A method of determining internal fuel return flow in an aeroengine

Abstract

The application provides a method for determining the internal fuel return flow of an aero-engine, comprising: determining a plurality of rotating speed state points of a centrifugal pump; forming a flow set according to a minimum fuel flow value, a maximum fuel flow value and a plurality of flow values selected in an interval of the centrifugal pump; adjusting the valve opening degree of the centrifugal pump in the range of the minimum fuel flow value and the maximum fuel flow value to obtain the inlet fuel pressure, the outlet fuel pressure and the fuel flow of the centrifugal pump; repeating the above steps to obtain a plurality of characteristic curve groups of the pressure difference and the fuel flow under the rotating speed state points; measuring the inlet fuel pressure, the outlet fuel pressure and the rotating speed of the centrifugal pump to obtain the inlet-outlet pressure difference and the centrifugal pump flow during the engine operation process in which the centrifugal pump return port is normally opened; and obtaining the internal fuel return flow of the engine fuel system according to the centrifugal pump fuel flow of the engine during the operation and the fuel flow to the combustion chamber.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of gas turbine engines, and particularly relates to a method for determining the internal fuel return flow of an aero-engine. BACKGROUND

[0002] As one of the important cold sources of a gas turbine engine, fuel is often used to cool high-temperature components or high-temperature gases, so during the design of the engine cooling scheme, the temperature and flow of the fuel that can be used for cooling need to be mastered, and then the temperature and flow distribution of the fuel inside the fuel system need to be mastered. The fuel system of a gas turbine engine is composed of pumps, pipes, valves, regulators and other structures, and its main functions are to supply fuel to the engine combustion chamber and to provide high-pressure fuel to the actuating cylinder of the engine to drive the engine actuators to act. During engine operation, the fuel flowing to the engine combustion chamber is controlled by the regulating system in terms of flow, and finally enters the combustion chamber for combustion; and the high-pressure fuel flowing to the actuating cylinder of the engine needs to return to the engine inlet after completing the driving function, and continue to circulate inside the fuel system. Among them, this part of the fuel circulating inside the fuel system has a certain temperature rise due to the work of the pump, thereby increasing the overall fuel temperature of the system and reducing the cooling quality of the fuel, and even possibly exceeding the maximum tolerance temperature of the pump, regulator and other elements, thereby affecting the safe operation of the engine.

[0003] To evaluate the impact of internal return oil on the temperature level of the engine fuel system, the temperature and flow data of the internal return oil of the engine fuel system under typical conditions need to be obtained. Under normal circumstances, the test data of the return oil temperature is easy to obtain, while the data of the return oil flow is difficult to measure.

[0004] The fuel flowmeter has strict requirements on the installation space. On the one hand, the fuel flowmeter is relatively large in size, and on the other hand, the fuel flowmeter needs to be installed on a relatively long straight pipe section, while the space arrangement of the engine fuel pipeline is very compact and there are few long straight pipe sections. Therefore, based on the existing engine fuel pipeline arrangement, it is difficult to directly install a flowmeter to measure the return oil flow of the engine fuel system.

[0005] Therefore, in order to obtain the return oil flow of the internal return oil of the engine fuel system under typical conditions, the existing technology changes the structure of the return oil pipeline of the engine, leads the return oil pipeline to an external space away from the engine, and then installs a flowmeter to measure the return oil flow.

[0006] However, the technical scheme changes the oil return pipeline structure of the engine, the resistance characteristics of the pipeline change, the oil return flow also changes, and the test results will have a large deviation; the adjustment of the oil return pipeline structure will affect the performance of the engine fuel system and also bring the risk of engine operation safety. In addition, in order to install the flowmeter, the fuel pipeline is greatly changed, the test modification period is usually long, and the test work efficiency is low. SUMMARY

[0007] The purpose of the present application is to provide a method for determining the internal fuel return flow of an aero-engine to solve or alleviate at least one problem in the background art.

