Nonaxisymmetric Turbine End Wall Design: Part I— Three-Dimensional Linear Design System

Abstract

A linear design system, already in use for the forward and inverse design of 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 design of a nonaxisymmetric end wall for a turbine rotor blade in linear cascade. The calculations show that nonaxisymmetric end wall profiling is a powerful tool for reducing secondary flows, in particular the secondary kinetic energy and exit angle deviations. Simple end wall profiling is shown to be at least as beneficial aerodynamically as the now standard techniques of differentially skewing aerofoil sections up the span, and (compound) leaning of the aerofoil. A design is presented that combines a number of end wall features aimed at reducing secondary loss and flow deviation. The experimental study of this geometry, aimed at validating the design method, is the subject of the second part of this paper. The effects of end wall perturbations on the flow field are calculated using a three-dimensional pressure correction 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 wall and resulting changes in the flow field. With these available, linear superposition theory is used to enable the designer to investigate quickly the effect on the flow field of many combinations of end wall shapes (a matter of minutes for each shape). [S0889-504X(00)00902-8]

The design of three-dimensional turbine blades combined with profiled endwalls

“…The application of the aggressive endwall decreases the suction side C p whereas the 'mild' endwall ameliorates this effect somewhat. Finally, the PEWs introduce a greater cross-passage pressure gradient towards both the leading and trailing edges of the bladewhich is an inevitable consequence of applying PEW as discussed by Harvey et al [8].…”

“…The profiles were generated through an optimization system at Rolls-Royce similar to the one described by Harvey et al [8]. The main development is that the design process is now automated and a design is produced without manual intervention using SKEH as a design variable.…”

“…The RCL and the modified blade sections were generated by a manual trial and error process using the designer's judgement. Once an acceptable blade design was obtained an automated PEW design system (a developed version of that described in Harvey et al [8]) was applied to the blade geometry to produce a final design. The CFD was undertaken using a Reynolds averaged Navier -Stokes solver based on the Moore's elliptic flow programme algorithm; further details can be found in Northall et al [14].…”

Numerical investigation of the influence of non-axisymmetric hub contouring on the performance of a shrouded axial compressor stator

“…Non-axisymmetric or 3D endwall contouring, meaning the additional degree of freedom that results when the annulus line of a turbine or compressor is no longer regarded to be axisymmetric, is already well established as a design feature for axial flow turbines. A large number of both numerical and experimental investigations at different levels of complexity has been reported [1,5,6,7,10,20,21]. Today, turbines with non-axisymmetric endwalls are present in several certified turbofan engines.…”

Secondary Flow Loss Reduction in a Turbine Cascade with a Linearly Varied Height Streamwise Endwall Fence

“…Duden et al [18] Endwall and leading edge modification Exit flow angle deviation and a secondary flow area with the least possible distance from the endwall Harvey et al [19] Endwall profiling Cross-passage static pressure gradient on endwall and exit flow angle deviation…”