NVH Improvement in D4/D6 Marine Diesel Engines: Design Change Proposals to reduce Noise and Vibrations in the D4 and D6 engines

Abstract

Noise, Vibration and Harshness (NVH) in marine diesel engines has gained recent attention, and many outboard competitors have shown significant improvements in this area. Optimal NVH standards ensure enhanced performance, environmental sustainability, and passenger comfort. This thesis aims to comprehensively investigate the NVH sources, their characteristics, and mitigation strategies in Volvo Penta’s D4 and D6 marine diesel engines. The research methodology adopts a multi-faceted approach, addressing various sources of noise. Through an extensive literature review and the development of a noise source separation algorithm, key factors influencing engine NVH and exhaust noise generation were identified. This is complemented by an in-depth user and stakeholder study, which includes numerous interviews and focus group responses. The outcome of this research laid the groundwork for proposing effective requirements and functions for NVH reduction. Several concepts were synthesized and compared. The most promising solution is further developed and simulated for acoustics and vibro-acoustics. The implications of these findings are profound, as reducing engine NVH and exhaust noise emissions not only enhances passenger comfort but also complies with strict regulatory requirements regarding noise pollution and emission standards in maritime environments.