Effect of Differential Sweep on a Three-Dimensional Sidewall-Type Intake at Mach 3.5

Abstract

An experimental study was carried out to understand the effect of the leading edge sweep for a three dimensional sidewall type compression intake in a Mach 3.5 flow. In order to reduce the mass spillage two different cowl plate was extended from the isolator (at 1.86 h and 0.42 h). The result shows minimum cowl length has better intake performance characteristics. The change in flow angle brought by 30° and 45° backward sweep(BS) in leading edge relative to the unsweep case showed a 4% reduction in mass flow capture ratio(MFC). Wherein by having forward sweep (FS) at 30° and 45° the MFC increased by 14% and 3%. The variation in sweep angle itself shows improvement on pressure recovery for both forward and backward sweep. For the various sweep combinations tested the differential sweep configuration 45°B-30°F seems to be optimal in terms of pressure recovery (10% relative to no sweep case) and improved MFC of 8.3%. INTRODUCTION For developing future hypersonic space transportation, air-breathing propulsion using scramjet engine is one of the key technologies. The inlet particularly is of great importance for the efficient operation of such propulsion system. The efficient design of intake greatly depends on the amount of mass flow captured (MFC) and the level of pressure recovery achieved. Most of the earlier research (1, 2) was focused on a two dimensional air intake which utilize vehicle nose generated shock wave for pre-compression. Although such intakes provide better aerodynamic characters at higher operational Mach number regime they induce severe performance penalties at low flight Mach numbers. It is primarily found to be caused due to the lack in mass handling capacity at off design conditions of such two dimensional type intakes leading to unwanted phenomenon like buzzing and unstart of intake. Such disadvantages made researchers (3-5) to look into three dimensional intakes as in figure 1 which provide stable operation in the entire Mach number regimes with the compromise in efficiency interms of MFC and pressure recovery.