Effect of Resonator Location on Resonator Effectiveness Using NASTRAN Mode Shape Prediction Analysis and LAMPS Acoustic Model

This paper describes a CAE methodology for optimizing the performance of induction system resonators on the basis of their location within the standing wave modes of the system. An acoustic modal analysis utility of NASTRAN [2], and a duct system acoustics model, LAMPS [1], are used interactively to determine resonator location and resonator size requirement. The NASTRAN code predicts the standing wave mode shapes for the resonant frequencies of the induction system which includes the air inlet system and the intake manifold. Resonator location is determined on the basis of the pressure anti-nodal points of the mode shapes. Maximum attenuation is achieved at or near the anti-nodal points and minimal attenuation at the nodal points. The LAMPS code is used to predict the acoustic response characteristics of the system with and without resonators. Induction noise measurements made on an operating engine agree fairly well with the computer predicted results.