[0008] The technical scheme of the present application is: a method for determining the internal fuel return flow of an aero-engine, the method comprising:

[0009] determining a plurality of rotational speed state points of a centrifugal pump through which the internal fuel return flows during engine operation;

[0010] determining a minimum fuel flow value and a maximum fuel flow value of the centrifugal pump, selecting a plurality of flow values at a predetermined interval between the minimum fuel flow value and the maximum fuel flow value to form a flow set comprising the minimum fuel flow value, the maximum fuel flow value and the plurality of flow values;

[0011] blocking the oil return port of the centrifugal pump, and carrying out a differential pressure-flow characteristic test of the centrifugal pump, adjusting the valve opening degree after the centrifugal pump in the range of the minimum fuel flow value and the maximum fuel flow value, and obtaining the inlet fuel pressure, the outlet fuel pressure and the fuel flow of the centrifugal pump;

[0012] adjusting the rotational speed of the centrifugal pump to any rotational speed state point to obtain the differential pressure between the outlet fuel pressure and the inlet fuel pressure and the fuel flow characteristic curve of the centrifugal pump at the rotational speed state point;

[0013] repeating the above steps to obtain a plurality of centrifugal pump outlet fuel pressure and inlet fuel pressure differential pressure and fuel flow characteristic curve groups at the rotational speed state points;

[0014] measuring the inlet fuel pressure, the outlet fuel pressure and the operating rotational speed of the centrifugal pump during engine operation with the centrifugal pump oil return port normally open, obtaining the inlet and outlet differential pressure during operation according to the inlet fuel pressure and the outlet fuel pressure during engine operation, and obtaining the centrifugal pump flow during operation according to the operating rotational speed and the characteristic curve group;

[0015] According to the centrifugal pump fuel flow during engine operation minus the fuel flow to the combustion chamber, the internal fuel return flow of the engine fuel system is obtained.

[0016] Further, the minimum fuel flow value and the maximum fuel flow value of the centrifugal pump are obtained according to the instruction manual of the centrifugal pump or through test.

[0017] Further, a plurality of flow values are selected at a predetermined interval between the minimum fuel flow value and the maximum fuel flow value to form a flow set comprising the minimum fuel flow value, the maximum fuel flow value and the plurality of flow values; when adjusting the valve opening degree of the centrifugal pump, the flow values in the flow set are used to control the flow of the centrifugal pump.

[0018] Further, the inlet fuel pressure and the outlet fuel pressure of the centrifugal pump are measured by a pressure gauge.

[0019] Further, the fuel flow of the centrifugal pump is measured by a flow meter.

[0020] Further, in the characteristic curve, the abscissa is the differential pressure and the ordinate is the fuel flow.

[0021] Further, when the operating speed of the engine does not correspond to the differential pressure and flow characteristic curve, the fuel flow corresponding to the operating speed is obtained by interpolating the characteristic curve group.

[0022] Compared with the prior art, the method of the present application can quickly and accurately obtain the fuel return flow information inside the engine fuel system without the need to install a flow meter, avoid the need to modify the engine fuel system pipeline, avoid the influence on the performance of the engine fuel system, greatly reduce the workload, and at the same time solve the problem of engine operation safety caused by the adjustment of the fuel return pipeline structure. The method of calculating the fuel flow by the speed of the centrifugal pump and the differential pressure between the inlet and outlet is simple and reliable, and can meet the engineering design requirements. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions provided by the present application, the following will briefly introduce the drawings. Obviously, the drawings described below are only some embodiments of the present application.

[0024] Figure 1 It is a schematic diagram of the flow path of a typical engine fuel system.

[0025] Figure 2 It is a flow chart of the method for determining the internal fuel return amount of an engine provided by the present application.

[0026] Figure 3 It is a schematic diagram of the differential pressure-flow characteristic test of the centrifugal pump in the present application.

[0027] Figure 4 It is a relationship curve between the differential pressure and the fuel flow of the centrifugal pump at a specific speed in the present application.

[0028] Figure 5The relationship curve between the differential pressure of the inlet and outlet of the centrifugal pump and the fuel flow under different rotating speeds in the present application.

[0029] Figure 6 The schematic diagram for obtaining the flow by the measured differential pressure in the present application.

[0030] Figure 7 The relationship curve between the differential pressure of the inlet and outlet of the centrifugal pump and the fuel flow under different rotating speeds in an embodiment of the present application.

[0031] Figure 8 The schematic diagram for obtaining the flow by the measured differential pressure in the embodiment of the present application. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the embodiments of the present application will be described in more detail below with reference to the drawings in the embodiments of the present application.

[0033] As shown in Figure 1 , it is a schematic diagram of the flow path of a typical engine fuel system. The fuel from the fuel tank enters the engine first, mixes with the return oil inside the engine, then enters the centrifugal pump to complete the first step of pressure increase, and then enters the gear pump to complete the second step of pressure increase. The adjusting device measures the fuel flow into the combustion chamber according to the demand of the combustion chamber, and the remaining fuel returns to the front of the centrifugal pump through the actuator mechanism. When the engine state is fixed, the fuel flow of each branch of the engine fuel system is fixed, and the fuel flow W 计量 to the combustion chamber can be measured by the adjusting device, while the return oil flow inside the fuel system cannot be directly measured at present.

