对置活塞二冲程汽油机动力学特性分析

结合对置活塞二冲程汽油机对置曲柄连杆机构的设计要求,提出了4种布置方案,利用Matlab/Simulink建立了动力学仿真模型,分析了不同方案的动力学特性。结果表明,活塞运动相位差一定时,4种方案的活塞相对运动规律和缸体横向力变化规律相同;随着相位差增大,缸体横向力波动幅值增大,平衡性变差。轴对称布置的对置曲柄连杆机构曲轴旋向相反,对置活塞对缸体的侧压力方向相同;中心对称布置的对置曲柄连杆机构曲轴旋向相同,对置活塞对缸体的侧压力方向相反。轴对称布置的缸体竖直方向合力受相位差的影响极小,约为传统发动机的2倍,相对缸体中心的力矩随相位差的增大其幅值增大;中心对称布置的缸体竖直方向合力随着相位差的增大而增大,且远小于传统发动机,相对缸体中心的力矩受相位差的影响极小。方案3中进排气侧缸体侧压力的方向及变化规律有利于气缸体水平布置的缸套润滑和实现两侧曲轴的同向同步。

Analysis on Dynamics Characteristic of Opposed Piston Two Stroke Gasoline Engine

Four schemes were proposed based on the design requirements of opposed crank and connecting rod mechanism for opposed piston two stoke gasoline engine.Selection of different schemes was completed by kinematics and dynamics model that was established by Matlab/Simulink.For the same piston motion phase difference,the relative movement process of opposed piston and cylinder horizontal force were consistent for four schemes.The increase of phase difference would increase amplitude of cylinder horizontal force which was not beneficial to system balance.For the axisymmetric arrangement scheme,the rotation directions of opposed crankshafts were opposite,but the lateral pressure direction of intake and exhaust piston were same.For the centrosymmetric scheme,the things were just opposite.The phase difference had less effect on the vertical direction force which was twice large as much as the force along the direction of cylinder axis in traditional engine for axisymmetric scheme.With the increase of phase difference,the amplitude of central moment for cylinder also increased.A larger piston moving phase difference increased the vertical direction force which was smaller than the force along the cylinder axis direction for traditional engine for centrosymmetric scheme.The phase difference had less effect on relative central moment.For the third scheme,the lateral pressure direction and change laws of intake and exhaust piston were more suitable to cylinder lubrication and crankshaft synchronization.