Investigation Of Mixing-Enhanced Mechanism Of Fuel Injection On The Shcramjet

This research concentrates on the Cantilevered ramp injector. Using a combination of theoretical analyse, numerical simulation and experimental investigation, the flowfield structure downstream of the Cantilevered ramp, fuel/air mixing properties and the effects of injector design and fuel injection parameters on fuel/air mixing performance are investigated systematically.The design technique, work properties and constitutes of the direct-connect supersonic wind tunnel are presented in detail. Based on the software of Fluent, we found the supersonic numerical simulation program by selecting the appropriate physical model and numerical method. According to the ramp injector non-reacting test case, the applicability and correctness of the numerical simulation program is validated. Finally, technology of the optics observation concerning the flowfield is introduced.In the research of flowfield structure on the pre-injected and after-injected of the Cantilevered ramp injector using the schlieren and numerical simulations, wave structures of different configurations are obtained. Compared the experimental pressure data with the numerical simulation results, the numerical method has been proved right. Oblique shock waves formed by the ramp behave strong three-dimensional effect. Besides, the injection of the fuel may largen the shock angle.Using PLIF imaging of the acetone and numerical simulation, we researched the fuel/air mixing and flow properties downstream of the Cantilevered ramp injector. The obtained results show that the mixing process of the fuel/air can complete in a short distance and the penetration of the fuel goes through a decline-raise course. The total pressure loss of the triangle is smaller than other models. And the cross section shape of the configuration has a powerful effect on the mixing action of the fuel/air. The higher mach number of the fuel exit will worsen the mixing process in the flowfield, which has no influence on the total pressure loss. On the contrary, the lower exit mach number of the fuel will decrease the penetration and distribution of the fuel. Additionally, the smaller spout is propitious to quicken the mixing process, but it will minish the fuel separation. Otherwise, it makes no difference on the mass fraction center and penetration of the fuel. Then, the fuel injection represents intensively non-constant characteristic in the flowfield.In the research of fuel/air mixing properties downstream of the Cantilevered ramp injector in the hypersonic flowfield, the influence on the fuel/air mixing characteristic of the injector design and injection parameters is analysed. With the decreasing of the compression angle, the total pressure loss will lessen and the distribution area of the fuel may become bigger. Increasing the expansion angle will increase the mixing efficiency and the total pressure loss of the fuel, but at the same time, the separation and the penetration will decrease in the flowfield. The sweep angle affects the mixing process slightly at the forepart, and then, it will change the fuel distribution shape downstream. The positive sweep angle will make extra total pressure loss, but the negative one shows the opposite situation.