Micro-Perforated Plates for Vehicle Applications

摘要: Mufflers are used in for instance exhaust system of cars or trucks to reduce noise. Perforated pipes one the main components modern mufflers. To study acoustic properties mufflers with perforated pipe is targets this thesis. Furthermore, how flow distributed along critical prediction since it controls impedance perforate. Therefore another goal thesis investigate a simple model which can predict distribution So called micro-perforated plates have large potential be applied vehicle applications. understand microperforated and their application purpose A set typical mufflers, through flow, plug eccentric, were built tested without flow. In work three issues studied: i) effects perforations, ii) higher order modes iii) presence mean The measurements compared numerical simulations using two commercial softwares 1-D Boost linear acoustics tool 3-D FemLab tool. quasi-steady semi-analytical proposed grazing-bias perforated-pipe muffler at low Mach numbers high Reynolds based on diameter perforation. Firstly one-hole models presented small hole model. next apply whole muffler. This allows steady pressure drop was experimental data from literature. Micro-perforated (MPP:s) subjected both temperatures as well sound levels effect MPP must known. present types MPP:s been investigated: circular holes slit-shaped holes. Non-linear investigated random noise pure tone excitation results grazing also correction terms proposed. As an new type has investigated. Based performed very efficient multi-chamber configuration found. performance verified by experiments.