A method for evaluating the multi-dimensional coupling aerodynamic performance of a modal selector valve and an engine

Abstract

This invention discloses a method for evaluating the multi-dimensional coupling aerodynamic performance of a modal selector valve and an engine, belonging to the field of aero-engines. The steps are as follows: establishing a three-dimensional model of the modal selector valve; simulating the model to obtain its flow performance; establishing a computational model of the modal selector valve and calculating the total pressure after the valve; integrating a high-fidelity characteristic calculation model of the component with a zero-dimensional model of the entire engine; inputting the engine's design point performance parameters and performing design point calculations; given the engine control law and the engine's non-design point operating conditions, performing calculations; determining the convergence of the computational model; obtaining the engine characteristic diagram and aerodynamic performance under arbitrary operating conditions, thus obtaining the aerodynamic performance results considering the overall coupling effect of the modal selector valve and the engine. This invention solves the problems in existing technologies where the calculation accuracy of the overall performance calculation code for variable cycle engines cannot meet the design requirements of variable cycle engines, and the coupling of various engine components is poor.

Description

Technical Field

[0001] This invention belongs to the field of aero-engines, specifically relating to a method for evaluating the multi-dimensional coupling aerodynamic performance of a modal selector valve and an engine. Background Technology

[0002] The design objective of a variable cycle engine is to achieve low fuel consumption, approaching that of a high-bypass turbofan engine, during subsonic flight, and high thrust with low fuel consumption during supersonic flight. Simultaneously, it aims to minimize installation losses during subsonic flight, thus adapting it to the needs of multi-mission aircraft. The key to achieving these requirements lies in its multiple geometrically adjustable components, one crucial one being the mode selection valve. This valve adjusts its angle to rationally distribute fan outlet flow, actively adjusting the bypass ratio to ensure the subsequent compression system operates within a stable range, thereby maintaining optimal engine flight performance.

[0003] However, in the actual design process, since the design and research of each component of the engine are relatively independent in the traditional sense, and considering that the operating conditions of the variable cycle engine are varied and the opening of the mode selection valve changes significantly with the engine operating conditions, the coupling effect between the mode selection valve and the overall engine cannot be taken into account at the beginning of the design using traditional design methods. It is often necessary to conduct repeated tests using large-scale scale models, which will lead to a significant increase in the engine development cost and cycle.

[0004] On the other hand, although computational fluid dynamics provides a means for high-precision aerodynamic performance simulation of the whole machine, it consumes a lot of computational resources and has a long calculation cycle. It cannot replace the traditional component-based engine overall aerodynamic performance calculation code and does not have practical engineering application value.

[0005] Therefore, it is necessary to establish an integrated aerodynamic performance evaluation method for modal selectable valves and the overall engine, allowing researchers to integrate higher-dimensional modal selectable valve models into the overall engine performance calculation code. This enables designers to consider the coupling effect between the modal selectable valve and other components, as well as between the modal selectable valve and the whole engine, from the initial design stage, and obtain more accurate engine performance parameters with limited computing power. Summary of the Invention

[0006] The technical problem to be solved:

[0007] To overcome the shortcomings of existing technologies, this invention provides a method for evaluating the multi-dimensional coupling aerodynamic performance of a modal selector valve and an engine. This method is an integrated evaluation method for the modal selector valve and overall aerodynamic performance of a variable cycle engine. It solves the problems in existing technologies where the calculation accuracy of the overall performance calculation code for a variable cycle engine cannot meet the design requirements of the engine, the coupling between various engine components is poor, and the coupling effect between the modal selector valve and other components, as well as between the modal selector valve and the overall system, cannot be considered.

[0008] The technical solution of this invention is: a method for evaluating the multi-dimensional coupling aerodynamic performance of a modal selector valve and an engine, characterized by the following specific steps:

[0009] Step 1: Establish a 3D model of the modal selectivity valve considering the double-duct effect;

[0010] Step 2: Simulate the 3D model of the modal selection valve established in Step 1 to obtain its flow performance;

[0011] Step 3: Establish a low-dimensional, high-fidelity characteristic calculation model for the modal selection valve and calculate the total pressure after the valve.

