Thermoacoustic Flow Instability in a Scramjet Combustor

Abstract

*† ‡ § ¶ This paper deals with the thermoacoustic instability and ensuing flow oscillation in a scramjet engine, a phenomenon commonly known as combustion instability. The analysis is based on a quasi-one-dimensional treatment of unsteady flow motion, which simulates the main features of the oscillatory flowfields in both the isolator and combustor. The model also accommodates the response of local heat release to acoustic excitation. The calculated oscillation frequency agrees well with the measured values of around 350 Hz. A companion analytical analysis is also established to help explore the underlying mechanisms responsible for driving and sustaining thermoacoustic flow instabilities. In particular, the interactions between the unsteady heat release, fuel injection and mixing, and shock response are examined. Their influence on the acoustic oscillation characteristics is identified.