A method for calibrating main fuel of aircraft engines based on pressure difference before and after the nozzle

Abstract

The present application belongs to the field of engine test technology, and specifically relates to a method for calibrating the main fuel of an aircraft engine based on the pressure difference before and after the nozzle. The method includes step S1, installing a nozzle front pressure sensor on the main fuel pipeline to measure the pressure before the nozzle; step S2, obtaining the nozzle front and rear pressure difference under each main fuel given value and the fuel value given by the main fuel metering valve through ground tests; step S3, determining the actual main fuel flow value based on the relationship between the nozzle front and rear pressure difference and the flow recorded in the engine logbook; step S4, determining the relationship between the fuel value and the actual main fuel flow value, and writing it into the controller. The present application improves the fuel supply accuracy of the engine after the main pump is replaced, reduces the risk of surging caused by excessive fuel supply, and the risk of forward matching and flameout caused by deviation from the minimum fuel quantity.

Description

Technical Field

[0001] The present application belongs to the technical field of engine testing, and specifically relates to a method for calibrating the main fuel of an aircraft engine based on the pressure difference before and after a nozzle. Background Art

[0002] In order to ensure the acceleration / deceleration of the engine, it is necessary to calibrate the main fuel flow according to the fuel flow meter installed on the test bench when the engine leaves the factory, and adjust the fuel flow calibration line of the main fuel pump regulator (referred to as "main pump") in the controller, so as to achieve the matching of the actual fuel supply and the required fuel supply under the condition of the whole machine. However, after the main pump of the field engine is replaced, since it is not feasible to install a fuel flow meter, the controller can only use its factory calibration line for control.

[0003] Generally speaking, fuel flow meters are not installed on field engines for reliability, safety, usage requirements and costs. In addition, there is no space for installing flow meters under installation conditions. Therefore, in the prior art, after the main pump is replaced in the field, the controller can only use its factory calibration line for control. After installation, there are certain differences in the factors affecting the oil supply accuracy such as the main pump return oil pressure compared to the factory inspection, resulting in certain differences in the actual oil output of the main pump. The engine may accelerate too quickly, causing surge, or the minimum oil volume may deviate, causing mismatch / stall. Summary of the invention

[0004] In order to solve one of the above problems, the present application provides an aircraft engine main fuel calibration method based on the pressure difference before and after the nozzle. Through the measurable parameters under installation, the calibration of the main pump fuel supply is realized, thereby ensuring the accuracy of the engine main fuel flow supply.

[0005] The main fuel calibration method of an aircraft engine based on the pressure difference before and after the nozzle provided in this application mainly includes:

[0006] Step S1, installing a pre-nozzle pressure sensor on the main fuel pipeline to measure the pre-nozzle pressure;

[0007] Step S2: Obtain the pressure difference ΔP before and after the nozzle at each main fuel given value through ground test f The fuel value L given by the main fuel metering valve m实际 ;

[0008] Step S3: Based on the nozzle front and rear pressure difference ΔP recorded in the engine log f Relationship with flow Q, determine the actual main fuel flow value Q 实际 ;

[0009] Step S4: Determine the fuel value L m实际 and the actual main fuel flow value Q 实际and write it to the controller.

[0010] Preferably, after step S4, the method further comprises:

[0011] Step S5: Determine the main fuel flow value Q 实际 Is the difference between the main fuel set value in this state and the main fuel set value in this state within the error range? If not, re-execute steps S2 to S4 based on the main fuel set value given by the controller until the main fuel flow value Q 实际 The difference from the main fuel set value in this state falls within the error range.

[0012] Preferably, in step S2, when the ground test is performed, a plurality of speed test stands are stopped to correspond to a plurality of different main fuel set values.

[0013] Preferably, in step S2, the pressure difference ΔP before and after the nozzle is f The nozzle front pressure measured by the nozzle front pressure sensor is formed by subtracting the nozzle rear pressure measured by the conventional measuring point on the aircraft. The nozzle front pressure sensor is arranged on the test joint on the main fuel pipeline in front of the nozzle.

[0014] Preferably, the test connector is connected to a sensor for pressure measurement when in use, and after the measurement is completed, the test connector is sealed by a plug.

[0015] Preferably, in step S3, the pressure difference ΔP before and after the nozzle is f The relationship with the flow rate Q is measured by a flow meter and a pressure sensor during the bench factory test and recorded in the engine log book.

