A method of designing an engine active clearance

Abstract

This application provides a method for designing active clearances for engines, belonging to the field of aero-engine technology. The method includes constructing a rigid-flexible coupled finite element model that combines multibody dynamics and finite element analysis; solving for deformations under gyroscopic effects and inertial loads, as well as deformations under thermo-coupling effects during engine operation; extracting rotor-to-rotor clearance deformations and rotor-to-stator clearance deformations based on the deformation solutions; identifying deformation-sensitive areas; performing multi-objective optimization on the structures of these areas; and designing an initial installation clearance value that balances safety and efficiency based on the optimization results and considering other factors affecting the rotor-to-stator clearance. These other factors include the radial movement of bearings and support elastic elements, rotor-to-stator runout, and changes in the relative axial position of the rotor and stator. This method improves the accuracy of active clearance design, balances engine safety and efficiency, and reduces the risk of engine rubbing.

Description

Technical Field

[0001] This application relates to the field of aero-engine technology, and in particular to a method for designing active clearance of an engine. Background Technology

[0002] An aero-engine is a complex system in which rotors (high-pressure and low-pressure rotors) and stator components (rotating and stationary parts) are tightly fitted together. Indispensable gaps exist between the rotors and stator components, serving as the main channels for the flow of combustion gases, air, or fuel. When these gaps are too large, high-temperature combustion gases and high-pressure air will leak from the high-pressure area to the low-pressure area, reducing the efficiency of the components and significantly increasing fuel consumption. Conversely, when the gaps are too small, the probability of friction and collision between the rotors and stator components increases significantly.

[0003] During aircraft flight, the engine is subjected to strong unsteady aerodynamic loads, inertial loads (especially gyroscopic effects), and transient temperature changes. These extreme dynamic conditions cause the rotor-rotor and rotor-stator clearances to change drastically and unpredictably. The elastic deformation, thermal deformation, and gyroscopic effects of the main shaft, blades, casing, and wheel disk, combined with the clearances, result in strong nonlinear characteristics that far exceed steady-state conditions.

[0004] Traditional passive clearance control for engines mainly relies on the passive thermal expansion or venting cooling of the casing. Its response speed is slow and it can only be limited to a small area between the casing and the blades. It cannot prevent radial clearances in high and low pressure rotors, etc., and is far from meeting the requirements of engine use.

[0005] Therefore, when faced with situations where the gyro load sensitivity between high- and low-pressure rotors and between rotor and stator differs, structural stiffness is inconsistent, resulting in large deformation differences and gaps that cannot meet design requirements, it is necessary to actively control the rotor-rotor and rotor-stator gaps. Summary of the Invention

[0006] To address the issues of varying gyroscopic load sensitivity between high- and low-pressure rotors and between rotors and stators during engine operation, inconsistent structural stiffness leading to large deformation differences, and inability to meet design requirements for clearances, this application provides an active clearance design method for engines. Through precise dynamic deformation calculation, local structural optimization design, and scientific initial installation clearance design, this method solves the problems of inaccurate deformation prediction, weak structural deformation resistance, and unreasonable initial clearance design in existing technologies. This allows for the simultaneous achievement of controllable and reasonable clearances between the rotor and rotor and between the rotor and stator during engine operation, ensuring a successful engine structural design from the outset.

[0007] This application provides an engine active clearance design method, including:

[0008] Construct a rigid-flexible coupled finite element model that couples multibody dynamics and finite element method; Based on the rigid-flexible coupled finite element model, the deformation under gyroscopic effect and inertial load and the deformation under thermo-mechanical coupling during engine operation are solved. Based on the deformation under gyroscopic effect and inertial load and the deformation under thermo-coupling effect during engine use, the rotor-rotor gap deformation and rotor-stator gap deformation are extracted respectively. Based on the deformation of the rotor-rotor gap and the rotor-stator gap, deformation-sensitive areas are identified, and the structure of the deformation-sensitive areas is optimized by multiple objectives to reduce dynamic deformation differences. Based on the optimized results, and taking into account other factors that affect the clearance between the rotor and stator, an initial installation clearance value that balances safety and efficiency is designed. Other factors include the radial movement of the bearings and fulcrum elastic elements, rotor and stator runout, and the relative axial position changes of the rotor and stator.

[0009] According to a specific implementation of an embodiment of this application, the construction of the rigid-flexible coupled finite element model includes: Model composition: The rigid-flexible coupled finite element model includes the engine high-pressure rotor, low-pressure rotor, bearings and casing. The high-pressure rotor and low-pressure rotor are simplified as elastic beam elements, the casing is simplified as shell elements, and the bearings are simplified as spring-damped elements. Coordinate definition: Based on the rigid-flexible coupled finite element model, the engine's center of mass is taken as the origin of the coordinate system. The X-axis coincides with the engine axis and is positive in the reverse direction. The Y-axis is perpendicular to the engine axis and is positive in the upward direction. Load input: Input maneuvering parameters, including angular velocity and angular acceleration, the values ​​of which are determined according to the aircraft's requirements for engine operation; input thermal loads, including the temperature fields of each stage of rotor and stator; input aerodynamic loads, including the pressure distribution on the blade surface.

