A multi-objective aerodynamic optimization method for tilting duct propulsion system

Abstract

This invention discloses a multi-objective aerodynamic optimization method for a tiltable ducted power system, including determining the design domain, representative tilting conditions, and overall process; constructing an equivalent tilting condition under a fixed computational coordinate system; automatically acquiring multi-condition aerodynamic responses; constructing comprehensive evaluation indices from the multi-condition responses; establishing and verifying a proxy model for the multi-condition indices; continuous optimization; CFD recalculation; determination of engineering recommended schemes; and auxiliary load evaluation. This invention can uniformly represent multiple tilting states without repeatedly rotating the ducted model; it ensures that the multi-condition responses have consistent geometric and mesh references, reduces redundant geometric processing and mesh generation, and allows thrust gains and power costs to participate in design decisions, avoiding the pursuit of maximum thrust under a single condition; it can directly obtain recommended design schemes from a given design domain without pre-specifying the basic configuration to be improved.

Description

Technical Field

[0001] This invention relates to the fields of aerodynamic design, computational fluid dynamics simulation and engineering optimization technology for ducted power systems, and particularly to a multi-objective aerodynamic optimization method for tiltable ducted power systems. Background Technology

[0002] During the transition from forward flight to vertical flight, the relative angle between the duct axis and the external incoming flow, as well as the velocity of the incoming flow, change in a tiltable ducted propulsion system. The same fan and duct design needs to operate under multiple conditions, including tilt initiation, tilt transition, and tilt termination. Therefore, selecting a design scheme based solely on the axial thrust at a fixed tilt angle cannot reflect the overall performance of that scheme across the entire tilt range.

[0003] On the other hand, design adjustments such as increasing the blade installation angle can usually improve axial thrust, but they also increase axial aerodynamic torque and shaft power requirements, thus reducing thrust per unit power. If only maximum thrust is considered as the target, the power cost may be ignored; if only thrust per unit power is compared, necessary thrust levels may be sacrificed. When the design scheme is not yet determined, it is necessary to find a design scheme from the given design space that balances thrust performance and power utilization levels and is applicable to multiple tilting conditions.

[0004] Existing parametric optimization processes typically include parameter sampling, simulation calculation, surrogate modeling, and optimization search. These steps are general implementation methods and cannot directly solve two specific problems of tiltable ducted power systems: first, how to uniformly represent multiple tilting states without repeatedly rotating the duct model and reconstructing the computational domain; second, how to ensure that the thrust gains and power costs of the same design scheme under multiple tilting conditions participate in a single design decision. Therefore, it is necessary to propose a multi-objective aerodynamic optimization method for tiltable ducted power systems applicable to multiple tilting conditions. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a multi-objective aerodynamic optimization method for tiltable ducted propulsion systems, which solves the problems of difficulty in uniformly simulating multiple tilt states during the design phase of tiltable ducted propulsion systems, and difficulty in determining the applicable design scheme for the entire tilt range under a single operating condition or with a single thrust target.

[0006] Technical solution: The multi-objective aerodynamic optimization method for a tiltable ducted power system described in this invention includes the following steps:

[0007] S1: Define the design domain, representative tilt conditions, and overall process;

[0008] S2: Construct the equivalent tilting condition under a fixed computational coordinate system;

[0009] S3: Automatically acquires pneumatic response under multiple operating conditions;

[0010] S4: A comprehensive evaluation index is constructed from multi-condition responses;

[0011] S5: Establish and validate a multi-condition index proxy model;

[0012] S6: Continuous optimization, CFD recalculation, and determination of recommended engineering solutions;

[0013] S7: Auxiliary load evaluation.

[0014] Furthermore, the design domain of step S1 includes the design object and the adjustable design quantity, which is the blade installation angle and the blade tip clearance. The blade installation angle and the blade tip clearance are combined by all factors to establish a design sample for multi-condition evaluation and prediction relationship.

[0015] The overall process includes defining design variables and load conditions, DOE sampling, parametric geometry update, automatic mesh and boundary processing, CFD solution for multiple load conditions, response extraction, construction of evaluation indices for multiple load conditions, establishment and verification of surrogate models, comprehensive evaluation optimization, CFD recalculation of continuous optimal points, and determination of recommended engineering solutions.