[0012] Step 4: Multi-dimensional integration of component high-fidelity characteristic calculation model and whole machine zero-dimensional model, that is, coupling the low-dimensional high-fidelity characteristic calculation model obtained in Step 3 with the zero-dimensional overall performance calculation program;

[0013] Step 5: Input the design point performance parameters of the engine and perform design point calculations;

[0014] Step Six: Given the engine control law and the engine's off-design point operating conditions, perform calculations;

[0015] Step 7: Determine the convergence of the multi-dimensional integrated performance calculation model;

[0016] Step 8: Obtain the engine characteristic diagram and aerodynamic performance under arbitrary operating conditions, that is, obtain the aerodynamic performance results that take into account the coupling effect of the mode selection valve and the overall engine.

[0017] A further technical solution of the present invention is as follows: In step one, establishing a three-dimensional model of the modal selector valve requires consideration of the compatibility between the inlet and outlet dimensions of the modal selector valve and the dimensions of the evaluated variable cycle engine, as well as the requirements of the modal selector valve in the actual engine, including: the profiles of the inner and outer bypass channels can suppress flow separation under various flow conditions; the baffle between the inner and outer bypass channels can reduce local losses; and the valve of the modal selector valve can adapt to its flow field at various opening degrees to avoid excessive losses and unstable flow phenomena caused by flow separation.

[0018] A further technical solution of the present invention is: the flow performance obtained in step two is the total pressure recovery coefficient σ and flow rate Wa at the inlet and outlet when the modal selection valve is at different opening degrees S and under different static pressure conditions at the outlets of the inner and outer bypasses.

[0019] A further technical solution of the present invention is: In step three, using the results obtained in step two, piecewise linear interpolation is performed on σ and Wa at the calculation points under different pressure differences before and after the same opening degree S to obtain the total pressure recovery coefficient corresponding to any flow rate under that opening degree.

[0020] σ=f S (Wa)

[0021] Among them, f S It is the piecewise linear interpolation function between σ and Wa obtained at each calculation point in step two under the corresponding opening degree;

[0022] After establishing linear interpolation for each aperture, characteristic interpolation between each aperture is then established:

[0023]

[0024] Where, σ S It is the total pressure recovery coefficient for any opening degree S and any flow rate, where S is the total pressure recovery coefficient. l and S h This represents the opening σ, which is located on the left and right sides of the selected S and was calculated in step two. l and σ h It is the total pressure recovery coefficient obtained by interpolation under these two opening degrees and the selected flow rate;

[0025] Thus, given the flow rate Wa and the valve opening S, the corresponding value of the total pressure recovery coefficient is obtained by interpolation on a low-dimensional, high-fidelity characteristic calculation model with the flow rate Wa as the abscissa, the total pressure recovery coefficient σ as the ordinate, and the valve opening S as the contour line. Therefore, the total pressure P after the valve is... t2 Represented as:

[0026] P t2 =σP t1

[0027] Among them, P t1 P t2 These are the total pressures before and after the valve;

[0028] Combined with the area A after the valve bypass The value of the pneumatic function q(λ) after valve operation is obtained:

[0029]

[0030] After obtaining q(λ), the Mach number Ma and the aerodynamic functions τ(λ) and π(λ) after the valve are obtained by consulting the aerodynamic function table. Then, the static pressure P2 and static temperature T2 after the valve are expressed as follows:

[0031] P2=π(λ)P t2

[0032] T2=τ(λ)T t .

[0033] A further technical solution of the present invention is as follows: the coupling method in step four is to simplify the inlet and outlet sections of each component of the engine into points arranged along a straight line through a zero-dimensional overall performance calculation program, with the points relying on aerodynamic functions for transmission; in the zero-dimensional model, the loss calculation of the modal selection valve relies on the abrupt loss model.

[0034]

[0035] Among them, P t1 P t2 These represent the total pressure before and after the valve; ξ represents the local loss coefficient, calculated according to the following formula:

[0036]

[0037] Where A1 and A2 are the valve throat area and valve back area, respectively;

[0038] The calculation model from step three is then embedded into the calculation program to replace the sudden loss model mentioned above. When the program starts calculating the modal selector valve, the upstream component transmits the flow rate, total temperature, total pressure, and valve opening to the modal selector valve. The total pressure, total temperature, and static parameters after the valve are obtained by interpolation based on the calculation model from step three. The total temperature is consistent with that before the valve.

