Numerical Simulation And Performance Research Of Flow-Path In A Ram-Rotor

With the development of the modern aircraft engines and gas turbine, high thrust-weight ratio and high power-to-weight ratio are the main directions of the research. For compressor, it needs to have good structure, in addition to excellent aerodynamic performance. As new and well designed structure could not only improve and enhance the aerodynamic performance of the compressor, it will also benefit the compressor with appropriately reducing the number of components, simplifying structure, and diminishing the axial and outside profile size, lightening weight. With all of the structure advantages, the compressor could significantly reduce the total weight of aircraft engine and gas turbine, and thus can effectively improve the thrust-weight ratio and power-to-weight ratio of modern aircraft engines and gas turbines.Ram-rotor based on shock compression technology is a new type of compression system with novel structure. Integrating the shock compression technology used in supersonic intake with the traditional axial and centrifugal compressor design technology, this new system has many advantages, such as high pressure ratio in a single-stage, high compression efficiency, small aerodynamic loss surface, simple structure, short axial length and light weight compared with the conventional compressor. With inherent advantages, the new compression system has wide application prospect in aircraft with steady flying conditions and low mass flow rate required in engines, ship power, vehicle engines and industrial gas turbines. So, there is theoretical significance and application value for us to carry out comprehensive and thorough research on the new compression system. The overall design program of the ram-rotor is investigated firstly in this dissertation. Three kinds of hollow shaft ram-rotor with different disk structure are presented and the overall structure parameters are given out. Then the possible seal leakage and support problems are discussed. According to the given overall structure parameters of the ram-rotor, especially the parameters of the flow-path, a 2D internal-compression supersonic intake is designed, and its flow field and performance are investigated numerically. The height ratio of throat and inlet, the divergent angle of the diffuser, back pressure and Mach number of the incoming flow are considered seriously. As the height ratio of throat and inlet increases, the total pressure recovery coefficient increases firstly and then decreases. Appropriate divergent angle can improve the total pressure recovery coefficient. Back pressure has a significant influence on the performance and aerodynamic parameters distribution at outlet. The increasing of the incoming flow Mach number will decrease the total pressure recovery coefficient.On the basis of the design and numerical research on the 2D internal- compression supersonic intake, 2D flow-paths of the ram-rotor are designed according to the design method of the supersonic intake. The influences of compression ramp shape, length-height-ratio of the throat, rotational speed and back pressure on shock structure, flow characteristics and performance are well studied. On the conditions appointed in this dissertation, the flow-path with convex curve compression ramp has the best overall performance, and the performance of the flow-paths with linear compression ramp and parabola compression ramp are secondary and worst respectively.Referring to the 2D flow-path with convex curve compression ramp, a 3D flow-path of the ram-rotor is designed using parametric cylindrical spiral equation and CAD software. Then 3D numerical simulation is adopted to study the flow field and performance of the ram-rotor at design point and off-design points. With the rotational speed increasing, the total pressure ratio of the ram-rotor rises, but the adiabatic efficiency decreases. When back pressure increases, the total pressure ratio rises, the adiabatic efficiency increases firstly, then decreases. Compared with the conventional axial compressor, the performance curves of the ram-rotor are vertical to the axis of mass flow rate. In order to improve the total performance, it needs not only make a compromise between the total pressure ratio and the adiabatic efficiency appropriately, but also optimize the shock structure and the 3D structure of the flow-path, and these will also give benefit to reducing the absolute speed at outlet.At the end of this dissertation, the starting problem and prospect of the ram-rotor are discussed.