[0016] Further, step S2 includes:

[0017] With the duct axis as the x-axis and the direction perpendicular to the duct axis in the tilt plane as the y-axis, the tilt transition speed is set based on the incoming flow speed during level flight. Based on the reference value, the incoming flow velocity of the j-th representative tilting condition. ,Mach number The inflow direction component is determined by the following formula:

[0018] ,

[0019] ,

[0020] ,

[0021] ,

[0022] As the tilt angle increases Following the cosine law of decay, the outer boundary of the calculation domain is subjected to pressure far-field boundary conditions, and the automated process will... , and Write the pressure far-field boundary to change the relative relationship between the duct axis and the external flow without rotating the duct model and computational domain.

[0023] Further, step S3 includes:

[0024] S31: Read the blade installation angle of the i-th design scheme to be evaluated. and leaf tip gap The design variables are then passed to the parametric geometry modeling module, which, based on... Adjust the fan blade installation position according to Adjust the gap between the blade tip and the inner wall of the duct, and update the geometric models of the fan blades, hub, and duct corresponding to the current design scheme;

[0025] S32: Transfer the updated geometric model of the ducted dynamic system to the computational domain processing module, and sequentially perform Boolean operations, fluid region extraction, region partitioning and topology sharing to obtain the external fluid domain, local fluid domain, rotating fluid domain and static fluid domain corresponding to the current design scheme;

[0026] S33: Based on the fluid region obtained in step S32, identify the external pressure far-field boundary, duct wall, fan blade wall, and the interface between the rotating fluid domain and the stationary fluid domain. Name each boundary object according to the preset naming rules and generate a computational mesh for the current design scheme.

[0027] S34: Under the condition that the current geometric model, computational domain, boundary topology and computational mesh remain unchanged, update the tilt angle, incoming flow velocity, Mach number and incoming flow direction component according to the determined representative tilt order, and transfer the Mach number and direction component corresponding to the current working condition to the CFD solution module to update the pressure far-field boundary conditions.

[0028] S35: Call the CFD solver module to solve the flow field for the j-th representative tilting condition. After the solution converges, extract the overall axial thrust of the ducted power system. and axial aerodynamic moment around the duct axis Simultaneously extract the pitching moment in the tilt plane. The above response and the corresponding , and The data is saved together as the j-th working condition record of the i-th design scheme;

[0029] S36: Determine whether all representative tilting conditions of the current design scheme have been completed. If there are still uncompleted conditions, read the next condition according to the tilt angle order and re-execute steps S34 and S35. If all conditions have been completed, organize the completed condition records into a multi-condition aerodynamic response set corresponding to the current design scheme according to the tilt angle order.

[0030] S37: Determine whether all design schemes to be evaluated have been completed. If there are still incomplete design schemes, exit the inner tilt condition loop and read the next set. and Then repeat steps S31 to S36; if all design schemes have been completed, then end the automated multi-condition CFD calculation.

[0031] Further, the calculation domain in step S32 includes an external spherical fluid domain, a local fluid domain set within the external fluid domain, and a rotating fluid domain set within the local fluid domain and used to accommodate the fan rotating components; the fluid region outside the rotating fluid domain is set as a stationary fluid domain, and its boundary includes at least the external pressure far-field boundary, the duct wall, the fan blade wall, and the interface between the rotating fluid domain and the stationary fluid domain.

[0032] Furthermore, in step S4, the shaft power of the i-th design scheme under the j-th representative tilting condition is determined by the axial aerodynamic torque and expressed as follows:

[0033] ,

[0034] in, Let n be the fan angular velocity; when the fan speed n is expressed in r / min... according to Conversion; thrust per unit power is expressed as:

[0035] ,

[0036] The thrust generated per unit shaft power is represented by dividing the thrust and the thrust per unit power under each operating condition by the normalized reference value preset for that operating condition. and .

