A method for determining the rotational speed in three-dimensional simulation of an aero-engine

Abstract

The present application provides a method for determining the rotational speed in a three-dimensional simulation of an entire aircraft engine, which belongs to the technical field of aircraft engine simulation. Specifically, the method includes constructing a fluid-solid coupling control equation on each grid cell of the entire aircraft engine geometric model; forming an overall coupling matrix and solving the overall coupling matrix; simulating the calculated thermal geometric model; making the compressor and turbine rotate only around the axis of rotation; calculating the aerodynamic forces acting on the compressor blades and the turbine blades; updating the rotational speed according to the angular acceleration in each time step; after several iterations, when the difference between the aerodynamic torque of the compressor and the aerodynamic torque of the turbine meets the preset range, the corresponding rotational speed is the steady-state operating speed of the engine under the thermal geometry. Through the processing scheme of the present application, the engine automatically matches and dynamically determines the operating speed during the simulation process, avoiding the inaccuracy of the pre-given rotational speed and improving the accuracy and reliability of the simulation results.

Description

Technical Field

[0001] The present application relates to the field of aero-engine simulation, and in particular to a method for determining the rotational speed in three-dimensional simulation of an entire aero-engine. Background Art

[0002] As a highly complex thermomechanical system, aircraft engines require performance studies that not only involve aerodynamics, heat transfer, and combustion processes, but also structural deformation and stress coupling in high-temperature and high-pressure environments. Traditional simulations often pre-set the speed, and then perform fluid-solid-thermal coupling simulations of the entire engine at that speed to obtain the full flow field and structural stresses. When the preset speed is inconsistent with the actual operating conditions, the accuracy of the simulation results will be affected. In existing technologies, the speeds of different engine operating conditions are generally manually pre-set, and then fluid-solid-thermal coupling analysis is performed separately. The speed cannot be automatically determined during the simulation process, which limits the simulation efficiency and accuracy. Summary of the Invention

[0003] In view of this, the present application provides a method for determining the speed in three-dimensional simulation of an aircraft engine as a whole, which solves the problems in the existing technology, enables the engine to automatically match and dynamically determine the operating speed during the simulation process, and improves the accuracy and reliability of the simulation results.

[0004] The present application provides a method for determining the rotational speed in a three-dimensional simulation of an entire aircraft engine using the following technical solutions:

[0005] A method for determining the rotational speed in a three-dimensional simulation of an entire aircraft engine comprises the following steps:

[0006] Step 1: constructing a complete geometric model and a complete physical model of the aero-engine;

[0007] Step 2: Establish data transmission between the rotating domain and the stationary domain of the aircraft engine;

[0008] Step 3: construct the fluid-structure coupling control equation on each grid cell of the aero-engine geometric model;

[0009] Step 4: Incorporate the heat conduction method into the fluid-structure coupling control equation to form an overall coupling matrix. Use the Newton-Raphson iteration to minimize the global residual as the goal, and embed multiple parallel preconditioned solvers to directly solve the overall coupling matrix;

[0010] Step 5: By solving the overall coupling matrix simulation, the engine is calculated from the cold state to the hot state, and the actual geometric shape of each engine component under the hot working condition and the hot state geometric model calculated by simulation are obtained;

[0011] Step 6: restrict the freedom of movement of the compressor and turbine so that they can only rotate around the axis of rotation;

[0012] Step 7, calculate the aerodynamic forces acting on the compressor blades and turbine blades;

[0013] Step 8: Calculate the current angular acceleration of the engine ;

[0014] Step 9: When the simulation starts, set the initial speed , in each time step, the rotation speed is updated according to the angular acceleration;

[0015] Step 10: Re-calculate the fluid dynamics to obtain a new torque value. After several iterations, when the difference between the aerodynamic torque of the compressor and the aerodynamic torque of the turbine meets the preset range, the corresponding speed is the steady-state operating speed of the engine under the hot geometry.

