Shi-bin Li

Variation of inlet boundary conditions on the combustion characteristics of a typical cavity-based scramjet combustor

The influences of wall functions, reaction model, and wall Prandtl number on the reacting flow field characteristics of a typical cavity-based scramjet combustor have been investigated numerically, and the computed results have been compared with the available experimental data in the open literature. The computed results are in reasonable agreement with the experimental data, but the pressure downstream of the leading edge of the cavity is overpredicted. Meanwhile, the grid discrepancy has been analyzed by employing three different grid scales, namely the coarse, the moderate, and the refined grids. The obtained results show that the moderate grid may be employed with confidence to compute the reacting flow field of the scramjet combustor. The wall functions, reaction model, and wall Prandtl number have a large impact on the pressure distribution along the floor face of the cavity, and this may be due to the influence of the variance of the flow separation point on the top wall for the different cases investigated with different inlet boundary conditions. The static pressure along the floor face of the cavity decreases with an increase in the wall Prandtl number, and then increases when the wall Prandtl number is large enough, namely 1.2 in the current study. This points out that there exists an optimal wall Prandtl number for the prediction of the reacting flow field of the cavity-based scramjet combustor.

Multiobjective Design Optimization of a Cantilevered Ramp Injector Using the Surrogate-Assisted Evolutionary Algorithm

AbstractThe mixing efficiency of the fuel and the supersonic freestream has a great impact on the operation of the scramjet engine because of the very short residence time. In the current study, the cantilevered ramp injector was used to promote mixing of the fuel and the supersonic flow, and the injector’s configuration was optimized by the surrogate-assisted evolutionary algorithm—namely, the nondominated sorting genetic algorithm coupled with the Kriging surrogate model. In the optimization process, the swept angle, the ramp angle, the compression angle, the length of the step, and the diameter of the injector were considered as the design variables, and the mixing efficiency, the total pressure recovery efficiency, and the drag force were taken as the objective functions. Finally, the Pareto front for the multiobjective design optimization results was obtained, and the relationship between the objective functions was explored. The results show that optimized drag force increases with increased mixing ...

Drag and Heat Reduction Performance for an Equal Polygon Opposing Jet

AbstractAn equal polygon opposing jet can withstand huge wave drag and serious aerodynamic heating in hypersonic flow conditions. The opposing jet is able to change the flow field structure, and then it improves the aerodynamic characteristic of the hypersonic vehicle. In order to get more information about the flow field characteristics of the opposing jet, the schemes with equal polygons for the opposing jet were designed and their properties with different polygons have been investigated numerically in the paper. Also, the numerical method has been validated against the available experimental data in the open literature. The obtained results show that the drag-reduction performance is best when the number of jet angles (N) is 7, and its value reaches 26.4%. At the same time, its wall maximum heat flux is the smallest and the performance for heat protection is the best. Moreover, the maximum heat flux can be decreased by 60.6%. N has a slight influence on the position of the shock wave. When N is big en...

Design and aerodynamic investigation of a parallel vehicle on a wide-speed range

In order to design a hypersonic vehicle for a wide-ranged Mach number, a novel parallel vehicle for a wide-speed range has been proposed. In this paper, we employ a numerical method to investigate a parallel vehicle’s aerodynamic performance and flow field characteristics. The obtained results show that the aerodynamic performance of the novel parallel vehicle is better than that of the waverider designed with a single Mach number for the wide-speed range. With the increase in Mach number, the lift-to-drag ratio of the novel parallel vehicle first increases and then decreases. When the Mach number is 7 and the angle of attack is 3°, the lift-to-drag ratio is the largest, and its value is 3.968. When the angle of attack is 3°, the lift-to-drag ratio is not lower than 3.786 in the range considered in the current study, and the novel parallel vehicle’s aerodynamic performance is good. The wing changes the drag performance of the parallel vehicle remarkably, and results in the decrease of the lift-to-drag ratio. Meanwhile, the wing can enhance the pitching moment performance.