Parametric 3D Modeling Method And Multi-Objective Optimization Of High-Performance Torque Converter Blades

Hydrodynamic torque converter is widely used in the field of automobile and engineering machinery.It is the key core component of automobile and engineering machinery transmission system.Its performance directly affects the power performance and fuel economy of the whole vehicle（machine）.As a typical multi-impeller coupled turbomachinery,the hydrodynamic torque converter realizes the mutual conversion of mechanical energy-fluid kinetic energy-mechanical energy through the interaction between the blade of the impeller and the fluid medium.The design of the blade determines the performance of the hydrodynamic torque converter.The blade design is the core part in the development of the hydrodynamic torque converter,and it is also the most difficult and time-consuming part.The traditional design theory and method of hydrodynamic torque converter blades often require repeated design,prototype trial production and external characteristic test to achieve the performance index,which has been restricting the rapid development of hydrodynamic torque converter in China and its application in the field of automobile and engineering machinery.It is of great practical significance to carry out in-depth research on the theory and method of parametric design of hydrodynamic torque converter blades.Therefore,based on the National Natural Science Foundation of China“Research on the temporal and spatial evolution law of turbulence,bionic control mechanism and cascade parameter coupling design method of automobile torque converter”and the school-enterprise cooperation project“Simulation optimization and technology development of high performance hydrodynamic components”,the parameterization and integrated optimization methods of hydrodynamic torque converter cascade are studied in this paper.The design system of hydrodynamic torque converter cascade integrating parameterization,integration and multi-objective optimization of hydrodynamic torque converter blades is studied.The main research work and related conclusions are as follows.（1）Based on the 375mm-baseline hydrodynamic torque converter（350kW）,a parametric modeling method of blade based on NURBS curve theory is proposed,and the relationship between NURBS curve control points and key parameters of cascade is established.In the spatial transformation of two-dimensional and three-dimensional blade curves,a more universal and reversible high-precision generalized conformal mapping method is proposed,which overcomes the disadvantages of irreversible mapping,large accumulation error and distortion of the traditional conformal mapping methods.The unreasonable problems and solutions of different key cascade parameters in the process of blade modeling are discussed,which avoids the continuity and process problems of cascade curve caused by unreasonable blade design.（2）Aiming at each tache in the process of parameterization and optimization of 375-baseline hydrodynamic torque converter cascade,a parametric and integrated optimization system of hydrodynamic torque converter cascade is built,which integrates blade parametric modeling,automatic meshing,CFD calculation,CFD post-processing and multi-objective optimization.The specific process and method of CFD performance calculation and cascade optimization of hydrodynamic torque converter are given.It effectively solves the problem that the design of hydrodynamic torque converter cascade is difficult to carry out parallel compution and automatic batch processing,and realizes the organic integration of parameterization,CFD analysis,intelligent optimization and algorithm and software interface.（3）Through the CFD performance calculation of the hydrodynamic torque converter,the sensitivity analysis of the blade parameters of the parametric cascade of the hydrodynamic torque converter is carried out,and the highly nonlinear relationship between the cascade parameters and the external characteristics is obtained.The sensitivity of the influence of multiple parameters of the parametric cascade on the characteristics of the hydrodynamic torque converter is obtained,and the key sensitive parameters of the blade that have a great influence on the performance of the hydrodynamic torque converter are extracted,which provides a basis for the selection of design variables for multi-objective optimization of cascade system parameters.Focusing on the key cascade parameters,the multi-objective optimization of single parameter and comprehensive cascade parameters of the baseline hydrodynamic torque converter is carried out,and the economic performance index of the hydrodynamic torque converter(peak efficiencyη_max and high efficiency zone width factor Gη)is improved.The flow mechanism of the pressure field and velocity field distribution and its change of the hydrodynamic torque converter before and after optimization are expounded and analyzed.（4）Taking the actual needs of an enterprise project as an opportunity,a high-performance heavy vehicle hydrodynamic torque converter（650kW）with an effective diameter of 440mm was developed by using the parameterization,integration and optimization methods of the hydrodynamic torque converter proposed in the study.The engineering application of the parametric and integrated optimization design system is realized.A multi-objective optimization was carried out with the parametric blade camberline peak height and blade deflection angle as design variables,the peak efficiencyη_max and high efficiency zone width factor Gηas objective functions,and the nominal torque and torque ratio of the hydrodynamic torque converter as constraints.Before optimization,the peak efficiencyη_max of the hydrodynamic torque converter calculated by the original cascade CFD is 0.8648,and the high efficiency zone width factor Gηis 1.750.After optimization,the peak efficiencyη_max of the hydrodynamic torque converter calculated by the optimal cascade CFD is 0.8933,which is increased by 3.30%,and the high efficiency zone width factor Gηis 1.823,which is increased by 4.17%.The trial production of the optimized heavy vehicle torque converter was carried out,and the one-time success was obtained through the bench external characteristic test.The error between the external characteristics calculated by CFD and the test results of the optimized hydrodynamic torque converter is compared and analyzed.The average errors of the efficiency,torque ratio and nominal torque of the hydrodynamic torque converter are less than 5%,and the maximum errors are less than 10%.The correctness and effectiveness of the parametric design method and integrated optimization system of the hydrodynamic torque converter cascade are verified.