Analysis of vibratory response and noise radiation of engine block coupled with the rotating crankshaft and gear train system

This paper presents the theoretical procedure to predict the vibratory response and radiated noise of the engine block coupled with the rotating crankshaft and gear train shafts which drives the fuel injection pump and valve system. The exciting forces acting on the engine block and shaft system are combustion pressure, inertia forces of the moving parts, piston slap forces, fuel injection pressure and valve driving force and torque. Theoretical procedures consist of the following four steps; (1) Dynamic characteristics of the engine block and shafts are determined separately by FEM or experimental modal analysis. (2) Normal mode expansion technique is employed to derive the equation of motion of the total system in which rotating shafts with gear train are combined to the engine block by the oil film and contact stiffness. (3) The time histories of the vibratory response of the engine block and rotating shafts are calculated by the numerical integration technique. (4) Engine noise radiated from the engine block surface is evaluated using the spatially averaged mean squared velocity and acoustic radiation efficiencies of the engine block. This method is applied to estimate the effect of the backlash of the gear train on the engine block vibration and radiated noise.