[0010] According to a specific implementation of an embodiment of this application, the solution for the gyroscopic effect and deformation under inertial load when the engine is in use includes: The gyroscopic torque of the rotor is calculated based on Euler's equations. The gyroscopic torque of the rotor is applied to the rigid-flexible coupled finite element model, and the rotor displacement under the gyroscopic effect is calculated. Based on angular acceleration and time of application, the rotor inertial displacement under inertial load is calculated; The solution for the deformation under the thermo-coupling effect includes: The sequential coupling calculation method is used to calculate the temperature fields of the rotor and stator by taking into account cooling airflow and thermal radiation; The temperature fields of the rotor and stator, as well as the aerodynamic forces obtained from fluid calculations, are applied to the rigid-flexible coupled finite element model to calculate the rotor displacement and stator displacement under thermo-mechanical coupling.

[0011] According to a specific implementation of an embodiment of this application, the expression for the gyro torque is: , Where I is the moment of inertia tensor, ω is the rotor's angular velocity, Ω is the angular velocity, and M is the moment of inertia tensor. g This refers to the gyroscopic torque. The expression for the rotor inertial displacement under the inertial load is: , Where, δ inertial Let α be the rotor inertial displacement under inertial load, α be the angular acceleration, and t be the time of application.

[0012] According to a specific implementation of an embodiment of this application, the expression for the deformation of the rotor-rotor gap is: , Where, Δδ z-z For the deformation of the gap between the rotor and the rotor, Δδ tuoluo Δδ represents the deformation of the gap between the high-voltage rotor and the low-voltage rotor under the gyroscopic effect. inertial Δδ represents the deformation of the gap between the high-pressure rotor and the low-pressure rotor under inertial load. RL-zz δ represents the deformation of the gap between the high-pressure rotor and the low-pressure rotor under thermo-coupling. tuoluo_高 δ represents the displacement of the high-voltage rotor under the gyroscopic effect. tuoluo_低 δ represents the displacement of the low-voltage rotor under the gyroscopic effect. inertial_高 δ represents the inertial displacement of the high-voltage rotor under inertial load. inertial_低 δ represents the inertial displacement of the low-pressure rotor under inertial load. RL-zz_高 δ represents the displacement of the high-voltage rotor under thermo-coupling. RL-zz_低 This refers to the displacement of the low-pressure rotor under thermo-coupling. The expression for the deformation of the rotor-stator gap is: , Where, Δδ z-j For the deformation of the rotor-stator gap, δ tuoluo δ represents the rotor displacement under the gyroscopic effect. RL-zz δ represents the rotor displacement under thermo-coupling. RL-zj This represents the stator displacement under thermo-mechanical coupling.

[0013] According to a specific implementation of an embodiment of this application, the multi-objective optimization of the structure in the deformation-sensitive region includes: The optimization objects and optimization parameters are set. The optimization objects include the casing and rotor disk in the deformation sensitive area. The optimization parameters include the local thickness of the casing, the layout of the reinforcing ribs of the casing, the inclination angle of the rotor disk spokes, and the thickness of the rotor disk spokes. Set optimization objectives and constraints. The optimization objective is to minimize the maximum rate of change of gap in the deformation-sensitive zone, and the constraint is that the structural weight is not greater than the preset mass change of the deformation-sensitive zone before and after optimization. A hybrid optimization algorithm combining topology optimization and size optimization is adopted. Based on the finite element simulation results, the optimal parameter combination is searched through a genetic algorithm to complete the structural optimization. The rotor-rotor gap deformation and rotor-stator gap deformation are recalculated for the optimized structure. If the rotor-rotor gap deformation or rotor-stator gap deformation is still greater than the preset threshold, the hybrid optimization algorithm is re-executed until the requirements are met.

[0014] According to a specific implementation of an embodiment of this application, the initial installation gap value designed to balance safety and efficiency includes: Define the limit clearance scenarios, including the minimum clearance scenario and the maximum clearance scenario. Obtain the minimum rotor-rotor clearance deformation and the minimum rotor-stator clearance deformation under the minimum clearance scenario. Obtain the maximum rotor-rotor clearance deformation and the maximum rotor-stator clearance deformation under the maximum clearance scenario. The initial clearance value for safety reference is obtained based on the minimum deformation of rotor-rotor clearance, the minimum deformation of rotor-stator clearance, the radial movement of bearing and support elastic elements, the runout of rotor and stator, and the relative axial position change of rotor and stator. The initial clearance value for efficiency reference is obtained based on the maximum value of rotor-rotor clearance deformation, the maximum value of rotor-stator clearance deformation, the radial movement of bearing and support elastic elements, rotor and stator runout, and the relative axial position change of rotor and stator. Based on the initial clearance values ​​of the safety benchmark and the initial clearance values ​​of the efficiency benchmark, the initial installation clearance between the rotor and the stator and the initial installation clearance between the rotor and the stator are obtained respectively.

