Study on Performance Characteristics of Supersonic Inlets with External Disturbance and Angle of Attack

Abstract

This thesis aims to development of anti-buzz system in order to make the engine operation stable. For doing this, the internal flow structures of inlets and performance are necessary to be studied with numerical simulation and 1D performance prediction code. Flow and performance characteristics according to the throttling, angle of attack and external disturbance will be described. At first, the performance parameters are investigated at each flight condition with air disturbance. Engine operation stability is evaluated as analysis of the normal shock position. The maximum performance of a supersonic inlet will be achieved when operating as close as possible to its buzz boundary. In order to maintain high performance without crossing the buzz boundary, an active buzz margin predictor and controller is necessary. The goal of a control system is to acquire inlet buzz margin and maintain it as the designated value and predict inlet buzz before it occurs and then take some measures to buzz mitigation or inlet restart. The inlet buzz boundary and the margin of supersonic intake were first discussed and analyzed in this thesis. Through these results, pitot-tubes adoption is investigated for controlling of the anti-buzz margin. To confirm an unstable operation region, a series of numerical simulations are carried out to analyze a supersonic inlet buzz, an unsteady pressure oscillation phenomenon around a supersonic inlet along the throttling ratio and angle of attack (AOA). A simple but efficient geometry, experimentally adopted by Nagashima, is chosen for the analysis of unsteady flow physics. Among the two sets of simulations considered in this study, the effects of various throttling conditions are firstly examined. The computed flow patterns inside and around the inlet are qualitatively consistent with the experimental observations. Dominant frequency of the inlet buzz increases as throttle area decreases. Secondly, inviscid calculations are performed to examine the effect of angle of attack. It is found that patterns of pressure oscillation histories and distortion due to asymmetric (or three-dimensional) shock structures are substantially affected by angle of attack. Dominant frequency of the inlet buzz, however, does not change noticeably even for a wide range of angle of attack. Accordingly, the design criteria of AOA for the stable flight conditions should be considered.