Reverse Design Of The Rotor And Study Of Flow CFD In Variable Geometry Turbocharger Of Vehicle

The turbocharger is one of the most efficient methods to improve the performance of vehicle engine. The conventional turbocharged engine has some defects, such as poor performance at low speed, the lag in instantaneous response, performance of over-pressure and excessive speed at high speed, etc. Variable geometry turbocharger can effectively solve these problems. The VGT is an ordinary equipment installed international advanced engine, but the domestic research of VGT is late, and the technology of VGT lags behind the foreign level, therefore it is necessary to master the technology as soon as possible. This article is about reverse design of rotor and the research of flow field based on a particular model of the VGT.Aim at the geometric characteristics of a type rotor model of the VGT,which is consist of turbine and compressor impeller, the method of reverse engineering of the rotor is used in reverse designing, The point cloud data of rotor is got by using non-contact 3D scanner with structured light, and curves and surfaces are remodeled in the CAD software. The geometry and accurate dimension of external profile of rotor blade are obtained with 2D projector. The obtained data are matched with the blade surface model, and the blade profile is trimmed, then the whole reconstruction rotor model is established with CAD software.Analysis of static strength of the turbine and impeller model and optimize the impeller, in order to ensure the strength performance of the digital the turbine and impeller model to meet the strength requirement. Analysis of the vibration modes and natural frequencies of each blade, in order to guarantee blade vibration meet the design requirement.The flow CFD of a type of nozzle structure of the VGT is researched. Create three-dimensional flow field modeling in the minimum and maximum opening, use Fluent software to analyze the CFD flow field. Through compare the flow field between the non-nozzle turbocharger and the nozzle turbocharger to conclude that the type of nozzle vanes guide the gas to expand power and change better the state of the gas at turbine inlet, velocity of gas is raised by 31%; Through analysis of the turbocharger internal flow field including pressure% temperature and velocity distribution in the variable nozzle vane ring opening in the minimum and maximum velocity points. According to the simulation results, the gas flow is instability through the low-speed vane in nozzle ring area in minimum velocity point, flow field change significantly, the expansion ratio is great, conversion of energy is fiercely, isentropic efficiency of turbine is 0.703, turbine have a good efficiency; the gas flow has small change through the high-speed vane in nozzle ring area in maximum velocity point, flow energy is abundant, energy conversion is not obvious, isentropic efficiency of turbine is 0.425, to avoid phenomenon of excessive speed of turbine in high velocity point; according to CFD numerical simulation, render angle of imported air attack in the turbine inlet, and study of gas flow in the turbine inlet, it turn out:the gas intake has a reasonable angle of attack in the minimum opening, and gas flow is suitable,so efficiency of turbine is better; the gas intake has a bigger angle of attack in the maximum opening. Flow separation phenomenon happens, so that the efficiency of turbine reduced.