Study On Flow Characteristics Of Cavity In A Scramjet Combustor

The scramjet is a new type of air-breathing propulsion device, which has remarkable performance and great potential superiority, and has a good prospect in the field of military aviation in the future. A number of experimental, theoretical and computational studies have been conducted to explore the Scramjet techniques in the past decades.Fuel injection, mixing enhancement, and flame holding are fundamental aspects of supersonic combustion, and critical to the development of a hypersonic air breathing propulsion engine. To achieve efficient combustion within a manageable length, a successful fuel injection scheme must provide rapid mixing and stable combustion between the fuel and airstreams. At the same time, the introduction of fuel into the combustor must be carried out in such a way that the air stream suffers acceptable total pressure losses.During the last few years, cavities have gained the attention of the scramjet community as a promising flame holding device, owing to the results obtained in flight tests and feasibility demonstrations in laboratory scale supersonic combustors.In this paper, the flow field characteristics of cavities and research efforts related to cavities employed in low and high speed flows are summarized. Open questions impacting the effectiveness of the cavities as flame holders in supersonic combustors are discussed.Firstly, the methods of supersonic flow field numerical simulation about cavity are discussed in this paper. Secondly, the flow field properties of various cavity geometric features are computationally evaluated under Mach 3 flow conditions. Thirdly, the computational study of ethylene fueled scramjet combustor employing cavity flame holder has been performed. The results of calculation show that the flame holding range of supersonic combustor can be enlarged and the combustion efficiency is improved by using cavities. Such information contributes to further understanding the flow field of hydrogen and hydrocarbon supersonic combustion, and is valuable for designing a high performance cavity flame holder in scramjet.