Analysis Of The Influencing Factors On Two-dimensional Hypersonic Inlet Self-starting Characteristics

As one of the most common inlet configurations of airbreathing hypersonic vehicle,two-dimensional inlet has simple geometry and flow field structure. To work in a wide range of Machnumber, fixed-geometry inlet often needs a large internal contraction ratio, which would probablylead to hard self-starting. Researches were taken on the self-starting characteristics in the inlet withlarge internal contraction ratio like X-51A in this thesis, and wish to get the primary factor.First, numerical simulation methods were investigated for the self-starting performance oftwo-dimensional hypersonic inlet. Research indicated that self-starting Mach number kept nodifference by using steady and unsteady calculation methods. Simulation under steady method costless time and memory space. By using RNG k turbulence model, simulating results ofself-starting performance fitted the wind tunnel test better.By means of numerical simulation, changes of separation area were analyzed during theself-starting process. Research showed that due to side-spillage, air flow capture coefficient was lowwhen the inlet unstarted. As incoming Mach number increased, separation area on the topwall wouldmove downstream and stay steadily near the root of the sidewall. From unstart state to start state,performance of the inlet changed continuously, which was quite different from the inlet withswept-back sidewall.The paper focused on the parametric researches carried out by some primary parametersinfluencing the self-starting performance. Side-spillage would reduce self-starting Mach number ofthe inlet with large internal contraction ratio obviously. However, with the area of side-spillagewindow growing to a certain extent, the decreasing trend of self-starting Mach number would be lessevident. With internal contraction ratio increasing under the same internal contraction ratio at the rootof sidewall, self-starting Mach number decreased and then increased. Only by increasing internalcontraction ratio at the root of sidewall, self-starting Mach number increased significantly. As cincreased, self-starting Mach number moved up sharply in the inlet with linear cowl surface. Althoughthe strength of cowl shockwave was stronger in the inlet with little c, self-starting Mach numberwas lower. As to bigger c, using arc surface at the root of second cowl shockwave could reduce theself-starting Mach number obviously.