[0039] A further technical solution of the present invention is: in step five, the design point performance parameters of the engine include flight altitude, flight speed, inlet converted flow rate, fan bypass ratio, outer bypass area, efficiency of each component design point, pressure ratio / pressure drop, and temperature rise / temperature drop.

[0040] A further technical solution of the present invention is: in the calculation of step five, the multi-dimensional integrated model of step four does not work, and the code calculates according to the aerodynamic performance given at the design point.

[0041] A further technical solution of the present invention is: in step six, the non-design point working status includes the flight altitude, flight speed, guide vane angle and characteristic diagrams of other components at the non-design point;

[0042] The engine performance calculation model using a multi-dimensional integrated model is used for non-design point calculations. Given the control law, iterative variables, and residual variables, the common working equations of the multi-dimensional integrated model for non-design point calculations are closed. When performing non-design point performance calculations, the multi-dimensional integrated model needs to iterate the variables of each component to satisfy the continuity of flow, static pressure balance, and power balance between the components. The residual variable refers to the difference between the same variable calculated by two methods.

[0043] A further technical solution of the present invention is: after obtaining the parameters of each component of the engine, the program uses the Newton-Raphson method to solve the common working equations of the engine.

[0044] A further technical solution of the present invention is as follows: the judgment process in step seven is to check the residuals of each iterative variable at this time to satisfy the continuity of flow, static pressure balance and power balance between each component; if the requirements are not met, return to step five to check whether the performance parameters given at the engine design point are reasonable; if they are not reasonable, they need to be given again, and then steps five to seven are executed again; if they are reasonable, a small perturbation is added on the basis, and then steps five to seven are executed again.

[0045] Repeat the above steps until the obtained iterative variables meet the convergence requirements.

[0046] Beneficial effects

[0047] The beneficial effects of this invention are as follows: The multi-dimensional integrated evaluation method of the modal selection valve and overall aerodynamic performance of the variable cycle engine can solve the problems in the prior art where the calculation accuracy of the overall performance calculation code of the variable cycle engine cannot meet the design requirements of the variable cycle engine, the poor coupling of various engine components, and the inability to consider the coupling effect between the modal selection valve and other components, and between the modal selection valve and the overall system.

[0048] The modal selector valve characteristic calculation model established in step three of this method solves the problem that the zero-dimensional model's sudden expansion loss model cannot accurately express the complete working characteristics of the modal selector valve: the sudden expansion loss model is based on incompressible flow at low speeds, while the modal selector valve has a high-velocity operating range where air is highly compressible, and pressure loss and dynamic head exhibit significant nonlinear relationships; secondly, the sudden expansion loss model expresses the relationship between the pressure difference and velocity across the valve, which has poor compatibility with engine performance calculation programs that primarily use the ratio of total parameters and Mach number as the velocity evaluation parameter; finally, the sudden expansion loss model cannot consider the valve's performance under blocked conditions. The characteristic calculation model in step three comprehensively evaluates the relationship between the incoming flow velocity, throat area, and downstream pressure loss, and considers the matching with the parameters called in the engine's zero-dimensional model. A schematic diagram of the low-dimensional characteristic calculation model of a certain type of modal selector valve established according to step three is shown below. Figure 3As shown in the figure, when the valves are on the same equal opening line, the larger the flow rate, the smaller the total pressure recovery coefficient. The two ends of each line are the near backflow zone and the blockage zone, respectively. Compared with the sudden expansion loss model, the characteristic diagram established in step three can reflect the nonlinear relationship between total pressure loss and flow rate, and can also express the near backflow and blockage working states of the MSV.

