Analysis and Improvement of the Cabin Low Frequency Noise Caused by Underbody Rear Cavity Airflow Oscillation in the Pure Electric Vehicle High Speed Cruise 2024-01-2350
During the pure electric vehicle high speed cruise driving condition, the unsteady air flow in the chassis cavity is susceptible to self-sustaining oscillations phenomenon. And the aerodynamic oscillation excitation could be coupled with the cabin interior acoustic mode through the body pressure relief vent, the low frequency booming noise may occur and seriously reduces the driving comfort.
This paper systematically introduces the characteristics identification and the troubleshooting process of the low frequency aerodynamic noise case. Firstly, combined with the characteristics of the subjective jury evaluation and objective measurement, the acoustic wind tunnel test restores the cabin booming phenomenon. The specific test procedure is proposed to separate the noise excitation source.
Secondly, according to the road test results, it is inferenced that the formation mechanism of low frequency noise is the self- sustaining oscillation with the underbody shedding vortex feedback enhancement mechanism at the bottom of the rear chassis. The low frequency exterior airflow oscillation is coupled with the interior cabin acoustic modality by the two air relief vents located at the vehicle rear body parts.
Furtherly, the modal coupling mechanism is verified by the volumetric acoustic source excitation test in the semi-anechoic chamber. Considering the engineering feasibility and cost, some improvement schemes are proposed and verified by comparison. Finally, the cover of the vehicle body pressure relief vent is determined to the actual application, the cabin noise level in the specific low frequency band is reduced by 10 dB(A).
This paper provides a guiding reference for solving the similar low frequency noise problem of electric vehicles at the high-speed cruise condition.