[0016] Optionally, in step 2, when the fluid domain contains rotating parts, a mixed interface is used between the rotating domain and the stationary domain, and data is transferred through circumferential data averaging; the fluid domain adjacent to the solid domain is consistent with the solid reference system, and data synchronization between the fluid domain and the solid is achieved through coupling partitioning.

[0017] Optionally, in step 3, the Navier–Stokes equations are solved in the fluid domain using a finite volume method, and the thermoelastic equations are solved in the structural domain using a finite element method, and discretized in the same formal framework to generate a coupling stiffness matrix as the fluid-structure coupling control equation;

[0018] During the discretization process, at the fluid-solid interface, the same surface units are set as shared grids to constrain the fluid velocity to be equal to the structural velocity and the fluid force to be mapped consistently with the structural force.

[0019] Optionally, in step 7, the torque on the compressor is calculated based on the fluid pressure distribution and shear stress distribution. The torque on the turbine .

[0020] Optionally, in step 8, according to the overall moment of inertia , use the dynamic equation to calculate the current angular acceleration of the engine , ,in, is the torque on the compressor, is the torque acting on the turbine.

[0021] Optionally, in step 9, the rotation speed is updated using the following formula: ;in, is the speed of the current time step, is the current angular acceleration, is the speed of the next time step, is the time step.

[0022] In summary, this application has the following beneficial technical effects:

[0023] This application first obtains the thermal geometric model of the engine through fluid-solid coupling simulation, ensuring that the geometry used in the simulation is consistent with the actual operating geometry. It adopts a dynamic fluid interaction method and uses the aerodynamic torque of the compressor and turbine to adaptively iteratively match the speed, so that the speed automatically converges to an equilibrium state and no longer relies on manual pre-setting. The automatic speed matching method can significantly improve the simulation accuracy, reduce the cost of human trial and error, and has higher reliability for design optimization and performance prediction under real working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0025] Figure 1 This is a flow chart of a method for determining the rotational speed in a three-dimensional simulation of an entire aircraft engine according to an embodiment of the present application. DETAILED DESCRIPTION

[0026] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0027] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the features in the following embodiments and embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of this application.

[0028] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on this application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement an apparatus and / or practice a method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this apparatus and / or practice this method.

[0029] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The illustrations only show components related to the present application and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0030] Additionally, in the following description, specific details are provided to provide a thorough understanding of the examples. However, one skilled in the art will appreciate that the aspects described can be practiced without these specific details.

[0031] An embodiment of the present application provides a method for determining the rotational speed in a three-dimensional simulation of an entire aircraft engine.

[0032] Based on the three-dimensional fluid-solid-thermal simulation of a complete aircraft engine and combined with the principle of dynamic fluid interaction, a method for determining the rotational speed in a three-dimensional simulation of a complete aircraft engine is provided, which includes the following steps:

[0033] Step 1: constructing a complete geometric model and a complete physical model of the aero-engine;

[0034] Step 2: Establish data transmission between the rotating domain and the stationary domain of the aircraft engine;

[0035] Step 3: construct the fluid-structure coupling control equation on each grid cell of the aero-engine geometric model;

[0036] Step 4: Incorporate the heat conduction method into the fluid-structure coupling control equation to form an overall coupling matrix. Use the Newton-Raphson iteration to minimize the global residual as the goal, and embed multiple parallel preconditioned solvers to directly solve the overall coupling matrix;

[0037] Step 5: By solving the overall coupling matrix simulation, the engine is calculated from the cold state to the hot state, and the actual geometric shape of each engine component under the hot working condition and the hot state geometric model calculated by simulation are obtained;

[0038] Step 6: restrict the freedom of movement of the compressor and turbine so that they can only rotate around the axis of rotation;

[0039] Step 7, calculate the aerodynamic forces acting on the compressor blades and turbine blades;

[0040] Step 8: Calculate the current angular acceleration of the engine ;

[0041] Step 9: When the simulation starts, set the initial speed , in each time step, the rotation speed is updated according to the angular acceleration;

[0042] Step 10: Re-perform the fluid dynamics calculation to obtain a new torque value. After several iterations, when the difference between the aerodynamic torque of the compressor and the aerodynamic torque of the turbine falls within the preset range, the corresponding speed is the steady-state operating speed of the engine under this thermal geometry.

