NVH benefit of the Frunk 2019-01-1456

Due to the increasing number of battery electric vehicles (BEVs), the engineering fields regarding driving comfort and NVH issues are becoming more and more challenging: many new factors affect the development of BEVs NVH package. The noise sources related to the powertrain are different from the traditional ones of internal combustion engines, for instance due to the presence of tonal components, strong harmonics and potential whining noise. To satisfy NVH specifications and the need for lightweight solutions to increase driving range, it is important to mask as much as possible the noise coming from the engine bay with materials both lightweight and acoustically performing. Moreover, for electric vehicles new interesting solutions are possible with the introduction of new components, that do not find room under the hood of ICE or hybrid vehicles. These components, if properly designed, could lead to non-negligible NVH benefits. The present paper reports the NVH effects of one of these new components, the frunk, a small compartment inside the engine bay, functionally similar to the trunk. In this paper, the design-by-simulation of a frunk is described. By means of simulation both acoustic and mechanical requirements are analysed. First, FE mechanical simulations are used to ensure that the right design to satisfy static and dynamic load conditions with a lightweight material is found. After this, the potential NVH benefits of adopting -for the frunk- a porous textile material in comparison to a glass-fiber reinforced plastic are assessed. Focus is also put on the possibility to reduce traditional engine bay treatments when an acoustic frunk is adopted. The model used in NVH simulations is a simplified engine bay mock-up, in which a simplified frunk was inserted. An acoustic point source excitation was placed where an e-motor is normally mounted. The effects of the frunk were judged simulating acoustic transfer functions (ATFs) in several positions, corresponding to microphones placed inside and outside the engine bay cavity.