A method for calculating magnetic-thermal-fluid coupling of an electrically assisted turbocharger based on tip clearance transmission and boundary feedback

Abstract

This invention relates to a magnetothermal-fluid-structure interaction (MFSE) calculation method for electrically assisted turbochargers based on tip clearance transfer and boundary feedback. The method involves establishing a parametric geometry, material properties, and a multiphysics sub-model; solving the electromagnetic field to obtain electromagnetic torque and losses, which are then transferred to the structural and thermal fields respectively; solving the fluid-structure conjugate heat transfer to obtain temperature, flow parameters, wall heat flux, and aerodynamic loads, and transferring the solid temperature and aerodynamic loads to the structural field; solving the structural response to obtain the radial displacement of the tip and casing; calculating the dynamic tip clearance at both ends and updating the flow channel geometry; resolving and feeding back the temperature, wall heat flux, and aerodynamic loads under the updated geometric boundaries; correcting numerical parameters or boundary conditions based on the coupling residuals and target operating condition deviations; and outputting the coupling calculation results after convergence. This invention can provide numerical basis for performance prediction, structural optimization, and safety margin assessment of electrically assisted turbochargers.

Description

Technical Field

[0001] This invention relates to the field of multiphysics coupling numerical calculation technology for turbochargers, specifically to a magnetothermal-fluid-structure interaction calculation method for electrically assisted turbochargers based on tip clearance transmission and boundary feedback. Background Technology

[0002] An electrically assisted turbocharger integrates a high-speed motor / generator on the high-speed rotor shaft system between the turbine and compressor, enabling the shaft system to operate in electric-assisted, generator-assisted braking, or no-load servo mode. Its operation is simultaneously subjected to electromagnetic torque, electromagnetic loss heat generation, high-temperature airflow at the turbine end, compressed airflow at the compressor end, lubrication and cooling heat exchange, high-speed rotating centrifugal loads, aerodynamic loads, and bearing supports, making it a typical problem involving the interaction of magnetic fields, thermal fields, flow fields, and solid structural fields.

[0003] Existing calculations typically solve for motor electromagnetic losses, fluid thermodynamics, and structural strength separately, or employ a unidirectional sequential transfer of the electromagnetic field to the thermal field and then to the structural field. These methods, after completing one field mapping, do not update the flow channel geometry based on structural deformation, nor do they transfer the updated aerodynamic loads back to the structural field. Therefore, they struggle to characterize the closed-loop response of a high-speed rotor under the combined action of multiple thermal and aerodynamic loads.

[0004] Tip clearance directly determines the effective area of ​​the leakage channels at the turbine and compressor ends, and is simultaneously affected by blade centrifugal elongation, rotor thermal expansion and radial motion, casing thermal deformation, and bearing support conditions. If tip clearance is treated as a fixed geometric quantity in flow field calculations, it cannot reflect the changes in leakage flow, pressure ratio, and efficiency caused by thermo-solid deformation, nor can it obtain the secondary effects of aerodynamic load changes on the rotor and casing structure.

[0005] Furthermore, different physical field models typically employ different grids, coordinate systems, time scales, and convergence criteria. Without a unified rotor phase reference, interface conservation mapping, and adaptive boundary feedback, misalignments in temperature, load, displacement, and clearance can easily occur between different grids, or iterative oscillations can result from mismatches between boundary conditions and target operating conditions. Therefore, a closed-loop magnetothermal-fluidic-structure interaction (MTI) calculation method is needed that uses dynamic tip clearance as a geometric intermediate quantity for the transfer of the thermo-mechanical field to the flow field, and corrects the computational boundary based on coupling residuals and deviations from the target operating conditions. Summary of the Invention

[0006] Therefore, the purpose of this invention is to provide a magnetothermal-fluid-structure interaction calculation method for electric-assisted turbochargers based on tip clearance transmission and boundary feedback. By using dynamic tip clearance as a geometric representation of the thermo-mechanical response transmitted to the flow field, and correcting numerical parameters and boundary conditions according to the coupling residual and the deviation of the target operating condition, a closed-loop coupled calculation system of electromagnetic, thermal, fluid, and solid fields is formed to reduce the performance prediction deviation caused by the fixed tip clearance assumption and the transmission of non-conservative field quantities.

