| Due to the relatively high thermal efficiency and operation reliability, Diesel Engine will still be main propulsion engine in the near future. Taking into account the deteriorating environmental problem caused by the emissions from ship main engine, people pay more attention to the pollution problems of Marine Diesel Engines. Under this situation, IMO Issued the ANNEX VI of MARPOL Convention, which has been carried out since January 1, 2000. Research points out that three key factors, which determine the NOx emissions, are maximum peak temperature, rich oxygen concentration and the duration in which combustion products stay at high temperature zone. Thereby this paper puts forward four ways to reduce NOx emissions: reduction of the highest combustion temperature, fuel emulsification, Exhaust Gas Recirculation and Selective Catalytic Reduction.According to the MARPOL Convention, NOx mass flow rate is to know NOx concentration in the exhaust and the exhaust mass flow rate. This paper discusses the computational method to get exhaust mass flow rate by carbon/oxygen balance method.This thesis analyses three performance parameters of influencing on NOx emission of main engine, respectively and discuss correction co-efficient KHDIES in MARPOL convention. By pointing out that ambient pressure should take the place of scavenging air temperature in the formula of NOx correction factor KHDIES, a new and more reasonable KHDIES has been brought forward.
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