[0049] Steps four and five in this method address the shortcomings of existing engine overall performance calculation codes, which cannot meet the design requirements of variable cycle engines due to insufficient accuracy. These issues include poor coupling between engine components and the inability to consider the coupling effects between the mode selector valve and other components, or between the mode selector valve and the overall engine system. In the zero-dimensional model, the impact of the ducting loss on thrust is indirect. The pressure loss of the bypass airflow after passing through the valve is transmitted backward to the aft variable area duct ejector, affecting the mixing process in the mixing chamber and ultimately altering the iterative solution of the common working equations, resulting in thrust changes. In contrast, in the multi-dimensional coupled model, the total pressure loss is directly related to the flow rate, characterizing the high degree of coupling between the mode selector valve and the overall engine system. Figure 7 The changes in engine thrust during valve closure are presented using two models. As shown in the figure, when the valve opening decreases to 70%, the throat area shrinks, the bypass airflow velocity increases, and compressibility becomes apparent. The zero-dimensional model gradually deviates from the actual operating condition, and the engine thrust still changes linearly. In reality, however, because the valve operates in the compressible section at this point, the flow rate decreases non-linearly, and the thrust increases non-linearly. The multi-dimensional coupled model accurately reflects the non-linear increase in engine thrust. Figure 8 The change in the bypass ratio of the fan (upstream component of the valve) during valve closure is presented. It can be seen that during valve closure, the fan bypass ratio decreases due to the reduced flow capacity of the outer bypass. However, the bypass ratio of the zero-dimensional model only decreases slightly during mode transition; while when the valve operates in the nonlinear region, the valve's throttling capacity increases rapidly due to the resistance generated by valve throttling and the valve's proximity to the blockage point, thus causing a sharp decrease in the bypass ratio of the multi-dimensional coupled model. Therefore, steps four and five used in this method can meet the design accuracy requirements of variable cycle engines and solve the problem of poor coupling between engine components in the zero-dimensional model, which cannot consider the coupling effects between the mode selection valve and other components, and between the mode selection valve and the overall system. Attached Figure Description

[0050] Figure 1 This is the three-dimensional model of the modal selection valve established in the embodiments of the present invention;

[0051] Figure 2 is a valve cross-section cloud diagram obtained during simulation in the embodiment of the present invention; 2(a) is a total pressure cloud diagram with 46% opening and MSV outlet back pressure of 275000Pa; 2(b) is a Mach number cloud diagram with 46% opening and MSV outlet back pressure of 195000Pa.

[0052] Figure 3 This is a schematic diagram of the low-dimensional characteristic calculation model built according to the embodiments of the present invention;

[0053] Figure 4 This is a schematic diagram of a multi-dimensional integrated variable cycle engine modal selection valve-overall aerodynamic performance integrated evaluation method according to an embodiment of the present invention;

[0054] Figure 5 This is a schematic diagram of the mathematical model of the multi-dimensional coupled variable cycle engine constructed according to an embodiment of the present invention;

[0055] Figure 6 This is a description of the variables selected for establishing the mathematical model of the multi-dimensional coupled variable cycle engine in this embodiment of the invention;

[0056] Figure 7 This is a comparison of the changes in engine thrust during valve closure between the multi-dimensional coupled model and the zero-dimensional model established in this embodiment of the invention.

[0057] Figure 8 This is a comparison of the changes in fan bypass ratio between the multi-dimensional coupling model and the zero-dimensional model established in the embodiments of the present invention during the valve closing process. Detailed Implementation

[0058] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0059] See Figure 4 This embodiment presents a multi-dimensional coupling aerodynamic performance evaluation method for a modal selector valve and an engine. A rapid calculation model for the modal selector valve is established and coupled with the overall aerodynamic performance calculation code for the aero-engine. Given engine operating conditions, this coupled model can calculate the aerodynamic performance parameters of each engine component. The overall aerodynamic performance calculation code for the aero-engine is a traditional component-level aerodynamic performance calculation code. Each component is simplified as a black box with inlets and outlets, and the parameters of each section are processed through the black box and then passed to subsequent components. Applying this overall performance evaluation method can take into account the strong coupling effect between the modal selector valve, the variable cycle compression system, and the entire variable cycle engine. It obtains the aerodynamic deviation caused by the flow details of the modal selector valve in the overall engine performance evaluation, avoiding the drawback of the traditional component-level overall aerodynamic performance calculation method, which cannot evaluate the coupling effect between the modal selector valve and the overall engine, thus resulting in decreased accuracy.

[0060] First, a modal selector valve model that meets the requirements is established, and its flow characteristics are simulated. Then, the relationship between pressure difference, flow rate and opening degree is fitted according to the selected modal selector valve mathematical model to establish a low-dimensional fast calculation model.

[0061] Furthermore, this rapid calculation model is coupled with the engine's overall aerodynamic performance calculation code to establish a multi-dimensional integrated modal selection valve-overall aerodynamic performance evaluation model.

