A valve spring relaxation failure life prediction method

Abstract

The application discloses a kind of valve spring relaxation failure life prediction methods, including the simulation model of fuel control system is built by utilizing AMEs im, according to the three-dimensional model of spring in the valve spring parameter of certain type engine fuel control system, linear regression processing is carried out to the stress loss rate and time logarithm relationship of each temperature point, obtain the linear relationship of stress loss rate and time logarithm under each temperature point, by the batch processing mode in AMEs im, set the initial stress of certain valve spring in fuel control system, the system performance obtained under different relaxation degree is compared with the system required performance index, and the relationship of relaxation degree and system performance such as fuel flow, response time etc.is fitted.The influence of spring in simulation system on system performance due to stress relaxation phenomenon can also predict the stress relaxation failure life of valve in system.

Description

Technical Field

[0001] This invention relates to the field of aerospace technology, and in particular to a method for predicting the lifespan of a valve due to spring relaxation failure. Background Technology

[0002] The reliability of fuel control system accessories directly affects an aircraft's technical and tactical performance, lifespan, reliability, and safety. A malfunction can severely impact engine operation and even lead to a major flight accident.

[0003] Chen Hongliang's 2006 paper, "Modeling and Simulation Study of the Fuel Regulation System of X-8 Aero-engine," analyzed the structure of the fuel regulation system and the working principle of the speed regulator of the X-8 aero-engine. Using AMESim's signal library and hydraulic component construction library, he established models of key components and the regulator itself, and conducted simulation analysis on the main characteristics and related parameters of each component. Zhang Dong's 2008 paper, "Modeling, Simulation, and Experimental Verification of the Main Fuel Control System of an Engine," used AMESim software to model the main fuel control system of a certain type of engine. The simulation model effectively reflected the physical model, providing strong theoretical support for the system's design. Regarding the problem of unstable performance of the temperature control system of a certain type of engine, leading to multiple engine overheating incidents during testing, AMESim software was used to simulate and demonstrate two design schemes, successfully obtaining a reasonable and highly feasible design. Wang Lei's 2012 paper, "Fault Diagnosis of Aero-engine Fuel Regulation System," focused on the fault analysis of the electro-hydraulic servo valve, a key actuator in the aero-engine fuel regulation system. He used AMESim software to build its model and simulated its fault mechanism by adjusting the model parameters. The 2011 paper by Sergei Godeiro Fernandes Rabelo Caldas, "Effects of stress relaxation in beta-titanium orthodontic loops," investigated the stress relaxation process of β-titanium springs. They first subjected 90 springs to concentrated pre-bending, then divided them into nine groups. The first group underwent stress relaxation measurements immediately after bending. The other eight groups were measured after continuous loading for varying periods. Stress relaxation curves for each group were obtained, and logarithmic fitting was performed to plot strain rate curves. The 2021 paper by Kong et al., "Reliability modeling-based tolerance design and process parameter analysis considering performance degradation," established an accelerated degradation model to reflect the effects of spring degradation and initial free length. They proposed a tolerance design method based on degradation performance to guide spring improvements. A novel reliability model incorporating parameter fluctuations was proposed, deriving the allowable fluctuation ranges of initial free length deviation and variance, and optimizing process parameters accordingly to improve manufacturing processes.

[0004] In system design, a significant disconnect exists between reliability design analysis and performance design analysis. In performance design, reliability is merely treated as a constraint, while performance design is not adequately reflected in reliability design. Separating system performance design from reliability design makes it difficult to achieve the optimal combination of performance and reliability indicators, resulting in a loss of overall optimality and hindering the advancement of aero-engine fuel control system development technology. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for predicting the lifespan of a valve due to spring relaxation.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for predicting the lifespan of a valve due to spring relaxation includes the following steps;

[0008] Step 1: Use AMEsim to build a simulation model of the fuel control system. The model includes the main fuel metering and regulating device, anti-surge, starting and stopping device, fan compressor guide vane regulating device, minimum pressure limiting device, and main fuel pump control device.

