On the Secondary Flow System of an Aggressive Inter Compressor Duct

Abstract

In contrast to the highly optimized rotating components, the inter compressor duct (ICD) is offering a high potential for further improvements. Due to a more aggressive design, the length of the whole engine can be reduced. Shorter and thus lighter engines are leading to further fuel savings for the next engine generation. The design of current ICDs is very conservative because of high uncertainties in design space. An extensive test campaign on two highly aggressive ICDs has been conducted at an annular cascade at German Aerospace Center (DLR) Cologne to explore these limitations. The test section consists of low-pressure compressor (LPC)-OGVs, struts, and high-pressure compressor (HPC)-inlet guide vanes (IGVs). To simulate the influence of the last rotor of the LPC and to vary the incidence of the OGV, a moveable swirler is placed in front of the OGV. This simplification results in differences compared to a real rotor outlet flow. Due to geometric constraints, the ability to move the swirler can only be achieved by adding partial gaps in the rear part of the swirler at hub and shroud. These gaps have a huge impact on the secondary flow structure of the swirler outflow and therefore on the inflow of the ICD. In this article, the secondary flow system of an aggressive ICD is analyzed in detail by the means of experimentally validated computational fluid dynamics (CFD) simulations. Special attention is given to the influence of the nonrotating swirler on the secondary flow system. Furthermore, a recommendation for future experimental setups with respect to the described effects is concluded.