Generally three cylinder engines due to less reciprocating masses are said to be more fuel efficient. Nevertheless, NVH problems caused by inherent imbalance forces and couples remain as draw back. NVH refinement levels can be improved by stiffening of the engine structure, material change, optimal design of the crank train, control of cylinder to cylinder pressure variation, etc.
The objective of this study is to reduce the radiated noise of diesel engine by 2-3 dB (A) in the frequency range up to 4 kHz. Simulation and test based approach was demonstrated for reducing radiated engine noise. The NVH performance of the baseline engine has been evaluated using CAE simulation tools. Radiated noise from the critical components like oil sump, crank pulley and timing cover has been predicted and the critical modes having severe effect on radiated noise levels of the engine has been identified. A series of DOE were carried out and parameters like Stiffness, material change, ribbing patterns, Shape of the components was modified to shift natural frequencies of the components to reduce the sound radiation. The modifications which are feasible from manufacturing point of view have been considered and analysed. The hybrid approach used has helped in reducing noise level with minimum increase in weight of the engine by simulation. Prototypes have correlated well with simulation results and achieved the target.