[0009] Step 2: Build a 3D model of the spring according to the valve spring parameters in the fuel control system of a certain type of engine. Import the model into ANSYS, set different temperatures and mesh it, fix the lower end of the spring, and apply a displacement to the upper end of the spring to simulate the initial stress of the spring, with the direction towards the lower end of the spring. Place a stress probe in the spring, and obtain the spring stress change data through simulation calculation.

[0010] Step 3: Perform linear regression on the relationship between stress loss rate and logarithm of time at each temperature point to obtain the linear relationship between stress loss rate and logarithm of time at each temperature point. Then, perform linear fitting on the relationship between relaxation rate and reciprocal of temperature at each temperature, and on the relationship between integral constant and reciprocal of temperature at different temperatures. Finally, obtain the stress relaxation equation for a certain type of spring.

[0011] Step 4: Using the batch processing mode in AMEsim, set the initial stress of a valve spring in the fuel control system to 100%, 90%, 80%, 70%, 60%, and 50% of the design point to simulate the degree of spring relaxation in the valve and obtain the performance of the fuel control system under different relaxation levels.

[0012] Step 5: Compare the system performance under different relaxation levels with the required system performance indicators to determine the spring relaxation limit range when the system fails due to spring relaxation. Within the relaxation failure range, further subdivide the relaxation range and put it into batch processing mode to obtain the performance of the control system under different relaxation levels.

[0013] Step 6: Fit the relationship between the degree of relaxation and system performance, such as fuel flow and response time, to obtain the mathematical relationship between the degree of relaxation of the valve spring and the system performance. Substitute the critical failure index of the system into the relationship to predict the valve spring relaxation failure boundary. Substitute this failure boundary into the spring stress relaxation equation to obtain the spring relaxation failure life.

[0014] Preferably, the main fuel pump control device mainly consists of a booster pump, a main fuel filter, a gear pump, a safety valve, and a return valve. Fuel from the aircraft fuel system enters the booster pump, and the boosted fuel flows through a conduit into the main fuel filter. The filtered fuel then flows through a conduit into the main fuel pump. After metering, the fuel after the main fuel pump flows to the engine combustion chamber. The remaining fuel returns through the return valve and the safety valve. The safety valve and the return valve work together to ensure that the pressure after the pump does not exceed a certain maximum value. When the pressure after the pump is too high, the safety valve opens, allowing the high-pressure fuel after the pump to return through the safety valve, thus reducing the pressure after the pump.

[0015] Preferably, the main fuel metering and regulating device in step one mainly consists of a main fuel electro-hydraulic servo valve, a constant pressure valve, a semi-constant pressure valve, a metering valve, a differential pressure valve, and a shut-off valve. The electronic controller sends a flow regulation signal to control the flow rate. The electro-hydraulic servo valve outputs control oil at a certain pressure and flow rate. The control oil enters the follower piston through the switching valve. By changing the pressure and flow rate of the control oil, the position of the follower piston is controlled. The follower piston controls the rotation of the metering valve to control the opening degree of the metering valve. The opening degree determines the fuel flow rate into the combustion chamber. The follower piston is connected to a displacement sensor, which feeds back the displacement signal to the electronic controller to achieve closed-loop control of the fuel flow rate.

[0016] Preferably, the differential pressure valve ensures a constant pressure difference between the inlet and outlet of the metering valve. When the pressure difference across the metering valve increases, the differential pressure valve moves to the left, increasing the contact area between the fuel in the return valve spring chamber and the fuel behind the metering valve. This leftward movement of the return valve allows more high-pressure fuel after the pump to return to the low-pressure tank, thus reducing the fuel pressure after the pump and maintaining a constant pressure difference across the metering valve. When the pressure difference across the metering valve decreases, the differential pressure valve moves to the right, reducing the contact area between the fuel in the return valve spring chamber and the fuel behind the metering valve. This rightward movement of the return valve reduces the fuel return flow rate after the pump, increasing the fuel pressure after the pump and ensuring a consistent pressure difference across the metering valve. Once the pressure difference is consistent, the fuel flow rate and the metering valve opening become a single function; knowing the metering valve opening allows the determination of the fuel flow rate.

