Modeling of Micro-Perforated Heat Baffle 2019-01-1582

Classical porous materials are used throughout the automobile with usually good success but there are limitations to their performance in areas where there are adverse environments. An example of this is the transmission tunnel section under the automobile, where there exist high air flow velocities and temperatures which will lead to quick deterioration of the material. Micro-Perforated Heat Baffles (MPHB) are showing success in the heating, ventilating, and air conditioning industry, and therefore there is an effort in applying MPHB extensively in the automotive field. The question with regards to which micro-perforation pattern gives the best performance plus where and how much should be allocated in the automobile still remains. This paper shows how to address these issues by applying Hybrid Statistical Energy Analysis (HSEA) technology. An expression for the Absorption Coefficient (AC) which incorporates the micro-perforation pattern is explained. This equation models the absorption of sound due to friction losses in the holes. Thereafter calculations for flat sample AC are completed and good correlation with experimental data is shown. Flat sample AC is necessary to know but by itself it does not answer the important question whether SPL suppression is being realized on a real car and how this is addressed without building multiple prototypes. Thus, the paper emphasizes the importance of having a HSEA model and how with this model an noise and vibration specialist can run multiple MPHB concepts. This paper shows this capability by applying MPHB to cover the transmission tunnel under the automobile and the calculated SPL under different input modes such as road noise and engine noise.