An aeroengine modeling method with RVABI structure

Abstract

The present application belongs to the field of aero-engines, and in particular, relates to an aero-engine modeling method with an RVABI structure. It includes: step one, a guessed value of the iterative static pressure at the inlet of the mixing chamber is given; step two, judging whether it is blocked according to the iterative static pressure at the inlet of the mixing chamber and the critical static pressure at the outlet of the first culvert, and constructing the flow balance equation of the first culvert outlet according to the inlet flow rate and the outlet flow rate; step three: judging whether it is blocked according to the iterative static pressure at the inlet of the mixing chamber and the critical static pressure at the outlet of the turbine after the turbine, and constructing the flow balance equation of the outlet of the turbine after the turbine according to the inlet flow rate and the outlet flow rate; step four, constructing a mixing model of the mixing chamber. The present application can establish a consistent model of four different types of blockage conditions of the mixing chamber during the RVABI adjustment process, and there will be no calculation interruption and model jitter due to cross-sectional blockage.

Description

Technical Field

[0001] The present application relates to the field of aero-engines, and in particular to an aero-engine modeling method with an RVABI structure. Background Art

[0002] Aircraft engine models are very important for the development of aircraft engines. Overall performance models can be used for engine concept design, etc. Real-time simulation models can be used for control system design and verification, which can reduce development costs and shorten development cycles.

[0003] In the development of aviation engine configurations, advanced variable cycle engines, adaptive cycle engines, STOVL (Short Take-Off Vertical Landing) aircraft engines, etc. all have RVABI (Rear Variable Area Bypass Injector) structures, which are used to adjust the parameters of the two airflows mixed in the mixing chamber, thereby optimizing engine performance. However, during the RVABI adjustment process, the two sections directly related to it, including the first outer bypass outlet and the rear inner bypass outlet of the turbine, may shrink, forming a gradually converging duct, so it is easy to cause airflow blockage, that is, the Mach number reaches the maximum value of 1, and the flow is blocked. The existing engine model does not accurately describe this phenomenon, and even calculation interruptions will occur when blockage occurs, so this situation has to be avoided. This is very unfavorable for the design of the robustness of the control system.

[0004] Therefore, how to accurately describe the RVABI and mixing chamber performance when blockage occurs is an urgent problem to be solved. Summary of the invention

[0005] Based on this, it is necessary to establish a modeling method for aircraft engines with RVABI structure that can accurately characterize the blocking phenomenon of RVABI related sections in response to the above technical problems.

[0006] The technical solution of this application is:

[0007] In a first aspect, the present application provides a modeling method for an aircraft engine having an RVABI structure, wherein the aircraft engine comprises a first outer duct, a turbine rear duct, an RVABI and a mixing chamber, wherein the RVABI is between an outlet of the first outer duct and an outlet of the turbine rear duct, and both the outlet of the first outer duct and the outlet of the turbine rear duct are connected to an inlet of the mixing chamber, and the method comprises:

[0008] Step 1: Assign a guess value to a predefined variable, mixing chamber inlet iterative static pressure;

[0009] Step 2: using the guessed value of the iterative static pressure at the mixing chamber inlet to determine whether the outlet of the first culvert is in a blocked state, and constructing a flow balance equation at the outlet of the first culvert according to whether the outlet of the first culvert is in a blocked state;

[0010] Step 3: using the guessed value of the iterative static pressure at the mixing chamber inlet, determining whether the outlet of the turbine rear connotation is in a blocked state, and constructing a flow balance equation of the turbine rear connotation outlet according to whether the outlet of the turbine rear connotation is in a blocked state;

[0011] Step 4: constructing a numerical model of the mixing chamber, wherein the constructing the numerical model of the mixing chamber includes calculating the flow rate, total pressure, total temperature, and oil-gas ratio of the outlet of the mixing chamber.

[0012] In one embodiment, determining whether the outlet of the first outer vent is in a blocked state comprises:

[0013] Obtaining the area of ​​the outlet of the first culvert;

[0014] Calculate the critical static pressure and critical flow rate of the outlet of the first culvert using the total pressure, total temperature, oil-gas ratio and area of ​​the outlet of the first culvert;

[0015] The critical static pressure and critical flow rate at the outlet of the first outer cannula are the static pressure and flow rate calculated assuming that the outlet Mach number of the first outer cannula is equal to 1;

[0016] The static pressure at the outlet of the first outer duct is calculated using the iterative static pressure at the inlet of the mixing chamber. If the static pressure at the outlet of the first outer duct is greater than the critical static pressure at the outlet of the first outer duct, the outlet of the first outer duct is not in the blocked state; otherwise, the outlet of the first outer duct is in the blocked state.

