Nonaxisymmetric turbine end wall design: Part I - Three-dimensional lineardesign system

A linear design system, already in use for the forward and inverse design o f three-dimensional turbine aerofoils, has been extended for the design of their end walls. This paper shows how this method has been applied to the d esign of a nonaxisymmetric end wall for a turbine rotor blade in linear cas cade. The calculations show that nonaxisymmetric end wall profiling is a po werful tool for reducing secondary flows, in particular the secondary kinet ic energy and exit angle deviations. Simple end wall profiling is shown to he at least as beneficial aerodynamically as the now standard techniques of differentially skewing aerofoil sections up the span, and (compound) leani ng of the aerofoil. A design is presented that combines a number of end wal l features aimed at reducing secondary loss and flow deviation. The experim ental study of this geometry aimed at validating the design method, is the subject of the second parr of this paper The effects of end wall perturbati ons on the flow field are calculated using a three-dimensional pressure cor rection based Reynolds-averaged Navier-Stokes CFD code. These calculations are normally performed overnight on a cluster of work stations. The design system then calculates the relationships between perturbations in the end w all and resulting changes in the flow field. With these available, linear s uperposition theory is used to enable the designer to investigate quickly t he effect on the flow field of many combinations of end wall shapes (a matt er of minutes for each shape). [S0889-504X(00)00902-8].