[0043] Based on the equilibrium speed automatically obtained through this iterative process, the engine's steady-state speed is output in its hot state. This method eliminates the need for manual speed settings and allows for adaptive matching. Furthermore, because it considers both thermal geometric deformation and aerodynamic-structural coupling effects, the simulation results more closely resemble actual engine operating conditions.

[0044] like Figure 1 As shown, taking the KJ66 aircraft engine as an example, this application provides a specific implementation of a method for determining the rotational speed in a three-dimensional simulation of an entire aircraft engine:

[0045] Step 1: Construct the geometric model and physical model of the entire aircraft engine.

[0046] Step 11: Use a full-circle modeling approach to create a comprehensive 3D geometric model of the inlet, compressor blades, combustion chamber, turbine, and nozzle. The inlet fluid domain is extended by six equivalent diameters along the airflow direction to ensure a well-developed inlet flow field; the nozzle is extended by 20 equivalent diameters along the exhaust direction to ensure adequate airflow expansion.

[0047] Step 12, Meshing: For the compressor and turbine, where the airflow direction is known, a structured hexahedral mesh is used, with the mesh arrangement parallel to the flow direction. Due to the turbulent flow in the combustion chamber, an unstructured tetrahedral mesh is used, with one to two layers of thin-walled mesh added to the combustion chamber walls. When using the low-Reynolds number k-ω SST turbulence model, meshing must ensure that the dimensionless distance Y+ of the first layer of mesh on the inner wall of the boundary layer is less than 1. Five layers of mesh are placed in the viscous bottom layer, three layers in the transition layer, and five layers in the logarithmic layer. SST stands for shear stress transfer model.

[0048] Step 13, boundary condition processing: the full-ring model directly applies the solid wall no-slip condition; the total pressure inlet condition is applied to the inlet duct inlet, and the total pressure outlet condition is applied to the nozzle outlet; the rotating domain method is used for the transient calculation of the rotating domain, and the rotating domain includes the compressor rotor and the turbine rotor.

[0049] Step 14, physical model establishment: For the fluid model, the low Reynolds number k-ω SST turbulence model is selected; the Lagrangian multiphase model is used in the combustion zone to calculate fuel injection atomization, secondary breakup, evaporation, and droplet-gas interaction; the ideal gas equation of state is used; for the structural model, the temperature-dependent properties of the alloy material are considered, and the finite element method is used to calculate the thermal expansion and stress distribution of the structure; for fluid-structure coupling, the displacement of the fluid node and the solid node at the interface is guaranteed to be consistent, and the flow channel shape is updated through the mesh deformation algorithm.

[0050] Step 2: Establish data transfer between the rotating domain and the stationary domain of the entire aircraft engine. When the fluid domain contains rotating parts, a mixed interface is used between the rotating domain and the stationary domain, and data transfer is performed through circumferential data averaging. The fluid domain adjacent to the solid domain is consistent with the solid reference system, and data synchronization between the fluid domain and the solid is achieved through coupled partitioning.

[0051] Step 3: Construct the fluid-solid coupling control equation on each grid element of the aero-engine complete geometric model; use the finite volume method to solve the Navier–Stokes equations in the fluid domain, and use the finite element method to solve the thermoelastic equations in the structural domain, and discretize them in the same formal framework to generate a coupling stiffness matrix as the fluid-solid coupling control equation; during the discretization process, set the same surface elements as the shared grid at the fluid-solid interface to constrain the fluid velocity to be equal to the structural velocity and the fluid force to be consistent with the structural force mapping.

