Cross-scale multi-physics field coupling aero-engine warm-up process analysis method

Abstract

The invention discloses a cross-scale multi-physics-field coupling aero-engine warming-up process analysis method. The method comprises the steps that firstly, an engine air system one-dimensional network model, a fuel and lubricating oil system one-dimensional network model, a wheel disc and cartridge receiver two-dimensional axial symmetry model, a blade parameterization model and a main runner quasi-one-dimensional model are established; then calculating an air system boundary and a fuel and lubricating oil system boundary by using a main runner cavity method, then calculating the fuel and lubricating oil system boundary and the air system boundary by using a one-dimensional transient fluid network method to obtain a heat exchange boundary of a wheel disc and a cartridge receiver, and considering a thermal load and a centrifugal load in an unsteady state heat conduction process; calculating the radial displacement of the wheel disc and the casing by using a two-dimensional axisymmetric finite element method, and calculating the temperature and the radial displacement of the blades by using an engineering algorithm; and finally, integrating the radial displacement of the wheel disc, the blades and the casing and the initial blade tip clearance value to obtain the blade tip clearance value of each stage in the transient process, and feeding back the blade tip clearance value to the mainstream model again to realize iterative calculation. The analysis precision of each physical field is improved, and the calculation time consumption is reduced.

Description

Technical Field

[0001] The present invention relates to a cross-scale multi-physical field coupled aero-engine warm-up process analysis method, belonging to the technical field of aero-engine warm-up. Background Art

[0002] According to aircraft engine manuals, after a successful start, the engine must be maintained at a certain speed for a period of time to warm up. This is a necessary step before takeoff, especially in low-temperature environments. According to research by Qian Renjun et al., an engine that is not warmed up is likely to result in a loss of thrust and excessively high oil temperatures, which in turn affects the payload that can be carried during takeoff and even the safety of the takeoff process. However, the existence of the warm-up process directly prolongs the aircraft's time on the ground or on the deck, restricting the aircraft's deployment efficiency. Therefore, studying the internal response mechanisms of the engine during the warm-up process, optimizing the warm-up procedure, and shortening the warm-up time are of great engineering significance.

[0003] Tip clearance refers to the radial gap between the compressor or turbine blades and the stator casing or outer ring. During typical transient states, such as takeoff and warm-up, tip clearance exhibits multi-extreme variations, significantly impacting the efficiency of the compressor or turbine components and the overall performance of the engine. The warm-up process directly alters the engine's thermal state, leading to changes in tip clearance and, in turn, affecting the engine's overall operating state. Therefore, accurately assessing tip clearance during transient states is key to studying the engine warm-up process.

[0004] The accurate evaluation of the transition state tip clearance involves a complex multi-physics coupling problem, and it is necessary to consider the interaction between the fluid domain and the solid domain at the same time. Specifically, it is necessary not only to consider the impact of the fluid domain, including the mainstream and secondary air systems, on the solid temperature and deformation, but also to feed back the changes in the solid domain, including the tip clearance, to the fluid domain in real time in order to update its calculated boundary conditions. In the research and development process, in order to balance accuracy and efficiency, a one-dimensional method is usually used for fluid domain calculations (such as the one-dimensional fluid network method, the main channel component method or the cavity method for the secondary air system), and a two-dimensional axisymmetric finite element method is used to calculate the changes in the solid domain. For the coupling of the secondary air system and the solid domain, Muller conducted secondary development based on the CaculiX software to realize steady-state calculations under flow-heat-solid coupling. The results show that after the coupled solid domain finite element calculation, the flow rate of some air system branches is reduced by more than 90%. Ganine et al. developed an unsteady flow-heat coupling calculation program for air systems, in which an unsteady heat transfer process was used in the solid domain and a quasi-steady-state process was used in the fluid domain. A strong coupling solution was performed within the time step of each solid domain solution. It was found that as the speed increased, the change in the grate tooth gap showed a fluctuating pattern, resulting in a significant difference in the air system flow rate compared to the decoupled calculation.

[0005] However, the aforementioned studies did not feed the calculation results of the air system and solid domain back into the main flow model for coupling analysis. In the public literature, there have been some explorations into the interaction between the secondary air system and the main flow, and the coupling effect between the tip clearance and the main flow. Regarding the effect of the secondary air system on the engine main flow, Liu Chuankai et al., Yang Xuesen et al., and Nikolaidis et al. have achieved coupled solutions in steady-state and transient states. Without considering the effect of solid deformation on the flow, these studies generally believe that under normal operating conditions, the internal response of the secondary air system has little effect on the main flow. Regarding the effect of solid deformation, represented by tip clearance, on the engine main flow, Chapman et al., Sheng et al., and Chen et al. have all achieved coupled analysis of tip clearance and main flow performance. However, in these studies, the air system flow distribution adopted a simplified fixed ratio, and the tip clearance prediction model also adopted a one-dimensional simplified treatment, which to a certain extent limited the simulation accuracy.