[0007] To achieve the above objectives, the technical solution adopted by this invention is: a magnetothermal-fluid-structure interaction calculation method for electrically assisted turbochargers based on tip clearance transmission and boundary feedback, comprising the following steps: S101, establish the parametric geometric model and material model of the electric-assisted turbocharger, and establish a unified coordinate and phase reference; S102, Based on step S101, construct electromagnetic field, thermal field, flow field and solid structure field sub-model and coupling interface. The coupling interface is used to transmit temperature, electromagnetic loss, electromagnetic torque, wall heat flux, wall temperature, aerodynamic load, structural displacement and dynamic tip clearance. S103, Solve the electromagnetic field sub-model to obtain the electromagnetic torque and loss heat source, map the loss heat source to the thermal field sub-model, and map the electromagnetic torque to the solid structure field sub-model; S104: Receive the heat loss source obtained in step S103, solve the flow and fluid-structure conjugate heat transfer at the turbine end and compressor end, and obtain the fluid temperature, pressure and velocity, solid temperature, wall heat flux and aerodynamic load; calculate the aerodynamic performance parameters based on the fluid temperature, pressure and velocity, map the wall heat flux as the thermal boundary to the thermal field sub-model, and map the solid temperature and aerodynamic load to the solid structure field sub-model. S105: Receive the electromagnetic torque obtained in step S103 and the solid temperature and aerodynamic load obtained in step S104. Combine the centrifugal load and bearing support boundary to solve the rotor and casing thermo-mechanical deformation and rotor dynamic response, and obtain the radial displacement, stress and vibration response. S106, Based on the reference tip clearance set in step S101 and the radial displacement obtained in step S105, calculate the dynamic tip clearance between the turbine end and the compressor end, and update the tip leakage channel and the effective geometric boundary of the flow channel based on the dynamic tip clearance. S107, under the updated effective geometric boundary conditions of the flow channel, resolve the flow field and fluid-structure conjugate heat transfer, reverse map the updated wall heat flux and aerodynamic load, and calculate the multiphysics coupling residual, tip clearance change and target operating condition deviation based on the field quantities of the current iteration step and the previous iteration step. S108, when the multiphysics coupling residual, tip clearance change or target operating condition deviation does not meet the convergence condition, adaptively correct the boundary conditions, coupling relaxation factor or flow channel near-wall mesh, and return to step S102. S109, when the multi-physics coupling residual, the blade tip clearance change and the target operating condition deviation all meet the convergence conditions, the magnetothermal-fluid-structure interaction calculation results are output.

[0008] Furthermore, the parametric geometric model includes a turbine impeller, a compressor impeller, a rotor shaft, a high-speed motor / generator rotor and stator, a turbine casing, a compressor casing, and a bearing housing; the material property model includes magnetic permeability, electrical conductivity, thermal conductivity, specific heat capacity, coefficient of thermal expansion, elastic modulus, Poisson's ratio, density, and yield strength.

[0009] Furthermore, the electromagnetic losses include winding copper losses, iron losses, and rotor eddy current losses; wherein, the winding copper losses are distributed to the stator winding region, the iron losses are distributed to the stator core and rotor core regions, the rotor eddy current losses are distributed to the rotor conductive region, and an equivalent torque load is established based on the position of the electromagnetic torque in the rotor shaft system.

[0010] Further, in step S104, the flow field model is solved using at least one of the following methods: rotating reference frame, sliding mesh, or moving mesh, based on the turbine end aerodynamic and thermodynamic boundary, the compressor end aerodynamic boundary, the lubricating medium thermal boundary, and the cooling medium thermal boundary. The wall heat flux and wall temperature are transferred at the fluid-solid interface, and the fluid energy equation and the solid heat conduction equation are used to solve the fluid-solid conjugate heat transfer.

[0011] Furthermore, the thermo-mechanical deformation of the rotor, blades, and casing is solved under the combined action of solid temperature, centrifugal load, electromagnetic torque, aerodynamic load, and bearing support boundary to obtain the radial displacement of the blade tip and the corresponding casing position.

[0012] Further, in step S106, let i represent the turbine end T or the compressor end C, and the dynamic tip clearance of the i-th end under rotor phase θ and physical time t is calculated by the following formula:

[0013] in Phase under reference state The leaf tip gap, To correspond to the inner wall of the casing in phase Radial displacement at the location, This is the combined radial displacement of the blade tip and the rotor radial motion at this phase; and based on each phase in the circumferential direction... Obtain the minimum tip gap, average tip gap, peak-to-peak value, and the phase corresponding to the minimum gap.

[0014] Furthermore, when updating the effective geometric boundary of the flow channel in step S106, node smoothing, local reconstruction, or layered mesh scaling are applied to the mesh near the blade tip, and the mesh deformation in adjacent iteration steps is limited by the gap geometric relaxation relation.

[0015] Furthermore, the boundary conditions or numerical settings in step S108 include at least one of electromagnetic boundary, aerodynamic boundary, lubricating medium thermal boundary, cooling medium thermal boundary, coupling relaxation factor, time step, or flow channel mesh.

[0016] Further, in step S108, a boundary vector B and a target response vector Y are constructed. The boundary vector B includes one or more of the following: motor current or torque, turbine inlet total pressure or total temperature, compressor outlet back pressure, lubricating medium inlet temperature or equivalent heat transfer coefficient, and cooling medium inlet temperature or equivalent heat transfer coefficient. The target response vector Y includes one or more of the following: rotational speed, mass flow rate, pressure ratio, efficiency, outlet temperature, minimum tip clearance, maximum temperature, maximum stress, and maximum displacement. Based on the difference between the target response vector and the current response vector, the boundary vector is corrected within preset upper and lower limits.

[0017] Furthermore, the coupling calculation results include electromagnetic torque and loss distribution, temperature field, fluid pressure and velocity field, aerodynamic load, rotor and casing deformation, stress or vibration response, dynamic tip clearance distribution at both ends, mass flow rate, pressure ratio, efficiency, outlet temperature, conservation error of each coupling interface, and boundary feedback iteration process.

