Effect of Sides-Spillage from Airframe on Scramjet Engine Performance

Abstract

Pre-compression by the windward surface of the aerospace plane is necessary for scramjet operation. However, this pre-compression causes spillage from the high-pressure windward surface toward the sides of the plane. In order to examine the effects of this side-spillage, the performance of a scramjet engine was evaluated using a 1-D flow model, and payload to the low earth orbit estimated using an aerospace plane flight simulation. Prior to the simulation, tests with scramjet inlet models were conducted in a Mach 4 wind tunnel to identify the primary features of the side-spillage to assist in the simulation. The models were inclined from the flow direction to simulate the skewed flow near the side of the plane during side-spillage, and the experiments proved that the aerodynamic performance of the inlet was not affected by the inclination for the entrance Mach number given to the models. However, the mass capture ratio decreased due to reduction in the density of airflow as a result of the expansion. In the numerical estimate, sidespillage was modeled not to reduce the performance of the inlet, but to reduce mass flow to the inlet. The resulting decrease in airflow delivered to the engine due to spillage reduced thrust by 15%, while the corresponding payload decreased around 60%. Side fences were effective in preventing spillage.

Evaluation of side spillage for a hypersonic air intake using computational fluid dynamic techniques

“…Provision of fences or walls in the sides of a nonaxisymmetric intake is suggested and used by many researchers 15,16 to reduce the amount of side spillage. In the present case also a side fence is provided stretching from the nose of the intake to the engine cowl lip.…”

“…However, these studies are carried out by considering two-dimensional (2D) domains without addressing the issue of side spillage. Only a few studies [13][14][15][16] are carried out to analyse the phenomenon of side spillage. A combined experimental and CFD study carried out by Nguyen et al 13 has shown a less than 4% difference for mass capture ratios predicted by CFD and those obtained experimentally.…”

“…15 It is shown that the mass spillage for the intake with side walls is around 21% while that for without side wall is 44%. Tani et al 16 have carried out experimental and numerical studies for the effect of side spillage on the performance of a scramjet powered vehicle which shows a 15% reduction of thrust occurs with side spillage as compared with a model having side walls. For the mission considered in these studies, there is a 60% reduction in the payload value due to thrust reduction caused by side spillage.…”

Shock tunnel studies on cowl/ramp shock interactions in a generic scramjet inlet

“…Mrozinski and Hayes examined a variablegeometry inlet design consisting of a cowl and a sidewall with a gap in the cowl-sidewall interface [2]. Tani et al [3] conducted their experiments in a Mach 4 wind tunnel to investigate the effect of inclination of airflow due to side spillage on inlet performance with the variable geometry inlet model, achieved by exchangeable ramp blocks. Bedarev et al [4] studied a geometry variation, i.e.…”

Effect of Integration of Scramjet into Airframe on Engine Performance and Payload

“…The air entering the engine passed a planar shock wave generated by the forebody, which was calculated with the 2D oblique shock wave relations. The end effect at both sides of the forebody 16) was neglected for the sake of simplicity. In the calculation of the engine performance, the angle of attack, i.e., the angle between the free-stream direction and airframe axis, was fixed to be 3 degrees.…”