[0006] In summary, the current analysis of the warm-up process has not yet taken into account the dynamic coupling interaction effects of the tip clearance changes, mainstream, secondary air system and fuel and oil system. This has limited the accuracy of the engine transient tip clearance prediction, making it difficult to conduct in-depth research on the impact mechanism of the warm-up process on the overall engine working state. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide an analysis method for the warm-up process of an aircraft engine with cross-scale multi-physical field coupling. A weak coupling method is adopted, a multi-dimensional calculation model is established during the calculation process, and the two-way transmission of information between various physical fields is considered. This further improves the analysis accuracy of each physical field while reducing the calculation time.

[0008] The present invention adopts the following technical solutions to solve the above technical problems:

[0009] A cross-scale multi-physics coupling method for analyzing the warm-up process of an aero-engine is proposed. A multi-dimensional computational model is established, and a weak coupling method is used to achieve two-way interaction between the physical fields of the fluid and solid domains. The time steps of the fluid and solid domains are set to Δt respectively. f and Δt s , and NΔt f =Δt s After performing N fluid domain calculations, a solid domain calculation is performed. The method includes the following steps:

[0010] Step 1: Establish a one-dimensional network model of the aircraft engine's air system, a one-dimensional network model of the fuel and oil system, a two-dimensional axisymmetric finite element model of the impeller and casing, a parameterized model of the blades, and a quasi-one-dimensional model of the main flow channel; then proceed to step 2 to perform fluid domain calculations;

[0011] Step 2: Calculate the quasi-one-dimensional model of the main channel using the main channel volume method to obtain the pressure and temperature of the air system boundary and transmit them to the air system; also obtain the combustion chamber pressure boundary and engine pump speed and transmit them to the fuel and lubricating oil system; and also obtain the low-pressure physical speed and high-pressure physical speed of the engine.

[0012] Step 3: Calculate the one-dimensional network model of the fuel and lubricating oil system using a one-dimensional transient fluid network method to obtain the fuel flow rate and extraction power of the fuel and lubricating oil system, and transmit them to the main flow channel; also obtain the bearing cavity pressure and transmit it to the air system;

[0013] Step 4: Calculate the one-dimensional network model of the air system using a one-dimensional transient fluid network method to obtain the bleed air flow rate and transmit it to the main channel; also obtain the seal air flow rate and transmit it to the fuel and lubricating oil system;

[0014] Step 5: Repeat the fluid domain iterative calculation from Step 2 to Step 4, and determine whether the number of iterations reaches N. If so, proceed to Step 6 to perform solid domain calculation; otherwise, return to Step 2.

[0015] Step 6: Based on the results obtained from the Nth iteration of steps 2 to 4, the third type of heat transfer boundary conditions are converted to perform transient thermal analysis of the wheel and casing to obtain the temperature fields of the wheel and casing.

[0016] Step 7: Determine the centrifugal loads on the wheel, casing, and blades based on the low-pressure physical speed and high-pressure physical speed of the engine obtained in step 2 for the Nth iteration. Use the temperature fields of the wheel and casing obtained in step 6 as temperature loads to solve for the deformation of the wheel, casing, and blades.

[0017] Step 8: Update the dimension parameters of the components of the main channel, fuel and oil system, and air system according to the deformation of the wheel, casing, and blades, and return to step 2 to perform the next round of fluid domain calculation with the number of times N.

[0018] As a preferred solution of the present invention, in step 2, when the main channel volume method is used for calculation, the change rate of the inlet and outlet parameters of the combustion chamber in the main channel is:

[0019]

[0020] Among them, T3 is the combustion chamber outlet temperature, p3 is the combustion chamber outlet pressure, R is the fuel gas constant, V3 is the volume of the main combustion chamber, C v is the constant pressure heat capacity of gas, gto is the oil supply, H u is the calorific value of fuel, η3 is the main combustion efficiency, i cis the enthalpy value of the fuel when it enters the combustion chamber, i3 is the unit enthalpy at the combustion chamber outlet, k3 is the gas adiabatic index, g2 is the compressor outlet flow rate, i2 is the unit enthalpy at the compressor outlet, g3 is the combustion chamber outlet flow rate, and dt is the time step.