[0018] The beneficial effects of the above technical solution are as follows: The present invention uses the dynamic tip clearance at both ends as the geometric characterization quantity of the thermo-mechanical response transmitted to the flow field. The radial displacement of the tip and casing under multiple loads such as temperature, centrifugal force, and aerodynamic force is obtained by solving the structural field. Based on this, the dynamic clearance distribution of each iteration step is calculated and the leakage channel geometry is updated, so that the flow field calculation can reflect the influence of structural deformation on pressure ratio, efficiency and leakage flow.

[0019] This invention performs interpolation mapping and conservation correction of heat and load between non-common node meshes, so that the errors of total heat, resultant force and resultant moment at the interface before and after mapping are controlled, thereby improving the consistency of multi-field data transmission.

[0020] This invention feeds back the updated solid temperature to the electromagnetic field model, and feeds back the updated wall heat flux and aerodynamic load to the solid thermal field model and the solid structural field model, respectively, so that temperature change, electromagnetic loss, thermo-mechanical deformation, blade tip clearance, flow field performance and aerodynamic load form a closed-loop response chain.

[0021] This invention adjusts numerical parameters and boundary conditions based on coupling residuals and target operating condition deviations: when the multiphysics field has not yet converged, the relaxation factor, time step, or flow channel mesh is adjusted; when the coupled calculation has converged but the target operating condition does not meet the requirements, the electromagnetic, aerodynamic, lubrication, or cooling boundaries are adjusted, thereby improving the stability of the coupled calculation and the operating condition matching capability.

[0022] The output results cover the complete calculation chain from electromagnetic loss heat generation to blade tip clearance evolution, aerodynamic performance and load feedback. The dataset output by this invention not only includes the final state quantities of each physical field, but also the interface conservation error and boundary feedback iteration history, which can provide complete numerical basis for the structural optimization, performance prediction and safety margin assessment of electric assisted turbochargers. Attached Figure Description

[0023] Figure 1 This is a flowchart of the overall calculation method for magnetothermal-fluid-structure interaction of an electrically assisted turbocharger based on tip clearance transmission and boundary feedback.

[0024] Figure 2 This is a flowchart of the dynamic tip clearance transfer, flow channel geometry update, and calculation boundary feedback iteration of the present invention. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Example 1 The operation of an electrically assisted turbocharger involves the interaction of the electromagnetic field of the motor, the flow fields at the turbine and compressor ends, the overall temperature field, and the rotor-casing structural field. Electromagnetic losses (winding copper losses, iron losses, and rotor eddy current losses) act as a volumetric heat source, altering the temperature distribution. This change in temperature distribution causes thermal deformation of the rotor blades and casing. The centrifugal load, aerodynamic pressure load, and shear load generated by the high-speed rotation of the rotor act on the structure, causing changes in the clearance between the blade tip and the inner wall of the casing. Changes in the blade tip clearance directly alter the effective area of ​​the leakage channel, thereby affecting the flow characteristics and aerodynamic performance at the turbine and compressor ends.

[0026] To address the aforementioned multiphysics coupling characteristics, existing calculations typically solve for the electromagnetic, flow, thermal, and structural fields separately, or employ a unidirectional sequential transfer method from the electromagnetic field to the thermal field and vice versa. These methods, after completing one field mapping, do not update the flow channel geometry based on structural deformation, nor do they transfer the updated aerodynamic loads back to the structural field, thus making it difficult to characterize the closed-loop response of the rotor under the combined action of multiple loads. If the blade tip clearance is treated as a fixed geometric quantity in the flow field calculation, it cannot reflect the leakage flow changes and performance shifts caused by thermo-structure deformation. Different physics models typically use different meshes, coordinate systems, and convergence criteria; without a unified data mapping interface and conservation correction mechanism, misalignment of temperature, load, and displacement between different meshes can easily occur.

[0027] like Figure 1 As shown, step S101 establishes parametric geometry, material models, and unified coordinate and phase references; step S102 constructs sub-models of electromagnetic field, thermal field, flow field, and solid structure field, as well as coupling interfaces; step S103 solves for electromagnetic torque and loss heat sources and maps them to the thermal field and structural field; step S104 solves for double-ended flow and conjugate heat transfer and maps aerodynamic loads and thermal boundaries; step S105 solves for rotor and casing thermo-mechanical deformation and rotor dynamic response; step S106 calculates double-ended dynamic tip clearance and updates the effective geometric boundary of the flow channel; step S107 reverse maps the flow field loads and calculates the multiphysics coupling residuals; when the coupling residuals, tip clearance changes, or target operating condition deviations do not meet the convergence conditions, step S108 adaptively corrects the boundary conditions, coupling relaxation factor, or flow channel near-wall mesh and returns to step S102; when the convergence conditions are met, step S109 outputs the magnetothermal-fluid-structure interaction calculation results.

[0028] The specific implementation methods for each step are described below.