[0016] Preferably, the upper limit of the error range is any value from 5 to 10 kg / h, and the lower limit of the error range is any value from -10 to -5 kg / h.

[0017] The key point of this application is to obtain the nozzle pressure difference △P before and after the engine under the installation condition when the engine leaves the factory f The relationship between the fuel flow rate Q and the fuel flow rate Q is such that the field can obtain the actual fuel flow rate through the measured pressure difference before and after the nozzle.

[0018] This application provides a means for calibrating the main pump of an outfield engine. When the main pump of an outfield engine is replaced, the main pump is calibrated through the existing onboard measurement parameters and the measurement parameters that can be achieved by installing sensors, thereby improving the fuel supply accuracy of the engine after the main pump is replaced, reducing the risk of surging caused by excessive fuel supply, and the risk of engine mismatch and flameout caused by deviation from the minimum fuel quantity. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1The present invention is a flow chart of a preferred embodiment of a method for calibrating the main fuel of an aircraft engine based on the pressure difference before and after the nozzle. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the implementation of this application clearer, the technical scheme in the implementation of this application will be described in more detail in combination with the drawings in the implementation of this application. In the drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The described implementation is a part of the implementation of this application, not all of the implementations. The implementation described below with reference to the drawings is exemplary and is intended to be used to explain this application, and cannot be understood as a limitation on this application. Based on the implementation in this application, all other implementations obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The implementation of this application is described in detail below in combination with the drawings.

[0021] The present application provides a method for calibrating the main fuel of an aircraft engine based on the pressure difference before and after the nozzle, such as Figure 1 As shown, it mainly includes:

[0022] Step S1, installing a pre-nozzle pressure sensor on the main fuel pipeline to measure the pre-nozzle pressure;

[0023] Step S2: Obtain the pressure difference ΔP before and after the nozzle at each main fuel given value through ground test f The fuel value L given by the main fuel metering valve m实际 ;

[0024] Step S3: Based on the nozzle front and rear pressure difference ΔP recorded in the engine log f Relationship with flow Q, determine the actual main fuel flow value Q 实际 ;

[0025] Step S4: Determine the fuel value L m实际 and the actual main fuel flow value Q 实际 and write it to the controller.

[0026] It should be noted that according to the fuel flow calculation formula (1), the fuel flow is proportional to the fuel nozzle area, the square root of the pressure difference before and after the nozzle, and the square root of the density. Under a certain engine state, the fuel temperature after the main pump does not change much, and the square root of the fuel density does not change much and can be ignored. In addition, the nozzle area A 喷嘴 The change is not significant and can be ignored. After simplification, under the same engine state, the fuel flow rate is positively correlated with the square root of the pressure difference before and after the nozzle.

[0027]

[0028] Where, Q is the fuel flow rate; A 喷嘴 is the fuel nozzle area; ΔP is the pressure difference before and after the nozzle; ρ is the fuel density.

[0029] In addition, for the pressure after the nozzle (P 31 ) will be used to accelerate the fuel supply control, which is a conventional airborne measurement point and can be measured. f ), you can add a test connector to the fuel supply line and connect the sensor when measurement is needed; when not measuring, you can plug it with a plug to prevent fuel leakage, and there is no risk of use.

[0030] In order to reduce the fuel flow calculation error caused by the measurement error of the fuel nozzle area, the pressure difference △P before and after the nozzle can be obtained through the flow meter during the bench factory test. f =(P f -P 31 ) and the fuel flow Q, and record it in the engine logbook. Therefore, this application can perform ground test after replacing the main pump of the field engine to obtain the △P under each given oil volume. f , and the pressure difference △P recorded in the log book f The relationship with the flow rate Q is used to determine the actual fuel flow rate and complete the calibration of the main pump.

[0031] In some optional implementations, after step S4, the method further includes:

[0032] Step S5: Determine the main fuel flow value Q 实际 Is the difference between the main fuel set value in this state and the main fuel set value in this state within the error range? If not, re-execute steps S2 to S4 based on the main fuel set value given by the controller until the main fuel flow value Q 实际 The difference from the main fuel set value in this state falls within the error range.