[0017] Preferably, high-pressure oil enters the constant pressure valve and the semi-constant pressure valve after passing through the central oil filter. The constant pressure valve and the semi-constant pressure valve output control oil with constant pressure. By controlling the opening of the constant pressure valve throttle nozzle, the loss of oil flowing through the constant pressure valve is increased or decreased to ensure that the outlet control oil pressure is constant. The control oil with constant pressure flows to the spring chamber of the actuator piston and the main fuel electro-hydraulic servo valve, and together with the electro-hydraulic servo valve, realizes the opening control of the metering valve.

[0018] Preferably, the fan / compressor guide vane adjustment device in step one mainly consists of a fan / compressor guide vane actuator and a fan / compressor guide vane control electro-hydraulic servo valve.

[0019] Preferably, when the fan guide vane angle control signal is issued, the control valve for the fan guide vane controls the output of control oil with a certain flow rate and pressure, and controls the fan guide vane angle by controlling the guide vane actuator. When the control valve for the fan guide vane fails, the fan guide vane angle moves to the fully closed state by the zero bias of the electro-hydraulic servo valve. The displacement sensor is connected to the actuator and feeds the displacement signal back to the electronic controller, forming a closed-loop control of the guide vane actuator position.

[0020] Preferably, the surge relief, shutdown, and starting device in step one mainly consists of a shutdown valve, a shut-off valve, and a shutdown solenoid valve. When the engine starts, stops, or surge occurs, a shutdown signal is sent to the shutdown solenoid valve, which is then activated. Constant pressure oil flows to the lower chamber of the shutdown valve, causing the shutdown valve to move upward. The shut-off valve spring chamber is then connected to the high-pressure oil after the pump, and the shut-off valve moves to the left, shutting off the fuel supply to the combustion chamber. The return valve spring chamber is then connected to the low-pressure chamber, and the return valve moves to the left, allowing the fuel after the pump to flow back to the low-pressure chamber. After the surge disappears, the shutdown solenoid valve is closed, and the entire oil circuit operates normally.

[0021] Preferably, the minimum pressure limiting device in step one mainly consists of a minimum pressure valve, a stop valve, and a return valve.

[0022] Preferably, the minimum pressure valve ensures that the pump downstream pressure is maintained within a certain range when the pump stops. After the stop solenoid valve is turned on, the pump downstream pressure drops, the minimum safety valve moves down, and connects the low-pressure oil circuit. When the pump downstream pressure drops to a certain level, the minimum valve closes the low-pressure oil circuit under the action of the spring force and is no longer connected to the spring cavity of the return oil valve, so that the return oil valve maintains a certain opening and ensures that the pump downstream pressure is consistent.

[0023] The present invention has the following beneficial effects:

[0024] Using the method proposed in this patent, the impact of stress relaxation on system performance of springs in a system can be simulated, and the stress relaxation failure life of valves in the system can also be predicted. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the hydraulic structure of the fuel control system for a certain type of aircraft engine.

[0026] Figure 2 This is a simulation model diagram of an aircraft engine fuel control system.

[0027] Figure 3 This is a 3D model of a differential pressure valve spring.

[0028] Figure 4 This is a diagram showing the stress relaxation of a spring.

[0029] Figure 5 This is a performance diagram of a constant pressure valve.

[0030] Figure 6 This is a performance diagram of a metering valve piston.

[0031] Figure 7 This is a performance diagram of the metering valve.

[0032] Figure 8 This is a performance diagram of the parking valve.

[0033] Figure 9 This is a performance diagram of a valve with minimum pressure.

[0034] Figure 10 This is a diagram showing the performance of the fan guide vanes.

[0035] Figure 11 This is a diagram showing the performance of the compressor guide vanes.

[0036] Figure 12 Performance diagram of a safety valve.

[0037] Figure 13 This is the maximum fuel flow diagram.

[0038] Figure 14 This is a diagram showing the fuel flow rate when the differential pressure valve spring is relaxed.

[0039] Figure 15 Fuel flow diagram for a differential pressure valve spring that is 10-20% relaxed.

[0040] Figure 16 A curve showing the relationship between the pressure differential valve spring relaxation and fuel flow rate.

[0041] Figure 17 This is a block diagram illustrating the working principle of the main fuel pump control device.

