Noise Reduction Potential of an Engine Oil Pan

Abstract

Considering automobiles with internal combustion engines, the power train represents one of the main noise sources, especially during idling and slow driving speeds. One major contributor to the overall power train noise emission is the engine oil pan. The objective of this paper is to evaluate the noise reduction potential of an oil pan with a combined use of passive and active methods. The passive approach is best suited for a frequency range above 1,000 Hz and is implemented in this study using different substitute materials. Active noise control techniques are efficient in a frequency range below 1,000 Hz. In the present study piezoceramic patches are used as actuators as well as sensors. By means of FE simulations a smart system is designed to reduce passively and actively the structural vibrations and consequently the resulting sound radiation. Therefore, optimal locations of piezoelectric actuators are computed. A control algorithm with respect to a collocated design is used to obtain high active damping effects. With control, attenuations up to 15 dB in vibration level are achieved at the resonance frequency regions of the most dominant modes of the oil pans in laboratory. It is shown that significant reductions up to 4 dB are achieved on the engine test bench in a frequency range up to 1,000 Hz and at engine speeds below 2,000 rpm, where a multi-discrete excitation characteristic exists. Due to the use of a low-mass plastic oil pan, improvements at several engine operating points are measurable. Drawbacks of this material substitution are the higher temperature dependency and the lower electromechanical coupling of the piezoelectric patches due to the elasticity of the plastic ground material. An oil pan made of sheet steel has shown the worst acoustical properties.