Numerical Study of Scram Accelerator Starting Characteristics

Abstract

A numerical study is carried out to investigate the ignition and the detonation initiation process in a scram accelerator operating at a superdetonative mode. To simulate the scram accelerator launching process, a conical projectile is considered, injected with an initial velocity of 2500 m/s from the 1 atm air into a 25 atm 2H 2 + O 2 + mN 2 mixture. As a dilution gas, nitrogen is selected and assumed to be inert. The time accurate solutions of Reynolds averaged Navier-Stokes equations for chemically reacting flows are obtained by using a point-implicit method and an upwind-biased third-order scheme with a steady-state solution for airflow as an initial condition. To examine combustion characteristics and ram-accelerator operation limits, mixture compositions are varied from 2H 2 + O 2 + 3.76N 2 to 2H 2 + O 2 + 9N 2 by changing the amount of N 2 . The flowfield results show the detailed ignition mechanism, the initiation process of the oblique detonation, and the staring characteristics of the scram accelerator. The results also identify clearly the combustion characteristics of the operational failures at lower and upper dilution limits that have been observed in experiments