[0029] Step S101: Establish parametric geometry, material models, and unified coordinate and phase references. Based on the design drawings of the electrically assisted turbocharger, a parametric geometric model is established, including the turbine impeller, compressor impeller, rotor shaft, high-speed motor rotor and stator, turbine casing, compressor casing, and bearing housing. The parametric geometric model should maintain the coaxial assembly relationship between the turbine, compressor, high-speed motor / generator, and rotor shaft system, and retain the independent geometric names of the turbine blade tip, compressor blade tip, and corresponding casing inner wall. A double-end clearance coordinate system is established through the turbine end reference section and the compressor end reference section, so that the blade tip node and the casing inner wall node can correspond one-to-one according to the axial position and circumferential phase.

[0030] The material property model covers the physical parameters of each component at different temperatures: electromagnetic properties include magnetic permeability and electrical conductivity, thermal properties include thermal conductivity and specific heat capacity, and mechanical properties include coefficient of thermal expansion, elastic modulus, Poisson's ratio, density, and yield strength; for regions with significant temperature changes, temperature-related material parameters are defined according to the actual operating temperature range.

[0031] Define the reference tip clearances at the turbine and compressor ends, a unified coordinate system, a unified rotor phase reference, and a unified time step or iteration step; simultaneously set the initial temperature, rotor speed, bearing support parameters, electromagnetic boundaries, aerodynamic boundaries, lubricating medium thermal boundaries, and cooling medium thermal boundaries, and set the target response quantity, convergence threshold, and safety limits. The above data serve as the model inputs for steps S102 to S107 and the feedback judgment basis for step S108, respectively.

[0032] Step S102: Construct sub-models and data interfaces for electromagnetic field, flow field, solid thermal field, and solid structure field. Electromagnetic field sub-models for high-speed motors / generators, flow field sub-models at the turbine and compressor ends, solid thermal field sub-models, and solid structural field models are constructed respectively.

[0033] The electromagnetic field sub-model includes stator windings, stator core, rotor conductive region and air gap, and updates electromagnetic properties such as permeability and conductivity with the current temperature; the model outputs air gap magnetic flux density, electromagnetic torque, as well as winding copper loss, iron loss and rotor eddy current loss, where electromagnetic torque is transmitted to the solid structure field, and electromagnetic loss is converted into a heat source per unit volume or heat flow per unit area and then transmitted to the solid thermal field.

[0034] Under electric boost conditions, the direction of electromagnetic torque is the same as the direction of rotor rotation; under generator braking conditions, the direction of electromagnetic torque is opposite to the direction of rotor rotation; the electromagnetic torque is applied to the rotor shaft system in the form of equivalent body torque, end face torque or nodal torque, and its total torque is consistent with the torque calculated by the electromagnetic field.

[0035] The flow field sub-model includes the turbine end main flow path, turbine tip leakage path, compressor end main flow path, and compressor tip leakage path. The turbine end is solved based on the total inlet pressure, total inlet temperature, and outlet pressure, while the compressor end is solved based on the total inlet pressure, total inlet temperature, and outlet back pressure. The rotor region uses a rotating reference frame, a sliding mesh, or a moving mesh to represent the rotational effect.

[0036] The solid thermal field sub-model includes solid heat conduction domains for the impeller, rotor shaft, motor components, casing, and bearing housing. The flow field sub-model utilizes the fluid energy equation and transfers wall heat flux to the solid thermal field sub-model at the fluid-solid interface. The solid thermal field sub-model feeds back the wall temperature to the flow field sub-model to achieve fluid-solid conjugate heat transfer. The lubricating and cooling media can be represented by fluid domains or by inlet temperature and equivalent heat transfer coefficient to represent the thermal boundaries.

[0037] The solid structure field treats the temperature distribution as a thermal load, while simultaneously applying centrifugal loads, electromagnetic torques, fluid pressures, and wall shear loads corresponding to the rotational speed. The support effect is represented by the equivalent stiffness and damping of the bearings or by a fluid membrane force model. The steady-state calculation outputs thermal deformation and static displacement, while the transient calculation outputs the vibration response that varies with rotor phase and time.

[0038] Data interfaces are established between the various sub-models for the following data transfer mechanisms: temperature from the thermal field to the electromagnetic field, electromagnetic loss from the electromagnetic field to the thermal field, electromagnetic torque from the electromagnetic field to the structural field, wall heat flux from the flow field to the thermal field, wall temperature from the thermal field to the flow field, aerodynamic load from the flow field to the structural field, and dynamic tip clearance from the structural field to the flow field. These interfaces use area weighting, volume weighting, radial basis functions, or finite element shape functions to transfer data between non-common node meshes, and perform conservation corrections on interface heat, resultant force, and resultant torque.

[0039] Step S103: Solve for electromagnetic torque and heat loss sources. The electromagnetic field sub-model is solved based on the current temperature and electromagnetic boundary to obtain the electromagnetic torque and electromagnetic loss. The electromagnetic loss is transferred to the solid thermal field sub-model as a heat source, and the electromagnetic torque is transferred to the solid structural field sub-model as a torque load.

[0040] The initial coupling iteration uses the initial temperature set in step S101, and subsequent iterations use the solid temperature obtained in step S104 or step S107 to update the electromagnetic material properties. The stator current, air gap magnetic flux density, electromagnetic torque and electromagnetic loss are solved according to the motor current, speed, torque or power boundary, and the winding copper loss, iron loss and rotor eddy current loss are allocated to the corresponding heat generation region and then transferred to the solid thermal field sub-model.