[0015] According to a specific implementation of this application, the initial safety reference gap value includes a rotor-to-stator safety reference gap value and a rotor-to-stator safety reference gap value. The calculation formula for the initial rotor-to-stator safety reference gap value is as follows: , Among them, S m_z-z_aq S is the initial clearance value for the rotor-to-rotor safety reference. p_z-z_aq Δδ is the rotor-to-rotor working clearance value under the safety standard required by aerodynamics. z-z_min δ is the minimum value of rotor-to-rotor clearance deformation. zThis refers to the effect of the radial movement of the bearing and the elastic element at the support point on the radial clearance. The formula for calculating the initial clearance value of the rotor-stator safety reference is: , Among them, S m_z-j_aq S is the initial clearance value for rotor-stator safety reference. p_z-j_aq The rotor-stator clearance value, Δδ, is the value based on the pneumatic safety standard. z-j_min δ is the minimum value of rotor-stator gap deformation. t The influence of rotor and stator runout on radial clearance is given by k1, where k1 is the first safety factor and δ is the value of the rotor and stator runout. y This represents the change in clearance caused by the change in the relative axial position of the rotor and stator.

[0016] According to a specific implementation of this application, the initial gap value of the efficiency reference includes the initial gap value of the rotor-stator efficiency reference and the initial gap value of the rotor-stator efficiency reference. The calculation formula for the initial gap value of the rotor-stator efficiency reference is as follows: , Among them, S m_z-z_xl S is the initial clearance value for the rotor-to-rotor efficiency reference. p_z-z_xl Δδ is the rotor-rotor working clearance value under the efficiency benchmark required by aerodynamics. z-z_max This represents the maximum value of the rotor-rotor gap deformation. The formula for calculating the initial gap value of the rotor-stator efficiency baseline is: , Among them, S m_z-j_xl S is the initial gap value for the rotor-stator efficiency baseline. p_z-j_xl Δδ is the rotor-stator working clearance value under the efficiency benchmark required by aerodynamics. z-j_max k1 represents the maximum value of the rotor-stator gap deformation, and k2 represents the second safety factor.

[0017] According to a specific implementation of an embodiment of this application, the expression for the initial installation gap between the rotor and the rotor is: , The expression for the initial installation gap between the rotor and stator is: , Among them, S z-z_initial S is the initial installation gap between the rotor and the rotor. z-j_initial This refers to the initial installation gap between the rotor and stator.

[0018] Beneficial effects: The engine active clearance design method in this application embodiment uses a "multibody dynamics-finite element coupling" model to accurately calculate the rotor-rotor and rotor-stator clearance deformation under different load combinations, providing reliable input for clearance control design. It takes into account both engine safety and efficiency, and can reduce the initial clearance by more than 10% compared with traditional methods, while reducing the risk of collision and rubbing during engine use by more than 90%. This method can be directly integrated into the aero-engine design process and supports the development of various types of power systems. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart of an engine active clearance design method according to an embodiment of the present invention. Detailed Implementation

[0021] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0022] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one 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 set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0024] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The illustrations only show the components related to this application and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0025] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0026] In one embodiment, this application provides an active clearance design method for an engine, used for active clearance control between the engine rotor and stator (rotor-to-rotor) and between the rotor and stator (rotor-to-stator), referring to... Figure 1 Specifically, it includes the following steps: Construct a rigid-flexible coupled finite element model that couples multibody dynamics and finite element method; Based on the rigid-flexible coupled finite element model, the deformation under gyroscopic effect and inertial load and the deformation under thermo-mechanical coupling during engine operation are solved. Based on the deformation under gyroscopic effect and inertial load and the deformation under thermo-coupling effect during engine use, the rotor-rotor gap deformation and rotor-stator gap deformation are extracted respectively. Based on the deformation of the rotor-rotor gap and the rotor-stator gap, deformation-sensitive areas are identified, and the structure of the deformation-sensitive areas is optimized by multiple objectives to reduce dynamic deformation differences. Based on the optimized results, and taking into account other factors that affect the clearance between the rotor and stator, an initial installation clearance value that balances safety and efficiency is designed. Other factors include the radial movement of the bearings and fulcrum elastic elements, rotor and stator runout, and the relative axial position changes of the rotor and stator.

[0027] Furthermore, the construction of the rigid-flexible coupled finite element model includes: Model composition: The rigid-flexible coupled finite element model includes the engine high-pressure rotor, low-pressure rotor, bearings and casing. The high-pressure rotor and low-pressure rotor are simplified as elastic beam elements, the casing is simplified as shell elements, and the bearings are simplified as spring-damped elements. Coordinate definition: Based on the rigid-flexible coupled finite element model, the engine's center of mass is taken as the origin of the coordinate system. The X-axis coincides with the engine axis and is positive in the reverse direction. The Y-axis is perpendicular to the engine axis and is positive in the upward direction. Load input: Input maneuvering parameters, including angular velocity and angular acceleration, the values ​​of which are determined according to the aircraft's requirements for engine operation; input thermal loads, including the temperature fields of each stage of rotor and stator; input aerodynamic loads, including the pressure distribution on the blade surface.