[0042] Figure 18 This is a block diagram illustrating the working principle of the main fuel flow metering device.

[0043] Figure 19 This is a block diagram illustrating the working principle of the fan and compressor guide vane adjustment device.

[0044] Figure 20 This is a block diagram illustrating the working principle of the dyspnea relief, shutdown, and start-up devices.

[0045] Figure 21 This is a block diagram illustrating the working principle of the minimum pressure limiting device.

[0046] Figure 22 This is a graph showing the ambient temperature at 90℃. Detailed Implementation

[0047] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0048] Reference Figure 1-22 A method for predicting the lifespan of a valve due to spring relaxation includes the following steps;

[0049] Step 1, according to Figure 1 The diagram shown is a schematic of the hydraulic structure of a certain type of aircraft engine fuel control system. A model can be built using AMEsim. Figure 2 The simulation model of the fuel control system shown includes a main fuel metering and regulating device, a surge relief, starting and stopping device, a fan compressor guide vane regulating device, a minimum pressure limiting device, and a main fuel pump control device.

[0050] The working principles and processes of each device are as follows:

[0051] The main fuel pump control unit mainly consists of a booster pump, a main fuel filter, a gear pump, a safety valve, and a return valve.

[0052] Its working principle block diagram is as follows Figure 17 Fuel from the aircraft fuel system enters the fuel booster pump, and the boosted fuel flows through a conduit to the main fuel filter. The filtered fuel then flows through a conduit to the main fuel pump. After being metered, the fuel from the main fuel pump goes to the engine combustion chamber, and the remaining fuel returns through the return valve and safety valve.

[0053] The safety valve works in conjunction with the return valve to ensure that the pressure after the pump does not exceed a certain maximum value. When the pressure after the pump is too high, the safety valve opens, allowing the high-pressure oil after the pump to return through the safety valve, thereby reducing the pressure after the pump.

[0054] The main fuel metering and regulating device mainly consists of a main fuel electro-hydraulic servo valve, a constant pressure valve, a semi-constant pressure valve, a metering valve, a differential pressure valve, and a shut-off valve.

[0055] Its working principle block diagram is as follows Figure 18As shown, the electronic controller sends a flow regulation signal, controlling the electro-hydraulic servo valve to output control oil at a certain pressure and flow rate. The control oil enters the follower piston through a switching valve. By changing the pressure and flow rate of the control oil, the position of the follower piston is controlled. The follower piston controls the rotation of the metering valve, thus controlling the opening degree of the metering valve. The opening degree determines the fuel flow rate into the combustion chamber. The follower piston is connected to a displacement sensor, which feeds back the displacement signal to the electronic controller to achieve closed-loop control of the fuel flow rate.

[0056] The differential pressure valve ensures a constant pressure difference between the inlet and outlet of the metering valve. When the pressure difference across the metering valve increases, the differential pressure valve moves to the left, increasing the contact area between the fuel in the return valve spring chamber and the fuel behind the metering valve. This further increases the pressure difference, allowing more high-pressure fuel to return to the low-pressure tank after the pump, thus reducing the fuel pressure and maintaining a constant pressure difference. Conversely, when the pressure difference decreases, the differential pressure valve moves to the right, reducing the contact area between the fuel in the return valve spring chamber and the fuel behind the metering valve. This decreases the return flow rate and increases the fuel pressure, ensuring a consistent pressure difference across the metering valve. Once the pressure difference is consistent, the fuel flow rate becomes a single function of the metering valve opening; knowing the metering valve opening allows you to determine the fuel flow rate.

[0057] High-pressure oil enters the constant pressure valve and semi-constant pressure valve after passing through the central oil filter. The constant pressure valve and semi-constant pressure valve output control oil with constant pressure. By controlling the opening of the constant pressure valve throttle nozzle, the loss of oil flowing through the constant pressure valve is increased or decreased to ensure that the outlet control oil pressure is constant. The control oil with constant pressure flows to the spring chamber of the actuator piston and the main fuel electro-hydraulic servo valve, and together with the electro-hydraulic servo valve, realizes the opening control of the metering valve.

