The Role of Fuel Flammability on Shock Dynamics in Supersonic Combustion

Better understanding of unstart in scramjets is sought in this study, with motivations coming from several engine failures attributable to this phenomenon. Many studies have reported on the dynamics and control of the associated shock train. However, these studies are based on artificially blocking the flow downstream of the combustor to induce mechanical backpressure as a surrogate for the dynamics in the real, reactive system. Addressing the real system is needed, which is the objective of the present work, especially as it relates to the flammability of different fuels. Reactive calculations using hydrogen, ethylene, and methane [1, 2] are carried out for the purpose of determining the roles played by fuel flammability on shock dynamics in supersonic combustion, and the implication for the performance of the dual-mode scramjet engine. Keeping the injection conditions of the fuels similar, it has been observed in this study that only hydrogen exhibits the shock dynamics phenomenon for the parameters used. Moreover, under pure mixing conditions in the same scramjet model, hydrogen does not exhibit this behavior.

[1] Ladeinde, F. AIAA Paper 2009-127, doi: 10.2514/6.2009-127.

[2] Ladeinde, F. & Lou, Z. Journal of Propulsion and Power, 34(3), 2018, pp. 750-762.