[0028] Furthermore, the solution for the gyroscopic effect and deformation under inertial load during engine operation includes: The gyroscopic torque of the rotor is calculated based on Euler's equations. The gyroscopic torque of the rotor is applied to the rigid-flexible coupled finite element model, and the rotor displacement under the gyroscopic effect is calculated. Based on angular acceleration and time of application, the rotor inertial displacement under inertial load is calculated; The solution for the deformation under the thermo-coupling effect includes: The sequential coupling calculation method is used to calculate the temperature fields of the rotor and stator by taking into account cooling airflow and thermal radiation; The temperature fields of the rotor and stator, as well as the aerodynamic forces obtained from fluid calculations, are applied to the rigid-flexible coupled finite element model to calculate the rotor displacement and stator displacement under thermo-mechanical coupling.

[0029] Furthermore, the expression for the gyro torque is: , Where I is the moment of inertia tensor, ω is the rotor's angular velocity, Ω is the angular velocity, and M is the moment of inertia tensor. g This refers to the gyroscopic torque. The expression for the rotor inertial displacement under the inertial load is: , Where, δ inertial Let α be the rotor inertial displacement under inertial load, α be the angular acceleration, and t be the time of application.

[0030] Furthermore, the expression for the deformation of the rotor-rotor gap is: , Where, Δδ z-z For the deformation of the gap between the rotor and the rotor, Δδ tuoluo Δδ represents the deformation of the gap between the high-voltage rotor and the low-voltage rotor under the gyroscopic effect. inertial Δδ represents the deformation of the gap between the high-pressure rotor and the low-pressure rotor under inertial load. RL-zz δ represents the deformation of the gap between the high-pressure rotor and the low-pressure rotor under thermo-coupling. tuoluo_高 δ represents the displacement of the high-voltage rotor under the gyroscopic effect. tuoluo_低 δ represents the displacement of the low-voltage rotor under the gyroscopic effect. inertial_高 δ represents the inertial displacement of the high-voltage rotor under inertial load. inertial_低 δ represents the inertial displacement of the low-pressure rotor under inertial load. RL-zz_高 δ represents the displacement of the high-voltage rotor under thermo-coupling. RL-zz_低 This refers to the displacement of the low-pressure rotor under thermo-coupling. The expression for the deformation of the rotor-stator gap is: , Where, Δδ z-j For the deformation of the rotor-stator gap, δ tuoluo δ represents the rotor displacement under the gyroscopic effect. RL-zz δ represents the rotor displacement under thermo-coupling. RL-zj This represents the stator displacement under thermo-mechanical coupling.

[0031] Furthermore, the multi-objective optimization of the structure in the deformation-sensitive region includes: The optimization objects and optimization parameters are set. The optimization objects include the casing and rotor disk in the deformation sensitive area. The optimization parameters include the local thickness of the casing, the layout of the reinforcing ribs of the casing, the inclination angle of the rotor disk spokes, and the thickness of the rotor disk spokes. Set optimization objectives and constraints. The optimization objective is to minimize the maximum rate of change of gap in the deformation-sensitive zone, and the constraint is that the structural weight is not greater than the preset mass change of the deformation-sensitive zone before and after optimization. A hybrid optimization algorithm combining topology optimization and size optimization is adopted. Based on the finite element simulation results, the optimal parameter combination is searched through a genetic algorithm to complete the structural optimization. The rotor-rotor gap deformation and rotor-stator gap deformation are recalculated for the optimized structure. If the rotor-rotor gap deformation or rotor-stator gap deformation is still greater than the preset threshold, the hybrid optimization algorithm is re-executed until the requirements are met.

[0032] Furthermore, the initial installation clearance value, which balances safety and efficiency, includes: Define the limit clearance scenarios, including the minimum clearance scenario and the maximum clearance scenario. Obtain the minimum rotor-rotor clearance deformation and the minimum rotor-stator clearance deformation under the minimum clearance scenario. Obtain the maximum rotor-rotor clearance deformation and the maximum rotor-stator clearance deformation under the maximum clearance scenario. The initial clearance value for safety reference is obtained based on the minimum deformation of rotor-rotor clearance, the minimum deformation of rotor-stator clearance, the radial movement of bearing and support elastic elements, the runout of rotor and stator, and the relative axial position change of rotor and stator. The initial clearance value for efficiency reference is obtained based on the maximum value of rotor-rotor clearance deformation, the maximum value of rotor-stator clearance deformation, the radial movement of bearing and support elastic elements, rotor and stator runout, and the relative axial position change of rotor and stator. Based on the initial clearance values ​​of the safety benchmark and the initial clearance values ​​of the efficiency benchmark, the initial installation clearance between the rotor and the stator and the initial installation clearance between the rotor and the stator are obtained respectively.

