Variable cycle aero-engine mode switching instantaneous countercurrent simulation method and simulation system

Abstract

The invention relates to a variable cycle aero-engine mode switching instantaneous countercurrent simulation method and simulation system, belongs to the technical field of variable cycle engine mode switching simulation, and solves the problems that in the prior art, a flow direction needs to be preset and countercurrent calculation cannot be carried out in a traditional component method. Establishing a mainstream flow path model of the variable cycle aero-engine by adopting a component method; s2, establishing a mode switching local flow path model of the variable cycle aero-engine by adopting a network method; s3, constructing a mode switching instantaneous countercurrent simulation model, and coupling the main flow path model established by the component method with the mode switching local flow path model established by the network method to obtain the mode switching instantaneous countercurrent simulation model; and S4, performing simulation by using the mode switching instantaneous countercurrent simulation model, setting an aero-engine control rule and a mode selection valve adjustment rule in the model switching instantaneous countercurrent simulation model, and obtaining and outputting a simulation result.

Description

Technical Field

[0001] The present invention relates to the technical field of simulation of variable cycle engine mode switching, and particularly relates to a simulation method and a simulation system for instantaneous countercurrent during mode switching of a variable cycle aeroengine. Background Art

[0002] A variable cycle aeroengine can change the thermodynamic cycle parameters, such as pressure ratio, bypass ratio, turbine inlet temperature, air flow rate, etc., by variable geometry adjustment of components according to different mission requirements of an aircraft, so that the engine has good performance in each state, which is an important development direction of future aviation power. A variable cycle engine generally has multiple ducts and needs to change the flow state of each duct through a mode selection valve to achieve mode switching of the engine. However, during the mode switching process of a variable cycle engine, due to the pressure change caused by mode switching, the flow direction of gas between different ducts may change, and this instantaneous countercurrent phenomenon will cause calculation divergence. Currently, the methods for dealing with countercurrent during mode switching of variable cycle engines mainly include the local cycle method and the passive convergence method, etc. Limited by the sequential calculation required in component method modeling, the above methods cannot simulate the countercurrent phenomenon in the transient process of mode switching.

[0003] Therefore, there is a need in the technical field for a method to accurately simulate the mode switching process of a variable cycle aeroengine with a countercurrent phenomenon. Summary of the Invention

[0004] Aiming at the problem that the existing simulation methods cannot simulate the instantaneous countercurrent phenomenon during mode switching of a variable cycle aeroengine, the present invention proposes a simulation method and a simulation system for instantaneous countercurrent during mode switching of a variable cycle aeroengine. Among them, the local flow path of mode switching is modeled by the network method, and the main flow paths involving compression components, combustion components, and turbine components are modeled by the component method. The network method is a zero-dimensional simulation model based on the flow characteristics of components. The flow path and chamber of the system are decomposed into a network composed of corresponding components and nodes. Taking the gas parameters of each node as the initial trial parameters, a solution matrix for correcting the trial parameters is constructed by calculating an equal number of balance equations at the nodes, and then an iterative calculation is performed to obtain a convergent solution. The network method does not need to calculate each component one by one according to the flow direction. After determining the boundary information of the fluid network, iterative solution can be carried out. Therefore, the network method can better accommodate the instantaneous countercurrent process.

[0005] Furthermore, the coupling between the main flow path and the network of the local flow path of mode switching is realized through air extraction boundary nodes and confluence boundary nodes with an equation closing mechanism.

[0006] Furthermore, the mode-switching local flow path network consists of an air extraction boundary node, a confluence boundary node, internal nodes, and throttling elements connecting the air extraction boundary node, the confluence boundary node, and the internal nodes. Among them, the throttling area of the throttling element is given according to the geometric characteristics of the flow path of the mode-switching valve.

[0007] According to an embodiment of the present invention, a method for simulating instantaneous reverse flow during mode switching of a variable cycle aeroengine is provided, including the following steps:

[0008] Step S1, establish a mainstream flow path model of the variable cycle aeroengine using the component method. The mainstream flow path model includes the main functional components of the aeroengine: a compression system, a combustion system, a turbine system, a duct system, a casing, and a mixing chamber;

[0009] Step S2, establish a mode-switching local flow path model of the variable cycle aeroengine using the network method. The mode-switching local flow path model includes: a mode selection valve, internal nodes of the mode selection valve, an air extraction boundary node, a confluence boundary node, and connecting channels; among them, the air extraction boundary node includes an air extraction boundary node on the inner flow path of the mode selection valve and an air extraction boundary node on the outer flow path of the mode selection valve; among them, the confluence boundary node includes a confluence boundary node on the inner flow path of the mode selection valve and a confluence boundary node on the outer flow path of the mode selection valve; and among them, the connecting channels include a channel connecting the air extraction boundary node on the inner flow path of the mode selection valve to the internal nodes of the mode selection valve, a channel connecting the air extraction boundary node on the outer flow path of the mode selection valve to the internal nodes of the mode selection valve, a channel connecting the air extraction boundary node on the outer flow path of the mode selection valve to the confluence boundary node on the outer flow path of the mode selection valve, and a channel connecting the internal nodes of the mode selection valve to the confluence boundary node on the inner flow path of the mode selection valve; among them, the mode selection valve switches between a closed state and an open state, thereby adjusting the area of the channel connecting the air extraction boundary node on the outer flow path of the mode selection valve to the internal nodes of the mode selection valve, and adjusting the area of the channel connecting the air extraction boundary node on the outer flow path of the mode selection valve to the confluence boundary node on the outer flow path of the mode selection valve;

[0010] Step S3, construct a mode-switching instantaneous reverse flow simulation model. Through the air extraction boundary node and the confluence boundary node with an equation closure mechanism, couple the mainstream flow path model established by the component method with the mode-switching local flow path model established by the network method to obtain the mode-switching instantaneous reverse flow simulation model;

[0011] Step S4, use the mode-switching instantaneous reverse flow simulation model for simulation. Set the aeroengine control law and the mode selection valve adjustment law therein. Obtain and output the simulation results from the mode-switching instantaneous reverse flow simulation model, and draw a simulation chart according to the simulation results for the analysis and optimization design of the variable cycle aeroengine mode switching.