[0017] In one embodiment, constructing the first culvert outlet flow balance equation includes:

[0018] obtaining a flow rate at an inlet of the first culvert;

[0019] If the outlet of the first culvert is not in a blocked state, the static pressure of the outlet of the first culvert is calculated using the iterative static pressure at the inlet of the mixing chamber, and the flow rate of the outlet of the first culvert is calculated using the total pressure, total temperature, oil-gas ratio, static pressure and area of ​​the outlet of the first culvert;

[0020] If the outlet of the first outer culvert is in a blocked state, the static pressure of the outlet of the first outer culvert is equal to the critical static pressure of the outlet of the first outer culvert, and the flow rate of the outlet of the first outer culvert is equal to the critical flow rate of the outlet of the first outer culvert;

[0021] The residual between the flow rate at the inlet and the flow rate at the outlet of the first culvert is calculated.

[0022] In one embodiment, determining whether the outlet of the turbine rear end is in a blocked state comprises:

[0023] Obtaining the area of ​​the outlet of the turbine rear end;

[0024] Calculate the critical static pressure and critical flow rate of the outlet of the rear portion of the turbine using the total pressure, total temperature, oil-gas ratio and area of ​​the outlet of the rear portion of the turbine;

[0025] The critical static pressure and critical flow rate at the outlet of the turbine rear end are the static pressure and flow rate calculated assuming that the outlet Mach number of the turbine rear end is equal to 1;

[0026] The static pressure at the outlet of the rear part of the turbine is calculated using the iterative static pressure at the inlet of the mixing chamber. If the static pressure at the outlet of the rear part of the turbine is greater than the critical static pressure at the outlet of the rear part of the turbine, the outlet of the rear part of the turbine is not in the blocked state; otherwise, the outlet of the rear part of the turbine is in the blocked state.

[0027] In one embodiment, constructing the turbine outlet flow balance equation includes:

[0028] Obtaining the flow rate of the inlet of the turbine rear end;

[0029] If the outlet of the turbine rear end is not in a blocked state, the static pressure of the outlet of the turbine rear end is calculated using the iterative static pressure of the mixing chamber inlet, and the flow rate of the outlet of the turbine rear end is calculated using the total pressure, total temperature, oil-gas ratio, static pressure and area of ​​the outlet of the turbine rear end;

[0030] If the outlet of the turbine rear end is in a blocked state, the static pressure of the outlet of the turbine rear end is equal to the critical static pressure of the outlet of the turbine rear end, and the flow rate of the outlet of the turbine rear end is equal to the critical flow rate of the outlet of the turbine rear end;

[0031] The residual between the inlet flow rate and the outlet flow rate of the turbine after the turbine is calculated.

[0032] In one embodiment, the calculation of the flow rate, total pressure, total temperature, and oil-gas ratio at the outlet of the mixing chamber includes:

[0033] The flow rate, total pressure, total temperature, oil-gas ratio, static pressure and area of ​​the outlet of the first outer casing and the flow rate, total pressure, total temperature, oil-gas ratio, static pressure and area of ​​the outlet of the rear casing of the turbine are used to calculate the flow rate, total pressure, total temperature and oil-gas ratio of the outlet of the mixing chamber.

[0034] The invention has at least the following beneficial technical effects:

[0035] The aircraft engine modeling method with an RVABI structure of the present application can more accurately describe the performance of the aircraft engine when there is blockage at the first outer outlet and the inner outlet after the turbine; and provides a design method for equilibrium equations and guessed value variables, so that the model will not be interrupted in calculation when blockage occurs and the output is also very smooth. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of an aircraft engine with a RVABI structure in one embodiment of the present application;

[0037] Figure 2 The steps of the aircraft engine modeling method in one embodiment of the present application;

[0038] Figure 3 The static pressure relationship of the embodiment of the present application in which both the 16-section and the 6-section are not blocked;

[0039] Figure 4 The static pressure relationship between 16 blocked sections and 6 unblocked sections in one embodiment of the present application;

