Optimization Methodology for Flow & Acoustics Performance of Air Induction System

Noise Pollution has become one of the major environmental concerns for global automotive industry in the current era. Air Induction System (AIS) plays an important role in engine performance and vehicle noise. An ideal design of AIS provides debris free air for combustion and also reduces the engine noise heard at snorkel. Acoustic engineers always face challenges for achieving optimized AIS design with packaging space constraints. Conventionally, AIS optimization is an iterative procedure. This paper emphasizes a one dimensional (1D) approach for optimization of AIS to meet the functional requirements for flow and acoustics. Air flows from the snorkel to the intake manifold whereas the sound propagates in the opposite direction. Suitable design of ducts, air box and resonators are required to attenuate the snorkel noise (SN) to meet the required sound pressure levels. In this paper a detailed methodology is developed to study the AIS with different geometries and their impact on pressure drop and noise attenuation at different engine speed. GEM3D is used as a pre-processor for air box, resonators and duct modeling. The discretization of air box shell and ducts for element generation has played an important role in proper prediction of noise and pressure drop. Transmission loss (TL), pressure restriction and snorkel noise simulation is carried out using GT-POWER® tool. Four pole transfer matrix method is applied for the calculation of TL which allows us to understand attenuation of sound. The effect of TL in wide frequency range (0 to 1000 Hz) is studied. Pressure restriction study enabled us to understand flow characteristics through pressure difference between dirty side duct (DSD) and clean side duct (CSD). The TL and pressure drop plots are found to be in good correlation with test results. The optimized design of AIS will be tested at different engine speeds at full throttle conditions to achieve good correlation for snorkel noise. These optimization techniques shall be useful for future programs at an early stage of product development which reduces development time and cost.