[0012] Optionally, step S3 further includes:

[0013] Coupling the mainstream flow path model established by the component method with the local flow path model of the mode switching valve established by the network method. Specifically, it is achieved by coupling the air extraction boundary nodes of the inner flow path of the mode selection valve, the air extraction boundary nodes of the outer flow path of the mode selection valve, the internal nodes of the mode selection valve, the air confluence boundary nodes of the inner flow path of the mode selection valve, and the air confluence boundary nodes of the outer flow path of the mode selection valve with the mainstream flow path model;

[0014] The corresponding air extraction boundary nodes of the inner flow path of the mode selection valve and the air confluence boundary nodes of the inner flow path of the mode selection valve, and the air extraction boundary nodes of the outer flow path of the mode selection valve and the air confluence boundary nodes of the outer flow path of the mode selection valve are respectively formed into air extraction / confluence modules.

[0015] Optionally, in the mainstream flow path model established in step S1: the duct system includes a first outer duct, a second outer duct, and a third outer duct arranged from the inside to the outside.

[0016] Optionally, the local flow path model of the mode switching established in step S2 further includes: a core engine air extraction boundary node and a core engine air confluence boundary node; and a medium-pressure turbine rear casing flow path connecting the core engine air extraction boundary node and the core engine air confluence boundary node, and a connotation combustion chamber louver flow path connecting the core engine air confluence boundary node and the internal nodes of the mode selection valve.

[0017] Optionally, in the local flow path model of the mode switching established in step S2:

[0018] The air extraction boundary node of the inner flow path of the mode selection valve is the air extraction boundary node of the first outer duct;

[0019] The air extraction boundary node of the outer flow path of the mode selection valve is the air extraction boundary node of the second outer duct;

[0020] The air confluence boundary node of the inner flow path of the mode selection valve is the air confluence boundary node of the first outer duct;

[0021] The air confluence boundary node of the outer flow path of the mode selection valve is the air confluence boundary node of the second outer duct;

[0022] The flow path connecting the air extraction boundary node of the inner flow path of the mode selection valve and the internal nodes of the mode selection valve is the flow path from the first outer duct to the mode selection valve connecting the air extraction boundary node of the first outer duct and the internal nodes of the mode selection valve;

[0023] The flow path connecting the air extraction boundary node of the outer flow path of the mode selection valve and the internal nodes of the mode selection valve is the flow path from the second outer duct to the mode selection valve connecting the air extraction boundary node of the second outer duct and the internal nodes of the mode selection valve;

[0024] The flow path connecting the air extraction boundary node on the outer side of the connection mode selection valve and the confluence boundary node on the outer side of the mode selection valve is the flow path from the second bypass air extraction boundary node to the mode selection valve connecting the second bypass air extraction boundary node and the second bypass confluence boundary node;

[0025] The flow path connecting the internal node of the mode selection valve and the confluence boundary node on the inner side of the mode selection valve flow path is the flow path from the mode selection valve to the bypass combustion chamber connecting the internal node of the mode selection valve and the first bypass confluence boundary node.

[0026] Optionally, step S3 further includes:

[0027] Coupling the mainstream flow path model established by the component method and the local flow path model of the mode switching valve established by the network method. Specifically, it is achieved by coupling the core engine air extraction boundary node, the first bypass air extraction boundary node, the second bypass air extraction boundary node, and the core engine confluence boundary node, the first bypass confluence boundary node, and the second bypass confluence boundary node with the mainstream flow path model, which have equation closure mechanisms;

[0028] The core engine air extraction boundary node and the core engine confluence boundary node, the first bypass air extraction boundary node and the first bypass confluence boundary node, and the second bypass air extraction boundary node and the second bypass confluence boundary node are respectively formed into three air extraction / confluence modules.

[0029] Optionally, constructing the instantaneous reverse flow simulation model in step S3 further includes:

[0030] For any air extraction boundary node among the core engine air extraction boundary node, the first bypass air extraction boundary node, and the second bypass air extraction boundary node, set the total temperature T b1 * , total pressure p b1 * , mass flow rate W b1 , fuel-air ratio f b1 , moisture content D b1 of the upstream mainstream component connected to the air extraction boundary node, and obtain the total temperature T b2 * , total pressure p b2 * , mass flow rate W b2 , fuel-air ratio f b2 , moisture content D b2 of the air extraction boundary node;

[0031] Set the mass flow rate W b2 of any air extraction boundary node to satisfy the following relationship with the mass flow rates W b of the adjacent M j branches:

[0032]

[0033] Among them, ε b represents the air extraction boundary node flow balance equation, and W b2 represents the flow rate of the air extraction boundary node. b2 represents the number of the air extraction boundary node and b2 = 1, …, 3. W j represents the flow rate of the j-th branch adjacent to the air extraction boundary node. j represents the number of the branch adjacent to the air extraction boundary node and j = 1, …, M b , M b represents the total number of branches adjacent to the air extraction boundary node;

[0034] For any confluence boundary node among the core engine confluence boundary node, the first bypass confluence boundary node, and the second bypass confluence boundary node, set the total pressure, total enthalpy, flow rate, fuel-air ratio, and moisture content of the any confluence boundary node as trial given quantities. The total enthalpy, flow rate, fuel-air ratio, and moisture content of the N M branches adjacent to the confluence boundary node satisfy the following relationships:

[0035]

[0036] Among them, ε M.1 represents the confluence boundary node energy balance equation, ε M.2 represents the confluence boundary node flow balance equation, ε M.3 represents the confluence boundary node fuel-air ratio balance equation, ε M.4 represents the confluence boundary node moisture content balance equation, represents the total enthalpy of the confluence boundary node, W M represents the flow rate of the confluence boundary node, f M represents the fuel-air ratio of the confluence boundary node, D M represents the moisture content of the confluence boundary node. M represents the number of the confluence boundary node and M = 1, …, 3, represents the total enthalpy of the k-th branch adjacent to the confluence boundary node, W k represents the flow rate of the k-th branch adjacent to the confluence boundary node, W k represents the fuel-air ratio of the k-th branch adjacent to the confluence boundary node, f k represents the moisture content of the k-th branch adjacent to the confluence boundary node. k represents the number of the branch adjacent to the confluence boundary node and k = 1, …, N M , N M represents the total number of branches adjacent to the confluence boundary node.

