Flow Field Analysis And Structural Optimization Of Turbine Of Axial Adjustable Nozzle Turbocharger For Vehicle

The automotive axial adjustable nozzle turbocharger can solve the serious problems such as torque insufficiency at low speed and transient response lag,the axial adjustable nozzle technology is the core technology of variable nozzle turbocharger,which is able to achieve best performance matching between turbocharger and engine and improve the engine performance.With the variable frequently engine load,The turbocharger work under the variable operating condition to adapt with pretty wide engine operating conditions to achieve the best performance,which leads to the great change of turbine overall performance and forms complex internal flow.Therefore,combining the existing experimental condition and research hotspot in the field of the turbocharger,the internal flow characteristics of axial adjustable nozzle turbocharger turbine was obtained,and took parameters of the tip clearance ratio and diameter clearance ratio of turbine impeller to optimize the structure,which reduced effectively the loss of turbine internal flow and improved the turbine overall performance.The research provides the reference for the development,application and performance optimization of the turbocharger,and has some practical value in engineering.The main research work is listed as follows:This research considered a certain type of axial adjustable nozzle turbocharger turbine as the research object,created a turbine calculating model by blade data of the turbine 3D model,and the verified numerical model was simulated.Combined with the comparison of the turbine steady-state performance test under variable operating conditions,realized the verification of the effectiveness of calculation model.This study optimized the key parameters(harmonic order)of the nonlinear harmonic method in the process of unsteady calculation through the trial method,balance synthesizely calculation time and calculation accuracy,selected the third order harmonic approximation solution.Through the comparison of the steady and unsteady turbine characteristic data in test conditions,verified the applicability of nonlinear harmonic method in the unsteady calculation of the radial turbine,calculated the unsteady flow field of the turbine under the variable conditions on these bases.the results shows that the turbine impeller internal flow compared to the internal flow of nozzle ring is complicated,The influence range of passage vortex is the main factors of the internal flow of turbine impeller under the variable operating condition.The research hotspot in the field of impeller mechanical was considered,unsteady internal flow filed characteristics of turbine caused by the rotor and stator interference effect by numerical simulation method was studied,the cause of unsteady flow filed factors including wake and potential flow was shown,Studies have shown that the unsteady flow filed factors included the interference of wake and potential flow,and this research analyzed the mechanism of the internal flow in turbine passage,ensure interaction position and the formation mechanism of the stator interference effect,as well as the dominant factor causing the unsteady flow,which can be applied to controlling and reducing flow loss inside the turbine,and solve the problem of less turbine reliability and so on.the diameter clearance ratio had important influence on rotor static interference effects was deduced on these bases,therefore,optimized further the turbine diameter clearance ratio.Based on the impacting mechanism of the rotor stator interference effect,and the design requirements of the turbocharger performance,structure optimization of turbine impeller by the method of optimizing turbine diameter clearance ratio and the tip clearance ratio was proposed and implemented,promoted the turbine efficiency,improved the turbine internal flow,and proved the nature of the turbine unsteady flow field influenced by the diameter clearance ratio and the tip clearance ratio.The reference for the selection of the diameter clearance ratio and the tip clearance ratio of radial turbocharger turbine impeller was provided.