Optimization Design And Loss Mechanism Research Of Supersonic Turbine Blade Profile

Being a critical technique of the future aero engine,the supersonic turbine plays a significant role in affecting the overall performance.The traditional convergent airfoil is no longer optimally applicable in supersonic conditions because of aggravated losses in the flow passage.As a result,developing divergent-convergent airfoils is of great importance in order to improve the performance of supersonic turbines.In the current study,the baseline convergent airfoil has been modified to a divergent-convergent one in term of mastering supersonic conditions(Mach number larger than 1.3).To exploit the reason of convergent airfoils failing in supersonic conditions,comparisons of flow characteristics as well as variations of loss between the baseline case and modified case have been performed based on numerical results.The flow fields at high outlet Mach numbers of cases under consideration are analyzed and furthermore the sources of loss are classified.The results show that the variation of losses could be mainly attributed to the shock loss,providing the direction of further modifications.Besides,based on the divergent-convergent airfoil,the optimization employing Multi-Island Genetic Algorithm is performed at the Mach number of 1.3 with a number of airfoil parameters being the control variables and energy loss coefficient being the object function.By comparison of the optimized airfoil and the baseline case,the reason of loss reduction is exploited.Performances of baseline and optimized cases at varying working conditions are investigated numerically.The analysis of sources of loss turn out that the mixing between shock waves of the optimized cases leads to an increased loss.Local modification,by means of installing pits in both the suction and pressure surfaces in the vicinity of the trailing edge,based on the optimized airfoil is finally conducted.By comparison of modified cases,the influences of modifications on different types of loss are analyzed and the reason behind them is discussed.The results turn out that local-shaping on pressure surface leads to an effective reduction in shock wave losses at supersonic condition and therefore decreases the overall loss.By means of extracting loss model,the flow fields of divergent-convergent,optimized and locally modified airfoils are investigated in detail and the current study could be regarded as an effort to provide foundations for flow field analysis and designs of supersonic turbine airfoils aiming at improved performance and better feasibility to higher outlet Mach number.