be greater than 0.05%.

[0043] The general mounting base 1-3 is used to mount the total temperature test probe 1-8, the total static pressure test probe 1-9 and other flow field parameter test instruments, which are arranged on multiple measurement sections. 4 to 6 can be evenly arranged circumferentially on each section.

[0044] The circumferential static pressure measurement assembly 1-4 is 6 to 8 static pressure measurement structures evenly arranged circumferentially along the measurement section, used to measure the circumferential static pressure of the standard flow measurement section (1) and evaluate whether the circumferential pressure distribution of the measurement section of the measurement section is uniform.

[0045] The laser velocity measurement observation window 1-5 is made of high-strength optical glass. The laser emitted by the laser velocity measurement system (LDV) passes through the observation window and then passes through the inside of the standard flow measurement section, and then passes through the opposite observation window and enters the LDV receiver to accurately measure the air velocity in the standard flow measurement section.

[0046] The rear mounting flange 1-6 is a circular flange, mainly used to connect with the negative pressure suction type flow standard device (3) and the aeroengine. The flange interface is designed to match the requirements of the connection between the negative pressure suction type flow standard device (3) and the engine inlet.

[0047] The axial static pressure measurement assembly 1-7 is a group of static pressure measurement structures arranged axially along the surface of the barrel of the standard flow measurement section. A total of 2 groups of axial static pressure measurement assemblies are symmetrically arranged on the barrel 1-2, used to evaluate the pressure distribution along the whole process inside the standard flow measurement section and provide a reference basis for selecting the measurement section.

[0048] The total temperature test probe 1-8 is used to measure the total temperature of the air inside the standard flow measurement section, and uses a PT100 platinum thermal resistance as the temperature sensing element, which is accurately calibrated before installation. The total static pressure test probe 1-9 is used to measure the total pressure and static pressure of the air inside the standard flow measurement section, and is accurately calibrated before installation. The installation interfaces of the total temperature test probe 1-8 and the total static pressure test probe 1-9 are the same and can be installed interchangeably.

[0049] Step 2: Use the negative pressure suction type flow standard device (3) to perform an actual flow calibration on the standard flow measurement section (1) and the engine intake flow pipe A1 (2) to obtain their discharge coefficients.

[0050] The layout of the actual flow calibration test of the standard flow measurement section is as Figure 3 shown. The calibrated engine intake flow pipe A1 (2) is placed at the front end, and the standard flow measurement section (1) is located between the engine intake flow pipe A1 (2) and the negative pressure suction type flow standard device (3). When performing the actual flow calibration test, start the negative pressure suction type flow standard device (3), and the air first enters the engine intake flow pipe A1 (2), and then passes through the standard flow measurement section (1).

[0051] After reaching the steady flow state during the test, measure the total pressure P of the internal flow field in the engine intake air flow pipe A1(2). t2 , the total static pressure difference ΔP 2 , and the total temperature T t2 . First, assume that the discharge coefficient C 2 = 1, and calculate the theoretical air mass flow rate q through the engine intake air flow pipe A1(2) according to formula (1). m2TH .

[0052]

[0053] In the formula:

[0054] C - Discharge coefficient, dimensionless

[0055] d - Diameter of the flow pipe measurement section, in 2

[0056] g c - Gravitational acceleration constant, ft-lbm / lbf-s 2

[0057] M air - Molar mass of dry air, lbm / lbmol

[0058] P t - Total pressure at the flow pipe measurement section, lbf / in 2 (psi)

[0059] q m - Air mass flow rate, lbm / s

[0060] R - Universal gas constant, lbf-ft / lb-mol-°R

[0061] T - Total temperature at the flow pipe measurement section, °R

[0062] ΔP - Total static pressure difference at the flow pipe measurement section, lbf / in 2 (psi)

[0063] κ - Specific heat ratio of air, dimensionless

[0064] At this time, the actual air mass flow rate q of the engine intake air flow pipe A1(2) can be accurately measured by the back-end negative pressure suction type flow standard device (3), and then the discharge coefficient C of the engine intake air flow pipe A1(2) is calculated by the following formula. m2ACT 2 Calculated by the following formula.

[0065]

[0066] ​By changing the flow state of the negative pressure suction type flow standard device (3), the discharge coefficient C of the engine intake flow pipe A1 (2) under different flow states can be obtained. 2 , thus completing the calibration of the engine intake flow pipe A1 (2).

