Effects of Tip Endwall Contouring on the Three-Dimensional Flow Field in an Annular Turbine Nozzle Guide Vane: Part 1—Experimental Investigation

Tip endwall contouring is one of the most effective methods to improve the performance of low aspect ratio turbine vanes [1]. In view of the wide variety of geometric parameters, it appears that only the physical understanding of the three-dimensional flow field will allow us to evaluate the probable benefits of a particular endwall contouring. The paper describes the experimental investigation of the three-dimensional flow through a low-speed, low aspect ratio, high-turning annular turbine nozzle guide vane with meridional tip endwall contouring. The full impact of the effects of tip contouring is evaluated by comparison with the results of a previous study in an annular turbine nozzle guide vane of the same blade and cascade geometry with cylindrical endwalls [12]. In parallel, the present experimental study provides a fully three-dimensional test case for comparison with advanced theoretical calculation methods [15]. The flow is explored by means of double-head, four-hole pressure probes in five axial planes from far upstream to downstream of the blade row. The results are presented in the form of contour plots and spanwise pitch-averaged distributions.