[0037] According to another embodiment of the present invention, a variable cycle aeroengine mode switching instantaneous countercurrent simulation system is provided, including a mode switching instantaneous countercurrent simulation model established by coupling a mainstream flow path model and a mode switching local flow path model, where

[0038] The mainstream flow path model is established by the component method and includes the main functional components of an aeroengine: a compression system, a combustion system, a turbine system, a duct system, a casing, and a mixing chamber;

[0039] The mode-switching local flow path model is established by the network method and includes: a mode selection valve, internal nodes of the mode selection valve, air extraction boundary nodes, confluence boundary nodes, and connecting flow channels; among which the air extraction boundary nodes include an air extraction boundary node on the inner flow path of the mode selection valve and an air extraction boundary node on the outer flow path of the mode selection valve; the confluence boundary nodes include a confluence boundary node on the inner flow path of the mode selection valve and a confluence boundary node on the outer flow path of the mode selection valve; and the connecting flow channels include a flow channel connecting the air extraction boundary node on the inner flow path of the mode selection valve and the internal node of the mode selection valve, a flow channel connecting the air extraction boundary node on the outer flow path of the mode selection valve and the internal node of the mode selection valve, a flow channel connecting the air extraction boundary node on the outer flow path of the mode selection valve and the confluence boundary node on the outer flow path of the mode selection valve, and a flow channel connecting the internal node of the mode selection valve and the confluence boundary node on the inner flow path of the mode selection valve; wherein, the mode selection valve switches between a closed state and an open state, thereby adjusting the connection surface of the flow channel connecting the air extraction boundary node on the outer flow path of the mode selection valve and the internal node of the mode selection valve, and adjusting the area of the flow channel connecting the air extraction boundary node on the outer flow path of the mode selection valve and the confluence boundary node on the outer flow path of the mode selection valve;

[0040] The mode-switching instantaneous reverse flow simulation model is obtained by coupling the mainstream flow path model established by the component method with the mode-switching local flow path model established by the network method through air extraction boundary nodes and confluence boundary nodes with an equation closure mechanism.

[0041] Compared with the prior art, the variable cycle aeroengine mode-switching instantaneous reverse flow simulation method and simulation system provided by the present invention have at least the following beneficial effects: using the network method to handle the reverse flow problem of the local flow path of the mode-switching valve, overcoming the defect that the traditional component method needs to preset the flow direction and cannot perform reverse flow calculation, and at the same time using the component method to handle the mainstream flow path to describe the complex aerodynamic and thermal processes in the compression component and the turbine component. Through the coupling of the component method and the network method, the simulation of the instantaneous reverse flow of the mode selection valve of the variable cycle aeroengine is realized, and a high-precision resolution can be achieved for the reverse flow phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. By referring to the drawings, the features and advantages of the present invention can be more clearly understood. The drawings are schematic and should not be construed as limiting the present invention in any way. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0043] Figure 1 Flow chart of the transient reverse flow simulation method for mode switching of a variable cycle aeroengine according to an embodiment of the present invention.

[0044] Figure 2 Schematic diagram of the main flow path during mode switching in the transient reverse flow simulation method for mode switching of a variable cycle aeroengine according to an embodiment of the present invention.

[0045] Figure 3 Coupling model of the main flow path model and the local flow path model for mode switching of a variable cycle aeroengine transient reverse flow simulation system according to an embodiment of the present invention.

[0046] Figure 4 Simulation result of the reverse flow phenomenon in the louver flow path of the inner combustion chamber during the acceleration process in the fan mode of a "dual variable" cycle engine in an embodiment of the transient reverse flow simulation method for mode switching of a variable cycle aeroengine according to an embodiment of the present invention.

[0047] Figure 5 Control law of the valve angle of the mode selection valve during the mode switching process of a "dual variable" cycle engine in another embodiment of the transient reverse flow simulation method for mode switching of a variable cycle aeroengine according to an embodiment of the present invention.

[0048] Figure 6 Simulation result of the reverse flow phenomenon in the flow path from the second bypass duct to the mode selection valve (turbojet) during the mode switching process of a "dual variable" cycle engine in another embodiment of the transient reverse flow simulation method for mode switching of a variable cycle aeroengine according to an embodiment of the present invention.

[0049] Description of reference numerals:

[0050] 101, core fan;

[0051] 102, high-pressure compressor;

[0052] 103, main combustion chamber;

[0053] 104, high-pressure turbine;

[0054] 105, intermediate-pressure turbine;

[0055] 106, intermediate-pressure turbine rear casing;

[0056] 107, louver of the inner combustion chamber;

[0057] 108, mode selection valve (closed state);

[0058] 109, mode selection valve (open state);

[0059] 110. Third outer annulus;

[0060] 111. Second outer annulus;

[0061] 112. First outer annulus;

[0062] 113. Core engine flow path;

[0063] 114. Inner annulus combustion chamber;

[0064] 115. Outer annulus combustion chamber;

[0065] 116. Front mixing chamber;

[0066] 117. Mode selection valve regulating mechanism;

[0067] 118. Flow path of the rear casing of the medium-pressure turbine;

[0068] 119. Flow path of the louver of the inner annulus combustion chamber;

[0069] 120. Flow path from the first outer annulus to the mode selection valve;

[0070] 121. Flow path from the mode selection valve to the outer annulus combustion chamber;

[0071] 122. Flow path from the second outer annulus to the mode selection valve (turbojet);

[0072] 123. Flow path from the second outer annulus to the mode selection valve (turbofan);

[0073] 124. Core engine bleed boundary node;

[0074] 125. Core engine manifold boundary node;

[0075] 126. First outer annulus bleed boundary node;

[0076] 127. Inner node of the mode selection valve;

[0077] 128. First outer annulus manifold boundary node;

[0078] 129. Second outer annulus bleed boundary node;

[0079] 130. Second outer annulus manifold boundary node;

[0080] 131. Main flow path;

[0081] 132. Local flow path for mode switching. Detailed implementation method

[0082] In order to more clearly understand the above objects, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, without conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0083] In the following description, many specific details are set forth in order to provide a thorough understanding of the present invention. However, the present invention may be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below.

[0084] The following provides a detailed description of a variable cycle aeroengine mode switching instantaneous countercurrent simulation method and simulation system according to an embodiment of the present invention with reference to the accompanying drawings.

[0085] It should be noted that the variable cycle aeroengine mode switching instantaneous countercurrent simulation method and simulation system disclosed in the present invention can not only be used for simulating the instantaneous countercurrent process during the mode switching of the engine configuration described in the specific embodiments, but also for simulating similar instantaneous countercurrent characteristics in other engine configurations. Additionally, the present invention may be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below.

