Reducing the Perfomance Penalty Due to Turbine Inter-Platform Gaps

Individual nozzle guide vanes (NGV’s) in modern aero engines are often cast as a single unit with integral hub and casing endwalls. When in operation there is a leakage flow through the chord-wise inter-platform gaps. A previous paper [1] has shown that these gaps can result in a stage efficiency penalty of 0.5% – 1.5% depending upon how well they are sealed. In this paper, numerical calculations are used to re-design the inter-platform gaps with the aim of minimizing their effect on the mainstream aerodynamics and hence reduce the efficiency penalty. Experiments using a full scale, low speed model turbine and an improved gap-design show that significant performance improvements are possible regardless of how well the gap is sealed.Copyright © 2006 by ASME