[0033] Furthermore, the initial safety reference clearance value includes the rotor-stator safety reference initial clearance value and the rotor-stator safety reference initial clearance value. The calculation formula for the rotor-stator safety reference initial clearance value is as follows: , Among them, S m_z-z_aq S is the initial clearance value for the rotor-to-rotor safety reference. p_z-z_aq Δδ is the rotor-to-rotor working clearance value under the safety standard required by aerodynamics. z-z_min δ is the minimum value of rotor-to-rotor clearance deformation. z This refers to the effect of the radial movement of the bearing and the elastic element at the support point on the radial clearance. The formula for calculating the initial clearance value of the rotor-stator safety reference is: , Among them, S m_z-j_aq S is the initial clearance value for rotor-stator safety reference. p_z-j_aq The rotor-stator clearance value, Δδ, is the value based on the pneumatic safety standard. z-j_min δ is the minimum value of rotor-stator gap deformation. t The influence of rotor and stator runout on radial clearance is given by k1, where k1 is the first safety factor and δ is the value of the rotor and stator runout. y This represents the change in clearance caused by the change in the relative axial position of the rotor and stator.

[0034] Furthermore, the initial clearance value for the efficiency reference includes the initial clearance value for the rotor-to-stoker efficiency reference and the initial clearance value for the rotor-to-stator efficiency reference. The calculation formula for the initial clearance value for the rotor-to-stoker efficiency reference is as follows: , Among them, S m_z-z_xl S is the initial clearance value for the rotor-to-rotor efficiency reference. p_z-z_xl Δδ is the rotor-rotor working clearance value under the efficiency benchmark required by aerodynamics. z-z_max This represents the maximum value of the rotor-rotor gap deformation. The formula for calculating the initial gap value of the rotor-stator efficiency baseline is: , Among them, S m_z-j_xl S is the initial gap value for the rotor-stator efficiency baseline. p_z-j_xl Δδ is the rotor-stator working clearance value under the efficiency benchmark required by aerodynamics. z-j_max k1 represents the maximum value of the rotor-stator gap deformation, and k2 represents the second safety factor.

[0035] Furthermore, the expression for the initial installation gap between the rotor and the rotor is: , The expression for the initial installation gap between the rotor and stator is: , Among them, S z-z_initial S is the initial installation gap between the rotor and the rotor. z-j_initial This refers to the initial installation gap between the rotor and stator.

[0036] In one embodiment, a more detailed method for designing engine active clearance is provided, specifically including the following steps: Step 1: Calculation method for rotor-rotor and rotor-stator deformation during engine operation. Considering the complex deformation characteristics of the engine during operation due to gyroscopic effects, inertial loads, and thermo-mechanical coupling, a "multibody dynamics-finite element coupling" model is established to accurately calculate the dynamic deformation of the rotor-rotor and rotor-stator. This includes: Step 11: Construct a rigid-flexible coupled finite element model: Model composition: The rigid-flexible coupled finite element model includes the engine's high-pressure rotor, low-pressure rotor, bearings, and casing. The high-pressure rotor and low-pressure rotor are simplified as elastic beam elements (considering bending and torsional stiffness), the casing is simplified as shell elements (considering radial and circumferential stiffness), and the bearings are simplified as spring-damped elements (including radial and axial stiffness). Coordinate definition: Based on the rigid-flexible coupled finite element model, the engine's center of mass is taken as the origin of the coordinate system. The X-axis (axial direction) coincides with the engine axis and is positive in the reverse direction. The Y-axis (radial direction) is positive in the direction perpendicular to the engine axis and upward. The Z-axis is then determined according to the right-hand rule. Load inputs: ① Maneuvering parameters include angular velocity Ω and angular acceleration α, the values ​​of which are determined according to the aircraft's requirements for engine operation; ② Thermal loads include the temperature fields of each stage of rotor / stator; ③ Aerodynamic loads include the pressure distribution on the blade surface (calculated based on an unsteady aerodynamic model).

[0037] Step 12, Dynamic Deformation Solution: (1) Gyroscopic effect and deformation under inertial load during engine operation: Based on Euler's equation, the gyroscopic torque of the rotor is calculated. Where I is the moment of inertia tensor, ω is the rotor's angular velocity, Ω is the angular velocity, and M is the moment of inertia tensor. g This refers to the gyroscopic torque; based on the gyroscopic torque value M... g When applied to the finite element model of the engine rotor, the rotor displacement δ under the gyroscopic effect can be calculated. tuoluo Then, the inertial displacement under inertial load is obtained by the following formula: , where α is angular acceleration and t is the time of action.

[0038] (2) Deformation under thermo-coupling: The sequential coupling calculation method is adopted. First, the temperature field of the rotor and stator is calculated by considering the cooling airflow and thermal radiation. Then, based on the rigid-flexible coupling finite element model, the temperature field and the aerodynamic force obtained by the fluid calculation are applied to the rigid-flexible coupling finite element model, and the displacement values ​​of the rotor and stator are calculated to obtain δ. RL-zz δ RL-zj δ RL-zz δ represents the rotor displacement under thermo-coupling. RL-zj This represents the stator displacement under thermo-mechanical coupling.