[0040] Figure 5 The static pressure relationship between 16 sections without blocking and 6 sections blocked in one embodiment of the present application;

[0041] Figure 6 The static pressure relationship between the 16-section and the 6-section without blocking in one embodiment of the present application;

[0042] in:

[0043] 13-inlet of the first outer duct; 16-outlet of the first outer duct; 5-inlet of the inner duct after the turbine; 6-outlet of the inner duct after the turbine; 65-outlet of the mixing chamber; 7-inlet of the tail nozzle; 8-throat of the tail nozzle. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the implementation of this application clearer, the application is further described in detail below in conjunction with the accompanying drawings and embodiments. The described embodiments are part of the embodiments of this application, rather than all of the embodiments. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain this application, and should not be understood as limitations on this application. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The embodiments of this application are described in detail below in conjunction with the accompanying drawings.

[0045] An embodiment of the present application provides an aircraft engine modeling method with an RVABI structure, which can more accurately describe the performance of the aircraft engine when there is blockage at the first outer outlet and the rear inner outlet of the turbine; and provides a design method for equilibrium equations and guessed value variables, so that the model will not be interrupted in calculation when blockage occurs and the output is very smooth.

[0046] The technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems will be described in detail below through embodiments and in combination with the accompanying drawings.

[0047] In one embodiment, Figure 1 As shown in FIG. 1 , an aircraft engine with an RVABI structure includes: an air intake, a front fan, a second culvert, a culvert tail nozzle, a rear fan, a first culvert, an HPC (High Pressure Compressor), a combustion chamber, an HPT (High Pressure Turbine), an LPT (Low Pressure Turbine), a turbine rear end, an RVABI, a mixing chamber, an afterburner, and a main tail nozzle. The RVABI deflection angle can be deflected inward or outward, and the opening of the RVABI at the design point deflection position is defined as 1, that is, β RVABI =1; when RVABI deflects outwards and the first external outlet is reduced, β RVABI <1; when RVABI deflects outwards and the outlet after the turbine is reduced, β RVABI >1. The outlet of the first outer duct and the outlet of the inner duct after the turbine are both connected to the inlet of the mixing chamber.

[0048] In this embodiment, if Figure 2 As shown, an aircraft engine modeling method with an RVABI structure specifically includes the following steps:

[0049] S201, iterative static pressure P at the mixing chamber inlet sMixer Assign a guess value, P sMixer is an iterative variable used to calculate the static pressure at the two inlets of the mixing chamber. In the case of static pressure equilibrium, P sMixer =P s16 =P s6 ;

[0050] S202, assuming that when β RVABI =1, the outlet area of ​​the first culvert is A 16d , then the actual area of ​​the first outer culvert outlet can be calculated as follows: A 16 =β RVABI *A 16d ;

[0051] The total pressure P at the outlet of the first culvert is used t16 , total temperature T t16 , oil-gas ratio f ar16 and area A 16 , calculate the Mach number M a16 =1 when the critical static pressure P s16cr and critical flow W 16cr The calculation method is based on the thermodynamic calculation formula to convert M a16 Considered as static pressure P s16 The following nonlinear function

[0052] M a16 =f ps2m (P t16 ,P s16 ,T t16 ,f ar16 )

[0053] And use Newton's method to iteratively solve when M a16 =1 when P s16 The value of P s16cr , and then calculate the critical flow rate W by thermodynamic calculation formula 16cr .

[0054] Function f ps2m The calculation steps of () are: Assume the static pressure P s16 The value of P s16g , then calculate the static temperature T s16g , speed V 16g , density ρ 16g , specific heat ratio γ s16g and the gas constant R t16 , the specific calculation method can refer to the reference materials on engine performance modeling, such as the monograph "Gas Turbine Engine Performance" (Chinese Revised 2nd Edition, Shanghai Jiaotong University Press, 2019), and finally calculate the Mach number M a16g

[0055] M a16g =V 16g / sqrt(γ s16g *R t16 *T s16g )

[0056] Where sqrt() represents the function of finding the square root.

