NVH and modal analysis of thermal-acoustical protective shields

The exhaust manifold heat shield is made of different material layers and is bolted to the engine exhaust manifold. The exhaust manifold heat shield has been identified as a potential major noise contributor among the engine components during normal operation, which is to protect nearby components from damage due to high heat. To reduce the noise radiated from the exhaust system, a thermal acoustic protective shield (TAPS) has been developed to act as a partial acoustic enclosure. This paper will discuss the importance of controlling NVH and what can be done design-wise to improve the TAPS characteristics. The paper discusses the impact of damping and vibration, how they are modeled. Further the present study analyzes the radiated sound pressure level (SPL) of a thermal acoustic protective shield by using the finite element analysis (FEA). The analyses are performed using the fully coupled structural-acoustic method and the sequentially coupled structural-acoustic method. A damping material has been incorporated into the core of the multi-layer shield allowing it to dissipate the mechanical energy coming from the exhaust manifold. Results show that the radiated sound level of a shield with a damping layer is noticeably lower than that of an undamped shield.