[0041] The electromagnetic torque establishes an equivalent torque load based on its position in the rotor shaft system. Under electric boost conditions, the direction of the electromagnetic torque is consistent with the direction of rotor rotation; under generator braking conditions, the direction of the electromagnetic torque is opposite to the direction of rotor rotation. The equivalent torque load is applied to the corresponding section of the rotor shaft system through the mapping interface from electromagnetic field to structural field.

[0042] Step S104: Solve for two-end flow and fluid-structure conjugate heat transfer. The system receives the aerodynamic boundary, lubricating medium thermal boundary, and cooling medium thermal boundary set in step S101, as well as the electromagnetic loss heat source obtained in step S103. It then solves the fluid-structure conjugate heat transfer between the turbine end and compressor end flow field sub-model and the solid thermal field sub-model to obtain the fluid temperature, pressure and velocity, solid temperature, wall heat flux, wall pressure and wall shear force.

[0043] Cross-sectional mass averaging of fluid temperature, pressure, and velocity yields total inlet and outlet temperature, total pressure, and mass flow rate. Based on this, the pressure ratio, efficiency, and outlet temperature at the turbine end and compressor end are calculated. The aerodynamic performance parameters are used for the target operating condition deviation calculation in step S107 and the result output in step S109.

[0044] The flow at the turbine end and compressor end is solved using at least one of the following methods: rotating reference frame, sliding mesh, or moving mesh. At the fluid-solid interface, the heat flow from the fluid sidewall is transferred to the solid thermal field sub-model, and the solid sidewall temperature is fed back to the flow field sub-model. The fluid energy equation and the solid heat conduction equation are used to iteratively solve the fluid-solid conjugate heat transfer until the interface temperature and heat flow meet the preset convergence conditions.

[0045] The solid temperature is transferred to step S105 as a thermal load and used in the next iteration to update the temperature-related electromagnetic properties in step S103; the wall pressure and wall shear force are transferred to step S105 as aerodynamic loads; the wall heat flux, wall temperature and aerodynamic performance parameters are saved as field quantity feedback and residual calculation data in step S107.

[0046] Step S105: Solve for thermo-mechanical deformation The electromagnetic torque obtained in step S103 and the solid temperature, wall pressure, and wall shear force obtained in step S104 are received, and the solid structure field sub-model is solved by combining the rotor speed and bearing support parameters. For example... Figure 2 As shown, step S201 reads electromagnetic, temperature, flow and structural field data under the same iteration step and unified rotor phase; step S202 performs conservation interpolation and phase registration on the field quantities on the non-common node grid; and step S203 extracts the radial displacement between the double-ended blade tip and the corresponding casing position.

[0047] In this system, solid temperature is used as thermal load, rotor speed is used to determine centrifugal load, electromagnetic torque is applied according to the equivalent load established in step S103, aerodynamic load is applied according to the wall pressure and wall shear force obtained in step S104, and bearing support boundary is represented by equivalent stiffness and damping or fluid film force.

[0048] The solid structure field model includes at least one of a static structural model, a transient structural model, or a rotor dynamics model. The applied loads include temperature loads, centrifugal loads, electromagnetic torques, fluid pressure loads, wall shear loads, and bearing equivalent stiffness and damping. The outputs include one or more of the following: rotor radial displacement, axial thermal elongation, blade radial elongation, casing radial deformation, stress, and vibration response.

[0049] The solid structure field sub-model is solved using the finite element method, outputting the displacement field of each node. The radial displacement of the turbine tip node, the radial displacement of the turbine corresponding casing inner wall node, the radial displacement of the compressor tip node, and the radial displacement of the compressor corresponding casing inner wall node are extracted from the displacement field. During extraction, a unified rotor phase reference must be used to ensure that the tip node and the casing inner wall node correspond in the same circumferential phase.

[0050] The radial displacement of the blade tip, casing, and rotor is transferred to step S106 to calculate the dynamic blade tip clearance. The stress, vibration response, and maximum displacement are transferred to step S108 for safety limit comparison and are used as the output data for step S109.

[0051] Step S106: Calculate the dynamic tip clearance at both ends and update the flow channel geometry. Based on the reference tip clearance set in step S101 and the radial displacement of the tip, casing and rotor obtained in step S105, the dynamic tip clearance distribution at the turbine end and compressor end is calculated, and the effective geometric boundary of the tip leakage channel and flow channel is updated according to the clearance distribution.

[0052] In step S204, let i represent the turbine end T or the compressor end C. The dynamic tip clearance of the i-th end under rotor phase θ and physical time t is calculated by the following formula:

[0053] in, Phase under reference state The leaf tip gap, To correspond to the inner wall of the casing in phase Radial displacement at the location, The radial displacement is the resultant radial displacement of the blade tip and the radial motion of the rotor at this phase; t represents the physical time. For steady-state coupling calculation, the iteration step k is used instead of the physical time t; the minimum, average, peak-to-peak values ​​and the phase corresponding to the minimum clearance are obtained according to the dynamic blade tip clearance of each phase in the circumferential direction, and then passed to step S108 for convergence and safety limit judgment.

