ON THE SECONDARY FLOW SYSTEM OF AN AGGRESSIVE INTER COMPRESSOR DUCT

Abstract

In the last decades much effort has been spent in optimizing the performance of the rotating components of the compression system of civil aircraft engines. While these components are highly optimized, further improvements are limited. In this light, the interfaces between these components are coming into focus of research. Especially the inter compressor duct (ICD) is offering a high potential. 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 very aggressive ICD designs has been conducted at an annular cascade at German Aerospace Center (DLR) Cologne to explore these limitations and a vast amount of test data has been gathered. The test section is comprised of LPC-OGVs, struts and HPC-IGVs. To simulate the influence of the last rotor of the LPC and to vary the incidence of the OGV, a move-able swirler is placed in front of the OGV. This simplification results in differences relative to a real rotor outlet flow. Through geometrical restriction, 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, the inflow of the ICD. In this paper, the secondary flow system of an aggressive ICD is analyzed in detail by the means of experimentally validated CFD simulations. Attention is given to the impact of the stationary swirler on the secondary flow system. Furthermore, a recommendation for future experimental setups with respect to the described effects is concluded.