Slosh, a phenomenon occurring in a vehicle's tank during movement, significantly contributes to noise and vibration, often exceeding idle levels. Existing methods for evaluating NVH performance of fuel tanks primarily rely on subjective assessment, highlighting the need for a quantifiable approach to address this dynamic noise. This paper introduces a hybrid methodology to standardize the slosh phenomenon by establishing vehicle-level acceleration, braking, and driving profiles. Noise and vibration data capture, combined with defined boundary conditions, categorizes slosh noise into Impact and Roll noise, differentiated by distinct driving profiles and frequency content.
Vehicle level performance is then cascaded down to subsystem level. A dedicated test rig is designed that replicates these conditions at the subsystem level where vehicle speed and braking profiles are translated into rig-specific acceleration and deceleration profiles, enabling consistent data capture for correlation with vehicle-level results. Computational Fluid Dynamics (CFD) analysis utilizes these boundary conditions and profiles to predict forces on the fuel tank walls and identifying partial shortcomings, with forces directly correlating to noise levels.
The relationship between forces and noise supports design changes for existing fuel tanks, such as optimizing baffle designs. Several baffle designs were analyzed in CFD for their effectiveness during Impact and Roll events. The optimal design resulted in significant decrease in slosh noise and achieving acceptable cabin comfort levels. Additionally, this methodology facilitated the creation of design rules and target setting for NVH performance.
Insights gained from this study were applied to design new fuel tanks for subsequent programs, setting a new benchmark in the segment for reduced slosh noise. This not only improved occupant comfort but also reduced Direct Material Costs (DMC) by eliminating the need for additional baffles. The methodology presented in this paper offers a valuable tool for future vehicle development.