[0054] Step S205 updates the tip leakage channel and near-wall fluid mesh based on the dynamic tip clearance distribution obtained in step S204; the mesh update adopts at least one of node smoothing, local reconstruction or hierarchical mesh scaling, and the updated effective geometric boundary of the flow channel is transferred to step S206.

[0055] To avoid abrupt changes in the gaps leading to negative mesh volume, the mesh deformation in adjacent iterations is limited by the gap geometric relaxation relation. Specifically, the gap geometric relaxation relation adopts...

[0056] Perform gap relaxation, where ω is a relaxation factor between 0 and 1; This represents the final, relaxed tip gap value adopted in this iteration. This represents the gap value from the previous iteration; The raw gap values ​​(i.e., unrelaxed calculated values) are directly calculated for the structural field solution in this round. When the structural deformation in adjacent iterations is large, directly using the unrelaxed gap values ​​may lead to excessive distortion of mesh elements or even negative volumes. By introducing the gap values ​​from the previous iteration as a reference, the mesh deformation process is made smoother, and the numerical stability of the iterative calculation is improved.

[0057] Step S107: Reverse map the flow field load and calculate the multiphysics coupling residual. Step S206 resolves the flow field and fluid-structure conjugate heat transfer under the updated effective geometric boundary conditions of the flow channel to obtain the updated fluid temperature, pressure and velocity, solid temperature, wall heat flux, wall pressure, wall shear force, as well as mass flow rate, pressure ratio, efficiency and outlet temperature, and inversely maps the pressure, shear force and wall heat flux.

[0058] The updated solid temperature is fed back to the electromagnetic field sub-model to update the temperature-related electromagnetic properties and serve as the thermal load for the solid structure field. The updated wall heat flux is transferred to the solid thermal field sub-model, and the updated wall pressure and wall shear force are transferred to the solid structure field sub-model as the thermal boundary and aerodynamic load for the next coupling iteration.

[0059] Data mapping employs area weighting, volume weighting, finite element shape function, or radial basis function interpolation. After mapping the wall heat flux, the total heat at the interface before and after mapping is corrected. After mapping the pressure and shear force, the resultant force and resultant moment before and after mapping are corrected, thereby reducing energy and load errors caused by non-common node meshes.

[0060] Step S207 compares the electromagnetic loss, temperature field, flow field, structural displacement and dynamic tip clearance of the current iteration step with those of the previous iteration step, calculates the rate of change of field quantity, the amount of interfacial heat imbalance, the amount of interfacial load imbalance and the amount of tip clearance change; calculates the target operating condition deviation based on the difference between the current aerodynamic performance and structural response and the preset target response, and passes the above indicators to step S208.

[0061] Step S108: Adaptively adjust boundary conditions, coupling relaxation factor, time step, or flow channel mesh. Step S208 receives the field change rate, interface imbalance, blade tip clearance change and target operating condition deviation obtained in step S207, corrects the boundary vector, coupling relaxation factor or time step according to the target operating condition deviation and coupling residual, and returns the correction result to step S202.

[0062] Construct a boundary vector B and a target response vector Y. The boundary vector B consists of the motor current or torque, turbine inlet total pressure or total temperature, compressor outlet back pressure, lubricating medium inlet temperature or equivalent heat transfer coefficient, and cooling medium inlet temperature or equivalent heat transfer coefficient set in step S101. The target response vector Y consists of the aerodynamic performance obtained in step S104 or step S107 and the structural response and dynamic tip clearance obtained in step S105 or step S106.

[0063] When the deviation from the target operating condition does not meet the requirements, the boundary vector is corrected within the preset upper and lower limits according to the difference between the target response vector and the current response vector, using the following formula:

[0064] in, and These are the boundary vectors before and after the correction, respectively. For the target response vector, Let K be the current response vector, K be the boundary response gain matrix, and Λ be the boundary relaxation matrix. This means that the corrected boundary vector is restricted to a preset upper and lower limit; the boundary response gain matrix is ​​determined based on the pre-calculated sensitivity matrix or the secant relationship between adjacent iteration steps.

[0065] When the coupling residual is higher than the convergence threshold, only the numerical parameters are adjusted to improve the iteration stability; when the coupling residual meets the convergence threshold but the target operating condition deviation is still higher than the allowable value, the corresponding electromagnetic, pneumatic, lubrication or cooling boundaries are corrected according to the above formula to avoid changing the target operating condition before the multiphysics field has converged.

[0066] exist Figure 2 In the iterative process shown, after the correction is completed, the process returns to step S202 to perform conservatistic interpolation and phase registration again; Figure 1 In the overall process shown, the corrected boundary conditions, coupling relaxation factor or flow channel near-wall mesh are returned to step S102, and steps S102 to S107 are repeated until each convergence index meets the corresponding threshold.

[0067] In the steady-state calculation implementation, the initial electromagnetic field, flow field, and temperature field are first obtained under the reference gap, and then structural deformation and gap updates are gradually introduced. Each coupled iteration step performs loss heat source mapping, wall heat flux mapping, aerodynamic load mapping, structural solution, gap calculation, and flow channel geometry update until all convergence indices are below the threshold.

