スクラムジェットエンジン用の新たな点火装置の動作解析

抄録

SHSI, Supersonic Hot Streak Ignition, as a new concept of ignition system for supersonic combustion of hydrocarbon fuel in SCRAM jet engine installed on the small size hypersonic vehicle has been proposed. SHSI fuel of slight amount of hydrogen supplied into compressible turbulent boundary layer at forebody of the vehicle fuselage starts exothermic chemical reaction induced by high temperature at viscous sublayer, then during passing through intake and isolator the cold streak of pilot fuel is transformed to the hot streak as heat source for ignition and flame-holding at main combustor. Analytical research have been conducted to examine the potential for practical operation of SHSI. Damkohler number defined by the ratio between characteristic times of chemical reaction and flow is used to assess the possibility of forming of the hot streak, and it is found that the flight condition of Mach number around 5 at the relatively low altitude in the stratosphere is the limit to achieve auto-ignition of the anterior fuel. Also, compound compressible flow analysis based on one-dimensional stream-tube theory is applied to the validation of capability to avoid the fatal risk of engine unstart at the convergent part of intake, and it is confirmed that the biased distribution towards the downstream of heat release by the hot streak is effective to successfully suppress occurrence of the danger compound choking.