[0037] Furthermore, step S5 employs leave-one-out cross-validation to evaluate the accuracy of the surrogate model. If the cross-validation accuracy of the surrogate model does not meet the preset requirements, samples are added in the design region where the error is large or the response changes rapidly. Steps S31 to S37 are then re-executed to sequentially complete design variable transfer, geometric update, computational domain processing, boundary identification, mesh generation, multi-condition CFD solution, response extraction, and... and The calculation is performed, and then the supplementary samples are added to the original sample set and the surrogate model is updated. The updated surrogate model continues to be evaluated for accuracy using the same cross-validation method until the preset accuracy requirement is met.

[0038] Furthermore, step S6 includes based on accuracy-verified... and The proxy model obtains the changing relationship between the two objectives within the joint design domain and performs... and The trade-off analysis identifies the mutual constraints between thrust performance targets and power utilization targets.

[0039] Furthermore, in step S7, the pitching moment in the auxiliary load evaluation... Do not participate , The calculation and main optimization of J are only saved as auxiliary verification quantities. When a specific task requires limiting attitude loads, the pitching moment is used as an independent constraint or verification condition.

[0040] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0041] (1) The attitude change of the actual duct relative to the incoming flow is converted into the direction and velocity change of the incoming flow in a fixed coordinate system, which can uniformly represent multiple tilt states without repeatedly rotating the duct model;

[0042] (2) The same design scheme undergoes all representative tilt conditions in sequence under the same geometric model and computational grid, so that the multi-condition response has a consistent geometric and grid reference, and reduces repeated geometric processing and mesh generation;

[0043] (3) A multi-condition evaluation chain is formed by axial thrust, axial aerodynamic torque, shaft power and thrust per unit power, so that thrust benefits and power costs can be involved in design decisions together, avoiding the pursuit of maximum thrust in a single condition.

[0044] (4) Through automated multi-condition simulation, proxy model verification and continuous design domain optimization, recommended design schemes can be obtained directly from a given design domain without specifying the basic configuration to be improved in advance. Attached Figure Description

[0045] Figure 1 This is the overall flowchart of the multi-condition, multi-objective aerodynamic optimization of the tiltable ducted power system of the present invention;

[0046] Figure 2 This is a schematic diagram of the actual duct model, equivalent incoming flow velocity and its directional components under the fixed calculation coordinate system of this invention.

[0047] Figure 3 This is a comparison chart of axial thrust, shaft power, and unit power thrust under multiple operating conditions for the recommended configuration and representative comparative configuration of this invention. Detailed Implementation

[0048] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0049] The multi-objective aerodynamic optimization method for a tiltable ducted power system described in this embodiment includes the following steps:

[0050] Step 1: Determine the design domain, representative tilt conditions, and overall process;

[0051] This embodiment uses a tiltable ducted fan as the design object, and the adjustable design amount is the blade installation angle. and leaf tip gap The blade installation angles were successively selected from 25° to 42.5°, with values ​​of 25°, 27.5°, 30°, 32.5°, 35°, 37.5°, 40°, and 42.5°. The tip clearances were successively selected as 6 mm, 9 mm, and 12 mm, with the fan speed fixed at 5000 r / min. A full-factor combination of the eight blade installation angles and three tip clearances yielded 24 design samples for establishing multi-condition evaluation and prediction relationships.

[0052] Based on the tilt range of the ducted fan transitioning from forward flight to vertical flight, 0°, 15°, 30°, 45°, 60°, 75°, and 89.9° were selected as representative tilt angles. 0° characterizes the initial tilt state, 15°–75° characterize the transition state, and 89.9° approximates the 90° tilt termination state to avoid numerical anomalies in velocity or direction parameters during the termination condition. Each design sample was calculated for these seven representative tilt conditions, resulting in 168 design sample-tilt condition calculation points. The blade installation angle, tip clearance, and other geometric parameters of the same design sample remained constant under all seven conditions.

[0053] like Figure 1 As shown, the overall process includes defining design variables and load conditions, DOE sampling, parametric geometry update, automatic mesh and boundary processing, multi-load condition CFD solution, response extraction, construction of multi-load condition evaluation indicators, establishment and verification of surrogate models, comprehensive evaluation optimization, continuous optimum CFD recalculation, and determination of engineering recommended solutions. Among these, parameter sampling, software invocation, and surrogate models are implementation means; the construction of equivalent tilt load conditions and the comprehensive evaluation of thrust-power under multiple load conditions together constitute the core technology chain of the method.