[0058] The fan / compressor guide vane adjustment device mainly consists of a fan / compressor guide vane actuator and a fan / compressor guide vane control electro-hydraulic servo valve.

[0059] Its working principle block diagram is as follows Figure 19 As shown, the fan guide vane angle control signal is issued, controlling the electro-hydraulic servo valve to output control oil at a certain flow rate and pressure. This oil, in turn, controls the guide vane actuator to control the fan guide vane angle. When the electro-hydraulic servo valve fails, the zero-bias operation of the valve causes the fan guide vane angle to move towards the fully closed state. A displacement sensor is connected to the actuator, feeding back the displacement signal to the electronic controller, forming a closed-loop control of the guide vane actuator position. The compressor guide vane adjustment device operates on a similar principle to the fan guide vane adjustment device.

[0060] The suffocation relief, shutdown, and starting device mainly consists of a shutdown valve, a shutdown valve, and a shutdown solenoid valve.

[0061] Its working principle and structural block diagram are as follows: Figure 20As shown, when the engine starts, stops, or surge occurs, a stop signal is sent to the stop solenoid valve. The stop solenoid valve is activated, and constant pressure oil flows to the lower chamber of the stop valve, causing the stop valve to move upward. The shut-off valve spring chamber is connected to the high-pressure oil after the pump, and the shut-off valve moves to the left, stopping the fuel supply to the combustion chamber. The return valve spring chamber is connected to the low-pressure side, and the return valve moves to the left, allowing the fuel after the pump to flow back to the low-pressure side. After the surge disappears, the stop solenoid valve is closed, and the entire fuel circuit operates normally.

[0062] The minimum pressure limiting device mainly consists of a minimum pressure valve, a stop valve, and a return valve.

[0063] The working principle block diagram of the minimum pressure limiting device is as follows: Figure 21 As shown, the minimum pressure valve ensures that the pump downstream pressure is maintained within a certain range when the pump stops. After the stop solenoid valve is turned on, the pump downstream pressure drops, the minimum safety valve moves down, and connects the low-pressure oil circuit. When the pump downstream pressure drops to a certain level, the minimum valve closes the low-pressure oil circuit under the action of the spring force and is no longer connected to the spring cavity of the return oil valve, so that the return oil valve maintains a certain opening and ensures that the pump downstream pressure is consistent.

[0064] Step 2: Build a 3D model of the spring according to the valve spring parameters in the fuel control system of a certain type of engine. Import the model into ANSYS, set different temperatures and mesh it. Fix the lower end of the spring in ANSYS Workbench, and apply a constraint condition (displacement) to the upper end of the spring to simulate the initial stress of the spring, with the direction towards the lower end of the spring. The specific displacement information is shown in the figure. Place a stress probe in the spring, and obtain the spring stress change data through simulation calculation.

[0065] Step 3: In the 3D spring model built in ANSYS in Step 2, set the ambient thermal conditions to 20℃, 90℃, and 125℃, and the simulation time to 3.6 × 10⁻⁶. 7 s, taking 90℃ as an example, the temperature situation is as follows Figure 22 As shown, linear regression was performed on the stress loss rate versus the logarithm of time at each temperature point to obtain a linear relationship between the stress loss rate and the logarithm of time at each temperature. Linear fitting was then performed on the relaxation rate versus the reciprocal of temperature at each temperature, and on the integral constant versus the reciprocal of temperature at different temperatures. Finally, the stress relaxation equation for a certain type of spring was obtained.

[0066] Step 4: Using the batch processing mode in AMEsim, set the initial stress of a valve spring in the fuel control system to 100%, 90%, 80%, 70%, 60%, and 50% of the design point to simulate the degree of spring relaxation in the valve and obtain the performance of the fuel control system under different relaxation levels.

[0067] Step 5: Compare the system performance under different relaxation levels with the required system performance indicators to determine the spring relaxation limit range when the system fails due to spring relaxation. Within the relaxation failure range, further subdivide the relaxation range and put it into batch processing mode to obtain the performance of the control system under different relaxation levels.

