Abnormal Wear on Piston Top Groove

With the increase of thermal and mechanical loads, some spark ignition (SI) engines may present excessive wear on the piston top groove. The problem was studied first by numerical simulation. Several parameters were found to influence the groove wear. E.g., ring side face roughness and hardness. But the main influence found was the relative attitude between groove flank and ring side face. As the instantaneous attitude varies during the engine cycle, the problem was studied with a commercial ring dynamics computer program and considering thermal and mechanical deformations that occur in the piston during engine operation. The expected groove wear was estimated by the accumulated “wear load” during critical engine operation regimes. Experimental results of engines with groove wear solved by design optimization are shown.