Design And Performance Study On The Turbine Shell Of Variable Nozzle Mixed-flow Turbocharger

Turbocharger technology is the most important way for engine to strengthen,improve fuel economy and reduce emissions.The mixed flow turbocharger and variable nozzle ring turbocharger are the focus of application at present.Compared with the traditional radial turbocharger,flow capacity and efficiency of the mixed-flow turbocharger are improved.While the variable nozzle ring can regulate and control the turbocharger.The combination of mixed-flow tubine and variable nozzle ring can further improve the performance of the turbo,as well as optimize the matching between turbochager and engine.In this thesis,a non symmetric channel section turbine shell with different 0-0 cross section A/R value and a symmetric channel section turbine shell with changing channel core have been designed for the study on the effects of the turbine shells performance.First of all,this thesis designed three kinds of turbine shells with different 0-0 cross section A/R value,the turbine shell section is used in pear shaped unsymmetrical design.Calculate and analysis full working conditions of various speed of the three turbine shells assembled with three kinds opening of the nozzle ring.The calculation shows that with the same of similarity flow,the efficiency of three turbine shells increased with the increase of A/R value.Through the analysis of the Mach number,static temperature,static pressure,relative entropy,nozzle inlet flow angle and the total pressure loss coefficient of the turbine shell,the results show that different nozzle ring inlet flow angle distribution of the turbine shells are caused by the different A/R value,which may be the main reason for the difference of the internal flow field,resulting in differences in loss of air in a nozzle ring,causing the different energy loss of the turbine shell downstream,leading to different efficiency.The different flow of three kinds of turbine shell is mainly composed by the opening of the nozzle ring,in addition,the A/R value of the turbine shell can also infulence the flow to some extent.At the wide opening,the flow changes caused by different A/R value is more than small opening.Through the calculation,it is found that the effective flow area of the nozzle ring is approximately equal to the 0-0 section area of Ht₁0 with the middle opening,which results in the difference of the sensitivity of the different A/R value at different nozzle ring opening.In addition,a symmetrical cross section of the turbine shell is designed.The channel core of the design is not in the same plane but rises in space.Through the calculation and analysis of the Ht turbine shell and the VCC turbine shell with the same condition,this thesis has studied the turbine performance at different opening under different speed,the total pressure loss,the nozzle inlet flow angle,relative entropy and other factors.The results show that the flow characteristics as well as the efficiency characteristics of VCC turbine shell and Ht turbine shell are basically the same.The design of VCC is feasible,and can more accurately calculate the cross-sectional area of each channel section.