Concept study - lower exhaust gas temperature in Scania buses
The thesis aims to lower the exhaust gas temperature on the coming EU6 Scania buses D7 and Otto gas and is carried out as a final part of the studies in the mechanical engineering program, KTH Stockholm. Euro 6, a new emission standard requirements for heavy duty trucks and buses, puts new demands on the amount of particulate matter and nitrogen oxides that can be emitted. This led to that Scania has developed and improved their after treatment systems. The new after treatment systems generates high exhaust temperatures, and Scania have expressed a desire to reduce these to create a safer environment around the bus.The thesis started with a thorough feasibility study, where the current exhaust systems and its components were studied. Solutions to lower exhaust temperatures were studied, both in the automotive industry and in other fields. The concepts that were developed would be analyzed through CFD simulations, why basic fluid mechanics were studied. Two different exhaust systems were to be analyzed, one with a gas engine and roof outlet and one with a diesel engine and ground outlet. A total of eight concepts were presented, in which five were determined to undergo CFD simulations.A competitor analysis was conducted in which three different diffusers from competing bus and truck manufacturers were CFD simulated.The results showed that the diffusers were superior to the other concepts. The diffuser designed in this project performed well in comparison to the diffusers from competing bus and trucks manufacturers, but it was considered to be expensive and difficult to manufacture. New diffuser designs were suggested, which are believed to have the same good qualities but cheaper to manufacture. The authors recommend Scania to perform field tests of the redesigned diffusers, and also try the ones designed by their competitors. Also, Scania should investigate how a venturi solution can be optimized.
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