Low Noise Intake System Development for Turbocharged I.C. Engines Using Compact High Frequency Side Branch Resonators

Abstract

Turbochargers have become common in passenger cars as well as commercial vehicles. They have an excellent mechanism to effectively increase fuel efficiency and engine power, but they unfortunately cause several noise problems. Its noise are mainly classified as structure-borne noises, generated from the vibration of rotating shaft modules (cartridges), and air-borne noises, from air flow inside turbochargers or their coupling ducts. In this study an attempt to reduce the pulsation noise generated from the compressor wheels, whose frequency is the same as the whine noise is presented. This attempt is based on using the compact high frequency side branch resonators to develop low intake noise system. The design of such system, which is mainly based on the developed 1D linear acoustic theory and theoretical investigations to use more than one resonator connected to the main duct in series and/or in parallel are introduced. An optimization strategy to choose the appropriate resonator axis offset is presented. In case of complex unsymmetrical geometry in real resonators, a 3 D finite element is used. The presented models are validated via comparison with the measured results at room temperatures. The validated models are used to improve the acoustic performance of the real resonators. Based on the developed models and the optimization results, the internal design of resonators improves its acoustic performance; the serial arrangements increase the damping at the same peak frequency while the parallel arrangements make it wider. The amount of extra damping added to the intake system depends on the resonators geometry and their axis offset which can be around 50 dB at the peaks, and 30 dB between peeks at normal operating engine conditions. Extra improvement to the intake system noise reduction can be achieved by redesigning and optimizing the entire system with used resonators under both space and shape constrains.