[0057] When P s16cr After that, the speed V can be obtained at the same time 16cr and density ρ 16cr , then W can be solved by the following formula 16cr

[0058] W 16cr =ρ16cr *V 16cr *A 16cr

[0059] If P sMixer >P s16cr Then the first duct outlet is not in a blocked state, and the static pressure relationship is as follows: Figure 3 or Figure 5 As shown; if P sMixer <=P s16cr The first culvert outlet is in a blocked state, and the static pressure relationship is as follows: Figure 4 or Figure 6 shown.

[0060] Assume the flow rate at the first culvert inlet is W 13 If the exit of the first outer culvert is not blocked, then P s16 =P sMixer , and use the thermodynamic calculation formula to calculate the static temperature T s16 , speed V 16 and density ρ 16 , the method is the same as before, and the outlet flow W of the first culvert is calculated according to the following formula 16

[0061] W 16 =ρ 16 *V 16 *A 16

[0062] If the outlet of the first culvert is blocked, then

[0063] P s16 =P s16cr W 16 =W 16cr V 16 =V 16cr

[0064] The residual corresponding to the outlet flow balance equation of the first culvert is

[0065] E 16 =(W 13 -W 16 ) / W 13

[0066] S203, assuming that when β RVABI = 1, the outlet area after the turbine is A 6d , then the actual outlet area of ​​the turbine after the turbine can be calculated as follows: A6 = A 16d +A 6d -β RVABI *A 16d .

[0067] The total pressure P at the outlet after the turbine is used t6 , total temperature T t6 , oil-gas ratio f ar6 and area A6, calculate the Mach number M a6 =1 when the critical static pressure P s6cr and critical flow W 6cr The calculation method is based on the thermodynamic calculation formula to convert M a6 Considered as static pressure P s6 The following nonlinear function

[0068] M a6 =f ps2m (P t6 ,P s6 ,T t6 ,f ar6 )

[0069] And use Newton's method to iteratively solve when M a6 =1 when P s6 The value of P s6cr , and then calculate the critical flow rate W by thermodynamic calculation formula 6cr ; Function f ps2m The calculation steps of () are the same as before; when P is obtained s6cr After that, the speed V can be obtained at the same time 6cr and density ρ 6cr , then W can be solved by the following formula 6cr

[0070] W 6cr =ρ 6cr *V 6cr *A 6cr

[0071] If P sMixer >P s6cr Then the outlet after the turbine is not blocked, and the static pressure relationship is as follows: Figure 3 or Figure 4 As shown; if P sMixer <=P s6cr The outlet after the turbine is blocked, and the static pressure relationship is as follows: Figure 5 or Figure 6 shown.

[0072] Assume that the flow rate of the turbine after-inner inlet (i.e., the low-pressure turbine outlet) is W5. If the outlet of the turbine after-inner is not in a blocked state, then P s6 =P sMixer , and use the thermodynamic calculation formula to calculate the static temperature T s6 , velocity V6 and density ρ6, the method is the same as before, and the outlet flow W6 after the turbine is calculated according to the following formula

[0073] W6=ρ6*V6*A6

[0074] If the outlet of the turbine after the turbine is blocked, there is

[0075] P s6 =P s6cr W6=W 6cr V6=V 6cr

[0076] The residual corresponding to the outlet flow balance equation after the turbine is

[0077] E6=(W5-W6) / W5

[0078] In the iterative solution process of the engine component level model, the number of guessed variables should be equal to the number of residuals of the equilibrium equation, and there should be a certain corresponding relationship. 16 The two guessed variables corresponding to E6 are the first bypass ratio BPR1 and the iterative static pressure P at the mixing chamber inlet. sMixer .

[0079] S204, calculate the flow rate W7 and total pressure P at the outlet of the mixing chamber t7 , total temperature T t7 , oil-gas ratio f ar7 Flow rate W7 is

[0080] W7=W 16 +W6

[0081] Oil-gas ratio ar7 for

[0082] f ar7 =W6*f ar6 / (1+f ar6 ) / (W 16 +W6 / (1+f ar6 ))

[0083] Total enthalpy h t7 for:

[0084] h t7 =(W 16 *h t16 +W6*h t6 ) / W7

[0085] where h t16 and h t6 Use T t16 and T t6 And the corresponding oil-gas ratio f ar16 and f ar6 Calculation can be done through empirical formulas. For specific methods, please refer to "Gas Turbine Engine Performance". Then the total temperature T t7 According to h t7 and far7 The specific method is to iteratively solve the problem at f ar7 So that the total enthalpy is equal to h t7 T t7 .