[0021] As a preferred solution of the present invention, in step 4, when the one-dimensional transient fluid network method is used for calculation, the volume effect of the cavity in the air system is considered, and the relationship between the inlet and outlet flow and pressure is:

[0022]

[0023] Among them, m in 、m out are the cavity inlet flow rate and cavity outlet flow rate, A in is the cavity inlet cross-sectional area, is the total pressure of the inlet airflow, R1 is the ideal gas constant of air, is the total temperature of the inlet airflow, k is the adiabatic index, P0 is the static pressure in the middle of the cavity, C D is the flow correction coefficient, A out is the cavity outlet cross-sectional area, P r is the static pressure outside the cavity, is the average static temperature of the airflow in the cavity, P out is the static pressure of the airflow at the cavity outlet.

[0024] As a preferred solution of the present invention, in step 7, the deformation of the wheel disc and the casing is calculated as follows:

[0025] The two-dimensional axisymmetric finite element method is used to calculate the unsteady heat conduction. There is no internal heat source in the calculation model, and the thermal conductivity of the solid domain is isotropic. The unsteady heat conduction differential equation in the cylindrical coordinate system is as follows:

[0026]

[0027] Where ρ is the density of the solid domain, c is the specific heat capacity of the solid domain at constant pressure, T is the temperature of the solid domain, t is the time, λ is the thermal conductivity of the solid domain, r is the radial coordinate, and z is the axial coordinate;

[0028] The two-dimensional axisymmetric finite element method is used to solve the displacement of the wheel and casing. The temperature load and centrifugal load of each finite element grid unit are summed separately and superimposed to obtain the overall load matrix. Combined with the overall stiffness matrix, the linear equations for displacement solution are formed as follows:

[0029] [K][δ]=[L]

[0030] Among them, [K] is the overall stiffness matrix of the displacement solution, [δ] is the displacement matrix of each mesh node of the wheel disc and the casing, and [L] is the overall load matrix of each mesh node of the wheel disc and the casing.

[0031] As a preferred solution of the present invention, in step 7, the blade deformation is calculated as follows:

[0032] (1) Divide the blade into several sections along the radial direction according to the blade height, extract the geometric information of each section, and establish a parametric model of the blade;

[0033] (2) The energy conservation equation for each segment is established as follows:

[0034] Q=hA1ΔT1+λA2ΔT2-λ1A3ΔT3

[0035] QΔt s =c p mΔT

[0036] Where Q is the net heat flow of the blade segment, h is the heat transfer coefficient between the airflow and the wall, A1 is the gas-solid convection heat transfer area, ΔT1 is the heat transfer temperature difference between the gas and the solid, λ3 is the thermal conductivity of the blade segment, A2 is the heat-introducing end surface area of the blade segment, ΔT2 is the difference in average temperature between the upper and lower segments of the heat-introducing end surface, A3 is the heat-extracting end surface area of the blade segment, ΔT3 is the difference in average temperature between the upper and lower segments of the heat-extracting end surface, and Δt s is the solid domain time step, c p is the specific heat capacity of the blade segment, m is the mass of the blade segment, and ΔT is the change in the average temperature of the blade segment within a single solid domain time step;

[0037] (3) Based on the blade segment temperature load calculated in (2), the thermal displacement caused by each segment temperature load is superimposed as follows:

[0038]

[0039] Where ΔR is the total thermal deformation, α is the blade segment linear expansion coefficient, ΔT j is the temperature change of the jth segment, Δl j is the length of the jth segment, and n is the number of calculated blade segments;

[0040] The displacements caused by the centrifugal loads of each blade segment are superimposed as follows:

[0041]

[0042] Where ΔL is the total centrifugal deformation, σ j is the centrifugal stress of the j-th segment, and E is the elastic modulus of the j-th segment.

[0043] A computer device comprises a memory, a processor, and a computer program stored in the memory and capable of running on the processor. When the processor executes the computer program, the steps of the cross-scale multi-physics field coupled aircraft engine warm-up process analysis method are implemented.

[0044] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of the cross-scale multi-physics field coupled aircraft engine warm-up process analysis method.

[0045] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0046] 1. The present invention integrates the one-dimensional fluid network method of the air system and fuel and lubricating oil, the two-dimensional axisymmetric finite element method, the engineering algorithm of the blade temperature displacement and the main flow channel volume method. By establishing a computational model for cross-scale multi-physical field coupling, the invention adopts the bidirectional coupling of flow, heat and solid across time scales and the weak coupling of the same time scale in the fluid domain to carry out real-time information interaction, thereby realizing the warm-up process evaluation and analysis that comprehensively considers the changes in main flow channel parameters, air system parameters, fuel and lubricating oil parameters and solid deformation.