[0039] (3) Extraction of deformation in the gap between rotor and stator: Rotor-rotor gap deformation Δδ z-z The expression for calculating the radial clearance deformation difference between the high-pressure and low-pressure rotors is as follows: , Rotor-stator gap deformation Δδ z-j The expression for calculating the radial clearance displacement difference between adjacent stator casings and rotor blade tips is as follows: , In the formula, δ tuoluo For δ tuoluo_高 Or δ tuoluo_低 δ inertial For δ inertial_高 Or δ inertial_低 δ RL-zz For δ RL-zz_高 Or δ RL-zz_低 .

[0040] Step 2: Local Structural Optimization Method. Based on the deformation calculation results, stiffness matching and optimization are performed on areas with concentrated deformation (such as the thin-walled region of the stator casing and the edge of the rotor disk) to reduce dynamic deformation differences. This includes the following steps: Step 21, Weak Area Identification: Through deformation analysis, extract areas where the rotor-to-rotor clearance change rate or rotor-to-stator clearance change rate is greater than a preset threshold, and define them as "deformation sensitive areas". The preset threshold is adjusted according to the structural position of the engine (e.g., the preset threshold for the axial section of the stator casing is 10%, and the preset threshold for the rotor wheel disc spokes is 8%).

[0041] Step 22: Perform local multi-objective optimization for each deformation-sensitive region: (1) Set the optimization objects and optimization parameters. The optimization objects include the casing and rotor disk in the deformation sensitive area. The optimization parameters include the local thickness of the casing, the layout of the reinforcing ribs of the casing, the inclination angle of the rotor disk spokes, and the thickness of the rotor disk spokes. (2) Set the optimization objective and constraints. The optimization objective is to minimize the maximum value of the gap change rate Δδ in the deformation-sensitive zone._max The constraint condition is that the structural weight is not greater than the mass change Δm before and after optimization of the preset deformation sensitive area, and the value of Δm is determined according to actual needs; (3) Optimization algorithm: A hybrid algorithm combining topology optimization and size optimization is adopted. The optimal parameter combination is searched by genetic algorithm based on the finite element simulation results (displacement values).

[0042] Step 23, Verification and Iteration: The optimized structure is recalculated as in step 1. If the rotor-to-rotor gap change rate or rotor-to-stator gap change rate is still greater than the preset threshold (determined according to actual needs), then return to step 22 to readjust the stiffener density or wheel disc spoke thickness, etc., until the requirements are met.

[0043] Step 3: Initial Installation Clearance Design Method. Based on the deformation calculation results of the optimized rotor and stator structures during engine use, and considering the influence of radial movement of bearings and support elastic elements, rotor / stator runout, and changes in the relative axial position of the rotor and stator on the clearance between the rotor and stator, an initial installation clearance value that balances safety and efficiency is proactively designed. Specifically, this includes: Step 31, Defining the Limit Gap Scenarios: Minimum clearance scenario (ensuring no collision between rotor and stator): When the engine is under negative overload (such as during a dive), the rotor's inertial sinking and thermal contraction dominate. Based on the rotor-rotor and rotor-stator deformation calculation methods, the minimum rotor-rotor clearance deformation is obtained as Δδ. z-z_min Minimum deformation of rotor-stator gap Δδ z-j_min ; Maximum clearance scenario (ensuring the rotor-rotor and rotor-stator clearances do not exceed the aerodynamic efficiency requirements): When the engine is under positive overload (such as a jump), the rotor's centrifugal expansion and the casing's thermal expansion dominate. Based on the rotor-rotor and rotor-stator deformation calculation methods, the maximum rotor-rotor clearance deformation is obtained as Δδ. z-z_max The maximum value of rotor-stator gap deformation Δδ z-j_max .

[0044] Step 32, Initial gap calculation: (1) Initial clearance value for safety reference: For the initial gap between the rotor and the rotor , among which, S m_z-z_aq S is the initial clearance value for the rotor-to-rotor safety reference. p_z-z_aq Δδ is the rotor-to-rotor working clearance value under the safety standard required by aerodynamics. z-z_min δ is the minimum value of rotor-to-rotor clearance deformation. z The influence of the radial movement of the bearing and the elastic element at the support point on the radial clearance (provided by the bearing design unit). For the initial gap between the rotor and the stator , among which, S m_z-j_aq S is the initial clearance value for rotor-stator safety reference. p_z-j_aq The rotor-stator clearance value, Δδ, is the value based on the pneumatic safety standard. z-j_min δ is the minimum value of rotor-stator gap deformation. t The influence of rotor and stator runout on radial clearance is given by (provided by the structural design department or obtained by measurement), k1 is the first safety factor (provided by the structural design department), and δ y The change in clearance caused by the relative axial position change between the rotor and the stator (provided by the structural design department).

[0045] (2) Initial gap value for efficiency baseline: For the initial gap between the rotor and the rotor , among which, S m_z-z_xl S is the initial clearance value for the rotor-to-rotor efficiency reference. p_z-z_xl Δδ is the rotor-rotor working clearance value under the efficiency benchmark required by aerodynamics. z-z_max This represents the maximum value of the rotor-rotor gap deformation. For the initial gap between the rotor and the stator , among which, S m_z-j_xl S is the initial gap value for the rotor-stator efficiency baseline. p_z-j_xl Δδ is the rotor-stator working clearance value under the efficiency benchmark required by aerodynamics. z-j_max k2 is the maximum value of rotor-stator gap deformation, and k2 is the second safety factor (provided by the structural design department).