[0054] Step 2: Construct the equivalent tilting condition under a fixed computational coordinate system;

[0055] In actual tilt characterization, the direction of the incoming flow can be considered fixed, while the duct changes attitude relative to the flow. In numerical equivalent characterization, the overall attitude of the duct dynamic system, the duct axis, and the computational coordinate system remain unchanged, while the direction and velocity of the incoming flow change according to the tilt angle and a preset tilt transition speed. Both characterizations have the same duct-flow relative relationship.

[0056] The duct axis is taken as the x-axis, and the direction perpendicular to the duct axis in the tilt plane is taken as the y-axis. In this embodiment, the tilt transition speed is scheduled based on the incoming flow speed during level flight. Based on the reference value, the incoming flow velocity of the j-th representative tilting condition. ,Mach number The inflow direction component is determined by the following formula:

[0057]

[0058]

[0059]

[0060]

[0061] in, Take 60 m / s², and a = 340 m / s². As the tilt angle increases, The decay follows a cosine law. The outer boundary of the computational domain uses pressure far-field boundary conditions, and the automated process will... , and By writing pressure far-field boundaries, the relative relationship between the duct axis and the external inflow can be changed without rotating the duct model and computational domain. For example... Figure 2 The diagram shows the actual duct model, equivalent incoming flow velocity, and their directional components in a fixed computational coordinate system. This model is used for configuration comparison under a given equivalent tilt condition; it does not represent free-flight closed-loop trim, nor does it represent continuous transient tilt solution.

[0062] Step 3: Automatically acquire pneumatic response under multiple operating conditions;

[0063] like Figure 1 As shown, the automated process employs an outer design scheme loop and an inner tilting condition loop, and its specific execution includes steps S31 to S37. The outer loop is responsible for reading and transmitting the blade installation angle of the current design scheme to be evaluated. and leaf tip gap The first loop updates the geometric model, computational domain, and computational grid. The second loop updates the representative tilt case sequentially and completes the solution and response extraction, while keeping the geometric model, computational domain, and computational grid corresponding to the current design scheme unchanged.

[0064] S31: Read the blade installation angle of the i-th design scheme to be evaluated. and leaf tip gap The design variables are then passed to the parametric geometry modeling module. The parametric geometry modeling module, based on... Adjust the fan blade installation position according to Adjust the gap between the blade tip and the inner wall of the duct to update the geometric model of the fan blade, hub, and duct corresponding to the current design.

[0065] S32: Transfer the updated ducted dynamic system geometric model from step S31 to the computational domain processing module, and sequentially perform Boolean operations, fluid region extraction, region partitioning, and topology sharing to obtain the external fluid domain, local fluid domain, rotating fluid domain, and static fluid domain corresponding to the current design scheme.

[0066] The computational domain includes an external spherical fluid domain, a local fluid domain within the external fluid domain, and a rotating fluid domain within the local fluid domain that houses the fan's rotating components. The fluid region outside the rotating fluid domain is designated as a stationary fluid domain, with boundaries including at least the external pressure far-field boundary, the duct wall, the fan blade wall, and the interface between the rotating and stationary fluid domains. In the automatic processing of different design samples, boundaries are automatically identified through preset naming rules, geometric topological relationships, or spatial location relationships to ensure consistency in mesh generation, boundary condition updates, and result extraction objects.

[0067] S33: Based on the fluid region obtained in step S32, identify the far-field boundary of the external pressure, the duct wall, the fan blade wall, and the interface between the rotating fluid domain and the stationary fluid domain. Name each boundary object according to the preset naming rules, and generate a computational mesh for the current design scheme. After completing the geometric model update, computational domain processing, boundary identification, and mesh generation for the current design scheme, enter the inner tilt condition cycle.