[0047] 2. The present invention can efficiently calculate and evaluate the aircraft engine warm-up process, with an efficiency improvement of more than 90% compared to full three-dimensional simulation, and the tip clearance calculation error is less than 10%, which can accurately reproduce the physical phenomena before and after the engine warm-up. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a schematic diagram of the main components and cross-section of an aircraft engine;

[0049] Figure 2 This is a schematic diagram of the two-dimensional solid domain computational model of an aircraft engine core;

[0050] Figure 3 This is a schematic diagram of the calculation model of the core engine mainstream blade;

[0051] Figure 4 It is a one-dimensional fluid network calculation model of the core engine air system;

[0052] Figure 5 This is a schematic diagram of the finite element mesh of the core engine solid domain;

[0053] Figure 6 It is a schematic diagram of the engine fuel and lubricating oil system;

[0054] Figure 7 It is a curve diagram of speed change during the warm-up process;

[0055] Figure 8It is a schematic diagram of data interaction and time step coupling between physical fields;

[0056] Figure 9 It is a flow chart of the cross-scale multi-physics coupling algorithm;

[0057] Figure 10 The following diagram shows the changes in the main performance parameters of the engine during the process, where (a) is the change in N1, (b) is the change in N2, (c) is the change in exhaust temperature T6, and (d) is the change in thrust F.

[0058] Figure 11 It is the temperature change diagram of the lubricating oil cavity during the process;

[0059] Figure 12 This is a diagram of the change in the high-pressure turbine tip clearance during the process. DETAILED DESCRIPTION

[0060] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be interpreted as limiting the present invention.

[0061] The present invention proposes a cross-scale multi-physical field coupled aircraft engine warm-up process analysis method, which integrates the one-dimensional fluid network method, the two-dimensional axisymmetric finite element method, the temperature and displacement engineering algorithm and the main flow channel volume method, and adopts a weak coupling method to realize the two-way interaction between the physical fields within each coupling iteration step, and simultaneously obtains the air system parameters, fuel and lubricating oil parameters, main flow channel parameters and solid temperature and deformation distribution.

[0062] Figure 1 The following is a schematic diagram of the main components and cross-section of an aircraft engine. Figure 2 Taking the core engine of the aircraft engine shown as an example, the implementation process of the present invention for analyzing the engine warm-up process is described in detail.

[0063] First, the solid domain model of the core engine is established. Considering the symmetry of the structure of the core engine casing and the wheel, a two-dimensional axisymmetric model of the casing and the wheel is established, as shown in the figure. Figure 2 As shown in . As for the mainstream blades, a parameterized model is used due to their axial discrete arrangement, as shown in Figure 3 As shown in the figure, the blade is divided into several segments along the radial direction according to its height, and the parameters such as the perimeter, area, and chord length of each interface at the corresponding height are extracted. Then, a calculation model of the core engine air system is established, as shown in the figure. Figure 4 As shown, the air system is simplified into a fluid network consisting of elements and nodes, and is divided into four independent flow paths according to the structural characteristics of each network.

[0064] Since the blade temperature and displacement in the solid domain are solved using engineering algorithms, and the air system in the fluid domain is solved linearly using the one-dimensional fluid network method, and the main channel uses the quasi-one-dimensional cavity method, the above model does not need to be meshed. However, the temperature and displacement of the casing wheel are calculated using the finite element method, so it is necessary to divide the finite element mesh. The casing wheel mesh is divided using ANSYS MECHANICAL APDL, and the mesh is encrypted at the grate teeth. The final number of mesh elements is 33988. The overall mesh division effect is as follows: Figure 5 In addition, the calculation process takes into account the material type of each component and divides the grid unit into several material partitions, with a total of more than 14 material types.

[0065] In order to better illustrate the implementation process of the present invention, the warm-up process is calculated. Figure 6 The curve of the throttle lever angle (PLA) during the whole process is shown in Figure 2. During the whole process, the engine maintains the inlet and ambient temperature T1 = 258K and the total pressure P1 = 101325Pa. Figure 7 As shown, it includes four stages: starting, slow running, warming up and taking off. The specific parameters are shown in Table 1. 2max The maximum physical speed of the engine. The warm-up time is defined as 3 minutes, and the target speed during warm-up is 0.9N. 2max It should be noted that since this engine model is equipped with a full authority digital electronic controller, the target speed N during operation is 2,Z It is not the actual speed that can be achieved during engine operation. The actual speed of the engine needs to be calculated through the main channel model.