[0086] As Figure 2 shown, in the variable cycle aeroengine mode switching instantaneous countercurrent simulation method according to an embodiment of the present invention, the main flow paths involved in mode switching in the variable cycle aeroengine may include: a core fan 101, a high-pressure compressor 102, a main combustion chamber 103, a high-pressure turbine 104, an intermediate-pressure turbine 105, an intermediate-pressure turbine rear casing 106, an inner combustion chamber louver 107, a mode selection valve (which may be in a closed state 108 or an open state 109), a mode selection valve adjustment mechanism 117, a third bypass duct 110, a second bypass duct 111, a first bypass duct 112, a core engine flow path 113, an inner combustion chamber 114, an outer combustion chamber 115, a front mixing chamber 116, an intermediate-pressure turbine rear casing flow path 118, an inner combustion chamber louver flow path 119, a first bypass duct to mode selection valve flow path 120, a mode selection valve to outer combustion chamber flow path 121, a second bypass duct to mode selection valve flow path (turbojet) 122, a second bypass duct to mode selection valve flow path (turbofan) 123, a core engine bleed boundary node 124, a core engine confluence boundary node 125, a first bypass duct bleed boundary node 126, a mode selection valve internal node 127, a first bypass duct confluence boundary node 128, a second bypass duct bleed boundary node 129, and a second bypass duct confluence boundary node 130.

[0087] See Figures 1 to 3, the instantaneous countercurrent simulation method for mode switching of a variable cycle aeroengine provided by an embodiment of the present invention includes the following steps.

[0088] Step S1, establish a main flow path 131 model using the component method. The main flow path 131 model includes the main functional components of the aeroengine: a compression system, a combustion system, a turbine system, a duct system, a casing, and a mixing chamber. The component method performance model is a zero-dimensional simulation model based on the characteristics of engine components. According to the aerodynamic and thermal processes of the engine, the aeroengine is divided into several major functional components. Using the working parameters or performance parameters of each component of the aeroengine as the initial trial parameters, calculate each component sequentially in the flow direction, and establish a solution matrix for the correction amount of the trial parameters based on the common working conditions that must be satisfied between components and the selected engine control law, and iteratively correct the initial trial parameters.

[0089] Optionally, the duct system may specifically include a first outer duct 112, a second outer duct 111, and a third outer duct 110 arranged from the inside to the outside. The compression system may specifically include a core fan 101 and a high-pressure compressor 102. The combustion system may specifically include a main combustion chamber 103, an inner flow combustion chamber 114, and an outer flow combustion chamber 115. The turbine system may specifically include a high-pressure turbine 104 and a medium-pressure turbine 105. The mixing chamber may specifically include a front mixing chamber 116. The casing may specifically include a medium-pressure turbine rear casing 106, a core engine flow path 113, and a medium-pressure turbine rear casing flow path 118.

[0090] Step S2, establish a mode switching local flow path 132 model using the network method. The mode switching local flow path model includes a mode selection valve, an internal node 127 of the mode selection valve, an air extraction boundary node, a confluence boundary node, and a connecting flow path; wherein, the air extraction boundary node includes an air extraction boundary node on the inner flow path of the mode selection valve and an air extraction boundary node on the outer flow path of the mode selection valve; wherein, the confluence boundary node includes a confluence boundary node on the inner flow path of the mode selection valve and a confluence boundary node on the outer flow path of the mode selection valve; and wherein, the connecting flow path includes a flow path connecting the air extraction boundary node on the inner flow path of the mode selection valve to the internal node 127 of the mode selection valve, a flow path connecting the air extraction boundary node on the outer flow path of the mode selection valve to the internal node 127 of the mode selection valve, a flow path connecting the air extraction boundary node on the outer flow path of the mode selection valve to the confluence boundary node on the outer flow path of the mode selection valve, and a flow path connecting the internal node of the mode selection valve to the confluence boundary node on the inner flow path of the mode selection valve; wherein, the mode selection valve switches between a closed state and an open state, thereby adjusting the area of the flow path connecting the air extraction boundary node on the outer flow path of the mode selection valve to the internal node 127 of the mode selection valve, and adjusting the area of the flow path connecting the air extraction boundary node on the outer flow path of the mode selection valve to the confluence boundary node on the outer flow path of the mode selection valve.

[0091] As Figure 3 shown, optionally, in an embodiment where the duct system includes a first outer duct 112, a second outer duct 111, and a third outer duct 110 arranged from inside to outside, the air extraction boundary node of the inner flow path of the mode selection valve is the first outer duct air extraction boundary node 126; the air extraction boundary node of the outer flow path of the mode selection valve is the second outer duct air extraction boundary node 129; the confluence boundary node of the inner flow path of the mode selection valve is the first outer duct confluence boundary node 128; the confluence boundary node of the outer flow path of the mode selection valve is the second outer duct confluence boundary node 130. In this embodiment, the mode switching local flow path 132 may specifically include: the first outer duct air extraction boundary node 126, the second outer duct air extraction boundary node 129, the mode selection valve internal node 127, the first outer duct confluence boundary node 128, and the second outer duct confluence boundary node 130; and the first outer duct to mode selection valve flow path 120 connecting the first outer duct air extraction boundary node 126 and the mode selection valve internal node 127, the second outer duct to mode selection valve flow path (turbojet) 122 connecting the second outer duct air extraction boundary node 129 and the mode selection valve internal node 127, the second outer duct to mode selection valve flow path (turbofan) 123 connecting the second outer duct air extraction boundary node 129 and the second outer duct confluence boundary node 130, and the mode selection valve to outer duct combustion chamber flow path 121 connecting the mode selection valve internal node 127 and the first outer duct confluence boundary node 128. In addition, in this embodiment, it may further include a core engine air extraction boundary node 124 and a core engine confluence boundary node 125, as well as the medium-pressure turbine rear casing flow path 118 connecting the core engine air extraction boundary node 124 and the core engine confluence boundary node 125, and the inner combustion chamber louver flow path 119 connecting the core engine confluence boundary node 125 and the mode selection valve internal node 127. The above-mentioned nodes and flow paths together form a network method model of the mode switching local flow path 132.

