Design of a Highly Loaded Turbine Exit Case Airfoil With Active Flow Control

Abstract

In this paper a design process of a highly loaded profile for a turbine exit case (TEC) application is described. The profile has an increased pitch to chord ratio which is approximately 50% higher compared to conventional airfoils. For the design of the airfoil a two-dimensional (2D) computational fluid dynamics (CFD) prediction method was used in addition to in-house design rules and low Reynolds number experience from previous experiments. Furthermore, common knowledge from turbine and compressor design as well as turbine exit guide vane studies was evaluated and taken as basis for the new design. To verify the highly loaded design, the profile was tested over a wide Reynolds number range in the high speed cascade wind tunnel of the Institute of Jet Propulsion (ISA) at the University of the German armed forces in Munich. The experiments showed a very good agreement between the CFD predictions and the measurements for high Reynolds numbers. In the low Reynolds number regime the tendency to massive flow separation was slightly underestimated by the CFD predictions. It is particularly challenging as the CFD predictions still have problems to calculate open separation bubbles. Active flow control (AFC) by fluidic oscillators was also part of the design process and successfully applied on the profile.