[0062] Furthermore, the engine design point performance parameters are set, and the aerodynamic performance of the engine design point is calculated.

[0063] Furthermore, by selecting iterative and residual variables and specifying control laws that satisfy certain quantities, the system of equations for solving the engine's off-design point performance is closed. The Newton-Raphson method is then used to solve the engine's common operating equations.

[0064] Furthermore, the results are evaluated for convergence. If the convergence condition is not met, the rationality of the engine design point performance parameters needs to be reconsidered, or a small perturbation needs to be added to the engine design point parameters. The calculation is then repeated until the convergence condition is met. At this point, the engine performance parameters are high-precision results that take into account the coupling effect of the modal selection valve and the overall engine performance.

[0065] The specific steps of this embodiment are as follows:

[0066] Step 1: Establish a 3D model of the modal selectivity valve considering the double-duct effect, the specific structure of which is as follows: Figure 1 As shown. This model needs to consider the compatibility of the inlet and outlet dimensions of the modal selector valve with the dimensions of the variable cycle engine being evaluated, and should take into account as much as possible the requirements of the modal selector valve in the real engine, including but not limited to: the profile of the inner and outer bypass ducts should suppress flow separation under various flow conditions as much as possible; the baffle between the inner and outer bypass ducts should minimize local losses as much as possible; the valve of the modal selector valve should be adapted to its flow field at each opening to avoid excessive losses and unstable flow phenomena such as flow separation.

[0067] Step two involves simulating the modal selector valve model established in Step one to obtain its flow characteristics, specifically the total pressure recovery coefficient and flow rate at the outlet of the modal selector valve under different opening degrees S and different static pressure conditions at the outlets of the inner and outer bypass ducts. During the simulation, it is necessary to check the convergence of each physical quantity and ensure that the obtained flow field's total pressure, static pressure, and Mach number contour plots conform to basic flow principles. Simultaneously, it is necessary to determine the back pressure boundary when the valve is blocked; that is, when the back pressure continuously decreases while the flow rate of the modal selector valve does not change significantly, this back pressure is selected as the blockage boundary at that opening degree.

[0068] Figure 2(a) shows the contour plot of the valve at 46% opening and a total pressure of 275,000 Pa at the outer bypass outlet when the simulation residual converges. It can be seen that a large low-total-pressure zone exists behind the modal selector valve due to backflow. This zone gradually mixes with the high-total-pressure airflow flowing in from the valve throat as the flow develops. This flow condition conforms to physical laws, therefore the calculation is considered reasonable and credible. However, Figure 2(b) shows that the Mach number at the valve throat has reached the speed of sound, and an expansion wave appears behind it. Even after the valve is placed under a lower back pressure, the flow rate does not change significantly. This back pressure is considered the blockage boundary at this opening.

[0069] Step 3: Establish a low-dimensional, high-fidelity characteristic calculation model for the modal selector valve to quickly calculate the total pressure downstream of the valve. Using the results obtained in Step 2, calculate the σ and Wa at different pressure differences before and after the valve for the same opening degree S. i Piecewise linear interpolation is performed to obtain the total pressure recovery coefficient for any flow rate at this opening degree:

[0070] σ=f S (Wa)

[0071] Among them, f S It is the piecewise linear interpolation function between σ and Wa obtained at each calculation point in step two, corresponding to the opening degree.

[0072] After establishing linear interpolation for each aperture, characteristic interpolation between each aperture is then established:

[0073]

[0074] Where, σ S It is the total pressure recovery coefficient under any opening degree S and any flow rate, S l and S h This represents the opening σ, which is located on the left and right sides of the selected S and was calculated in step two. l and σ h It is the total pressure recovery coefficient obtained by interpolation under these two openings and the selected flow rate.