[0066] Table 1 Working conditions at each stage

[0067] stage <![CDATA[N 2,Z ]]> Duration / min <![CDATA[Start 0 - t1]]> <![CDATA[0.675N 2max ]]> 1 <![CDATA[Slow train t1 - t2]]> <![CDATA[0.675N 2max ]]> 2 <![CDATA[Warm-up t2 - t3]]> <![CDATA[0.9N 2max ]]> 3 <![CDATA[Takeoff from T3 to T4]]> <![CDATA[N 2max ]]> 3

[0068] During the warm-up analysis, mainstream blade calculations will be performed. Figure 3 The segment shown is the research object. Based on the energy conservation principle, the following control equation is established to calculate the temperature:

[0069] Q=hA1ΔT1+λ1A2ΔT2-λA3ΔT3 (1)

[0070] QΔt s =c p mΔT (2)

[0071] Formula (1) represents the heat transferred to the blade by airflow through convection heat transfer, the heat input from one end of the segment through heat conduction, and the heat extracted from the other end of the segment. The average convection heat transfer coefficient of the blade adopts the empirical relationship formula (3).

[0072] The heat transfer coefficient of the blade is calculated with the chord length as the qualitative dimension, according to the airflow around the flat plate without separation, and considering the influence of rotation, the correction coefficient of formula (4) is established.

[0073] Nu=0.032Re 0.8 (3)

[0074]

[0075] Wherein, u is the linear velocity of the segment rotation; l is the length of the segment; v is the relative velocity of the airflow inlet; and D is the average diameter of the segment.

[0076] When calculating blade displacement, the total thermal displacement ΔR of the blade is the sum of the displacements of each segment, as shown in formula (5):

[0077]

[0078] When calculating centrifugal displacement, the displacement Δl caused by the centrifugal load of each segment is j as follows:

[0079] ΔP i =ρω 2 A i r i Δr i (6)

[0080]

[0081] Δl j =l·(σ j / E) (8)

[0082] Where ΔP i is the centrifugal force on the segment; σ j is the stress on the low radius end face of this section; E is the elastic modulus of the blade, and the total centrifugal displacement ΔL of the blade is as follows:

[0083]

[0084] The total radial displacement of the blade is obtained by superimposing the total thermal displacement of the blade and the total centrifugal displacement.

[0085] After the blade displacement is obtained, the displacement of the casing wheel is calculated. At this time, it is necessary to consider the cross-time scale information transmission problem between different physical fields, so the following method is used: Figure 8 The fluid-solid weak coupling mode shown is that in a solid domain time step Δt sMultiple fluid domain calculations are performed within the timeframe. During this period, the solid wall temperature is assumed to be constant. When the number of fluid domain calculation steps reaches the set value, the solid domain parameter calculation is carried out to complete a coupled iterative step calculation. For the mainstream, air system, and fuel and lubricating oil system, they all belong to the fluid domain and use the same time step Δt. f Perform calculations.

[0086] The above weak coupling method is used to carry out multi-physics cross-scale coupling calculation to simulate the warm-up process. Figure 9 The specific process is:

[0087] 1) The main channel model reads in relevant preset information such as the characteristic parameters of engine components. The air system model reads in preset information such as the dimensional parameters and fluid parameters of relevant components. The fuel and lubricating oil system model reads in information such as the dimensional parameters and operating characteristics of relevant components. The two-dimensional axisymmetric finite element model of the impeller and casing and the parametric model of the blades use the Ansys APDL finite element analysis module to process the geometric information and output the relevant dimensional coordinate information to the finite element calculation module.

[0088] 2) The calculation starts from the main channel model, calculates the main channel parameters and the total temperature, total pressure, and flow rate of the fluid in each key section at the initial moment, and outputs relevant information such as the engine low-pressure physical speed N1, high-pressure physical speed N2, engine combustion chamber pressure p3, and pump speed.

[0089] 3) The fuel and lubricating oil system model reads relevant information such as the high-pressure physical speed N2 and the engine combustion chamber pressure p3, calculates and outputs the fuel flow rate, temperature, bearing chamber pressure and extracted power at each position in the fuel and lubricating oil system in the flow path.

[0090] 4) The one-dimensional transient fluid network calculation model of the air system obtains the aerodynamic boundary from the main channel model and the fuel and lubricating oil system model and starts the calculation, outputting the sealed air flow, pressure and fluid temperature of the internal components of the air system.

