ABSTRACT

Fuel consumption in petrol engines is about 20-30% higher than that of diesel engines that causes high CO₂ emission as well as greater pollution of environment. DI diesel engines have the lowest fuel consumption as well as CO₂ emissions. So, DI diesel engine vehicles are becoming popular day by day. But this increases both regulated and unregulated emissions like NO_X, PM, exhaust odor and others. Among the various exhaust emission problems of DI diesel engine, odor is still a prominent exhaust 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 shown that the reduction of odor is not significant. The other is that the use of alternative fuels. Some alternatives fuels can reduce the exhaust odor significantly but the cost is must higher than diesel fuel. The last one is exhaust gas after treatment. It is also of two types. One is to use the catalyst system. The catalyst system works only at high temperature condition i.e. when the vehicle is in running condition (under load). This system hence can not be applied at idling and at low temperature operation. The other is the non-catalytic system like adsorption type system, water washing system, air dilution system and others. Since the exhaust emission and odor at idling and low temperature operation is higher than any other engine condition and the exhaust gas temperature is much lower at idling and low speed operations, the charcoal adsorption system can be used. Some previous researches have showed that several organic compounds (aldehyde, organic acids and oxygenated compounds) are important odorous groups in exhaust and they correlate well with exhaust odor. Odor can be reduced greatly by adsorbing these odorous components by charcoal adsorption system. Last few years thesis report on odor reduction by charcoal-adsorption system showed that charcoal-adsorption system can reduce exhaust odor around 0.75 points. This thesis report focuses on the temperature and pressure effect of charcoal adsorption system. The experiment was performed first with a 1.5 ft long double chamber adsorption system and the odor is reduced about 0.25 points. It is clear that if a larger cold charcoal adsorption system (5 ft) is used the odor could be reduced far more, even more than 0.75 points. The double chamber adsorption system in which temperature was controlled can also reduce other emissions significantly. CO emissions also can be reduced with this system. Some combination of charcoal adsorption and air dilution systems were also used. These systems reduced odor level from 3.75 to 2.25. Other emissions (NOx, CO) are also significantly reduced.

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