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The Diesel Particulate Filter (DPF) is used on today's diesel vehicles to reduce the amount of soot being released into the atmosphere from diesel exhaust. The DPFs are typically wall-flow filtration devices of various extruded porous ceramic materials with more than 95% efficiency. Once the filter has loaded with soot, the DPF undergoes regeneration where the exhaust temperature is raised to burn off the soot. With the DPF being relatively new aftertreatment technology, the exhaust industry must investigate the acoustic and performance effects of the DPF when added to an exhaust system. In many applications the DPF replaces the exhaust muffler because of limited packaging space. The acoustic performance of the DPF changes with increasing soot density and exhaust backpressure. The acoustic response is measured with physical testing at multiple soot load densities. This study is part of a graduation thesis project for Kettering University[1].

Urea injection is required to meet EU IV to EU VI emission regulations as a main stream technical route to reduce nitrogen oxides (NOx). In heavy and medium duty trucks, compressed air at 3-5 bar is often available, therefore can assist urea injection by mixing with urea, forming liquid droplets, and releasing mixed fluid into the exhaust gases. The development of air assisted urea pump and injectors, or the assembly, seemingly simpler than airless counterparts, however poses multiple challenges. One challenge is to properly mix urea in the mixing chamber inside pump with the compressed air, leaving no residual deposits while achieving high mixing efficiency. Another is to maintain good spray quality for a given length of delivery pipe as the liquid phase and gas phase tend to coalesce as they propagate along the pipe flow direction. In addition, the urea pump and injector need to provide robust and reliable performance under stringent road conditions.