[0091] The calculation process of the one-dimensional transient fluid network method solution is as follows:

[0092] According to the mass conservation equation, the sum of the mass flow rates in and out of node i is zero. However, due to the deviation between the preset pressure value and the actual value when solving the fluid network method, a flow residual will be generated. The residual value is obtained by the following formula:

[0093] Δm i =m ij +m ik +m il

[0094] To satisfy the flow conservation equation, each component needs to perform flow compensation, and the flow after compensation should satisfy:

[0095] (mij +Δm ij )+(m ik +Δm ik )+(m il +Δm il )=0

[0096] So we can get:

[0097] -Δm i =Δm ij +Δm ik +Δm il

[0098] Because when the geometric parameters are constant, the mass flow rate is a function of the inlet and outlet pressures, so:

[0099]

[0100] The combination can be obtained:

[0101]

[0102] By writing similar relationships for all nodes in the network, we can obtain relationships equal to the number of nodes, forming a system of equations for solving the pressure correction amount, which can be expressed in the following matrix form:

[0103] [A] N {Δp} N =-{Δm} N

[0104] Where [A] is the N-dimensional Jacobian coefficient matrix, which consists of the partial derivatives of the flow rate of each branch with respect to the inlet and outlet pressures, and Δp and Δm are the pressure correction value and flow residual, respectively.

[0105] 5) Since the fluid domain response time is relatively fast, in a typical transition process, iterative calculations between fluid domains are first performed, looping 2)-4), with the number of iterations being N.

[0106] 6) When the number of iterations N satisfies NΔt f =Δt s Afterwards (where Δt s is the solid domain time step), suspend the fluid calculation, use the current fluid calculation results as a benchmark, convert the third-type heat transfer boundary conditions, perform transient thermal analysis of engine components, and output the temperature field of the impeller and casing.

[0107] 7) Determine the centrifugal loads on the wheel, casing, and blades using the rotational speeds N2 and N1 calculated using the main channel model. Use the wheel and casing temperature fields calculated in step 5 as temperature loads to solve for the deformation of the wheel, casing, and blades, and output the calculated new deformations.

[0108] 8) Update the geometric model node parameter information according to the deformation of the wheel and casing, recalculate the aerodynamic parameters and fuel and oil system parameters, and perform the next round of fluid calculation with a number N.

[0109] In the above calculations, the main channel model transmits the pressure and temperature of the air system boundary to the air system model, and the air system model feeds back the bleed air flow rate to the main channel model; the main channel model provides the combustion chamber pressure boundary and pump speed to the fuel and lubricating oil system model, and the fuel and lubricating oil system model provides the fuel flow rate and extracted power to the main channel model; the main channel model provides the third-type heat transfer boundary conditions to the solid domain two-dimensional axisymmetric finite element model. After the two-dimensional axisymmetric finite element model is calculated, the solid domain wall temperature and grate gap changes are provided to the air system flow field, the tip gap changes are provided to the main channel, and the solid wall temperature and grate gap changes are provided to the fuel and lubricating oil model; the fuel and lubricating oil system model provides the bearing cavity pressure to the air system model, and the air system provides the sealing air flow to the fuel and lubricating oil system.

[0110] In the above process, transient temperature calculation is carried out by establishing a matrix-form linear equation system (10), where [K] τ is the temperature global stiffness matrix, [t] τ is the node temperature matrix, [F] τ is the load matrix.

[0111] [K] τ [t] τ =[F] τ (10)

[0112] For the calculation of displacement, the linear equation group (11) is solved, where [K] is the displacement overall stiffness matrix, [δ] is the node displacement matrix, and [L] is the sum of the temperature load matrix and the centrifugal load matrix.

[0113] [K][δ]=[L] (11)

[0114] The calculation method of the present invention takes into account both calculation accuracy and calculation speed, and can simultaneously calculate engine performance parameters, air system parameters, fuel and oil system parameters, solid temperature field deformation field and other parameters during the warm-up process. Compared with traditional full three-dimensional analysis, the calculation efficiency is improved by more than 90%, and it has important engineering reference value for the evaluation of aircraft engine warm-up effect.

[0115] Figure 10 、 11 , 12 are the typical performance parameters, oil cavity temperature changes and blade tip clearance changes of the engine during takeoff.

[0116] Before 360s, the changing trends of N1, N2, and F are basically the same. N1 and F both increase with the increase of N2. The basic trend of T6 is consistent with N2, but there will be a large overshoot in the acceleration stage at the beginning of each moment. Although there is a large overshoot, T6 is always within the exhaust temperature limit boundary T 6,limit There is a certain distance and no overheating occurs. In addition, the irregular change of T6 in the middle of the 0-t1 startup phase is caused by the ignition of the combustion chamber.

[0117] By observing the acceleration process from 360s to 365s, it can be found that the parameters do not increase monotonically, but there is a certain fluctuation during the increase (around 363s). This phenomenon is mainly caused by the engine's transient control plan and the disturbance of the main flow channel parameters during the afterburner opening process.

