Numerical Simulation Of Underwater Two-phase Ramjet Working Mechanism

With the development of high speed and capability ship and underwater vehicle, the engine technology becomes key factor that determines their performance. The underwater two-phase ramjet can provide higher thrust and efficiency at much more higher velocity by use of ram effect; the ramjet occupies mach more smaller payload and effective space; the cavitation erosion do not mangle the ramjet structure; the capability fitted the complex conditions is very strong. Therefore, the underwater two-phase ramjet technology has attracted extensive attention in recent years.The working mechanism of underwater two-phase ramjet is that when the water flows through the water-inlet, the velocity of the water decreases and the pressure increases; the high pressure gas, which is injected from the gas-injector, mixes with the water in the mixing chamber, and the gas-water mixture forms; the gas-water mixture injects from the nozzle with high velocity, and the ramjet generates the thrust. In this paper, the numerical method is used to investigate the hydrokinetics characteristics of the gas-water mixture flow in underwater two-phase ramjet inner flow field. The relation between inner thrust and efficiency of the underwater two-phase ramjet and the relation parameters are investigated. The valuable results are obtained, which provide technical provision and prophase research production for the underwater two-phase ramjet technology research. The main works are as follows:First, the indetermination and error of the numerical methods are analysed. Based on the homogeneous balance flow theory and the velocity slip between the air and the water is taken into account, the N-S equations and 8 kinds of the RANS turbulence models are used to simulate numerically the gas-water mixture flow of the 2 D axisymmetric underwater two-phase ramjet inner flow field computational model. The simulation results are compared with the experimental results, which validates that the numerical methods are effective. The Realizable k ?? turbulence model is chosen that fits the steady numerical simulation.Secondly, based on the effective Realizable k ?? turbulence model which is validated, the inner flow field of typical underwater two-phase ramjet is studied numerically. The research results show that the air-water mixture flow has an analogy to annular flow. The air forms a gaseous annulus along the inner wall of mixing chamber and nozzle, and the water forms a liquid axis. There is an obvious interface. The distribution of the inner flow field parameters, such as pressure, velocity and gaseous volume fraction, are studied in this paper. The effects of the gaseous parameters, and the flow field parameters on the inner flow field parameters and the thickness of interface are also investigated in the present paper. The natural cavitation at the inlet of ramjet is investigated, and the results show that the natural cavitation disappears when the air is injected into the ramjet.Based on the momentum-flux method, the inner thrust and its dynamic component and static component calculation equations expressed in terms of node parameters are decuced in the paper. The relations between inner thrust, dynamic component and static component and gaseous parameters, flow field parameters and structure parameters of ramjet inner channel are investigated. Based on the direct thrust integration method, the relations between inner thrust and its pressure force and viscous force and relation parameters are obtained.The inner efficiency, propel efficiency and total efficiency calculation equations expressed in terms of node parameters are deduced in the paper. The relations between inner efficiency, propulsive efficiency and total efficiency and gaseous parameters, flow field parameters and structure parameters of ramjet inner channel are analyzed.