车用柴油机活塞在增压和扩缸条件下的运动轨迹研究

Piston Movement Trajectory Under Conditions of Supercharge and Cylinder Diameter Enlargement

依据实验测得增压前后的燃烧气体压力,采用扩缸前后的不同活塞设计尺寸,根据流体动力润滑与活塞动力学理论建立数学模型,使用Newton-Raphson方法求解动力学模型,使用有限差分法和超松弛迭代法(SOR)求解平均Reynolds方程,研究车用柴油机的活塞运动轨迹和横向运动速度。结果表明:增压与扩缸后,活塞运动轨迹的摆动范围增大,横向运动速度也加大,从而增大了擦缸的可能性,也加剧了活塞对气缸的冲击;增压后活塞与气缸的润滑表面要求润滑油粘性有相应的提高;柴油机的增压与扩缸设计中,同时应当考虑增强气缸壁的抗擦伤能力。

Combustion gas pressures were tested experimentally both before and after supercharge. The designed dimensions of piston were introduced both before and after cylinder diameter enlargement. To find out piston＇s movement trajectory and transversal velocity, an analysis model was established based on hydrodynamic lubrication theory and piston dynamics. Newton-Raphson method was chosen to solve the dynamical equation. Finite difference method and successive over-relaxation method were used to solve average Reynolds equation. The resuits show that the swing range of the piston movement trajectory is enlarged after supercharge and cylinder diameter enlargement, and the transversal velocity is raised. Those factors lead to the increase of the possibility of scuffing cylinder liner and bringing about stronger shock to cylinder. The lubricant viscosity between surface of piston and cylinder liner must be denser to adapt to work condition after the supercharge design. The anti-scuffing function should be enhanced simultaneously in the design of supercharge and cylinder diameter enlargement.