[0118] After the acceleration is completed (365s later), by Figure 10 (a) shows that N1 has reached the control boundary N 1,limit , the engine is in the working state of limiting N1. This is because in low temperature environment, the fan conversion speed N 1,cor Higher, to prevent too high N 1cor This causes blade flutter, which FADEC controls by limiting the amount of fuel supplied.

[0119] Since the oil supply is limited, Figure 10 (b) shows that N2 fails to reach N during the takeoff phase. 2,Z , N2 generally shows a trend of first decreasing and then slowly increasing, but it can never reach N 2,Z The trends of T6 and F are basically consistent with those of N2, which decrease first and then increase, but the change of F is greater, as shown in Figure 2. Figure 10 As shown in (c) and (d).

[0120] The oil cavity temperature during takeoff is as follows: Figure 11 As shown in the figure, the temperature of the lubricating oil chamber remains basically stable after startup, with only a fluctuation of about 20K during acceleration and deceleration.

[0121] High-pressure turbine tip clearance δ HPT and compressor tip clearance δ HPC As N2 changes, Figure 12 As shown. It can be seen that in process 1 and process 2, δ HPT The change range compared with δ HPC The tip clearances at each location are always changing and cannot reach a steady state. HPC and δ HPT The speed will increase sharply, and will first increase and then decrease after approaching the target speed.

[0122] Based on the same inventive concept, an embodiment of the present application provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the aforementioned cross-scale multi-physical field coupled aircraft engine warm-up process analysis method are implemented.

[0123] Based on the same inventive concept, an embodiment of the present application provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it implements the steps of the aforementioned cross-scale multi-physical field coupled aircraft engine warm-up process analysis method.

[0124] It will be understood by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0125] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0126] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0127] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0128] The above embodiments are only for illustrating the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the present invention.

Claims

1. A cross-scale multi-physics field coupled aircraft engine warm-up process analysis method, characterized by: A multi-dimensional computational model is established, and a weak coupling method is used to realize the two-way interaction between the physical fields of the fluid domain and the solid domain. The time steps of the fluid domain and the solid domain are set to Δt f and Δt s , and NΔt f =Δt s After performing N fluid domain calculations, a solid domain calculation is performed. The method includes the following steps: Step 1: Establish a one-dimensional network model of the aircraft engine's air system, a one-dimensional network model of the fuel and oil system, a two-dimensional axisymmetric finite element model of the impeller and casing, a parametric model of the blades, and a quasi-one-dimensional model of the main flow channel; Go to step 2 to perform fluid domain calculation; Step 2: Calculate the quasi-one-dimensional model of the main channel using the main channel volume method to obtain the pressure and temperature of the air system boundary and transmit them to the air system; also obtain the combustion chamber pressure boundary and engine pump speed and transmit them to the fuel and lubricating oil system; and also obtain the low-pressure physical speed and high-pressure physical speed of the engine. Step 3: Calculate the one-dimensional network model of the fuel and lubricating oil system using a one-dimensional transient fluid network method to obtain the fuel flow rate and extraction power of the fuel and lubricating oil system, and transmit them to the main flow channel; It also gets the bearing chamber pressure and transmits it to the air system; Step 4: Calculate the one-dimensional network model of the air system using a one-dimensional transient fluid network method to obtain the bleed air flow rate and transmit it to the main channel; also obtain the seal air flow rate and transmit it to the fuel and lubricating oil system; Step 5: Repeat the fluid domain iterative calculation from Step 2 to Step 4, and determine whether the number of iterations reaches N. If so, proceed to Step 6 to perform solid domain calculation; otherwise, return to Step 2. Step 6: Based on the results obtained from the Nth iteration of steps 2 to 4, the third type of heat transfer boundary conditions are converted to perform transient thermal analysis of the wheel and casing to obtain the temperature fields of the wheel and casing. Step 7: Determine the centrifugal loads on the wheel, casing, and blades based on the low-pressure physical speed and high-pressure physical speed of the engine obtained in step 2 for the Nth iteration. Use the temperature fields of the wheel and casing obtained in step 6 as temperature loads to solve for the deformation of the wheel, casing, and blades. Step 8: Update the dimension parameters of the components of the main channel, fuel and oil system, and air system according to the deformation of the wheel, casing, and blades, and return to step 2 to perform the next round of fluid domain calculation with the number of times N.

