Distortion Management Effects on Jet Engine Performance

Abstract

Boundary layer separation studies have been going on for many years. The concept of flow control is not new, with boundary layer blowing or suction to delay separation known since Prandtl. Many flow control methods are considered nowadays to introduce improvements on flow characteristics both for internal and external applications. This work is concerned with the application of flow control methods for improving the flow characteristics within intake ducts. Flow control applications are presented with a challenge to improve the flow characteristics of intake ducts with complex geometries that are used to deliver airflow to buried propulsion systems, common for military engine applications. This work is analysing the flow control capabilities for improving s-shaped ducts flow characteristics and how these improvements translate onto engine performance. For the purpose of this study a methodology was created in order to simulate an intake/compressor/engine interaction and analyse the characteristics of all three components. Three-dimensional flow simulations have been carried out for the intake and compressor models and compressor performance results have been transferred to an engine performance tool to investigate performance parameters under different inflow conditions. The case studies involved axial inflow simulations and cases with inflow of different pitch and yaw angles. The influence of these conditions has been transferred from the intake model to the compressor model and the performance characteristics used to analyse the engine operation under these conditions. Flow control methods have been applied to the system in order to minimise the negative effects of the inflow and improve the flow characteristics at the intake duct. Furthermore, air or power off-takes requested from the engine in order to operate the flow control mechanisms have also been considered. The results showed that the application of flow control introduces improvements throughout the system components. These improvements are sufficient in order to compensate for the air and power off-takes requested by the engine for the use of the flow control mechanisms. Although the results support such a conclusion it is also important to point out that some case studies especially for low distorted flows showed a very small improvement in engine performance which can conclude that flow control may not be as effective when the cost and complexity introduced to the system is considered.