[0075] Therefore, given the flow rate Wa and the aperture S, the corresponding total pressure recovery coefficient can be interpolated onto a low-dimensional characteristic model with the flow rate Wa as the x-axis, the total pressure recovery coefficient σ as the y-axis, and the aperture S as the contour lines, to obtain the value of the total pressure recovery coefficient. A schematic diagram of the low-dimensional high-fidelity characteristic calculation model established in this embodiment is shown below. Figure 3 As shown. Then the total pressure P after the valve... t2 It can be represented as:

[0076] P t2 =σP t1

[0077] Combined with the area A after the valve bypass This allows us to obtain the value of the pneumatic function q(λ) after the valve:

[0078]

[0079] After obtaining q(λ), the Mach number Ma and the aerodynamic functions τ(λ) and π(λ) after the valve are obtained by consulting the aerodynamic function table. Then, the static pressure P2 and static temperature T2 after the valve can be expressed as:

[0080] P2=π(λ)P t2

[0081] T2=τ(λ)T t

[0082] Step 4: Multi-dimensional integration of the high-fidelity characteristic calculation model for components and the zero-dimensional model of the whole machine. The low-dimensional high-fidelity characteristic model obtained in Step 3 is coupled with the overall performance calculation code at the component level. A simplified visualization of the coupling process is shown below. Figure 5 As shown.

[0083] A zero-dimensional overall performance calculation program simplifies the inlet and outlet sections of each engine component into points arranged along a straight line. Communication between these points relies on aerodynamic functions, such as flow rate, total temperature, and total pressure. In the zero-dimensional model, the loss calculation for the modal selection valve utilizes a sudden-breach loss model.

[0084]

[0085] Where Pt1 and Pt2 are the total pressures before and after the valve, respectively; ξ represents the local loss coefficient, calculated according to the following formula:

[0086]

[0087] A1 and A2 are the valve throat area and valve back area, respectively.

[0088] The characteristic model described in step three is now embedded into the calculation program, replacing the sudden throttling loss model mentioned above. When the program starts calculating the modal selector valve, the upstream component (usually a fan) transmits flow rate, total temperature, and total pressure to the modal selector valve, as well as the valve opening at that time. Based on the model established in step three, the total pressure, total temperature (consistent with that before the valve), and static parameters after the valve can be interpolated.

[0089] Step 5: Input the design point parameters of the engine and perform design point calculation.

[0090] In this embodiment, some design point parameters are as follows: engine flight speed 1.555 Mach, flight altitude 12000 meters, intake design point equivalent flow rate 173.4140 kg / s, fan design point pressure ratio 4.5, bypass ratio 0.32, outer bypass area 0.1405, fan design point efficiency 86%, and combustion chamber outlet total temperature 1950 K. At this point, the multi-dimensional coupling model described in step four is not working; the code only calculates based on the aerodynamic performance given at the design points.

[0091] Step Six: Given the engine control laws and the engine's operating conditions at non-design points, perform non-design point calculations using a multi-dimensional integrated engine performance calculation model. The operating conditions at non-design points include flight altitude, flight speed, guide vane angle, and characteristic diagrams of other components.

[0092] A multi-dimensional integrated model is used to perform non-design point calculations on the engine performance calculation model. When performing non-design point performance calculations, it is necessary to iterate the variables of each component to ensure flow continuity, static pressure balance, and power balance among them. At this point, it is necessary to consider the iterative variables and residual variables of the variable cycle engine operating in the dual-bypass mode. The residual variable refers to the difference between the same variable calculated using two methods. Taking the fan as an example, the flow residual refers to the difference between the flow rate delivered to the fan inlet by the upstream component (inlet) and the flow rate calculated using the model fan characteristic diagram. The β value of the inlet is the ratio of the non-design point inlet converted flow rate to the design point inlet converted flow rate. The β values ​​of the compressor and turbine components are auxiliary variables for characteristic diagram interpolation. A fan model is formed by combining and encapsulating the compressor model and the splitter model. The aerodynamic and thermodynamic processes of the variable-area duct ejector are simulated using a variable-area mixing chamber model. The difference between the number of iterative variables and the number of residuals is the number of control variables. Generally, for variable cycle engines, the combustion chamber fuel flow rate is selected as the control variable. In this case, the number of iterative variables and residual variables are equal, and the engine's common operating equations are closed. During calculation, the flow rate and total parameters of the fan after splitting according to the bypass ratio are transmitted to the modal selection valve model of the outer bypass. The total and static parameters after the valve are provided by the model and transmitted downstream to the front variable area duct ejector. After obtaining the parameters of each engine component, the program uses the Newton-Raphson method to solve the common working equations of the engine.