[0068] S34: Under the condition that the current geometric model, computational domain, boundary topology and computational mesh remain unchanged, update the tilt angle, incoming flow velocity, Mach number and incoming flow direction component in the order of 0°, 15°, 30°, 45°, 60°, 75° and 89.9°, and transfer the Mach number and direction component corresponding to the current working condition to the CFD solution module to update the pressure far-field boundary conditions.

[0069] In this embodiment, the tilt angle, incoming flow velocity, Mach number, and two incoming flow direction components are set as tilt_angle, vtotal, machtotal, flowx, and flowy, respectively. The inner loop calculates vtotal, machtotal, flowx, and flowy based on the current tilt_angle and passes the corresponding values ​​to the CFD solver module to update the pressure far-field boundary conditions. The fan speed is maintained at 5000 r / min in all design samples and representative tilt conditions, and other solver settings are kept consistent to ensure a unified calculation benchmark for the aerodynamic response under different design samples and conditions.

[0070] S35: Call the CFD solver module to solve the flow field for the j-th representative tilting condition. After the solution converges, extract the overall axial thrust of the ducted power system. and axial aerodynamic moment around the duct axis Simultaneously extract the pitching moment in the tilt plane. This is used for auxiliary load evaluation of the final recommended scheme, comparing the above response with the corresponding , and The data is saved together as the j-th working condition record of the i-th design scheme.

[0071] S36: Determine whether all representative tilting conditions of the current design scheme have been completed. If there are still incomplete conditions, read the next condition according to the tilt angle order and re-execute steps S34 and S35; if all seven conditions have been completed, organize the seven condition records into a multi-condition aerodynamic response set corresponding to the current design scheme according to the tilt angle order.

[0072] S37: Determine if all design schemes to be evaluated have been completed. If there are still incomplete design schemes, exit the inner tilt condition loop and read the next set. and Then, steps S31 to S36 are repeated; if all design schemes have been completed, the automated multi-condition CFD calculation ends. Therefore, each of the 24 design samples forms a set of multi-condition aerodynamic responses containing seven condition records. The entire automated calculation yields a total of 168 configuration-condition response records, instead of treating the 168 responses as unrelated single-condition data points.

[0073] In one implementation, an integrated optimization platform is used to handle process scheduling and variable transfer, parametric modeling software is used to update the geometry, geometry preprocessing software is used to process the computational domain and boundaries, and a CFD solver is used to perform flow field calculations. This embodiment can utilize Isight, Rhino / Grasshopper, SpaceClaim, and Fluent to implement the above functions, but these software names do not constitute a necessary limitation of this method.

[0074] Step 4: Construct a comprehensive evaluation index based on multi-condition response;

[0075] The shaft power of the i-th design scheme under the j-th representative tilting condition is determined by the axial aerodynamic torque:

[0076]

[0077] in, Let n be the fan angular velocity; when the fan speed n is expressed in r / min... according to Conversion. Further calculation of thrust per unit power:

[0078]

[0079] The thrust generated per unit shaft power is used to characterize power utilization level and is not considered propulsion efficiency in the strict sense. Since the aerodynamic magnitudes differ at different tilt angles, the thrust and unit power thrust under each operating condition are divided by a preset normalized reference value for that condition. and .

[0080] This embodiment uses =30° =9 mm sample provides response under seven representative operating conditions and This sample is only used for dimensionless design and to unify the evaluation scale. It is not referred to as the basic configuration, nor is it used as the starting point for optimization, nor does it limit the search direction for other design schemes to be evaluated.

[0081] For the i-th design scheme, the index calculation is performed in the following order: First, based on the seven working conditions... Calculate the angular velocity of the fan separately. Secondly, by and Calculate separately Then for each working condition and Divide by the same working condition respectively and Finally, the dimensionless thrust results and dimensionless unit power thrust results for the seven operating conditions were aggregated separately. Thus, each design scheme formed a set of... and a group All representative tilting conditions participated in the same design evaluation.

