旋转对置活塞发动机运动学特性研究

Kinematics Characteristics of Opposed Rotary Piston Engine

高功率密度发动机是未来内燃机的发展趋势.旋转对置活塞发动机结构简单,做功频率是传统往复式活塞发动机的两倍,可以显著提高发动机的理论功率密度,是小型无人机、混合动力系统的理想动力源.文中通过建立数学模型,探究了旋转对置活塞发动机的结构参数对活塞运动规律、气缸容积变化规律和压缩比的影响,分析了相邻活塞运动碰撞的边界条件.研究结果表明,活塞线速度对椭圆齿轮节曲线偏心率的变化最为敏感,当线速度大于平均值时,线速度与偏心率成正比,线速度小于平均值时则成反比;偏心率的增大可以减小气缸的余隙容积,且使下止点对应的气缸容积增大,进而调节发动机的压缩比;活塞端面夹角增大可以减小气缸的余隙容积;偏心率和活塞端面夹角在±10%的范围内变化时,压缩比相应的变化范围分别为5.62~12.04和5.01~23.45,当偏心率过大时将导致相邻活塞发生碰撞.

High power density engine is a development direction of internal combustion engines.Due to its simple structure and twice the power stroke frequency compared with conventional reciprocating piston engines,the opposed rotary piston engine can significantly improve the theoretical power density of an engine,being an ideal power source for small unmanned aerial vehicles and hybrid propulsion systems.In this paper,a mathematical model was developed to investigate the effect of structural parameters of the opposed rotary piston engine on piston motion,cylinder volume variation,and compression ratio.And the boundary conditions,bring the collision between adjacent pistons during their motion,were also analyzed.The results show that the piston linear velocity is the most sensitive element to the eccentricity variation of the elliptical gear pair curve.When the linear velocity exceeds the average value,its variation is direct proportion with eccentricity,and it varies inversely with eccentricity when it is below the average value.Increasing the eccentricity can reduce the clearance volume of the cylinder and increase the cylinder volume corresponding to the bottom dead center,making the compression ratio of the engine be adjusted.Enlarging the angle between the two sides of the piston can reduce the clearance volume of the cylinder.When the eccentricity and the angle between the two sides of the piston vary within a range of−10%and+10%,the corresponding ranges of compression ratio are 5.62~12.04 and 5.01~23.45,respectively.Excessive eccentricity will lead to collisions between adjacent pistons.