Study On The Flow Characteristics And Structural Optimization Of A Automotive Turbine

Compared with the traditional turbocharger,variable geometry turbocharger(VGT)can avoid serious problem such as stable Operating Condition of narrow,inadequacy of low-speed torque and poor transient response.Variable geometry technology is the core of the VGT,which achieve the good match performance between the engine and the VGT.Because of the wide operating range of an automotive engine,the VGT operating conditions at a wide range is formed,and the turbine performance variation range is wide,and the complicated flow within the turbine stage is created.Therefore,the internal flow of turbine stage of VGT under Variable Operating Conditions is analyzed,and based on it the turbine structure is optimized,which have certain engineering practical value in order to control the internal flow loss in the turbine,and to improve turbine efficiency.In consideration of the existing research conditions and the purpose of research,the research topic mainly focuses on the internal flow field analysis and Structural optimization of turbine stage of the VGT.This main research work is as follows:The point cloud of bending twist blade of turbine and the geometry data of the nozzle ring are obtained,which combines the non-contact structured light scanner and the two-dimensional profiler advantages of data measurement,and the UG/Imageware reverse modeling platform is used to establish the accurate three-dimensional model of turbine and related geometric features.The grid model was processed by technology of Structured Block Mesh,and that was evaluated for grid independence.The calculation parameters of verified calculation model of turbine were set and internal flow field of turbine stage under low,medium,and high speed operating conditions was solved,which were calculated by CFD software of NUMECA FINE/Turbo.The internal flow field characteristics of turbine stage under low,medium and high speed operating conditions were analyzed,which provides reference for the improvement internal flow condition of turbine stage.The shaping method of the nozzle ring and turbine blades,which results the local flow loss at the front and trailing edges of the nozzle ring and the turbine blades,The internal flow loss of the turbine channel is mainly caused by the formation and development of the channel vortex,the turbine leakage flow at tip clearance,and the angular vortices.It is found that the influence range and intensity of the vortex structure that cause the loss of flow under various operating conditions are different.The strength of the channel vortex at the turbine passage under the low speed operating conditions is bigger than that under high speed operating conditions,which is the main reason for low efficiency under low speed operating conditions.The flow situation of the nozzle ring is complicated,which causes big flow loss in turbine under high speed condition..To conclude,the internal flow is complex at turbine stage,which has great significance for controlling the flow loss and improving turbine characteristic of turbine stage.The turbine design parameters were optimized and the turbine efficiency was optimized by the uniform test design method.The turbine structure was optimized and the optimization results were improved and the flow efficiency was improved.By comparing the front and rear turbine flow fields,it is shown that the fluctuation range of the channel vortex and the leakage vortex is restrained,and the turbine efficiency is provided,which provides flow field basis for the turbocharger development,application and performance optimization.