[0082]

[0083]

[0084] For all operating conditions, thrust evaluation quantity These are the power utilization evaluation metrics under all operating conditions. They respectively characterize the axial thrust performance and the unit power thrust performance under multiple operating conditions. Both are dimensionless, and larger values ​​indicate better performance. Currently, there is no explicit task preference, and both evaluation metrics have been normalized. Therefore, this embodiment uses an equal-weighted scalarization method to construct a comprehensive evaluation index:

[0085]

[0086] and Since all objectives are to be maximized, after taking the reciprocal, they are uniformly converted into a minimization form, and the optimization objective is:

[0087]

[0088] Step 5: Establish and validate a multi-condition indicator proxy model;

[0089] In this embodiment, the DOE samples are the 24 design samples obtained by combining the aforementioned eight-stage blade installation angle and the three-stage tip clearance full factor. Each design sample completes the calculation of seven representative tilt conditions through the aforementioned automated process; therefore, the basic data used for proxy modeling comes from 168 configuration-condition response records. For each design sample, a set of calculations is first performed based on the original responses of the seven conditions. and Then, respectively and For input, with and Establish a response surface proxy model for the output.

[0090] Leave-one-out cross-validation was used to evaluate the accuracy of the surrogate model. The results listed in Table 1 show that... The cross-validation determination coefficient of the surrogate model was 0.9964, the root mean square error was 0.0165, and the mean absolute percentage error was 1.09%. The corresponding metrics for the surrogate models are 0.9984, 0.0046, and 0.39%, respectively. Both surrogate models can be used for continuous optimization prediction within the design domain of this embodiment.

[0091] Table 1. Leave-one-out cross-validation results of the multi-condition index proxy model

[0092]

[0093] If the cross-validation accuracy of the surrogate model does not meet the preset requirements, supplementary samples should be added in the design region where the error is large or the response changes rapidly. The supplementary samples should not only perform single-condition prediction, but steps S31 to S37 should be executed again to sequentially complete design variable transfer, geometric update, computational domain processing, boundary identification, mesh generation, seven-condition CFD solution, response extraction, and... and The calculation is performed, and then the supplementary samples are added to the original sample set to update the surrogate model. The updated surrogate model continues to use the same cross-validation method to evaluate its accuracy until the preset accuracy requirement is met. In this embodiment, the accuracy listed in Table 1 already meets the prediction requirements of the continuous design domain, so it directly enters the continuous optimization stage. The role of the surrogate model is to reduce the number of CFD calls in the continuous search stage, without changing the technical relationship that the same design scheme must be evaluated by all seven representative tilt conditions.

[0094] Step Six: Continuous optimization, CFD recalculation, and determination of the recommended engineering solution;

[0095] Based on accuracy verification and The proxy model obtains the changing relationship between the two objectives within the joint design domain and performs... and A trade-off analysis was conducted to identify the constraints between thrust performance targets and power utilization targets. Given that the current mission does not have explicitly defined performance preferences, a comprehensive evaluation index J was constructed using an equal-weighted quantification method, and the Pointer optimization method was employed. =25°~42.5° The minimum value of J is searched within a continuous design domain of 6 mm to 12 mm. The continuous optimum obtained from response surface prediction is... =35.42° =6 mm.

[0096] Table 2. Proxy model prediction and CFD recalculation results for continuous optimal points

[0097]

[0098] Table 2 shows that the surrogate model predictions and CFD calculations at continuous optimal points exhibit good agreement. Considering the performance differences and ease of engineering implementation for near-integer installation angle configurations, the final recommendation is... =35° =6 mm is used as the engineering solution. This recommended value is not the stall point, not the maximum thrust point, nor the installation angle boundary of the design domain in this embodiment; it is an engineering compromise solution obtained under the current design space, 5000 r / min rotation speed, preset tilt transition speed scheduling, and equal weight evaluation criteria.

[0099] To illustrate the selection of recommended options, we selected... =30° =6 mm and =42.5° =6 mm is used as a representative performance comparison scheme. The former is used to characterize the thrust and power utilization performance at a smaller installation angle, while the latter is used to characterize the corresponding performance at a larger installation angle in the upper part of the design domain; neither of them are geometrically nearest to the continuous optimal point. Figure 3 The results show that increasing the installation angle can improve axial thrust, but at the same time significantly increases shaft power and reduces thrust per unit power. =35° =6 mm falls within the trade-off between thrust gain and power utilization. These comparative schemes are used to interpret the recommended results and are not intended as a normalization reference sample.