2. The cross-scale multi-physics field coupled aircraft engine warm-up process analysis method according to claim 1, characterized in that: In step 2, when the main channel volume method is used for calculation, the change rate of the inlet and outlet parameters of the combustion chamber in the main channel is: Among them, T3 is the combustion chamber outlet temperature, p3 is the combustion chamber outlet pressure, R is the fuel gas constant, V3 is the volume of the main combustion chamber, C v is the constant pressure heat capacity of gas, gto is the oil supply, H u is the calorific value of fuel, η3 is the main combustion efficiency, i c is the enthalpy value of the fuel when it enters the combustion chamber, i3 is the unit enthalpy at the combustion chamber outlet, k3 is the gas adiabatic index, g2 is the compressor outlet flow rate, i2 is the unit enthalpy at the compressor outlet, g3 is the combustion chamber outlet flow rate, and dt is the time step.

3. The cross-scale multi-physics field coupled aircraft engine warm-up process analysis method according to claim 1, characterized in that: In step 4, when the one-dimensional transient fluid network method is used for calculation, the volume effect of the cavity in the air system is considered, and the relationship between the inlet and outlet flow and pressure is: Among them, m in 、m out are the cavity inlet flow rate and cavity outlet flow rate, A in is the cavity inlet cross-sectional area, is the total pressure of the inlet airflow, R1 is the ideal gas constant of air, is the total temperature of the inlet airflow, k is the adiabatic index, P0 is the static pressure in the middle of the cavity, C D is the flow correction coefficient, A out is the cavity outlet cross-sectional area, P r is the static pressure outside the cavity, is the average static temperature of the airflow in the cavity, P out is the static pressure of the airflow at the cavity outlet.

4. The cross-scale multi-physics field coupled aircraft engine warm-up process analysis method according to claim 1, characterized in that: In step 7, the deformation of the wheel disc and the casing is calculated as follows: The two-dimensional axisymmetric finite element method is used to calculate the unsteady heat conduction. There is no internal heat source in the calculation model, and the thermal conductivity of the solid domain is isotropic. The unsteady heat conduction differential equation in the cylindrical coordinate system is as follows: Where ρ is the density of the solid domain, c is the specific heat capacity of the solid domain at constant pressure, T is the temperature of the solid domain, t is the time, λ is the thermal conductivity of the solid domain, r is the radial coordinate, and z is the axial coordinate; The two-dimensional axisymmetric finite element method is used to solve the displacement of the wheel and casing. The temperature load and centrifugal load of each finite element grid unit are summed separately and superimposed to obtain the overall load matrix. Combined with the overall stiffness matrix, the linear equations for displacement solution are formed as follows: [K][δ]=[L] Among them, [K] is the overall stiffness matrix of the displacement solution, [δ] is the displacement matrix of each mesh node of the wheel disc and the casing, and [L] is the overall load matrix of each mesh node of the wheel disc and the casing.

5. The cross-scale multi-physics field coupled aircraft engine warm-up process analysis method according to claim 1, characterized in that: In step 7, the blade deformation is calculated as follows: (1) Divide the blade into several sections along the radial direction according to the blade height, extract the geometric information of each section, and establish a parametric model of the blade; (2) The energy conservation equation for each segment is established as follows: Q=hA1ΔT1+λA2ΔT2-λ1A3ΔT3 QΔt s =c p mΔT Where Q is the net heat flow of the blade segment, h is the heat transfer coefficient between the airflow and the wall, A1 is the gas-solid convection heat transfer area, ΔT1 is the heat transfer temperature difference between the gas and the solid, λ1 is the thermal conductivity of the blade segment, A2 is the heat-introducing end surface area of the blade segment, ΔT2 is the difference in average temperature between the upper and lower segments of the heat-introducing end surface, A3 is the heat-extracting end surface area of the blade segment, ΔT3 is the difference in average temperature between the upper and lower segments of the heat-extracting end surface, and Δt s is the solid domain time step, c p is the specific heat capacity of the blade segment, m is the mass of the blade segment, and ΔT is the change in the average temperature of the blade segment within a single solid domain time step; (3) Based on the blade segment temperature load calculated in (2), the thermal displacement caused by each segment temperature load is superimposed as follows: Where ΔR is the total thermal deformation, α is the blade segment linear expansion coefficient, and ΔT j is the temperature change of the jth segment, Δl j is the length of the jth segment, and n is the number of calculated blade segments; The displacements caused by the centrifugal loads of each blade segment are superimposed as follows: Where ΔL is the total centrifugal deformation, σ j is the centrifugal stress of the j-th segment, and E is the elastic modulus of the j-th segment.

6. A computer device comprising a memory, a processor, and a computer program stored in the memory and capable of running on the processor, characterized in that: When the processor executes the computer program, the steps of the cross-scale multi-physics field coupled aircraft engine warm-up process analysis method according to any one of claims 1 to 5 are implemented.

7. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the cross-scale multi-physics field coupled aircraft engine warm-up process analysis method according to any one of claims 1 to 5 are implemented.

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