[0068] In the transient calculation implementation, the electromagnetic field time step, flow field time step, thermal field time step, and structural field time step are set to integer multiples of a unified physical time step, and interpolation is performed according to a unified rotor phase at each coupling exchange moment. The dynamic tip clearance is updated over time, enabling the calculation of the clearance and performance transient responses caused by motor torque steps, turbine inlet temperature changes, or compressor outlet back pressure changes.

[0069] When the coupling residual or the target operating condition deviation does not meet the corresponding threshold, step S208 is executed. Figure 2 The local iteration returns to step S202. Figure 1 The overall iteration returns to step S102. When the minimum tip clearance at any end is less than the design limit, or the maximum temperature, maximum stress, maximum displacement, and vibration response exceed the corresponding limit, the current operating condition is marked as an over-limit state, and the iteration step, physical time, rotor phase, spatial position, boundary vector, and physical field response of the over-limit occurrence are recorded.

[0070] Step S109: Output the magnetothermal-fluid-structure interaction calculation results Step S209 outputs the coupled calculation results of this iteration when the interface conservation error, the change in tip clearance, and the deviation of the target quantity are all below the corresponding thresholds; when Figure 1 When the overall convergence conditions shown are met simultaneously, step S109 outputs magnetothermal-fluid-structure interaction calculation results with unified coordinates, rotor phase, physical time or iteration step index, including electromagnetic torque and loss, temperature field, fluid pressure and velocity field, wall heat flux, aerodynamic load, rotor and casing deformation, stress or vibration response, dynamic tip clearance at both ends, mass flow rate, pressure ratio, efficiency, outlet temperature, interface conservation error, boundary feedback iteration history and safety status.

[0071] In this embodiment, the data transfer relationship is as follows: solid temperature is used to update electromagnetic material properties and serve as structural thermal load; electromagnetic loss serves as the heat source of the solid thermal field; electromagnetic torque serves as the structural torque load; wall heat flux and wall temperature are used for fluid-structure conjugate heat transfer; wall pressure and wall shear force serve as structural aerodynamic load; structural radial displacement is used to calculate dynamic tip clearance; dynamic tip clearance is used to update the flow channel geometry; and the updated temperature, heat flux, and aerodynamic load are then fed back to the corresponding sub-model to form a magnetothermal-fluid-solid closed-loop coupling.

[0072] This invention does not limit the specific electromagnetic, fluid, heat transfer, and structural solution software, nor does it limit the use of finite element, finite volume, or other discretization methods for the sub-model. Equivalent substitutions made to the mesh form, turbulence model, material model, coupling order, and iterative algorithm, while maintaining the relationships between electromagnetic losses and torque transmission, temperature feedback, heat and fluid-structure load conservation mapping, dynamic tip clearance geometry updates at both ends, and computational boundary feedback, are all within the scope of this invention.

Claims

1. A magnetothermal-fluid-structure interaction calculation method for an electrically assisted turbocharger based on tip clearance transmission and boundary feedback, characterized in that, Includes the following steps: S101, establish the parametric geometric model and material model of the electric-assisted turbocharger, and establish a unified coordinate and phase reference; S102, Based on step S101, construct electromagnetic field, thermal field, flow field and solid structure field sub-model and coupling interface. The coupling interface is used to transmit temperature, electromagnetic loss, electromagnetic torque, wall heat flux, wall temperature, aerodynamic load, structural displacement and dynamic tip clearance. S103, Solve the electromagnetic field sub-model to obtain the electromagnetic torque and loss heat source, map the loss heat source to the thermal field sub-model, and map the electromagnetic torque to the solid structure field sub-model; S104: Receive the heat loss source obtained in step S103, solve the flow and fluid-structure conjugate heat transfer at the turbine end and compressor end, and obtain the fluid temperature, pressure and velocity, solid temperature, wall heat flux and aerodynamic load; calculate the aerodynamic performance parameters based on the fluid temperature, pressure and velocity, map the wall heat flux as the thermal boundary to the thermal field sub-model, and map the solid temperature and aerodynamic load to the solid structure field sub-model. S105: Receive the electromagnetic torque obtained in step S103 and the solid temperature and aerodynamic load obtained in step S104. Combine the centrifugal load and bearing support boundary to solve the rotor and casing thermo-mechanical deformation and rotor dynamic response, and obtain the radial displacement, stress and vibration response. S106, Based on the reference tip clearance set in step S101 and the radial displacement obtained in step S105, calculate the dynamic tip clearance between the turbine end and the compressor end, and update the tip leakage channel and the effective geometric boundary of the flow channel based on the dynamic tip clearance. S107, under the updated effective geometric boundary conditions of the flow channel, resolve the flow field and fluid-structure conjugate heat transfer, reverse map the updated wall heat flux and aerodynamic load, and calculate the multiphysics coupling residual, tip clearance change and target operating condition deviation based on the field quantities of the current iteration step and the previous iteration step. S108, when the multiphysics coupling residual, tip clearance change or target operating condition deviation does not meet the convergence condition, adaptively correct the boundary conditions, coupling relaxation factor or flow channel near-wall mesh, and return to step S102. S109, when the multi-physics coupling residual, the blade tip clearance change and the target operating condition deviation all meet the convergence conditions, the magnetothermal-fluid-structure interaction calculation results are output.