[0068] Step Six: Fit the relationship between the degree of relaxation and system performance, such as fuel flow rate and response time, to derive the mathematical relationship between the valve spring relaxation degree and system performance. Substitute the system's critical failure index into the relationship to predict the valve spring relaxation failure boundary. Substitute this failure boundary into the spring stress relaxation equation to obtain the spring relaxation failure life.

[0069] Experimental Example 1: The advantages of this invention can be further illustrated by the following simulation experiment:

[0070] 1. Simulation Object and Performance Indicators

[0071] like Figure 2 As shown in the diagram, based on the hydraulic structure schematic of a certain type of aircraft engine fuel control system, an AMEsim simulation model of the fuel control system is built, and its performance indicators are as follows:

[0072] 1) Constant pressure valve: The outlet servo oil pressure of the constant pressure valve is 2.2±0.1MPa, and the outlet servo oil pressure of the semi-constant pressure valve is 1.1±0.05MPa.

[0073] 2) Differential pressure valve: The differential pressure of the differential pressure valve is determined to be 0.9±0.05MPa.

[0074] 3) Shut-off valve: The opening pressure of the shut-off valve is 1.3±0.05MPa.

[0075] 4) Minimum pressure valve: The minimum pressure limit of the minimum pressure valve is 3.2±0.1MPa.

[0076] 5) Safety valve: The opening pressure of the safety valve is 11.76±0.1MPa.

[0077] 6) Dynamic characteristics of the follow-up device: The total actuation time of the metering valve follow-up piston, fan guide vane actuator, and high-pressure compressor actuator is 1±0.1s.

[0078] 7) Dynamic characteristics of the anti-dyne and dynene device: The dynene relief time after stopping does not exceed 0.2s.

[0079] 8) Fuel pump technical parameters: Fuel metering can start from 120 kg / h and supply fuel according to the actual metered value. When the main fuel pump speed is 100%, the fuel flow rate of the main fuel pump regulator should be greater than 8540 kg / h. The error should not exceed 5%.

[0080] 2. Simulation results, construction as follows Figure 3 The three-dimensional model of the differential pressure valve spring shown is used to simulate the spring stress change according to the above steps. Figure 4 As shown. The stress relaxation equation for the differential pressure valve spring is obtained by fitting.

[0081]

[0082] like Figures 5-13 As shown, the performance of the constructed model conforms to the actual system performance indicators. Taking the spring relaxation of the differential pressure valve as an example, following the above steps, the initial spring stress of the differential pressure valve in the model is changed to simulate the spring relaxation phenomenon. The simulation conditions are given as follows: the gear pump speed is 5917 r / min, the piston displacement signal is given as follows: 0 mm from 0 to 10 s, a step signal of 15 mm is given as follows: 10 to 20 s, and a step signal of 29.6 mm is given as follows: The fuel flow change is shown in the figure. Figure 14 As shown. Further simulations were conducted with a relaxation level of 10-20%, yielding the fuel flow rate change as shown. Figure 15 As shown. The curve of fitting relaxation degree versus fuel flow rate is as follows. Figure 16 As shown, the mathematical model for the fuel flow rate and the degree of relaxation of the differential pressure valve is as follows:

[0083] Q = -2586x + 8614

[0084] Substituting the critical failure flow rate of 8113 kg / h into the above formula, we obtain a failure relaxation boundary of 19.4%. From the principle of the fuel control system, the mathematical expression for fuel flow rate is:

[0085]

[0086] In the formula, Q represents the actual volumetric flow rate of the liquid passing through the slide valve window;

[0087] μ - Flow coefficient of the slide valve;

[0088] A - The flow area determined by the valve opening degree is a function of the valve displacement;

[0089] ρ - Liquid density, typically 780 kg / m³ for aviation fuel. 3 ;

[0090] P q - Oil pressure before the throttle window;

[0091] p h - The oil pressure after the throttling window.

[0092] The force balance equation of the differential pressure valve under steady-state conditions is shown in the following equation.

[0093]

[0094] In the formula Δp - Measuring the pressure difference across the valve;

[0095] D yc -Diameter of the differential pressure valve;

[0096] F - Differential pressure valve spring force;

[0097] K yc - Pressure differential valve spring stiffness coefficient;

[0098] Δx yc -Compression of the differential pressure valve spring.

