ABSTRACT

DI diesel engine vehicles are becoming popular because of their friendly behavior to the environment as it emits lower CO₂ . The main cause of it is that it consumes relatively smaller amount of fuel than a gasoline engine vehicle. But this increases both regulated and unregulated emissions like No_x, PM, exhaust odor and others. The regulated emissions are No_x, PM etc and unregulated emissions is the exhaust odor. Most diesel engine researches put their attention to reduce the regulated emissions. The attention of the authors is to reduce the unpleasant exhaust odor of DI diesel engines at idling. Among the various exhaust emission problems of DI diesel engine, odor is still a prominent emission problem. Reduction of exhaust odor can be done mainly in three ways. One of them is to optimize the engine parameters. But researches have been shown that the reduction of odor is not significant. The other is that the use of alternative fuels. Some alternative fuels can reduce the exhaust odor significantly but the cost is much higher than diesel fuel. The one is to use the catalyst system. The catalyst system hence cannot be applied at idling and at low temperature operation. The other is the absorption type system like water-washing system. By EGR, NOx reduces but PM emission increases, with which odorous emission increases. For this reason, EGR and Water- Washing System is used to improve emissions by reducing NOx & odor. Odorous emissions seems to be reduced using EGR, While reading is taken directly. This is due to the reason that EGR reduces the speed of exhaust gas. For this reason, indirect odor assessment is done, from which it is found that odor increases with the increase in EGR. The water washing system can be applied at idling and at low temperature operation. Since the emission of exhaust odor at idling at low temperature operation is higher than any other engine condition, and exhaust gas temperature is much lower at idling and low speed operation, the water washing system can be used. Some previous researches have shown that odor can be reduced greatly by washing the exhaust gas by water. Since there are no proper systems to reduce the exhaust odor at idling, this thesis report focuses on the water washing system. In the water washing system the exhaust was first passed through EGR system and then through water. Also, experiments were performed with EGR only and water washing only. From these experiments, it was found that odor reduced to 1point (a significant odor reduction) by using total setup (combination of EGR and water-washing). But individual components could not able to reduce the odor significantly.    

 

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