[0067] For the standard flow measurement section (1), two methods can be used to obtain its discharge coefficient C. 1 .

[0068] Method 1: Measure the total pressure, total temperature T t1 , P t1 and the total static pressure difference ΔP 1 of the internal flow field of the standard flow measurement section (1) respectively through the total temperature test probe 1-8 and the total static pressure test probe 1-9. First, assume that the discharge coefficient C 1 =1, and calculate the theoretical air mass flow rate q m1TH passing through the standard flow measurement section (1) according to formula (1).

[0069] At this time, the actual air mass flow rate q m1ACT of the standard flow measurement section (1) can be accurately measured by the negative pressure suction type flow standard device (3) at the back end. Then, the discharge coefficient C 1 of the standard flow measurement section (1) is calculated by formula (3).

[0070]

[0071] By changing the flow state of the negative pressure suction type flow standard device (3), the discharge coefficient C of the standard flow measurement section (1) under different flow states can be obtained. 1 , thus completing the calibration of the standard flow measurement section (1).

[0072] Method 2: Measure the air velocity V 1 of the standard flow measurement section (1) through the laser Doppler velocimeter (LDV). Then, the theoretical air mass flow rate q m1TH of the standard flow measurement section (1) can be calculated by formula (4).

[0073]

[0074] Similarly, the actual air mass flow rate q m1ACT of the standard flow measurement section (1) can be accurately measured by the negative pressure suction type flow standard device (3) at the back end. Then, the discharge coefficient C 1 of the standard flow measurement section (1) is calculated by formula (3). By changing the flow state of the negative pressure suction type flow standard device (3), the discharge coefficient C of the standard flow measurement section (1) under different flow states can be obtained. 1 , thus completing the calibration of the standard flow measurement section (1).

[0075] Step 3: Conduct a calibration test on the engine intake flow tube. Through the flow transfer of the standard flow measurement section (1), the discharge coefficient of the calibrated engine intake flow tube A2 (4) is obtained.

[0076] The layout of the in-situ calibration test for the flow transfer of the standard flow measurement section is as Figure 3 shown. The calibrated engine intake flow tube A2 (4) is placed at the forefront, and the standard flow measurement section (1) is located between the calibrated engine intake flow tube A2 (4) and the aero-engine. When conducting the in-situ calibration test, the rear aero-engine is started, and the air first enters the calibrated engine intake flow tube A2 (4), and then passes through the standard flow measurement section (1).

[0077] Measure the total pressure P t4 , the total static pressure difference ΔP 4 , and the total temperature T t4 of the internal flow field of the calibrated engine intake flow tube A2 (4). First, assume that the discharge coefficient C 4 = 1, and calculate the theoretical air mass flow rate q m4TH passing through the calibrated engine intake flow tube A2 (4) according to formula (1).

[0078] Measure the total pressure, total temperature T t1 , P t1 , and the total static pressure difference ΔP 1 of the internal flow field of the standard flow measurement section (1) through the total temperature test probe 1-8 and the total static pressure test probe 1-9 respectively. The discharge coefficient C 1 has been obtained through the calibration test in step two. Calculate the actual air mass flow rate q m1ACT passing through the standard flow measurement section (1) according to formula (1).

[0079] Since q m4ACT = q m1ACT , the discharge coefficient C 4 of the calibrated engine intake flow tube A2 (4) is calculated through formula (5).

[0080]

[0081] Change the working state of the engine, and the discharge coefficient C 4 of the calibrated engine intake flow tube A2 (4) under different flow states can be obtained, thereby completing the calibration of the calibrated engine intake flow tube A2 (4).

[0082] As described above, it is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims described above.