[0099] From equations 1 and 2, we can derive the relationship between the flow rate of the metering valve and the spring force of the differential pressure valve.

[0100]

[0101] Substituting the model parameters and the failure flow rate of 8113 kg / h into the above formula, the calculated failure spring force is 34.5 N and the relaxation rate is 19.8%, which basically matches the critical failure relaxation rate obtained from the fitting. Substituting the critical failure relaxation rate and the normal operating temperature of 90℃ into the formula, it can be seen that under normal operating conditions, the differential pressure valve spring will experience relaxation failure after 258 hours of use.

[0102] 3. Results Analysis

[0103] Simulation results show that the method proposed in this patent can simulate the impact of stress relaxation on system performance of springs in the system, and can also predict the stress relaxation failure life of valves in the system.

[0104] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for predicting the lifespan of a valve due to spring slack, characterized in that: Includes the following steps; Step 1: Use AMEsim to build a simulation model of the fuel control system. The model includes the main fuel metering and regulating device, anti-surge, starting and stopping device, fan compressor guide vane regulating device, minimum pressure limiting device, and main fuel pump control device. Step 2: Build a 3D model of the spring according to the valve spring parameters in the fuel control system of a certain type of engine. Import the model into ANSYS, set different temperatures and divide the mesh, fix the lower end of the spring, and apply a displacement to the upper end of the spring to simulate the initial stress of the spring, with the direction towards the lower end of the spring; place stress probes in the spring and obtain the spring stress change data through simulation calculation. Step 3: Perform linear regression on the relationship between stress loss rate and logarithm of time at each temperature point to obtain the linear relationship between stress loss rate and logarithm of time at each temperature point; perform linear fitting on the relationship between relaxation rate and reciprocal of temperature at each temperature, and on the relationship between integral constant and reciprocal of temperature at different temperatures; finally obtain the stress relaxation equation of a certain type of spring. Step 4: Using the batch processing mode in AMEsim, set the initial stress of a valve spring in the fuel control system to 100%, 90%, 80%, 70%, 60%, and 50% of the design point to simulate the degree of spring relaxation in the valve and simulate the performance of the fuel control system under different degrees of relaxation. Step 5: Compare the system performance under different relaxation levels with the required system performance indicators to obtain the spring relaxation limit range when the system fails due to spring relaxation. Within the relaxation failure range, further subdivide the relaxation range and put it into batch processing mode to obtain the performance of the control system under different relaxation levels. Step 6: Fit the relationship between the degree of relaxation and system performance, such as fuel flow and response time, to obtain the mathematical relationship between the degree of relaxation of the valve spring and the system performance. Substitute the critical failure index of the system into the relationship to predict the valve spring relaxation failure boundary. Substitute this failure boundary into the spring stress relaxation equation to obtain the spring relaxation failure life. The main fuel metering and regulating device in step one consists of a main fuel electro-hydraulic servo valve, a constant pressure valve, a semi-constant pressure valve, a metering valve, a differential pressure valve, and a shut-off valve. The electronic controller sends a flow regulation signal to control the flow rate. The electro-hydraulic servo valve outputs control oil at a certain pressure and flow rate. The control oil enters the follower piston through the switching valve. The position of the follower piston is controlled by changing the pressure and flow rate of the control oil. The follower piston controls the rotation of the metering valve to control the opening degree of the metering valve. The opening degree determines the flow rate of fuel into the combustion chamber; The follow-up piston is connected to a displacement sensor, which feeds the displacement signal back to the electronic controller to achieve closed-loop control of fuel flow. The differential pressure valve ensures a constant pressure difference between the inlet and outlet of the metering valve. When the pressure difference across the metering valve increases, the differential pressure valve moves to the left, increasing the contact area between the fuel in the return valve spring chamber and the fuel behind the metering valve. This causes the return valve to move to the left, allowing more high-pressure fuel from the pump to return to the low-pressure tank via the return valve. Conversely, when the pressure difference across the metering valve decreases, the differential pressure valve moves to the right, reducing the contact area between the fuel in the return valve spring chamber and the fuel behind the metering valve. This reduces the return flow rate of fuel after the pump and increases the fuel pressure after the pump. Once the pressure difference is consistent, the fuel flow rate and the metering valve opening become a single function; knowing the metering valve opening allows you to determine the fuel flow rate.

