Pressure Recovery Calculation And Analysis Of The System Layout And Efficiency

Based on the 2D, 3D and axisymmetric Navier-Stokes equations using the mass weighted averaging of Favre, a finite volume method, with implicit LU-SGS and explicit 4 step Runge-Kutta iteration procedure is developed. A 2nd order TVD scheme is used in this method to capture the shock more clearly, and two turbulence models is used to solve the complicated supersonic/hypersonic turbulence flow field.In this paper, the flow field of the supersonic diffuser and the subsonic-supersonic ejector is simulated by numerical method. As to the supersonic diffuser, the structure of the shock train, the phenomenon of shock/boundary-layer interaction and the vortex structure in it is studied. Also, the capability of the pressure recovery and the factors affect it of the diffuser is analyzed, the flow field in several typical vaned diffusers are simulated and the results are studied. As to the sub-supersonic ejector, the mixing procedure of the ejecting and ejected gas is simulated, the results of it are analyzed combined the technical design. With computations and analysis, the comprehension on shock/boundary-layer interaction in internal turbulence flow and knowledge about the performance of pressure recovery system are increased, and, some significative results are listed below:First, for the rectangular section diffuser, the aspect ratio of the section affect the length of shock train and the structure of the bifurcated shock. For the convenience of technical design, a combined parameter D using the width and height can be used as characteristic dimension, with it the length of the shock train L can be calculated according to L/D is constant.Second, performance of the diffuser is seriously affected by the arrangement/thickness of the vanes in it, to find out the pressure recovery capability of the diffuser, simulation should be carried out aiming at the arrangement and thickness of the vanes.Third, the mixing flow field in the ejector is most complicated. The ejection efficiency, capability of pressure recovery, and the startup of the total system are effected by several factors. In the technical design, the theory analysis with engineering approximate method should be applied firstly to find the suited flux ratio of the ejecting/ejected gas, the length of the mixing chamber, and, the arrangement/direction of the ejector nozzle. Only after the incipient design project has been established, numerical simulation of the ejector flow field could be used to certificate the design.Last, the oscillation phenomenon of shock train was captured through Runge-Kuttamethod when the free stream mach number is more than 3, the results of it is compared with experimental data and analysis is also given in the last chapter of this paper.