[0100] Continuous Optimum =35.42° =6 mm CFD recalculation was used to validate the surrogate model predictions; engineering recommended value =35° =6 mm was determined based on the continuous optimal results, taking into account the ease of machining, assembly, and reproduction of integer installation angles. Therefore, the continuous optimal point and the engineering recommended configuration play different roles, and 35° cannot be described as the design domain boundary or the location of maximum thrust.

[0101] Step 7: Conduct auxiliary load evaluation;

[0102] Pitch moment Do not participate , The calculation of J is not included in the main optimization; it is only stored as an auxiliary verification quantity. When a specific task requires limiting attitude loads, the pitch moment can be used as an independent constraint or verification condition.

[0103] Alternative implementation methods;

[0104] The number and location of representative tilt angles can be adjusted according to specific flight missions, and the preset tilt transition velocity scheduling can also be achieved using lookup tables, piecewise functions, or mission-given curves. The surrogate model can employ multinomial response surfaces, radial basis functions, kriging, or other models suitable for continuous variable prediction. The optimizer can use gradient methods, sequential quadratic programming, evolutionary algorithms, or other search methods. Regardless of the specific software or algorithm used, the following technical relationships should be maintained: construct an equivalent tilt condition sequence under a fixed computational coordinate system, enabling the same design scheme to obtain multi-condition responses under the same geometric and grid references, and determine a set of design schemes applicable to multiple tilt conditions based on the multi-condition thrust and power utilization evaluation results.

Claims

1. A multi-objective aerodynamic optimization method for a tiltable ducted power system, characterized in that, Includes the following steps: S1: Define the design domain, representative tilt conditions, and overall process; S2: Construct the equivalent tilting condition under a fixed computational coordinate system; S3: Automatically acquires pneumatic response under multiple operating conditions; S4: A comprehensive evaluation index is constructed from multi-condition responses; S5: Establish and validate a multi-condition index proxy model; S6: Continuous optimization, CFD recalculation, and determination of recommended engineering solutions; S7: Auxiliary load evaluation.

2. The multi-objective aerodynamic optimization method for a tiltable ducted power system according to claim 1, characterized in that, The design domain of step S1 includes the design object and adjustable design quantities. The adjustable design quantities are the blade installation angle and the blade tip clearance. The blade installation angle and the blade tip clearance are combined with all factors to establish a design sample for multi-condition evaluation and prediction relationship. The overall process includes defining design variables and load conditions, DOE sampling, parametric geometry update, automatic mesh and boundary processing, CFD solution for multiple load conditions, response extraction, construction of evaluation indices for multiple load conditions, establishment and verification of surrogate models, comprehensive evaluation optimization, CFD recalculation of continuous optimal points, and determination of recommended engineering solutions.

3. The multi-objective aerodynamic optimization method for a tiltable ducted power system according to claim 1, characterized in that, Step S2 includes: With the duct axis as the x-axis and the direction perpendicular to the duct axis in the tilt plane as the y-axis, the tilt transition speed is set based on the incoming flow speed during level flight. Based on the reference value, the incoming flow velocity of the j-th representative tilting condition. ,Mach number The inflow direction component is determined by the following formula: ， ， ， ， As the tilt angle increases Following the cosine law of decay, the outer boundary of the calculation domain is subjected to pressure far-field boundary conditions, and the automated process will... , and Write the pressure far-field boundary to change the relative relationship between the duct axis and the external flow without rotating the duct model and computational domain.