Claims

1. A method for calibrating an aircraft engine intake flow tube, characterized in that: Step S1: After the negative pressure suction flow standard device (3) is connected to the standard flow measurement section (1), the engine intake flow pipe A1 (2) is connected before the standard flow measurement section (1); Step S2: Measure the internal flow field parameters in the standard flow measurement section (1) through multiple sensors and calculate the theoretical air mass flow q of the standard flow measurement section (1) m1TH The actual air mass flow rate q of the standard flow measurement section (1) is measured by the negative pressure suction flow standard device (3). m1ACT ; Step S3: Theoretical air mass flow rate q passing through the standard flow measurement section (1) m1TH The actual air mass flow rate q m1ACT , calculate the outflow coefficient of the standard flow measurement section (1); Step S4: before connecting the calibrated engine intake flow tube A2 (4) to the standard flow measurement section (1), and after connecting the engine to the standard flow measurement section (1); Step S5: Measure the internal flow field parameters in the standard flow measurement section (1) through multiple sensors, and calculate the actual air mass flow of the standard flow measurement section (1) based on the outflow coefficient, and use it as the actual air mass flow q of the calibrated engine intake flow pipe A2 (4) m4ACT ; Step S6: Measure the internal flow field parameters of the calibrated engine intake flow tube A2 (4) through multiple sensors and calculate the theoretical air mass flow rate q m4TH ; Step S7: Based on the calibrated theoretical air mass flow rate q of the engine intake flow tube A2 (4) m4TH And the actual air mass flow rate q m4ACT Calculate the calibrated engine intake flow tube A2 (4) discharge coefficient.

2. The method for calibrating an aircraft engine intake flow tube according to claim 1, characterized in that: The standard flow measurement section (1) is provided with no less than three measurement sections along the axial direction, and flow field total temperature and total pressure parameter measurement probes and wall surface static pressure measurement points are arranged along the circumferential direction of the measurement sections for measuring internal flow field parameters flowing through the standard flow measurement section (1).

3. The method for calibrating an aircraft engine intake flow tube according to claim 1, characterized in that: The internal flow field parameters include total pressure, total static pressure difference and total temperature.

4. The method for calibrating an aircraft engine intake flow tube according to claim 1, characterized in that: Theoretical air mass flow rate q m The calculation formula is: Where C is the outflow coefficient, dimensionless; d is the flow tube measurement cross-sectional diameter, in 2 ; g c is the gravitational acceleration constant, ft-lbm / lbf-s 2 ;M air is the molar mass of dry air, lbm / lbmol; P t is the total pressure in the flow tube measuring section, lbf / in 2 (psi); q m is the air mass flow rate, lbm / s; R is the universal gas constant, lbf-ft / lb-mol-°R; T is the total temperature of the flow tube measurement section, °R; ΔP is the total static pressure difference of the flow tube measurement section, lbf / in 2 (psi); κ is the specific heat ratio of air, dimensionless.

5. The aircraft engine intake flow tube calibration method according to claim 1, characterized in that: The standard flow measurement section (1) comprises: a cylinder (1-2), a front mounting flange (1-1) located at the front end of the cylinder (1-2), a rear mounting flange (1-6) located at the rear end of the cylinder (1-2), a universal mounting seat (1-3) arranged on the cylinder (1-2) for mounting a sensor, a circumferential static pressure measurement assembly (1-4) arranged on the cylinder (1-2), a laser speed measurement observation window (1-5), an axial static pressure measurement assembly (1-7), a total temperature test probe (1-8) and a total static pressure test probe (1-9).

6. The method for calibrating an aircraft engine intake flow tube according to claim 3, characterized in that: The deviation of the diameter of any cross section of the cylinder (1-2) from the average diameter shall not exceed 0.05%.

7. The method for calibrating an aircraft engine intake flow tube according to claim 5, characterized in that: Theoretical air mass flow rate q of the standard flow measurement section (1) m1TH The calculation formula also includes: for the air flow rate measured by the laser flow velocity measurement system (LDV) 1-standard flow measurement section q m1TH =AρV1; Wherein, A is the cross-sectional area of ​​the standard flow measurement section (1); ρ is the air density; and V1 is the air velocity of the standard flow measurement section measured by the laser velocity measurement system (LDV).

8. The method for calibrating an aircraft engine intake flow tube according to claim 5, characterized in that: The laser emitted by the laser flow velocity measurement system passes through the laser velocity measurement observation window (1-5), passes through the inside of the standard flow measurement section (1), and then passes through the opposite laser velocity measurement observation window (1-5) to enter the LDV receiver to read the air flow velocity in the standard flow measurement section (1).

9. The aircraft engine intake flow tube calibration method according to claim 5, characterized in that: The installation interfaces of the total temperature test probe (1-8) and the total static pressure test probe (1-9) remain consistent and are used to interchange the installation positions.

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