Acoustic modeling and testing of exhaust and intake system components

Abstract: Intake and exhaust orifice noise contributes to interior and exterior vehicle noise. The order noise radiated from the orifice of the intake and exhaust systems is caused by the pressure pulses generated by the periodic charging and discharging process and propagates to the open ends of the duct systems.The propagation properties of these pulses are influenced by the dimensions and acoustic absorption properties of the different devices in the intake/exhaust line (muffler, turbocharger, catalyst, intercooler, particulate filter, etc.). Additional to this pulse noise, the pulsating flow in the duct system generates flow noise by vortex shedding and turbulence at geometrical discontinuities.Several turbochargers, catalytic converters, Diesel particulate filters and intercoolers elements were investigated and analyzed by performing two-port acoustic measurements with and without mean flow at both cold conditions (room temperature) and hot conditions (running engine test bed) to investigate these devices as noise reduction elements. These measurements were performed in a frequency range of 0 to 1200 Hz at no flow conditions and at flow speeds: 0.05 and 0.1 Mach.A new concept for the acoustic modeling of the catalytic converters, Diesel particulate filters and Intercoolers, and a new geometrical model for the turbocharger were developed. The whole test configuration was modeled and simulated by means of 1-D gas dynamics using the software AVL-Boost. The results were validated against measurements. The validation results comprised the acoustic transmission loss, the acoustic transfer function and the pressure drop over the studied test objects. The results illustrate the improvement of simulation quality using the new models compared to the previous AVL-Boost models.