Use of Combined CAE and Experimental Testing Approach for Engine Noise Reduction

The work presented in this paper deals with the use of combined Computer Aided Engineering (CAE) and experimental testing approach for reducing engine noise. The paper describes a systematic approach for giving solutions to the structure borne engine noise related problems. Noise Source Identification (NSI) was carried out on diesel engine to identify noise radiating sources, ranking of noise sources was carried out and contribution of individual engine component in radiated Sound Power Level (SWL) was computed. Detailed Finite Element Model (FEM) of engine assembly was developed and model was correlated in terms of natural frequencies and transfer functions by performing modal testing. Correlated FEM was used for predicting surface vibration velocities under various engine speeds and loading conditions in frequency domain. Velocities so predicted in frequency domain were used as an input for SWL prediction using Boundary Element Method (BEM) approach. Acoustic Transfer Vector (ATV) approach was used for building mathematical relation between Noise source and measurement location i.e. field point. Predicted results and experimentally measured values were found to be in close agreement. Structural modifications viz. ribbing pattern, stiffeners and gusset additions were suggested by taking reference of NSI findings to improve the overall stiffness of the engine assembly. The hybrid approach so used helped in reducing noise level of engine to meet set noise level targets.