Abstract
Main causes of engine noise level and sound quality are piston slap, main bearing impact force, gear impact force, fuel injection pressure and valve train opening and closing force. This paper presents the theoretical procedure to predict the vibratory response and radiated noise of the engine block considering the dynamic effect of motion and impact vibration of components of internal combustion engine. Engine noise radiated from the engine block surface is evaluated using the acoustic radiation efficiency determined by Boundary Element Method and spatially averaged mean squared velocity of the engine surface. These method enables us to predict the engine noise in the early design stage. In this study, engine structure consists of piston, connecting rod, crankshaft, gear train shaft and engine block. Equation of motion of each structure is derived taking into account the inertia forces induced by vibration and constrained motion, external force, restoring force and reaction force at the connecting point. Modal analysis technique is employed to describe the equation of motion of each structure in the stationary and rotating coordinate and time history of vibration response is obtained by numerical integration technique. This method is applied to evaluate the vibratory response and radiated noise of actual diesel engine and its applicability is confirmed.