[0092] Step S3: Construct a transient countercurrent simulation model for mode switching. By means of the bleed boundary nodes and the confluence boundary nodes with equation closure mechanisms, couple the mainstream flow path 131 model established by the component method with the local flow path 132 model for mode switching established by the network method to obtain the transient countercurrent simulation model for mode switching. Specifically, this coupling can be achieved by coupling the core engine bleed boundary node 124, the first bypass bleed boundary node 126, the second bypass bleed boundary node 129, and the core engine confluence boundary node 125, the first bypass confluence boundary node 128, and the second bypass confluence boundary node 130 with equation closure mechanisms to the mainstream flow path model. Among them, the core engine bleed boundary node 124 and the core engine confluence boundary node 125, the first bypass bleed boundary node 126 and the first bypass confluence boundary node 128, and the second bypass bleed boundary node 129 and the second bypass confluence boundary node 130 are respectively composed of three bleed / confluence modules, and each bleed / confluence module satisfies the following conditions.

[0093] In step S3, when constructing the transient countercurrent simulation model for mode switching, it may further include, for any one of the bleed boundary nodes among the core engine bleed boundary node 124, the first bypass bleed boundary node 126, and the second bypass bleed boundary node 129, setting the total temperature T b1 * , total pressure p b1 * , mass flow rate W b1 , fuel-air ratio f b1 , moisture content D b1 based on the upstream mainstream component connected to the bleed boundary node, to obtain the total temperature T b2 * , total pressure p b2 * , mass flow rate W b2 , fuel-air ratio f b2 , moisture content D b2 of the bleed boundary node. Set the mass flow rate W b2 of the bleed boundary node to satisfy the following relationship with the mass flow rates W b of the adjacent M j branches:

[0094]

[0095] where ε b represents the mass flow rate balance equation of the bleed boundary node, W b2 represents the mass flow rate of the bleed boundary node, b2 represents the number of the bleed boundary node and b2 = 1, …, 3, W j represents the mass flow rate of the j-th branch adjacent to the bleed boundary node, j represents the number of the branch adjacent to the bleed boundary node and j = 1, …, M b , and M bIndicates the total number of branches adjacent to the bleed boundary node.

[0096] For any of the manifold boundary nodes, i.e., the core manifold boundary node 125, the first bypass manifold boundary node 128, and the second bypass manifold boundary node 130, set its total pressure p M * 、total enthalpy h M * 、total pressure p M * 、flow rate W M 、fuel-air ratio f M and moisture content D M as trial values. These trial values can be automatically given during the simulation and the final results can be obtained through the balance equations.

[0097] Set the trial values of the total enthalpy h M * 、flow rate W M 、fuel-air ratio f M and moisture content D M of any manifold boundary node. The total enthalpy h M 、flow rate W k * 、fuel-air ratio f k 、and moisture content D k of the N k branches adjacent to this manifold boundary node satisfy the following relationships:

[0098]

[0099] where ε M.1 represents the energy balance equation of the manifold boundary node, ε M.2 represents the flow rate balance equation of the manifold boundary node, ε M.3 represents the fuel-air ratio balance equation of the manifold boundary node, ε M.4 represents the moisture content balance equation of the manifold boundary node, p M * represents the total pressure of the manifold boundary node, represents the total enthalpy of the manifold boundary node, W M represents the flow rate of the manifold boundary node, f M represents the fuel-air ratio of the manifold boundary node, D M represents the moisture content of the manifold boundary node, M represents the number of the manifold boundary node and M = 1, …, 3, represents the total enthalpy of the k-th branch adjacent to the manifold boundary node, W k represents the flow rate of the k-th branch adjacent to the manifold boundary node, f k represents the fuel-air ratio of the k-th branch adjacent to the manifold boundary node, D kDenote the moisture content of the k-th branch adjacent to the confluence boundary node, where k represents the number of the branch adjacent to the confluence boundary node and k = 1, …, N M , N M Denote the total number of branches adjacent to the confluence boundary node.

[0100] In the mode-switching instantaneous countercurrent simulation model established above, in each air extraction / confluence module, there are 0 trial givens and 1 balance equation at the air extraction boundary node, and 5 trial givens and 4 balance equations at the confluence boundary node. Therefore, the number of trial givens in the air extraction / confluence module composed of the corresponding air extraction boundary node and confluence boundary node is equal to the number of balance equations, ensuring that the simulation method proposed by the present invention has a perfect equation closure mechanism and can be solved.

[0101] Step S4, perform simulation using the mode-switching instantaneous countercurrent simulation model, set the engine control law and the mode selection valve adjustment law. The selectable control laws include the relative fuel supply flow rate of the combustion chamber, flight speed, etc., and the mode selection valve adjustment law can be the opening degree of the mode selection valve, etc.; then, obtain and output the simulation results from the mode-switching instantaneous countercurrent simulation model. The obtained simulation results can include, for example, the instantaneous countercurrent characteristics of mode switching, etc. Finally, draw a simulation chart for the analysis and optimization design of the variable cycle aeroengine mode switching.

[0102] Reference Figure 2 and Figure 3 , according to another embodiment of the present invention, there is provided a variable cycle aeroengine mode-switching instantaneous countercurrent simulation system, including a mode-switching instantaneous countercurrent simulation model established by coupling a mainstream flow path model and a mode-switching local flow path model.

[0103] Among them, the mainstream flow path model is established by the component method and includes the functional components of the aeroengine: compression system, combustion system, turbine system, duct system, casing, and mixing chamber.

[0104] The mode switching local flow path model is established by a network method and includes: a mode selection valve, an internal node of the mode selection valve, an air bleed boundary node, a confluence boundary node, and a connecting flow channel; wherein the air bleed boundary node includes an air bleed boundary node of the flow path inside the mode selection valve, and an air bleed boundary node of the flow path outside the mode selection valve; wherein the confluence boundary node includes a confluence boundary node of the flow path inside the mode selection valve, and a confluence boundary node of the flow path outside the mode selection valve; and wherein the connecting flow channel includes a flow channel connecting the air bleed boundary node of the flow path inside the mode selection valve and the internal node of the mode selection valve, and connecting the mode selection valve. The mode selection valve is connected to the flow channel connecting the air bleed boundary node of the outer flow path of the mode selection valve and the internal node of the mode selection valve, the flow channel connecting the air bleed boundary node of the outer flow path of the mode selection valve and the flow confluence boundary node of the outer flow path of the mode selection valve, and the flow channel connecting the internal node of the mode selection valve and the flow confluence boundary node of the inner flow path of the mode selection valve; wherein the mode selection valve is switched between a closed state and an open state, thereby adjusting the area of ​​the flow channel connecting the air bleed boundary node of the outer flow path of the mode selection valve and the internal node of the mode selection valve, and adjusting the area of ​​the flow channel connecting the air bleed boundary node of the outer flow path of the mode selection valve and the flow confluence boundary node of the outer flow path of the mode selection valve.