[0086] Assuming that the cross-sectional area of ​​complete mixing in the mixing chamber is A7, the total outlet pressure P t7 By iteratively solving the momentum continuity equation, we get:

[0087] P s16 *A 16 +W 16 *V 16 +P s6 *A6+W6*V6=P s7 *A7+W7*V7

[0088] Where P s7 Using P t7 The guessed value of and flow W7 are solved by iterative method.

[0089] It should be noted that:

[0090] 1) In steps S202 and S203 of the present application, since the guessed value of the first outer inlet flow or the inner inlet flow after the turbine is not used to calculate the static pressure at the corresponding outlet, the problem of calculation interruption when the guessed flow is greater than the critical flow will not occur, and the model is always correct in terms of mechanism and continuous in terms of iterative method.

[0091] 2) When calculating the mixing model of the mixing chamber, if one of the inlets of the mixing chamber is blocked, it can be considered that the two airflows do not meet the static pressure balance at the inlet of the mixing chamber, but may reach equilibrium after complex flow field changes downstream. However, it is not necessary to consider this process when performing mixing modeling. Instead, the two inlet airflow parameters can be directly used to calculate the mixing result. The mathematical principle for doing so is that the flow rate of the blocked inlet reaches the boundary and no longer needs to be determined by iterative calculation of the participating equilibrium equation. Of course, if the complex mixing process in the mixing chamber is considered, such as the energy loss when the blockage is introduced, the modeling can be made more accurate.

[0092] 3) In a relatively rare special case, that is, the first outer outlet and the inner outlet after the turbine are blocked at the same time, the guessed variables in the engine joint working equation will be reduced in dimension, resulting in the Jacobi matrix being singular, and the whole machine iterative calculation fails. To solve this problem, a virtual tail nozzle calculation method is proposed in this embodiment, which can not only ensure that the whole machine iterative calculation process always converges, but also the output is always smooth. The method is introduced below.

[0093] First use P sMixerCalculate the total pressure P at the outlet of a virtual mixing chamber t7vt and static pressure P s7vt , when P s16cr >P s6cr When , solve the momentum continuity equation

[0094] P s16 *A 16 +W 16 *V 16 +P sMixer *A6+W6*V6=P s7vt *A7+W7*V 7vt

[0095] When P s16cr <=P s6cr When , solve the momentum continuity equation

[0096] P sMixer *A 16 +W 16 *V 16 +P s16 *A6+W6*V6=P s7vt *A7+W7*V 7vt

[0097] Virtual mixing chamber outlet total pressure P t7vt The flow rate of the virtual tail nozzle is transferred downstream to the numerical model, and the tail nozzle flow continuous balance equation is calculated, and the whole machine iteration calculation is involved to ensure that the model always converges; the actual mixing chamber outlet total pressure P t7 The actual tail nozzle parameters and thrust are outputted to the numerical model of the actual tail nozzle downstream. The principle of this calculation method is that when the first outer outlet and the inner outlet after the turbine are blocked at the same time: 1) the main tail nozzle is in a subcritical state, but reaches the flow boundary like the critical and supercritical states; 2) all the airflow parameters after the mixing chamber have been determined by the two inlets of the mixing chamber, and the balance equation of the tail nozzle is invalid. Therefore, the virtual tail nozzle is only used to ensure the continuity of the calculation mathematically and to correctly find the time to exit the blocked state, and it will not have any effect on the actual performance of the engine.