[0052] The governing equations of fluid-structure coupling are as follows:

[0053] ;

[0054] in:

[0055] and Corresponding fluid equations, including convection, diffusion, momentum source terms, etc.;

[0056] and Corresponding structural equations, including elastic stiffness, thermal expansion loads, etc.;

[0057] is the fluid-solid interface fluid side coupling term, It is the coupling term on the solid side of the fluid-solid interface, ensuring the continuity of velocity / displacement and the balance of force / stress on the interface;

[0058] is the fluid displacement, is the solid displacement.

[0059] Furthermore, the overall mesh utilizes the Arbitrary Lagrangian-Euler (ALE) method, allowing fluid elements to follow the motion of structural nodes without the need for explicit mesh mapping. Geometric deformations at the fluid-solid interface are directly reflected in the element stiffness within the global stiffness matrix, and fluid mesh deformations are updated synchronously with structural deformations, automatically maintaining mesh quality.

[0060] Step 4: Incorporate the heat conduction method into the fluid-solid coupling control equation to form an overall coupling matrix. Use the Newton-Raphson iteration to minimize the global residual as the goal, and embed multiple parallel preconditioning solvers to directly solve the overall coupling matrix. The heat source comes from the wall heat flow at the fluid end, ensuring the simultaneous solution of temperature, thermal deformation, and fluid heat transfer. Use the Newton-Raphson iteration to minimize the global residual as the goal, and embed multiple parallel preconditioning solvers to directly solve the overall coupling matrix. In each iteration, update the fluid velocity, pressure, structural displacement, temperature and other variables at the same time until the overall residual meets the preset convergence criterion, requiring the relative residual to be less than 10 −3 .

[0061] The fluid-structure coupling simulation of the entire aero-engine unifies the control equations of the two subdomains of fluid and structure into an overall set of equations. Through two solvers and a unified solution step, the fluid motion and structural deformation are solved simultaneously to ensure that the strict continuity of velocity-displacement and force-stress is met at the fluid-solid interface.

[0062] Step 5: By solving the overall coupling matrix simulation, the engine is calculated from the cold state to the hot state, and the actual geometric shape of each engine component under the hot working condition is obtained. The hot state geometric model calculated by simulation fully reflects the thermal expansion and warping of the blades, disk and other components caused by the temperature increase.

[0063] Step 6: Use finite element constraints to limit the degrees of freedom of the compressor and turbine movements, retain one overall rotational degree of freedom, and constrain other non-rotational degrees of freedom so that the compressor and turbine can only rotate around the axis of rotation.

[0064] Step 7: Calculate the aerodynamic forces acting on the compressor blades and turbine blades: Based on the fluid pressure distribution and shear stress distribution, calculate the fluid pressure and shear stress distribution on the compressor blades based on the thermal geometry, and integrate them to obtain the aerodynamic torque of the compressor. Similarly, calculate the aerodynamic torque on the turbine blades .

[0065] Step 8: When the simulation starts, set the initial speed , in each time step, the rotation speed is updated according to the angular acceleration.

[0066] Let the time step be , assuming the current time step speed is At this speed, the torque on the compressor obtained by fluid simulation is The torque on the turbine is , according to the rotor dynamics equation:

[0067] ,in, is the angular velocity, is the rotation speed, is the overall moment of inertia, is the angular acceleration;

[0068] The current angular acceleration can be calculated :

[0069] ,in, is the overall moment of inertia;

[0070] Update the angular velocity at the next time step using the explicit Euler method , and then update the speed of the next time step :

[0071] , , is the angular velocity of the current time step.

[0072] Step 9: In step k+1, the new speed Substitute the fluid simulation and recalculate the torque on the turbine and the torque on the turbine. If the balance criterion is met: the absolute value of the difference between the torque on the turbine and the torque on the turbine is less than the threshold;

[0073] It is considered that the speed has converged. That is, the engine's steady-state matching speed under the current thermal geometry. Otherwise, continue iterating until convergence. In one embodiment, the threshold is .