[0046] Step 33: Determine the installation gap: For the initial installation gap between the rotor and the rotor , For the initial installation gap of the rotor-stator , Among them, S z-z_initial S is the initial installation gap between the rotor and the rotor. z-j_initial This refers to the initial installation gap between the rotor and stator.

[0047] The embodiments provided by this invention, through the "multibody dynamics-finite element coupling" model, achieve accurate calculation of rotor-rotor and rotor-stator clearance deformation under different load combinations of the engine, providing reliable input for clearance control design; this method takes into account both engine safety and efficiency, and can reduce the initial clearance by more than 10% compared with traditional methods, while reducing the risk of collision and rubbing during engine use by more than 90%; this method can be directly integrated into the aero-engine design process, supporting the development of various types of power systems.

[0048] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for designing active clearance of an engine, characterized in that, include: Construct a rigid-flexible coupled finite element model that couples multibody dynamics and finite element method; Based on the rigid-flexible coupled finite element model, the deformation under gyroscopic effect and inertial load and the deformation under thermo-mechanical coupling during engine operation are solved. Based on the deformation under gyroscopic effect and inertial load and the deformation under thermo-coupling effect during engine use, the rotor-rotor gap deformation and rotor-stator gap deformation are extracted respectively. Based on the deformation of the rotor-rotor gap and the rotor-stator gap, deformation-sensitive areas are identified, and the structure of the deformation-sensitive areas is optimized by multiple objectives to reduce dynamic deformation differences. Based on the optimized results, and considering other factors that affect the clearance between the rotor and stator, an initial installation clearance value that balances safety and efficiency is designed. Other factors include the radial movement of the bearings and fulcrum elastic elements, rotor and stator runout, and the relative axial position change of the rotor and stator. Constructing a rigid-flexible coupled finite element model includes: Model composition: The rigid-flexible coupled finite element model includes the engine high-pressure rotor, low-pressure rotor, bearings and casing. The high-pressure rotor and low-pressure rotor are simplified as elastic beam elements, the casing is simplified as shell elements, and the bearings are simplified as spring-damped elements. Coordinate definition: Based on the rigid-flexible coupled finite element model, the engine's center of mass is taken as the origin of the coordinate system. The X-axis coincides with the engine axis and is positive in the reverse direction. The Y-axis is perpendicular to the engine axis and is positive in the upward direction. Load input: Input maneuvering parameters, including angular velocity and angular acceleration, the values ​​of which are determined according to the aircraft's requirements for engine operation; input thermal loads, including the temperature fields of each stage of rotor and stator; input aerodynamic loads, including the pressure distribution on the blade surface; The solution for the gyroscopic effect and deformation under inertial load when the engine is in use includes: The gyroscopic torque of the rotor is calculated based on Euler's equations. The gyroscopic torque of the rotor is applied to the rigid-flexible coupled finite element model, and the rotor displacement under the gyroscopic effect is calculated. Based on angular acceleration and time of application, the rotor inertial displacement under inertial load is calculated; The solution for the deformation under the thermo-coupling effect includes: A sequential coupling calculation method is used to calculate the temperature fields of the rotor and stator by taking into account cooling airflow and thermal radiation. The temperature fields of the rotor and stator, as well as the aerodynamic forces obtained from fluid calculations, are applied to the rigid-flexible coupled finite element model to calculate the rotor displacement and stator displacement under thermo-mechanical coupling.

2. The engine active clearance design method according to claim 1, characterized in that, The expression for the gyro torque is: ， Where I is the moment of inertia tensor, ω is the rotor's angular velocity, Ω is the angular velocity, and M is the moment of inertia tensor. g This refers to the gyroscopic torque. The expression for the rotor inertial displacement under the inertial load is as follows: ， Where, δ inertial Let α be the rotor inertial displacement under inertial load, α be the angular acceleration, and t be the time of application.

3. The engine active clearance design method according to claim 2, characterized in that, The expression for the deformation of the rotor-rotor gap is: ， Where, Δδ z-z For the deformation of the gap between the rotor and the rotor, Δδ tuoluo Δδ represents the deformation of the gap between the high-voltage rotor and the low-voltage rotor under the gyroscopic effect. inertial Δδ represents the deformation of the gap between the high-pressure rotor and the low-pressure rotor under inertial load. RL-zz δ represents the deformation of the gap between the high-pressure rotor and the low-pressure rotor under thermo-coupling. tuoluo_高 δ represents the displacement of the high-voltage rotor under the gyroscopic effect. tuoluo_低 δ represents the displacement of the low-voltage rotor under the gyroscopic effect. inertial_高 δ represents the inertial displacement of the high-voltage rotor under inertial load. inertial_低 δ represents the inertial displacement of the low-pressure rotor under inertial load. RL-zz_高 δ represents the displacement of the high-voltage rotor under thermo-coupling. RL-zz_低 This refers to the displacement of the low-pressure rotor under thermo-coupling. The expression for the deformation of the rotor-stator gap is: ， Where, Δδ z-j For the deformation of the rotor-stator gap, δ tuoluo δ represents the rotor displacement under the gyroscopic effect. RL-zz δ represents the rotor displacement under thermo-coupling. RL-zj This represents the stator displacement under thermo-mechanical coupling.

