Effect of geometric parameters on the drag of the cavity flameholder based on the variance analysis method

Wall cavities have been widely used as flameholders in scramjet engines to prolong the residence time of the fuel and the air in supersonic flow. These devices improve the combustion efficiency of the scramjet combustor, and also impose additional drag on the engine. In this paper, the two-dimensional coupled implicit NS equations, the standard k-epsilon turbulence model and the finite-rate/eddy-dissipation reaction model have been applied to simulate numerically the combustion flow field of a hydrogen-fueled scramjet combustor with a cavity flameholder. The effects of the geometric parameters, i.e. the upstream depth, the ratio of the length to the upstream depth, the ratio of the downstream to the upstream depth and the swept angle, on the drag force of the cavity flameholder for a heated flow are investigated using the variance analysis method. The obtained results show that the variance analysis method can be used to accurately analyze the effects of the geometric parameters on the performance of the cavity flameholder. The effects of the ratios of the length to the upstream depth and of the downstream to the upstream depth on the drag force of the cavity flameholder are substantial, and they must be foremost when considering the design of the cavity flameholder. At the same time, when the downstream depth is equal to the upstream depth, the drag force of the cavity flameholder is the largest, and on increasing the ratio of the length to the upstream depth, the drag force on the cavity flameholder varies from negative to positive. A cavity flameholder with a large ratio of the length to the upstream depth brings large drag force in the combustion flow field. (C) 2011 Elsevier Masson SAS. All rights reserved.