[0093] In this embodiment, the main parameters at the non-design point are as follows: valve opening decreases sequentially from 100% to 0%, engine flight speed is 1.555 Mach, flight altitude is 12,000 meters, engine control law maintains a constant total temperature at the combustion chamber outlet, and the performance parameters of other components are given according to the given characteristic diagram. When performing non-design point performance calculations, it is necessary to iterate the variables of each component to satisfy the requirements of continuous flow, static pressure balance, and power balance among the components. Figure 6The iterative variables and residual variables of the variable cycle engine operating in the dual bypass mode in this embodiment are given.

[0094] Step 7: Determine the convergence of the multi-dimensional integrated performance calculation model. Check the residuals of each iterated variable to ensure continuous flow, static pressure balance, and power balance among the components. If these requirements are not met, return to Step 5 to check if the performance parameters given at the engine design point are reasonable. If not, they need to be redefined, and then Steps 5 through 7 are executed again. In this embodiment, the engine component parameters are reasonable, and the performance matching of the engine components can be met when the valve opening changes. Only when the valve opening drops to 10% does non-convergence occur. Since the parameter design is reasonable, the valve opening is fine-tuned to 9.9%, and then Steps 5 through 7 are executed again, after which the model calculation converges.

[0095] Step eight: Obtain the engine characteristic diagram and aerodynamic performance under calculated operating conditions. The result at this point represents the aerodynamic performance considering the coupling effect between the mode selection valve and the overall engine.

[0096] In this embodiment, Figure 7 The changes in engine thrust during valve closure are presented using two different models. Figure 8 The changes in the bypass ratio of the fan (upstream component of the valve) during valve closure are presented under two models. It is clear that, compared to the zero-dimensional model, this method can obtain high-precision aerodynamic performance calculations for the engine that consider the coupling effects between the modal selector valve and other components, as well as between the modal selector valve and the overall system.

[0097] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for evaluating the multi-dimensional coupling aerodynamic performance of a modal selector valve and an engine, characterized in that... The specific steps are as follows: Step 1: Establish a 3D model of the modal selectivity valve considering the double-duct effect; Step 2: Simulate the 3D model of the modal selection valve established in Step 1 to obtain its flow performance; Step 3: Establish a low-dimensional, high-fidelity characteristic calculation model for the modal selection valve and calculate the total pressure after the valve. Specifically, using the results obtained in step two, piecewise linear interpolation is performed on σ and Wa at the calculation points under different pressure differences before and after the same opening degree S to obtain the total pressure recovery coefficient corresponding to any flow rate at that opening degree. Among them, f S It is the piecewise linear interpolation function between σ and Wa obtained at each calculation point in step two under the corresponding opening degree; After establishing linear interpolation for each aperture, characteristic interpolation between each aperture is then established: Where, σ S It is the total pressure recovery coefficient for any opening degree S and any flow rate, where S is the total pressure recovery coefficient. l and S h This represents the opening σ, which is located on the left and right sides of the selected S and was calculated in step two. l and σ h It is the total pressure recovery coefficient obtained by interpolation under these two opening degrees and the selected flow rate; Thus, given the flow rate Wa and the valve opening S, the corresponding value of the total pressure recovery coefficient is obtained by interpolation on a low-dimensional, high-fidelity characteristic calculation model with the flow rate Wa as the abscissa, the total pressure recovery coefficient σ as the ordinate, and the valve opening S as the contour line. Therefore, the total pressure P after the valve is... t2 Represented as: Among them, P t1 P t2 These are the total pressures before and after the valve; Combined with the area A after the valve bypass The value of the pneumatic function q(λ) after valve operation is obtained: After obtaining q(λ), the Mach number Ma and the aerodynamic functions τ(λ) and π(λ) after the valve are obtained by consulting the aerodynamic function table. Then, the static pressure P2 and static temperature T2 after the valve are expressed as follows: ； Step 4: Multi-dimensional integration of high-fidelity component characteristic calculation model and zero-dimensional whole machine model, that is, coupling the low-dimensional high-fidelity characteristic calculation model obtained in Step 3 with the zero-dimensional overall performance calculation program; the coupling method is to simplify the inlet and outlet sections of each component of the engine into points arranged along a straight line through the zero-dimensional overall performance calculation program, and the points are transmitted through aerodynamic functions; in the zero-dimensional model, the loss calculation of the modal selection valve is performed using the sudden expansion loss model: Among them, P t1 P t2 These represent the total pressure before and after the valve; ξ represents the local loss coefficient, calculated according to the following formula: Where A1 and A2 are the valve throat area and valve back area, respectively; The calculation model from step three is then embedded into the calculation program to replace the sudden expansion loss model mentioned above. When the program starts calculating the modal selection valve, the upstream component transmits the flow rate, total temperature, total pressure, and valve opening to the modal selection valve. The total pressure, total temperature, and static parameters after the valve are obtained by interpolation based on the calculation model from step three. The total temperature is consistent with that before the valve. Step 5: Input the design point performance parameters of the engine and perform design point calculations; Step Six: Given the engine control law and the engine's off-design point operating conditions, perform calculations; Step 7: Determine the convergence of the multi-dimensional integrated performance calculation model; Step 8: Obtain the engine characteristic diagram and aerodynamic performance under arbitrary operating conditions, that is, obtain the aerodynamic performance results that take into account the coupling effect of the mode selection valve and the overall engine.