4. The multi-objective aerodynamic optimization method for a tiltable ducted power system according to claim 1, characterized in that, Step S3 includes: S31: Read the blade installation angle of the i-th design scheme to be evaluated. and leaf tip gap The design variables are then passed to the parametric geometry modeling module, which, based on... Adjust the fan blade installation position according to Adjust the gap between the blade tip and the inner wall of the duct, and update the geometric models of the fan blades, hub, and duct corresponding to the current design scheme; S32: Transfer the updated geometric model of the ducted dynamic system to the computational domain processing module, and sequentially perform Boolean operations, fluid region extraction, region partitioning and topology sharing to obtain the external fluid domain, local fluid domain, rotating fluid domain and static fluid domain corresponding to the current design scheme; S33: Based on the fluid region obtained in step S32, identify the external pressure far-field boundary, duct wall, fan blade wall, and the interface between the rotating fluid domain and the stationary fluid domain. Name each boundary object according to the preset naming rules and generate a computational mesh for the current design scheme. S34: Under the condition that the current geometric model, computational domain, boundary topology and computational mesh remain unchanged, update the tilt angle, incoming flow velocity, Mach number and incoming flow direction component according to the determined representative tilt order, and transfer the Mach number and direction component corresponding to the current working condition to the CFD solution module to update the pressure far-field boundary conditions. S35: Call the CFD solver module to solve the flow field for the j-th representative tilting condition. After the solution converges, extract the overall axial thrust of the ducted power system. and axial aerodynamic moment around the duct axis Simultaneously extract the pitching moment in the tilt plane. The above response and the corresponding , and The data is saved together as the j-th working condition record of the i-th design scheme; S36: Determine whether all representative tilting conditions of the current design scheme have been completed. If there are still uncompleted conditions, read the next condition according to the tilt angle order and re-execute steps S34 and S35. If all conditions have been completed, organize the completed condition records into a multi-condition aerodynamic response set corresponding to the current design scheme according to the tilt angle order. S37: Determine whether all design schemes to be evaluated have been completed. If there are still incomplete design schemes, exit the inner tilt condition loop and read the next set. and Then repeat steps S31 to S36; if all design schemes have been completed, then end the automated multi-condition CFD calculation.

5. The multi-objective aerodynamic optimization method for a tiltable ducted power system according to claim 4, characterized in that, The calculation domain in step S32 includes an external spherical fluid domain, a local fluid domain set within the external fluid domain, and a rotating fluid domain set within the local fluid domain and used to accommodate the fan rotating components; the fluid region outside the rotating fluid domain is set as a stationary fluid domain, and its boundary includes at least the external pressure far-field boundary, the duct wall, the fan blade wall, and the interface between the rotating fluid domain and the stationary fluid domain.

6. The multi-objective aerodynamic optimization method for a tiltable ducted power system according to claim 1, characterized in that, The shaft power of the i-th design scheme in step S4 under the j-th representative tilting condition is determined by the axial aerodynamic torque and expressed as follows: ， in, Let n be the fan angular velocity; when the fan speed n is expressed in r / min... according to Conversion; thrust per unit power is expressed as: ， The thrust generated per unit shaft power is represented by dividing the thrust and the thrust per unit power under each operating condition by the normalized reference value preset for that operating condition. and .

7. The multi-objective aerodynamic optimization method for a tiltable ducted power system according to claim 1, characterized in that, Step S5 employs leave-one-out cross-validation to evaluate the accuracy of the surrogate model. If the cross-validation accuracy of the surrogate model does not meet the preset requirements, samples are added in the design region where the error is large or the response changes rapidly. Steps S31 to S37 are then re-executed to sequentially complete design variable transfer, geometric update, computational domain processing, boundary identification, mesh generation, multi-condition CFD solution, response extraction, and... and The calculation is performed, and then the supplementary samples are added to the original sample set and the surrogate model is updated. The updated surrogate model continues to be evaluated for accuracy using the same cross-validation method until the preset accuracy requirement is met.

8. The multi-objective aerodynamic optimization method for a tiltable ducted power system according to claim 1, characterized in that, Step S6 includes based on accuracy verification. and The proxy model obtains the changing relationship between the two objectives within the joint design domain and performs... and The trade-off analysis identifies the mutual constraints between thrust performance targets and power utilization targets.

9. The multi-objective aerodynamic optimization method for a tiltable ducted power system according to claim 1, characterized in that, In step S7, the pitching moment is used in the auxiliary load evaluation. Do not participate , The calculation and main optimization of J are only saved as auxiliary verification quantities. When a specific task requires limiting attitude loads, the pitching moment is used as an independent constraint or verification condition.

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