Effect of endwall contouring on performance of ultra-low aspect ratio transonic turbine inlet guide vanes

In our previous work on ultra-low aspect ratio transonic turbine inlet guide vanes for a small turbofan engine [1], we used numerical stochastic design optimization to propose the new design concept of an extremely aft-loaded airfoil to improve the difficult-to-control aerodynamic loss. At the same time, it is well known that endwall contouring is an effective method for reducing the secondary flow loss. In the literature, both "axisymmetric" and "non-axisymmetric" endwall geometries have been suggested. Almost all of these geometric variations have been based on the expertise of the turbine designer. In our current work, we employed a stochastic optimization method - the evolution strategy (ES) - to optimize and analyze the effect of the axisymmetric endwall contouring on the inlet guide vanes' performance. In the optimization, the design of the endwall contour was divided into three different approaches: 1) only hub contour, 2) only tip contour, and 3) hub and tip contour together with the possibility to observe the correlation between hub/tip changes with regard to their joint influence on the pressure loss. Furthermore, three dimensional flow mechanisms, related to a secondary flow near the endwall region in the low-aspect ratio transonic turbine IGV, was investigated, based on above optimization results. A design concept and secondary flow characteristics for the low-aspect ratio full annular transonic turbine IGV is discussed in this paper.