Dynamic Simulation Of Variable Compression Ratio Mechanism Of High Power Engine

Variable compression ratio technology is one of the energy-saving technologies of automobile engine.It can realize the continuous change of compression ratio of engine under different loads,give full play to the potential of engine,and make the engine in a high efficiency state in the whole operation condition.The variable compression ratio engine has good fuel adaptability,which can improve the thermal efficiency of the engine,reduce the emission of pollutants and improve the comprehensive performance of the engine.In this paper,a new type of variable compression ratio mechanism is designed,which is based on the traditional engine crank and connecting rod mechanism,adding rack and pinion transmission device and hydraulic mechanism with control,changing the position of the supporting point in the control part to change the stroke of the piston in the cylinder,and realizing the function that the compression ratio of the engine changes continuously between 15-19.The variable compression ratio mechanism has the same structure size and quality as the traditional engine,which meets the function realization and stable work.In order to analyze the rationality of the variable compression ratio mechanism design and ensure the reliable operation of the variable compression ratio mechanism engine,the kinematic analysis,dynamic calculation and force analysis are carried out.The results lay the foundation for the simulation analysis in the following paper.Using AVL cruise software to build the whole vehicle model and analyze the performance of the engine under different compression ratio,the results show that improving the compression ratio can improve the power and economy of the engine.Using CATIA and Solid Works software to carry out the three-dimensional modeling and assembly of the variable compression ratio mechanism,and importing the model into ADAMS software,applying constraints and driving,verifying the motion relationship of the model,and obtaining the information of the speed,displacement curve of different parts of the variable compression ratio mechanism.After that,the dynamic simulation of the variable compression ratio mechanism is carried out by using ANSYS software,and the mechanical stress nephogram and thermal stress coupling nephogram of the components in the actual working process are obtained.The simulation results are in line with the reality.Finally,the dynamic characteristics of the crankshaft under different working conditions are simulated,and the modal analysis results of the crankshaft under free state and constraint state are obtained,and the modal frequencies and corresponding modal shapes are obtained.Among them,the constrained modal analysis considers the influence of the crankshaft in two aspects of different compression ratio and rotation speed.The compression ratio of 17 and 19 are selectedfor the modal analysis under different rotation speed.It can be seen from the results that the lowest modal frequency is higher than the engine frequency at rated speed,which can avoid resonance.In addition,the deformation of crankshaft journal is large,and it is easy to break and fatigue damage in the process of actual work,so it provides a basis for further dynamic analysis and optimization of designers.There are 66 figures,8 tables and 68 references in this paper.