Effect of Flow Distortions on Pin Fins in the Entry Region of Circular Channels

Abstract

Utilizing heat transfer augmentation features at the inlet of aircraft engines as an additional heat sink requires further understanding of entry region heat transfer and flow field interactions. The effect of asymmetric flow fields or distortions on entry region heat transfer has not been studied. Typically, distortion screens are attached to the inlet of an engine to simulate non-ideal flow that occurs in flight. Because the addition of augmentation features will create a near-wall distortion that can impact downstream aircraft components, comparing entry region features to standard distortion screens can provide insight on the performance impact to aircraft engines. This study investigates the effect of inlet distortion screens on pin fin entry region heat transfer, in order to understand if flow field disturbances disrupt the benefits of augmented entry region heat transfer. In addition, the superposition of the distortion caused by pin fin features onto a screen distorted smooth entry region is also tested. Three distortion screens are investigated with pin fin arrays: tip, hub, and an asymmetric aircraft distortion, each based on SAE standard designs. Reynolds numbers ranging from 1.5 × 105 to 3.50 × 105 are investigated. From this study, inlet heat transfer augmentation due to pin fins is not significantly impacted by inlet distortion flowfields. This is due to the near-wall boundary layer impact of augmentation features overshadowing the effect of distortion. Due to the insensitivity of the near-wall boundary layer for pin fin arrays with distortions, superimposing the smooth entry region distorted flow with the non-distorted pin fin array flow provides an adequate estimate of the flow field of the pin fin array with a distorted inlet.