2. The magnetic-thermal-fluid-structure interaction calculation method for an electrically assisted turbocharger based on tip clearance transmission and boundary feedback as described in claim 1, characterized in that: The parametric geometric model includes turbine impeller, compressor impeller, rotor shaft, high-speed motor / generator rotor and stator, turbine casing, compressor casing and bearing housing; the material property model includes magnetic permeability, electrical conductivity, thermal conductivity, specific heat capacity, coefficient of thermal expansion, elastic modulus, Poisson's ratio, density and yield strength.

3. The magnetic-thermal-fluid-structure interaction calculation method for an electrically assisted turbocharger based on tip clearance transmission and boundary feedback as described in claim 1, characterized in that: The electromagnetic losses include winding copper losses, iron losses, and rotor eddy current losses; wherein, winding copper losses are distributed to the stator winding region, iron losses are distributed to the stator core and rotor core regions, rotor eddy current losses are distributed to the rotor conductive region, and an equivalent torque load is established based on the position of the electromagnetic torque in the rotor shaft system.

4. The magnetic-thermal-fluid-structure interaction calculation method for an electrically assisted turbocharger based on tip clearance transmission and boundary feedback as described in claim 1, characterized in that: Step S104: Based on the turbine end aerodynamic and thermodynamic boundary, compressor end aerodynamic boundary, lubricating medium thermal boundary, and cooling medium thermal boundary, solve the flow field model using at least one of the following methods: rotating reference frame, sliding mesh, or moving mesh. Transfer wall heat flux and wall temperature at the fluid-solid interface, and solve the fluid-solid conjugate heat transfer using the fluid energy equation and the solid heat conduction equation.

5. The magnetic-thermal-fluid-structure interaction calculation method for an electrically assisted turbocharger based on tip clearance transmission and boundary feedback as described in claim 1, characterized in that: The thermo-mechanical deformation of the rotor, blades, and casing is solved under the combined action of solid temperature, centrifugal load, electromagnetic torque, aerodynamic load, and bearing support boundary to obtain the radial displacement of the blade tip and the corresponding casing position.

6. The magnetic-thermal-fluid-structure interaction calculation method for an electrically assisted turbocharger based on tip clearance transmission and boundary feedback as described in claim 1, characterized in that: In step S106, let i represent the turbine end T or the compressor end C. The dynamic tip clearance of the i-th end under rotor phase θ and physical time t is calculated by the following formula: ; in Phase under reference state The leaf tip gap, To correspond to the inner wall of the casing in phase Radial displacement at the location, This is the combined radial displacement of the blade tip and the rotor radial motion at this phase; and based on each phase in the circumferential direction... Obtain the minimum tip gap, average tip gap, peak-to-peak value, and the phase corresponding to the minimum gap.

7. The magnetic-thermal-fluid-structure interaction calculation method for an electrically assisted turbocharger based on tip clearance transmission and boundary feedback as described in claim 6, characterized in that: When updating the effective geometric boundary of the flow channel in step S106, node smoothing, local reconstruction or layered mesh scaling are applied to the mesh near the blade tip, and the mesh deformation in adjacent iteration steps is limited by the gap geometry relaxation relation.

8. The magnetic-thermal-fluid-structure interaction calculation method for an electrically assisted turbocharger based on tip clearance transmission and boundary feedback as described in claim 1, characterized in that: The boundary conditions or numerical settings in step S108 include at least one of electromagnetic boundary, aerodynamic boundary, lubricating medium thermal boundary, cooling medium thermal boundary, coupling relaxation factor, time step or flow channel mesh.

9. The magnetic-thermal-fluid-structure interaction calculation method for an electrically assisted turbocharger based on tip clearance transmission and boundary feedback as described in claim 8, characterized in that: In step S108, a boundary vector B and a target response vector Y are constructed. The boundary vector B includes one or more of the following: motor current or torque, turbine inlet total pressure or total temperature, compressor outlet back pressure, lubricating medium inlet temperature or equivalent heat transfer coefficient, and cooling medium inlet temperature or equivalent heat transfer coefficient. The target response vector Y includes one or more of the following: rotational speed, mass flow rate, pressure ratio, efficiency, outlet temperature, minimum tip clearance, maximum temperature, maximum stress, and maximum displacement. Based on the difference between the target response vector and the current response vector, the boundary vector is corrected within preset upper and lower limits.

10. A magnetothermal-fluidic-structure interaction calculation method for an electrically assisted turbocharger based on tip clearance transmission and boundary feedback, as described in any one of claims 1 to 9, characterized in that: The coupling calculation results include electromagnetic torque and loss distribution, temperature field, fluid pressure and velocity field, aerodynamic load, rotor and casing deformation, stress or vibration response, dynamic tip clearance distribution at both ends, mass flow rate, pressure ratio, efficiency, outlet temperature, conservation error of each coupling interface, and boundary feedback iteration process.

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