[0105] The mode switching instantaneous counterflow simulation model is obtained by coupling the mainstream flow path model established by the component method with the mode switching local flow path model established by the network method through the air entrainment boundary nodes and the confluence boundary nodes with equation closure mechanisms.

[0106] The following continues to refer to Figure 2 and Figure 3 , and combined with Figures 4 to 6 , two exemplary embodiments of the variable cycle aircraft engine mode switching transient reverse flow simulation method provided by the embodiment of the present invention are described. In this embodiment, the transient reverse flow phenomenon in the mode switching valve of the "double variable" cycle engine is simulated and analyzed. The obtained results can be used for further optimization design and analysis of the mode switching process regulation law. In the following embodiment, adjusting the working mode of the engine in the "double variable" cycle engine includes setting the mode selection valve in the closed state 108 as a turbofan mode, and setting the mode selection valve in the open state 109 as a turbojet mode.

[0107] Example 1

[0108] Figure 4 The simulation results of the reverse flow phenomenon of the shutter flow passage of the combustion chamber contained in the acceleration process of the "dual variable" cycle engine in turbofan mode of Example 1 are shown.

[0109] In this embodiment, according to the variable cycle aircraft engine mode switching transient reverse flow simulation method provided by the embodiment of the present invention, a mode switching transient reverse flow simulation model is established, and the flow direction of the flow channel is set to Figure 3When the arrow directions are the same, the flow direction is positive; otherwise, it is negative. For example, when the fluid flow direction in the inner combustion chamber louver channel 119 is the same as Figure 3 the arrow direction in Figure 3 and flows from the internal node 127 of the mode selection valve to the core engine confluence boundary node 125, it is positive. Set the mode selection valve in the closed state 108, in the turbofan mode.

[0110] In the initial state Ma = 2.4, the flow direction of the inner combustion chamber louver channel 119 is reverse, and the flow direction of the second bypass to the mode selection valve channel (turbojet) 122 is also reverse. Currently in the turbofan mode, the mode selection valve is in the closed state 108, and the inner combustion chamber louver 107 is in the closed state. Most of the air flow in the second bypass 111 enters the front mixing chamber 116 and converges with the air flow in the third bypass 110. A small part of the air flow in the first bypass 112 leaks into the second bypass 111 through the second bypass to the mode selection valve channel (turbojet) 122. The gas in the core engine channel 113 at the outlet of the medium-pressure turbine 105 flows reversely through the inner combustion chamber louver channel 119 and leaks into the first bypass 112.

[0111] Next, the Ma number increases. When the Ma number increases to Ma = 2.8, the flow direction in the inner combustion chamber louver channel 119 reverses and becomes positive, and the flow direction of the second bypass to the mode selection valve channel (turbojet) 122 also reverses and becomes positive. This is because the boosting capabilities of the core fan 101 and the high-pressure compressor 102 decrease. At this time, the air flow pressures at the outlets of the first bypass 112 and the medium-pressure turbine 105 decrease, and the inner combustion chamber louver 107 is still in the closed state. The air flow in the second bypass 111 leaks into the first bypass 112 through the second bypass to the mode selection valve channel (turbojet) 122, and the air flow in the first bypass 112 leaks into the core engine channel 113 through the inner combustion chamber louver channel 119.

[0112] Figure 4 The simulation result record chart generated for this embodiment shows that during this process, the air flow direction through the inner combustion chamber louver channel 119 changes, achieving a high-precision simulation of the instantaneous countercurrent process of the mode switching valve during the acceleration process.

[0113] Embodiment 2

[0114] Figure 5 Shows the simulation results of the valve angle control law of the mode selection valve during the mode switching process of the "dual variable" cycle engine in Embodiment 2. Figure 6 Shows the simulation results of the countercurrent phenomenon of the second bypass to the mode selection valve channel (turbojet) during the mode switching process of the "dual variable" cycle engine in Embodiment 2.

[0115] In this embodiment, a transient countercurrent simulation model for mode switching of a variable cycle aeroengine is established according to the transient countercurrent simulation method provided by the embodiments of the present invention, and it is set that when the flow direction of the flow passage is the same as the Figure 2 arrow direction in, the flow direction is positive, otherwise it is negative. For example, when the flow direction of the fluid in the flow passage from the second bypass to the mode selection valve (turbojet) 122 is the same as the Figure 2 arrow direction in, and flows from the second bypass air extraction boundary node 129 to the internal node 127 of the connection mode selection valve, the flow direction is positive, otherwise it is negative.

[0116] In this embodiment, in the turbofan mode, the mode selection valve is in the closed state 108, and the inner combustion chamber shutter 107 is in the closed state. The flow area of the flow passage from the second bypass to the mode selection valve (turbojet) 122 is the minimum value, which is 565 mm 2 , and the flow area of the inner combustion chamber shutter flow passage 119 is the minimum value of 283 mm 2 , and the flow area of the flow passage from the second bypass to the mode selection valve (turbofan) 123 is the maximum value of 336464 mm 2 .

[0117] In the turbojet mode, the mode selection valve is in the open state 109, and the inner combustion chamber shutter 107 is in the open state. The flow area of the flow passage from the second bypass to the mode selection valve (turbojet) 122 is the maximum value, which is 336465 mm 2 , and the flow area of the inner combustion chamber shutter flow passage 119 is the maximum value, which is 65973 mm 2 , and the flow area of the flow passage from the second bypass to the mode selection valve (turbofan) 123 is the minimum value of 565 mm 2 . The above values are determined based on the design of the variable cycle aeroengine.

[0118] The flow areas of the remaining flow passages are all fixed values determined by the structure of the variable cycle aeroengine. Among them, for example, the flow area of the flow passage of the rear casing of the intermediate pressure turbine 118 is 274889 mm 2 , the flow area of the flow passage from the first bypass to the mode selection valve 120 is 515314 mm 2 , and the flow area of the flow passage from the mode selection valve to the outer combustion chamber 121 is 379282 mm 2 .