[0098] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0099] The above-described embodiments only express the specific implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A modeling method for an aircraft engine with a RVABI structure, wherein the aircraft engine comprises a first outer duct, a turbine rear duct, an RVABI and a mixing chamber, wherein the RVABI is between an outlet of the first outer duct and an outlet of the turbine rear duct, and both the outlet of the first outer duct and the outlet of the turbine rear duct are connected to an inlet of the mixing chamber, characterized in that: The method comprises: Step 1: Assign a guess value to a predefined variable, mixing chamber inlet iterative static pressure; Step 2: using the guessed value of the iterative static pressure at the mixing chamber inlet to determine whether the outlet of the first culvert is in a blocked state, and constructing a flow balance equation at the outlet of the first culvert according to whether the outlet of the first culvert is in a blocked state; Step 3: using the guessed value of the iterative static pressure at the mixing chamber inlet, determining whether the outlet of the turbine rear connotation is in a blocked state, and constructing a flow balance equation of the turbine rear connotation outlet according to whether the outlet of the turbine rear connotation is in a blocked state; Step 4: constructing a numerical model of the mixing chamber, wherein the numerical model of the mixing chamber comprises: calculating the flow rate, total pressure, total temperature, and oil-gas ratio of the outlet of the mixing chamber; The determining whether the outlet of the first outer duct is in a blocked state comprises: Obtaining the area of ​​the outlet of the first culvert; Calculating the critical static pressure and critical flow rate at the outlet of the first culvert using the total pressure, total temperature, oil-gas ratio and area at the outlet of the first culvert; the critical static pressure and critical flow rate at the outlet of the first culvert are the static pressure and flow rate calculated assuming that the outlet Mach number of the first culvert is 1; Calculating the static pressure at the outlet of the first culvert using the iterative static pressure at the inlet of the mixing chamber, if the static pressure at the outlet of the first culvert is greater than the critical static pressure at the outlet of the first culvert, the outlet of the first culvert is not in the blocked state, otherwise the outlet of the first culvert is in the blocked state; The step of judging whether the outlet of the turbine rear end is in a blocked state comprises: Obtaining the area of ​​the outlet of the turbine rear end; Calculate the critical static pressure and critical flow rate of the outlet of the rear portion of the turbine using the total pressure, total temperature, oil-gas ratio and area of ​​the outlet of the rear portion of the turbine; The critical static pressure and critical flow rate at the outlet of the turbine rear end are the static pressure and flow rate calculated assuming that the outlet Mach number of the turbine rear end is equal to 1; The static pressure at the outlet of the rear part of the turbine is calculated using the iterative static pressure at the inlet of the mixing chamber. If the static pressure at the outlet of the rear part of the turbine is greater than the critical static pressure at the outlet of the rear part of the turbine, the outlet of the rear part of the turbine is not in the blocked state; otherwise, the outlet of the rear part of the turbine is in the blocked state.

2. The aircraft engine modeling method with RVABI structure according to claim 1, characterized in that: The construction of the first culvert outlet flow balance equation includes: obtaining a flow rate at an inlet of the first culvert; If the outlet of the first culvert is not in a blocked state, the static pressure of the outlet of the first culvert is calculated using the iterative static pressure at the inlet of the mixing chamber, and the flow rate of the outlet of the first culvert is calculated using the total pressure, total temperature, oil-gas ratio, static pressure and area of ​​the outlet of the first culvert; If the outlet of the first outer culvert is in a blocked state, the static pressure of the outlet of the first outer culvert is equal to the critical static pressure of the outlet of the first outer culvert, and the flow rate of the outlet of the first outer culvert is equal to the critical flow rate of the outlet of the first outer culvert; The residual between the flow rate at the inlet and the flow rate at the outlet of the first culvert is calculated.

3. The aircraft engine modeling method with RVABI structure according to claim 1, characterized in that: The construction of the turbine outlet flow balance equation includes: Obtaining the flow rate of the inlet of the turbine rear end; If the outlet of the turbine rear end is not in a blocked state, the static pressure of the outlet of the turbine rear end is calculated using the iterative static pressure of the mixing chamber inlet, and the flow rate of the outlet of the turbine rear end is calculated using the total pressure, total temperature, oil-gas ratio, static pressure and area of ​​the outlet of the turbine rear end; If the outlet of the turbine rear end is in a blocked state, the static pressure of the outlet of the turbine rear end is equal to the critical static pressure of the outlet of the turbine rear end, and the flow rate of the outlet of the turbine rear end is equal to the critical flow rate of the outlet of the turbine rear end; The residual between the inlet flow rate and the outlet flow rate of the turbine after the turbine is calculated.

4. The aircraft engine modeling method with RVABI structure according to claim 1, characterized in that: The calculation of the flow rate, total pressure, total temperature, and oil-gas ratio at the outlet of the mixing chamber includes: The flow rate, total pressure, total temperature, oil-gas ratio, static pressure and area of ​​the outlet of the first outer casing and the flow rate, total pressure, total temperature, oil-gas ratio, static pressure and area of ​​the outlet of the rear casing of the turbine are used to calculate the flow rate, total pressure, total temperature and oil-gas ratio of the outlet of the mixing chamber.

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