Hydraulic exhaust valve actuating system is generally applied on a 2-stroke large diesel engine for the purpose of structural stability and simplification. In this type of system, damping unit has the function of decreasing impact at the moment of valve closing and preventing damage of exhaust valve and valve seat. However, in the opening stage of exhaust valve, existing damping unit substantially increases maximum hydraulic pressure and causes the cavitation inside which lead to vibration, noise, and higher pressure fluctuation and cavitation damage. Design modification of damping unit was performed to solve existing problems. Hydraulic simulation of exhaust valve actuating system was carried out to verify the application possibility of design modification. Also the effect of design modification could be verified by the rig test of prototype. Finally, it was applied on actual engines and proved to give satisfactory results in solving the substantial problems of the existing damping unit.

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