[0119] Figure 5 shows the valve angle control law of the mode selection valve during the mode switching process of the "dual variable" cycle engine in this embodiment. As the mode selection valve gradually switches from the closed state 108 to the open state 109, its valve angle gradually increases, so that the flow areas of the flow passage from the second bypass to the mode selection valve (turbojet) 122 and the inner combustion chamber change from 565 mm 2Increased to 336465 mm 2 , the flow area of the inner combustion chamber louver flow passage 119 increases from 283 mm 2 to 65973 mm 2 , the flow area of the second bypass to mode selection valve flow passage (turbofan) 123 decreases from 336464 mm 2 to 565 mm 2 .

[0120] Figure 6 The simulation results of the reverse flow phenomenon of the second bypass to mode selection valve flow passage (turbojet) 122 during the mode switching process of the "dual variable" cycle engine in this embodiment are shown. It shows that during the transition process of mode switching, the flow in the second bypass to mode selection valve flow passage (turbojet) 122 reverses, achieving a high-precision simulation of the instantaneous reverse flow of the mode switching valve during the mode switching transition process, with a time resolution of up to 0.1 ms.

[0121] Through the above embodiments of applying a method for simulating the instantaneous reverse flow during mode switching of a variable cycle aero engine provided by the present invention, it can be concluded that the method and system for simulating the instantaneous reverse flow during mode switching of a variable cycle aero engine provided by the present invention achieve the simulation of the instantaneous reverse flow of the mode selection valve of a variable cycle aero engine, and achieve a high-precision resolution simulation of the reverse flow phenomenon, providing support for the analysis and optimization design of the mode switching of a variable cycle aero engine.

[0122] All the above optional technical solutions can be combined arbitrarily to form optional embodiments of the present application, which will not be elaborated here one by one.

[0123] It should be understood that the magnitudes of the sequence numbers of the steps in the above embodiments do not mean the order of execution. The order of execution of each process should be determined according to its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0124] The above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for simulating transient reverse flow during mode switching of a variable cycle aircraft engine, characterized in that: The following steps are involved: Step S1, using a component method to establish a mainstream flow path model of a variable cycle aircraft engine, where the mainstream flow path model includes main functional components of the aircraft engine: a compression system, a combustion system, a turbine system, a duct system, a casing, and a mixing chamber; Step S2, adopting the network method to establish the mode switching local flow path model of the variable cycle aircraft engine, the mode switching local flow path model includes: a mode selection valve, an internal node of the mode selection valve, an air bleed boundary node, a confluence boundary node, and a connecting flow channel; wherein the air bleed boundary node includes an air bleed boundary node of the flow path inside the mode selection valve, and an air bleed boundary node of the flow path outside the mode selection valve; wherein the confluence boundary node includes an air confluence boundary node of the flow path inside the mode selection valve, and an air confluence boundary node of the flow path outside the mode selection valve; and wherein the connecting flow channel includes connecting the air bleed boundary node of the flow path inside the mode selection valve with the internal node of the mode selection valve A flow channel at a point, a flow channel connecting an air bleed boundary node of an outer flow path of a mode selection valve and an inner node of a mode selection valve, a flow channel connecting an air bleed boundary node of an outer flow path of a mode selection valve and a flow confluence boundary node of an outer flow path of a mode selection valve, and a flow channel connecting an inner node of a mode selection valve and a flow confluence boundary node of an inner flow path of a mode selection valve; wherein the mode selection valve switches between a closed state and an open state, thereby adjusting an area of ​​a flow channel connecting an air bleed boundary node of an outer flow path of a mode selection valve and an inner node of a mode selection valve, and adjusting an area of ​​a flow channel connecting an air bleed boundary node of an outer flow path of a mode selection valve and a flow confluence boundary node of an outer flow path of a mode selection valve; Step S3, constructing a mode switching instantaneous counterflow simulation model, coupling the mainstream flow path model established by the component method with the mode switching local flow path model established by the network method through the air entrainment boundary node and the confluence boundary node with the equation closure mechanism to obtain the mode switching instantaneous counterflow simulation model; Step S4, use the mode switching instantaneous reverse flow simulation model to perform simulation, set the aircraft engine control law and the mode selection valve adjustment law, obtain and output the simulation results by the mode switching instantaneous reverse flow simulation model, draw a simulation chart based on the simulation results, and use it for the analysis and optimization design of the variable cycle aircraft engine mode switching.

2. The variable cycle aircraft engine mode switching transient reverse flow simulation method according to claim 1, characterized in that: Step S3 further comprises: The mainstream flow path model established by the component method is coupled with the local flow path model of the mode switching valve established by the network method. Specifically, the mode selection valve inner flow path air bleed boundary node, the mode selection valve outer flow path air bleed boundary node, the mode selection valve internal node, the mode selection valve inner flow path confluence boundary node, and the mode selection valve outer flow path confluence boundary node are coupled with the mainstream flow path model. The corresponding mode selection valve inner flow path bleed boundary node and mode selection valve inner flow path confluence boundary node, the mode selection valve outer flow path bleed boundary node and mode selection valve outer flow path confluence boundary node are respectively formed into a bleed / confluence module.

3. The variable cycle aircraft engine mode switching transient reverse flow simulation method according to claim 1, characterized in that: In the mainstream flow path model established in step S1: The duct system includes a first outer duct, a second outer duct and a third outer duct arranged from the inside to the outside.

4. The variable cycle aircraft engine mode switching transient reverse flow simulation method according to claim 3, characterized in that: The mode switching local flow path model established in step S2 also includes: a core engine bleed air boundary node and a core engine confluence boundary node; and an intermediate pressure turbine rear casing flow channel connecting the core engine bleed air boundary node and the core engine confluence boundary node, and an internal combustion chamber louver flow channel connecting the core engine confluence boundary node and the internal node of the mode selection valve.