2. The method for predicting the lifespan of a valve due to spring relaxation according to claim 1, characterized in that: The main fuel pump control unit consists of a booster pump, a main fuel filter, a gear pump, a safety valve, and a return valve. Fuel from the aircraft fuel system enters the booster pump, and the boosted fuel flows through a conduit into the main fuel filter. The filtered fuel then flows through a conduit into the main fuel pump. After metering, the fuel from the main fuel pump flows into the engine combustion chamber. The remaining fuel returns through the return valve and the safety valve. The safety valve and the return valve work together to ensure that the pressure after the pump does not exceed a certain maximum value. When the pressure after the pump is too high, the safety valve opens, allowing the high-pressure fuel after the pump to return through the safety valve, thereby reducing the pressure after the pump.

3. The method for predicting the lifespan of a valve due to spring relaxation according to claim 1, characterized in that: High-pressure oil enters the constant pressure valve and semi-constant pressure valve after passing through the central oil filter. The constant pressure valve and semi-constant pressure valve output control oil with constant pressure. By controlling the opening of the constant pressure valve throttle nozzle, the loss of oil flowing through the constant pressure valve is increased or decreased to ensure that the outlet control oil pressure is constant. The control oil with constant pressure flows to the spring chamber of the actuator piston and the main fuel electro-hydraulic servo valve, and together with the electro-hydraulic servo valve, realizes the opening control of the metering valve.

4. The method for predicting the lifespan of a valve due to spring relaxation according to claim 1, characterized in that: The fan and compressor guide vane adjustment device in step one consists of a fan / compressor guide vane actuator and a fan / compressor guide vane control electro-hydraulic servo valve.

5. The method for predicting the lifespan of a valve due to spring relaxation according to claim 4, characterized in that: When the fan guide vane angle control signal is sent, the electro-hydraulic servo valve controlling the fan guide vane outputs control oil with a certain flow rate and pressure. This oil controls the fan guide vane angle by controlling the guide vane actuator. When the electro-hydraulic servo valve controlling the fan guide vane fails, the zero bias of the electro-hydraulic servo valve causes the fan guide vane angle to move towards the fully closed state. The displacement sensor is connected to the actuator and feeds back the displacement signal to the electronic controller, forming a closed-loop control of the guide vane actuator position.

6. The method for predicting the lifespan of a valve due to spring relaxation according to claim 1, characterized in that: The surge relief, shutdown, and start-up device in step one consists of a shutdown valve, a shut-off valve, and a shutdown solenoid valve. When the engine starts, stops, or surge occurs, a shutdown signal is sent to the shutdown solenoid valve, which is then activated. Constant pressure oil flows to the lower chamber of the shutdown valve, causing the shutdown valve to move upward. The shut-off valve spring chamber is then connected to the high-pressure oil after the pump, and the shut-off valve moves to the left, shutting off the fuel supply to the combustion chamber. The return valve spring chamber is then connected to the low-pressure chamber, and the return valve moves to the left, allowing the fuel after the pump to flow back to the low-pressure chamber. After the surge disappears, the shutdown solenoid valve is closed, and the entire oil circuit operates normally.

7. The method for predicting the lifespan of a valve due to spring relaxation according to claim 6, characterized in that: The minimum pressure limiting device in step one consists of a minimum pressure valve, a stop valve, and a return valve.

8. The method for predicting the lifespan of a valve due to spring relaxation according to claim 7, characterized in that: The minimum pressure valve ensures that the pump pressure remains within a certain range when the pump stops. After the stop solenoid valve is activated, the pump pressure drops, the minimum safety valve moves down, and connects the low-pressure oil circuit. When the pump pressure drops to a certain level, the minimum valve closes the low-pressure oil circuit under the action of the spring force and is no longer connected to the spring cavity of the return oil valve, so that the return oil valve maintains a certain opening and ensures that the pump pressure is consistent.

Images