[0034] In order to obtain the internal return oil flow of the engine under the typical working state, solve the problem of engine operation safety caused by the adjustment of the return oil pipeline structure, and the problem of measurement result deviation caused by the modification of the engine return oil pipeline, as shown in Figure 1 , the present application provides a method for quickly measuring the internal return oil flow of the engine fuel system. The method selects the fuel centrifugal pump through which the engine internal return oil flows, carries out the flow test of the fuel pump, obtains the differential pressure-flow characteristics under the rotating speed of the fuel pump, tests the rotating speed and the pump inlet and outlet differential pressure of the fuel pump under the working state of the engine, and obtains the return oil flow by the interpolation method, as shown in Figure 2 .

[0035] Specifically, the method provided by the present application comprises the following steps:

[0036] 1) According to the actual working rotating speed range of the centrifugal pump in the engine running process, a series of rotating speed state points are determined, forming N rotating speed values R min , R1, R2…R max .

[0037] 2) According to the instruction manual of the centrifugal pump, determine the minimum fuel flow rate W of the centrifugal pump at different rotating speeds min and the maximum fuel flow rate W max If it is not specified in the manual, it can be obtained by trial and error; take several flow rate values at certain intervals from the minimum fuel flow rate W min to the maximum fuel flow rate W max , forming M flow rate values W min , W1, W2, …, W max .

[0038] 3) As shown in Figure 3 , block the oil return port of the centrifugal pump, and carry out differential pressure-flow characteristic test of the centrifugal pump, install pressure gauges at the inlet and outlet of the centrifugal pump to measure the inlet and outlet fuel pressures, control the fuel flow rate by adjusting the valve opening, and measure the fuel flow rate with a flowmeter. When adjusting, refer to the M flow rate values for adjustment.

[0039] 4) Adjust the rotating speed of the centrifugal pump to a certain rotating speed state point, adjust the inlet pressure to the normal operating inlet pressure range of the engine, control the output fuel flow rate of the centrifugal pump to the specified value through the adjusting device, and record the actual inlet pressure P in , outlet pressure P out and fuel flow rate W.

[0040] The differential pressure between the inlet and outlet of the centrifugal pump measured in the above process is taken as the abscissa, and the measured fuel flow rate of the centrifugal pump is taken as the ordinate, to draw the curve of the flow rate of the centrifugal pump changing with the differential pressure between the inlet and outlet at the rotating speed state point, as shown in Figure 4 .

[0041] Under normal circumstances, the curve is in the form of: as the differential pressure between the inlet and outlet increases, the fuel flow rate through the centrifugal pump gradually decreases.

[0042] 5) Similarly, adjust the rotating speed of the centrifugal pump to the next rotating speed state point, repeat steps 4 and 5, and the differential pressure-flow characteristic curves at N rotating speed state points can be obtained, which finally become a differential pressure-flow characteristic curve group, as shown in Figure 5 .

[0043] 6) During the operation of the engine (i.e. the oil return port of the centrifugal pump is normally opened), measure the inlet and outlet fuel pressures of the centrifugal pump and the rotating speed to calculate the differential pressure between the inlet and outlet. In this application, the curve group obtained from step 6 is processed by image method, and the fuel flow rate W through the centrifugal pump can be obtained, as shown in Figure 6 .

[0044] If the engine state has no corresponding differential pressure-flow characteristic curve, an interpolation method can be used to obtain the fuel flow.

[0045] 7) The fuel flow W obtained from step 6 is the total fuel flow through the centrifugal pump, and the fuel flow W to the combustion chamber is subtracted from the total fuel flow to obtain the internal fuel flow of the engine fuel system. 计量 (the data is recorded during engine operation), the internal fuel flow of the engine fuel system can be obtained.

[0046] Generally, the more the number of differential pressure-flow characteristic curves obtained in step 5, the more accurate the fuel flow obtained by step 7, but it also brings more workload, therefore, in engineering practice, the number of curves, i.e. the number of speed state points, needs to be given by weighing the workload and the accuracy of the result analysis according to the work cycle.