5. The variable cycle aircraft engine mode switching transient reverse flow simulation method according to claim 4, characterized in that: In the mode switching local flow path model established in step S2: The air bleed boundary node of the inner flow path of the mode selection valve is the first outer duct air bleed boundary node; The air bleed boundary node of the flow path outside the mode selection valve is the second outer duct air bleed boundary node; The inner flow path confluence boundary node of the mode selection valve is a first outer flow confluence boundary node; The flow confluence boundary node of the outer flow path of the mode selection valve is a second outer flow confluence boundary node; The flow channel connecting the air bleed boundary node of the inner flow path of the mode selection valve and the internal node of the mode selection valve is the first outer culvert to mode selection valve flow channel connecting the air bleed boundary node of the first outer culvert and the internal node of the mode selection valve; The flow channel connecting the air bleed boundary node of the outer flow path of the mode selection valve and the internal node of the mode selection valve is a second outer culvert to mode selection valve flow channel connecting the air bleed boundary node of the second outer culvert and the internal node of the mode selection valve; The flow channel connecting the mode selection valve outer flow path air bleed boundary node and the mode selection valve outer flow path confluence boundary node is the second outer culvert to mode selection valve flow channel connecting the second outer culvert air bleed boundary node and the second outer culvert confluence boundary node; The flow channel connecting the mode selection valve internal node and the mode selection valve inner side flow path confluence boundary node is a mode selection valve to outer culvert combustion chamber flow channel connecting the mode selection valve internal node and the first outer culvert confluence boundary node.

6. The variable cycle aircraft engine mode switching transient reverse flow simulation method according to claim 5, characterized in that: Step S3 further comprises: The mainstream flow path model established by the component method is coupled with the local flow path model of the mode switching valve established by the network method. Specifically, the core engine bleed air boundary node, the first outer duct bleed air boundary node, the second outer duct bleed air boundary node, the core engine confluence boundary node, the first outer duct confluence boundary node and the second outer duct confluence boundary node with the equation closure mechanism are coupled with the mainstream flow path model. The core engine air bleed boundary node and the core engine confluence boundary node, the first outer duct air bleed boundary node and the first outer duct confluence boundary node, and the second outer duct air bleed boundary node and the second outer duct confluence boundary node are respectively formed into three air bleed / confluence modules.

7. The variable cycle aircraft engine mode switching transient reverse flow simulation method according to claim 6, characterized in that: Step S3 of constructing a mode switching instantaneous countercurrent simulation model also includes: For any of the core engine bleed air boundary nodes, the first duct bleed air boundary node, and the second duct bleed air boundary node, a total temperature T of the upstream mainstream component connected to the bleed air boundary node is set. b1 * , total pressure p b1 * 、Flow rate W b1 , oil-gas ratio b1 , moisture content D b1 , and obtain the total temperature T of the bleed air boundary node b2 * , total pressure p b2 * 、Flow rate W b2 , oil-gas ratio f b2 , moisture content D b2 ; Set the flow rate W of any bleed air boundary node b2 With adjacent M b The flow rate of each branch is W j The following relations are satisfied: Among them, ε b represents the flow balance equation of the bleed air boundary node, W b2 represents the flow rate of the bleed air boundary node, b2 represents the number of the bleed air boundary node and b2=1,…,3, W j represents the flow rate of the jth branch adjacent to the bleed air boundary node, j represents the number of the branch adjacent to the bleed air boundary node and j=1,…,M b , M b Indicates the total number of branches adjacent to the bleed air boundary node; For any of the core engine confluence boundary nodes, the first outer culvert confluence boundary node, and the second outer culvert confluence boundary node, set the total pressure, total enthalpy, flow rate, oil-gas ratio, and moisture content of any confluence boundary node as the trial supply value, and the N adjacent to the confluence boundary node M The total enthalpy, flow rate, oil-gas ratio and moisture content of each branch satisfy the following relationship: Among them, ε M.1 represents the energy balance equation of the confluence boundary node, ε M.2 represents the flow balance equation at the confluence boundary node, ε M.3 represents the oil-gas ratio balance equation at the confluence boundary node, ε M.4 represents the moisture balance equation of the confluence boundary node, represents the total enthalpy of the confluence boundary node, W M represents the flow rate at the confluence boundary node, f M represents the oil-gas ratio at the confluence boundary node, D M represents the moisture content of the confluence boundary node, M represents the number of the confluence boundary node and M=1,…,3, represents the total enthalpy of the kth branch adjacent to the confluence boundary node, W k represents the flow of the kth branch adjacent to the confluence boundary node, f k represents the oil-gas ratio of the kth branch adjacent to the confluence boundary node, D k represents the moisture content of the kth branch adjacent to the confluence boundary node, k represents the number of the branch adjacent to the confluence boundary node and k=1,…,N M , N M Represents the total number of branches adjacent to the confluence boundary node.

8. A simulation system constructed based on the variable cycle aircraft engine mode switching transient reverse flow simulation method according to any one of claims 1 to 7, characterized in that: Including a mode switching instantaneous counterflow simulation model established by coupling a mainstream flow path model and a mode switching local flow path model; The mainstream flow path model is established by the component method and includes functional components of the aircraft engine: compression system, combustion system, turbine system, duct system, casing and mixing chamber; The mode switching local flow path model is established by a network method and includes: a mode selection valve, an internal node of the mode selection valve, an air bleed boundary node, a confluence boundary node, and a connecting flow channel; wherein the air bleed boundary node includes an air bleed boundary node of the flow path inside the mode selection valve, and an air bleed boundary node of the flow path outside the mode selection valve; wherein the confluence boundary node includes a confluence boundary node of the flow path inside the mode selection valve, and a confluence boundary node of the flow path outside the mode selection valve; and wherein the connecting flow channel includes a flow channel connecting the air bleed boundary node of the flow path inside the mode selection valve and the internal node of the mode selection valve, and connecting the mode selection valve. The mode selection valve is connected to the flow channel of the air bleed boundary node of the outer flow path of the mode selection valve and the inner node of the mode selection valve, the flow channel connecting the air bleed boundary node of the outer flow path of the mode selection valve and the flow confluence boundary node of the outer flow path of the mode selection valve, and the flow channel connecting the inner node of the mode selection valve and the flow confluence boundary node of the inner flow path of the mode selection valve; wherein the mode selection valve is switched between a closed state and an open state, thereby adjusting the area of ​​the flow channel connecting the air bleed boundary node of the outer flow path of the mode selection valve and the inner node of the mode selection valve, and adjusting the area of ​​the flow channel connecting the air bleed boundary node of the outer flow path of the mode selection valve and the flow confluence boundary node of the outer flow path of the mode selection valve; The mode switching instantaneous counterflow simulation model is obtained by coupling the mainstream flow path model established by the component method with the mode switching local flow path model established by the network method through the air entrainment boundary nodes and the confluence boundary nodes with equation closure mechanisms.

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