4. The engine active clearance design method according to claim 1, characterized in that, The multi-objective optimization of the structure in the deformation-sensitive region includes: The optimization objects and optimization parameters are set. The optimization objects include the casing and rotor disk in the deformation sensitive area. The optimization parameters include the local thickness of the casing, the layout of the reinforcing ribs of the casing, the inclination angle of the rotor disk spokes, and the thickness of the rotor disk spokes. Set optimization objectives and constraints. The optimization objective is to minimize the maximum rate of change of gap in the deformation-sensitive zone, and the constraint is that the structural weight is not greater than the preset mass change of the deformation-sensitive zone before and after optimization. A hybrid optimization algorithm combining topology optimization and size optimization is adopted. Based on the finite element simulation results, the optimal parameter combination is searched through a genetic algorithm to complete the structural optimization. The rotor-rotor gap deformation and rotor-stator gap deformation are recalculated for the optimized structure. If the rotor-rotor gap deformation or rotor-stator gap deformation is still greater than the preset threshold, the hybrid optimization algorithm is re-executed until the requirements are met.

5. The engine active clearance design method according to claim 1, characterized in that, The initial installation clearance values, which balance safety and efficiency, include: Define the limit clearance scenarios, including the minimum clearance scenario and the maximum clearance scenario. Obtain the minimum rotor-rotor clearance deformation and the minimum rotor-stator clearance deformation under the minimum clearance scenario. Obtain the maximum rotor-rotor clearance deformation and the maximum rotor-stator clearance deformation under the maximum clearance scenario. The initial clearance value for safety reference is obtained based on the minimum deformation of rotor-rotor clearance, the minimum deformation of rotor-stator clearance, the radial movement of bearing and support elastic elements, the runout of rotor and stator, and the relative axial position change of rotor and stator. The initial clearance value for efficiency reference is obtained based on the maximum value of rotor-rotor clearance deformation, the maximum value of rotor-stator clearance deformation, the radial movement of bearing and support elastic elements, rotor and stator runout, and the relative axial position change of rotor and stator. Based on the initial clearance values ​​of the safety benchmark and the initial clearance values ​​of the efficiency benchmark, the initial installation clearance between the rotor and the stator and the initial installation clearance between the rotor and the stator are obtained respectively.

6. The engine active clearance design method according to claim 5, characterized in that, The initial clearance value of the safety reference includes the initial clearance value of the rotor-stator safety reference and the initial clearance value of the rotor-stator safety reference. The calculation formula for the initial clearance value of the rotor-stator safety reference is as follows: ， Among them, S m_z-z_aq S is the initial clearance value for the rotor-to-rotor safety reference. p_z-z_aq Δδ is the rotor-to-rotor working clearance value under the safety standard required by aerodynamics. z-z_min δ is the minimum value of rotor-to-rotor clearance deformation. z This refers to the effect of the radial movement of the bearing and the elastic element at the support point on the radial clearance. The formula for calculating the initial clearance value of the rotor-stator safety reference is: ， Among them, S m_z-j_aq S is the initial clearance value for rotor-stator safety reference. p_z-j_aq The rotor-stator clearance value, Δδ, is the value based on the pneumatic safety standard. z-j_min δ is the minimum value of rotor-stator gap deformation. t The influence of rotor and stator runout on radial clearance is given by k1, where k1 is the first safety factor and δ is the value of the rotor and stator runout. y This refers to the change in clearance caused by the change in the relative axial position of the rotor and stator.

7. The engine active clearance design method according to claim 6, characterized in that, The initial clearance value for the efficiency reference includes the initial clearance value for the rotor-stator efficiency reference and the initial clearance value for the rotor-stator efficiency reference. The calculation formula for the initial clearance value for the rotor-stator efficiency reference is as follows: ， Among them, S m_z-z_xl S is the initial clearance value for the rotor-to-rotor efficiency reference. p_z-z_xl Δδ is the rotor-rotor working clearance value under the efficiency benchmark required by aerodynamics. z-z_max This represents the maximum value of the rotor-rotor gap deformation. The formula for calculating the initial gap value of the rotor-stator efficiency baseline is: ， Among them, S m_z-j_xl S is the initial gap value for the rotor-stator efficiency baseline. p_z-j_xl Δδ is the rotor-stator working clearance value under the efficiency benchmark required by aerodynamics. z-j_max k1 represents the maximum value of the rotor-stator gap deformation, and k2 is the second safety factor.

8. The engine active clearance design method according to claim 7, characterized in that, The expression for the initial installation gap between the rotor and the spindle is: ， The expression for the initial installation gap between the rotor and stator is: ， Among them, S z-z_initial S is the initial installation gap between the rotor and the rotor. z-j_initial This refers to the initial installation gap between the rotor and stator.

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