Numerical Study On Influencing Factors Of Self-Starting Processes Of Hypersonic Inlet

In order to explore the factors affecting the self-starting performance of hypersonic inlets and establish the predicting method for the self-starting performance of hypersonic inlets,the accelerating self-starting process of two-dimensional hypersonic inlets have been studied by using numerical simulation method,and the key factors determining the starting performance of the inlet are further explored by changing the incoming boundary layer thickness.Firstly,in order to explore the influence of geometrical shape of internal compression section on the self-starting performance of hypersonic inlets,aerodynamic design of internal contraction section of two-dimensional hypersonic inlets with different initial compression angles of the cowl and different transition radius of the upper turning surface were carried out.The self-starting process of each case has been simulated.The effects of the transition radius on the self-starting performance of the inlet were compared,and the mechanism of the influence of the internal contraction section was also analyzed.The results show that the change of the radius of the upper turning surface of the internal contraction section has a certain effect on the self-starting performance of the inlet,and the improvement of the self-starting performance of the inlet increases with the decrease of the initial compression angle of the cowl in the situation of the same internal contraction ratio;the change of the compression strength around the primary separation bubble caused by the change of the upper turning surface of the internal contraction section is one important reason which causes the differences in self-starting performance.Then,the influence of incoming boundary layer thickness on the self-starting performance of hypersonic inlets have been explored by setting the thickness of boundary layer.The numerical simulation of flow field accelerating self-starting process of a simplified two-dimensional hypersonic inlet with different boundary layer thickness have been carried out.The variation trends of self-starting performance of the inlet,the primary separation bubble height,the compression strength across the primary separation bubble and viscous factor with different boundary layer thickness were studied.The results show that the momentum deficit thickness and dimensionless pressure rise of the boundary layer together have great influence on the self-starting performance of the inlet.With the increase of Mach number,the decrease of momentum loss thickness accelerates the inlet start eventually.