2. The method for evaluating the multi-dimensional coupling aerodynamic performance of a modal selection valve and an engine according to claim 1, characterized in that: In step one, establishing a three-dimensional model of the modal selector valve requires consideration of the compatibility between the inlet and outlet dimensions of the modal selector valve and the dimensions of the variable cycle engine being evaluated, as well as the requirements for the modal selector valve in the actual engine, including: the profiles of the inner and outer bypass channels can suppress flow separation under various flow conditions; the baffle between the inner and outer bypass channels can reduce local losses; and the valve of the modal selector valve can adapt to its flow field at various opening degrees to avoid excessive losses and unstable flow phenomena caused by flow separation.

3. The method for evaluating the multi-dimensional coupling aerodynamic performance of a modal selection valve and an engine according to claim 2, characterized in that: The flow performance obtained in step two is the total pressure recovery coefficient σ and flow rate Wa at the inlet and outlet of the modal selector valve under different opening degrees S and different static pressure conditions at the outlets of the inner and outer bypass ducts.

4. The method for evaluating the multi-dimensional coupling aerodynamic performance of a modal selection valve and an engine according to claim 3, characterized in that: In step five, the engine's design point performance parameters include flight altitude, flight speed, inlet converted flow rate, fan bypass ratio, outer bypass area, efficiency of each component's design point, pressure ratio / pressure drop, and temperature rise / temperature drop.

5. The method for evaluating the multi-dimensional coupling aerodynamic performance of a modal selection valve and an engine according to claim 4, characterized in that: In the calculation of step five, the multi-dimensional integrated model of step four does not work, and the code performs calculations according to the aerodynamic performance given at the design point.

6. The method for evaluating the multi-dimensional coupling aerodynamic performance of a modal selection valve and an engine according to claim 5, characterized in that: In step six, the non-design point working status includes the flight altitude, flight speed, guide vane angle, and characteristic diagrams of other components at the non-design point. The engine performance calculation model using a multi-dimensional integrated model is used for non-design point calculations. Given the control law, iterative variables, and residual variables, the common working equations of the multi-dimensional integrated model for non-design point calculations are closed. When performing non-design point performance calculations, the multi-dimensional integrated model needs to iterate the variables of each component to satisfy the continuity of flow, static pressure balance, and power balance between the components. The residual variable refers to the difference between the same variable calculated by two methods.

7. The method for evaluating the multi-dimensional coupling aerodynamic performance of a modal selection valve and an engine according to claim 6, characterized in that: After obtaining the parameters of each engine component, the program uses the Newton-Raphson method to solve the common working equations of the engine.

8. The method for evaluating the multi-dimensional coupling aerodynamic performance of a modal selection valve and an engine according to claim 7, characterized in that: The judgment process in step seven is as follows: check the residuals of each iterated variable at this time to ensure that the flow continuity, static pressure balance and power balance between each component are met; if the requirements are not met, return to step five to check whether the performance parameters given at the engine design point are reasonable; if they are not reasonable, they need to be given again, and then steps five to seven are executed again; if they are reasonable, a small perturbation is added on the basis, and then steps five to seven are executed again. Repeat the above steps until the obtained iterative variables meet the convergence requirements.

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