[0033] It can be understood that in step S2, the main fuel set value is determined by the controller according to the onboard calculation parameters, that is, by the fuel value L written into the controller in step S4. m实际 and the actual main fuel flow value Q 实际 Each main fuel given value corresponds to a nozzle pressure difference △P f The fuel value L given by a main fuel metering valve m实际 Therefore, in step S2, a calibration line is actually formed, and the abscissa is the fuel value L given by the main fuel metering valve m实际, the ordinate is the pressure difference. In step S3, according to the measured pressure difference, the corresponding actual main fuel flow value can be interpolated in the history book, and the ordinate of the calibration line can be replaced by this to obtain the calibration relationship to be written into the controller. With the calibration relationship, the main fuel set value can be obtained again in step S5, and substituted into step S2 to loop through the above process until the difference falls within the difference range. Calibration is completed.

[0034] In some optional embodiments, in step S2, when performing ground testing, the engine stops at multiple speed test benches to correspond to multiple different main fuel set values.

[0035] In some optional embodiments, in step S2, the pressure difference ΔP before and after the nozzle f The nozzle front pressure measured by the nozzle front pressure sensor is formed by subtracting the nozzle rear pressure measured by the conventional measuring point on the aircraft. The nozzle front pressure sensor is arranged on the test joint on the main fuel pipeline in front of the nozzle.

[0036] In some optional implementations, the test connector is connected to a sensor to perform pressure measurement when in use, and after the measurement is completed, the test connector is sealed with a plug.

[0037] In some optional embodiments, the upper limit of the error range is any value from 5 to 10 kg / h, and the lower limit of the error range is any value from -10 to -5 kg / h.

[0038] This application provides a means for calibrating the main pump of an outfield engine. When the main pump of an outfield engine is replaced, the main pump is calibrated through the existing onboard measurement parameters and the measurement parameters that can be achieved by installing sensors, thereby improving the fuel supply accuracy of the engine after the main pump is replaced, reducing the risk of surging caused by excessive fuel supply, and the risk of engine mismatch and flameout caused by deviation from the minimum fuel quantity.

[0039] Although the present application has been described in detail above with general descriptions and specific implementation schemes, it is obvious to those skilled in the art that some modifications or improvements may be made to the present application. Therefore, these modifications or improvements made without departing from the spirit of the present application all fall within the scope of protection claimed in the present application.

Claims

1. A method for calibrating the main fuel of an aircraft engine based on the pressure difference before and after the nozzle, characterized in that: include: Step S1, installing a pre-nozzle pressure sensor on the main fuel pipeline to measure the pre-nozzle pressure; Step S2: Obtain the pressure difference ΔP before and after the nozzle at each main fuel given value through ground test f The fuel value L given by the main fuel metering valve m实际 ; Step S3: Based on the nozzle front and rear pressure difference ΔP recorded in the engine log f Relationship with flow Q, determine the actual main fuel flow value Q 实际 ; Step S4: Determine the fuel value L m实际 and the actual main fuel flow value Q 实际 and write it into the controller; Step S5: Determine the main fuel flow value Q 实际 Is the difference between the main fuel set value in this state and the main fuel set value in this state within the error range? If not, re-execute steps S2 to S4 based on the new main fuel set value given by the controller until the main fuel flow value Q 实际 The difference from the main fuel set value in this state falls within the error range.

2. The method for calibrating the main fuel of an aircraft engine based on the pressure difference before and after the nozzle according to claim 1, characterized in that: In step S2, when performing the ground test, the vehicle stops at a plurality of speed test stands to correspond to a plurality of different main fuel set values.

3. The method for calibrating the main fuel of an aircraft engine based on the pressure difference before and after the nozzle according to claim 1, characterized in that: In step S2, the pressure difference before and after the nozzle △P f The nozzle front pressure measured by the nozzle front pressure sensor is formed by subtracting the nozzle rear pressure measured by the conventional measuring point on the aircraft. The nozzle front pressure sensor is arranged on the test joint on the main fuel pipeline in front of the nozzle.

4. The method for calibrating the main fuel of an aircraft engine based on the pressure difference before and after the nozzle according to claim 3, characterized in that: The test connector is connected to a sensor to measure pressure when in use, and after the measurement is completed, the test connector is sealed by a plug.

5. The method for calibrating the main fuel of an aircraft engine based on the pressure difference before and after the nozzle according to claim 1, characterized in that: In step S3, the pressure difference ΔP before and after the nozzle f The relationship with the flow rate Q is measured by a flow meter and a pressure sensor during the bench factory test and recorded in the engine log book.

6. The method for calibrating the main fuel of an aircraft engine based on the pressure difference before and after the nozzle according to claim 1, characterized in that: The upper limit of the error range is any value from 5 to 10 kg / h, and the lower limit of the error range is any value from -10 to -5 kg / h.

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