Study On Dynamics Simulation And Optimization Of Turbocharger Rotor System

Turbocharger is one of the core components to improve engine performance.The principle is to use the exhaust gas as the power source to drive the impeller coaxial with the turbine to rotate at high speed,so as to compress the external air to produce pressure difference and make it continuously enter the cylinder to improve the power of the engine.In this paper,the rotor system dynamic characteristics,internal flow field simulation and structural statics analysis of JP80 D turbocharger are carried out to solve the problem of low efficiency caused by the unbalance fault of the turbocharger rotor system under the action of base excitation and imbalance.The analysis results are compared to provide a method to avoid unbalanced fault under the action of basic excitation and unbalance.The complete turbocharger(such as compressor,intermediate,rotor system,turbine)is modeled by 3D modeling software.Then,the general mathematical model of rotor system with basic excitation is derived,including the theoretical formula of step shaft mass concentration and simplified bearing formula.Then,the modal and critical speed were analyzed and solved.It is concluded that the second-order critical speed of the rotor system will produce resonance hazards in the range of the system operating speed.Aiming at the resonance hazard,the rotor structure was optimized away from the critical speed.Three parameters of the impeller,namely,the combination of long and short blades,the thickness of blades and the tilt Angle of blades,were optimized by a single variable progressive optimization method.Finite element simulation was carried out on the compressor,and the optimal combination was obtained by comparing the distribution of flow field characteristics in the compressor.After modal analysis and critical speed solution,the critical speed changes before and after optimization were analyzed.Static simulation of the optimized impeller was carried out to study the optimized structural performance.By comparing and analyzing the stress and strain,natural mode,natural frequency,stiffness,life and moment of inertia of the impeller before and after optimization,it is concluded that the rotor system after optimization is not only much higher in strength and stiffness requirements than before optimization,but also has higher life than before optimization.This greatly improves the unbalance performance of the turbocharger rotor and can avoid the problem of unbalance fault under the action of base excitation and unbalance.