[0074] The converged speed and the corresponding aerodynamic and structural states are output together as the final simulation results under this simulation condition.

[0075] The above iterative process does not require a pre-specified speed. During the simulation, the speed is automatically adjusted based on the aerodynamic-structural interaction until torque equilibrium is achieved. Because the thermal geometry, dynamic aerodynamics, and structural coupling effects are simultaneously considered, the resulting speed is closer to the actual operating conditions. The speed convergence criterion is clear, and numerical stability can be guaranteed by setting reasonable thresholds and Δt.

[0076] In the KJ66 case simulation, if the initial speed is set to 5000 r / min, the calculation converges to approximately 5400 r / min after several iterations, and the error with the experimental calibration value ≈ 5380 r / min is less than 0.4%.

[0077] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for determining the rotational speed in a three-dimensional simulation of an entire aircraft engine, characterized in that: The steps include: Step 1: constructing a complete geometric model and a complete physical model of the aero-engine; Step 2: Establish data transmission between the rotating domain and the stationary domain of the aircraft engine; Step 3: construct the fluid-structure coupling control equation on each grid cell of the aero-engine geometric model; Step 4: Incorporate the heat conduction method into the fluid-structure coupling control equation to form an overall coupling matrix. Use the Newton-Raphson iteration to minimize the global residual as the goal, and embed multiple parallel preconditioned solvers to directly solve the overall coupling matrix; Step 5: By solving the overall coupling matrix simulation, the engine is calculated from the cold state to the hot state, and the actual geometric shape of each engine component under the hot working condition and the hot state geometric model calculated by simulation are obtained; Step 6: restrict the freedom of movement of the compressor and turbine so that they can only rotate around the axis of rotation; Step 7, calculate the aerodynamic forces acting on the compressor blades and turbine blades; Step 8: Calculate the current angular acceleration of the engine ; Step 9: When the simulation starts, set the initial speed , in each time step, the rotation speed is updated according to the angular acceleration; Step 10: Re-calculate the fluid dynamics to obtain a new torque value. After several iterations, when the difference between the aerodynamic torque of the compressor and the aerodynamic torque of the turbine meets the preset range, the corresponding speed is the steady-state operating speed of the engine under the hot geometry.

2. The method for determining the rotational speed in three-dimensional simulation of an entire aircraft engine according to claim 1, characterized in that: In step 2, when the fluid domain contains rotating parts, a mixed interface is used between the rotating domain and the stationary domain, and data is transferred through circumferential data averaging; the fluid domain adjacent to the solid domain is consistent with the solid reference system, and data synchronization between the fluid domain and the solid is achieved through coupled partitioning.

3. The method for determining the rotational speed in three-dimensional simulation of an entire aircraft engine according to claim 1, characterized in that: In step 3, the Navier–Stokes equations are solved in the fluid domain using the finite volume method, and the thermoelastic equations are solved in the structural domain using the finite element method. The equations are discretized in the same formal framework to generate a coupling stiffness matrix as the fluid-structure coupling governing equation. During the discretization process, at the fluid-solid interface, the same surface units are set as shared grids to constrain the fluid velocity to be equal to the structural velocity and the fluid force to be mapped consistently with the structural force.

4. The method for determining the rotational speed in three-dimensional simulation of an entire aircraft engine according to claim 1, characterized in that: In step 7, the torque on the compressor is calculated based on the fluid pressure distribution and shear stress distribution. The torque on the turbine .

5. The method for determining the rotational speed in three-dimensional simulation of an entire aircraft engine according to claim 4, characterized in that: In step 8, according to the overall moment of inertia , use the dynamic equation to calculate the current angular acceleration of the engine , ,in, is the torque on the compressor, is the torque acting on the turbine.

6. The method for determining the rotational speed in three-dimensional simulation of an entire aircraft engine according to claim 5, characterized in that: In step 9, the speed is updated using the following formula: ;in, is the speed of the current time step, is the current angular acceleration, is the speed of the next time step, is the time step.

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