[0047] As shown in Figure 7 and Figure 8 , for example, in this embodiment of the present application, for the test requirement of the internal hot fuel flow of an engine, first, according to the actual working speed range of the centrifugal pump during engine operation, the speed includes several state points of 5500r / min, 6500r / min, 7500r / min, 8800r / min, and 10000r / min, component tests of the centrifugal pump are carried out, and a set of differential pressure-flow characteristic curves of the centrifugal pump as shown in Figure 6 is formed.

[0048] If the actual operating speed of the centrifugal pump during engine operation is 7500r / min, and the actual inlet and outlet pressure difference is 2MPa, and the fuel flow to the combustion chamber is 1.0L / s. Using the image method, the fuel flow through the centrifugal pump at a speed of 7500r / min and an inlet and outlet pressure difference of 2Mpa, i.e. 1.6L / s, can be obtained. According to the fuel flow to the combustion chamber, i.e. 1.0L / s, and the total fuel flow through the centrifugal pump, the internal fuel flow of the fuel system can be obtained, i.e. 0.6L / s.

[0049] Compared with the prior art, the method of the present application can quickly and accurately obtain the internal fuel flow information of the engine fuel system without the need to install a flowmeter, avoid the need to modify the pipeline of the engine fuel system, avoid the impact on the performance of the engine fuel system, greatly reduce the workload, and at the same time, solve the problem of engine operation safety caused by the adjustment of the internal fuel flow pipeline structure. The method of calculating the fuel flow through the centrifugal pump by the speed and the inlet and outlet pressure difference is simple and reliable, and can meet the engineering design requirements.

[0050] The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method of determining internal fuel flowback flow in an aeroengine, characterized in that, The method comprises: Step 1, determining a plurality of rotating speed state points of the centrifugal pump through which the internal return oil flows during engine operation; Step 2, determining minimum and maximum fuel flow values of the centrifugal pump; Step 3, blocking the return oil port of the centrifugal pump, adjusting the valve opening degree of the centrifugal pump within the range of the minimum and maximum fuel flow values, and installing a device for obtaining the inlet fuel pressure, outlet fuel pressure and fuel flow of the centrifugal pump; Step 4, adjusting the rotating speed of the centrifugal pump to any rotating speed state point and the inlet pressure of the centrifugal pump to the inlet pressure range of normal engine operation, to obtain the differential pressure between the outlet fuel pressure and the inlet fuel pressure and the fuel flow characteristic curve of the centrifugal pump at the rotating speed state point; Step 5, repeating Step 4 to obtain a plurality of differential pressure between the outlet fuel pressure and the inlet fuel pressure and fuel flow characteristic curves of the centrifugal pump at the rotating speed state points; Step 6, during engine operation with the normal opening of the return oil port of the centrifugal pump, measuring the inlet fuel pressure, outlet fuel pressure and operating rotating speed of the centrifugal pump, obtaining the differential pressure between the inlet and outlet pressures during operation according to the inlet and outlet pressures during engine operation, and obtaining the fuel flow of the centrifugal pump during operation according to the operating rotating speed and the characteristic curve group; Step 7, obtaining the return oil flow in the internal fuel system of the engine by subtracting the fuel flow to the combustion chamber from the fuel flow of the centrifugal pump during engine operation.

2. The method of determining internal fuel flow in an aeroengine of claim 1, wherein, The minimum and maximum fuel flow values of the centrifugal pump are obtained according to the instruction manual of the centrifugal pump or through experiments.

3. The method of determining internal fuel flow in an aeroengine of claim 1, wherein, A plurality of flow values are selected at predetermined intervals between the minimum and maximum fuel flow values to form a flow set comprising the minimum and maximum fuel flow values and the plurality of flow values; When adjusting the valve opening degree of the centrifugal pump, the flow values in the flow set are used to control the fuel flow of the centrifugal pump.

4. The method of determining internal fuel flow in an aeroengine of claim 1, wherein, The inlet and outlet fuel pressures of the centrifugal pump are measured by pressure gauges.

5. The method of determining internal fuel flow in an aeroengine of claim 3, wherein, The fuel flow of the centrifugal pump is measured by a flow meter.

6. The method of determining internal fuel flow in an aeroengine of claim 1, wherein, In the characteristic curve, the abscissa is the differential pressure and the ordinate is the fuel flow.

7. The method of determining internal fuel flow in an aeroengine of claim 1, wherein, When the operating rotating speed of the engine does not correspond to the differential pressure and flow characteristic curve, the fuel flow corresponding to the operating rotating speed is obtained by interpolating the characteristic curve group.

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