Aerodynamic design of a wave rotor to high pressure turbine transition duct

Abstract

One approach to lowering the specific fuel consumption and/or increasing the power output of a gas turbine engine is to include a wave rotor topping spool. A wave rotor will effectively increase the cycle overall pressure ratio and peak cycle temperature. In order to incorporate a wave rotor into a gas turbine engine, efficient ducting must be designed to transition flow between the wave rotor ports and other engine components. A critical transition is accomplished by the duct that delivers the flow from the wave rotor to the turbine. The transition duct shape design is complicated by a relatively large circumferential variation in flow properties across the wave rotor exhaust port and yet it must operate with low pressure loss. In the work reported here, an Allison Engine Company Model 250 series gas turbine is used in an engine concept incorporating a wave rotor. The objective of the design study is to develop an aerodynamically efficient duct to transition flow from the partial annulus wave rotor exhaust ports to the full annulus high pressure turbine. This paper will discuss the design methods, geometry definition, and first order analysis techniques for a wave rotor to high pressure turbine transition duct fitting this application. Three classes of transition duct designs will be proposed, developed and assessed. The unique flow conditions of the wave rotor turbine exhaust port and complex transition duct geometries present new challenges in achieving an aerodynamically efficient transition design.