• International Journal of Automotive Technology
• /
• v.5 no.1
• /
• pp.23-31
• /
• 2004

Secondary movements of piston in the bore clearance are closely related to the side impact to the engine block as well as many tribological problems. Some of the major parameters that influence these kinds of movements are piston profile shapes (barrel and flat), piston pin offsets and the magnitudes of bore clearances. In our study, computational investigations are performed about the piston movements in the bore clearance by changing the skirt profiles and piston offsets. In this work, it is found that curved profile and larger offset magnitude to thrust side provide better performance that has low side impact during the engine cycle.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.12 no.3
• /
• pp.59-65
• /
• 2004

In this paper a numerical study was performed for the effect of the wall curvature on the behaviors of fuel sprays impinging on the concave Surface. Actually, in the real diesel engines, a piston head has a curved shape for the purpose of the controlling the movement of fuel droplets and the mixture formation. For past decades, although many experimental and numerical works had been performed on the spray/wall impingement phenomena, the curvature effect of impinged wall was rarely investigated. The wall curvature affects on the behaviors of the secondary droplets generated by impingement and the concave wall obstructs the droplets to advance from the impinging site to outward. In present study, the simulation code was validated for the flat surface case and three cases of the different curvature were calculated and compared with the flat surface case for several parameters, such as the spray radius, the spray height and the position of vortex center of gas phase. The simulation results showed that the radial advance of the wall spray and the vortex is decreased with increasing the curvature. It was concluded that the curvature of the impinged wall significantly affects the behaviors of both the gas-phase and the droplet-phase.