Serpentine or S-shaped engine inlet geometries are conducive to the emergence of significant secondary flow structures, leading to high pressure loss and flow distortion. Poor pressure recovery results in reduced overall engine performance and decreased fuel efficiency, while distortion at the engine face plane causes instabilities in the compressor dynamics that lower engine surge and stall limits. Using various methods such as computational fluid dynamics CFD, flow visualization tests, particle image velocimetry PIV, pressure probe and wall static tap experiments at various locations, the development and evolution of the secondary flow structures were observed. With this information, flow control devices were designed and constructed to control and suppress secondary flows and eliminate the associated pressure loss and flow non-uniformities that are detrimental to engine performance. The results of this effort are presented using a variety of industry standard performance descriptors that allow quantification of the gains achieved by flow control. Additionally, the PIV data will be used for future CFD code validation and modeling.
