Mechanism Study Of The Production And Decomposition Of Nitrous Oxide Related Reaction During The Combustion In Marine Engine

Recently,ocean-going vessels have become one of the most important forms of trade and transportation in the world,however,a large amount of pollutants will be discharged through the exhaust gas,which will seriously damage the ecological environment.Due to the great harm of nitrogen oxides(NOx)in ship exhaust emissions,the relating methods of reducing NOx emission from ships have always been the focus of research.Nitrous oxide(N2O)is one component of NOx,which not only causes serious Greenhouse effect and Ozone Depletion,but also is an important intermediate of other NOx.Therefore,it is necessary to study the reaction mechanism related to N2O in the combustion processes,which contirbutes to comprehending the generation and consumption processes of N2O.According to the Zeldovich and GRI-Mech 3.0 mechanism,this paper determines the reactions of N2O reaction system.Moreover,by means of Gaussian 09 software,the configurations of reactants,transition states and intermediates are obtained,and the molecular vibration frequency,energy and other related parameters are calculated.According to the RRKM(Rice-Ramsperger-Kassel-Marcus)theory and transition state theory,the rate constant is obtained by YL(Yao Li-Lin Shengxian)method.Furthermore,the Morse potential vibration model is utilized to calculate anharmonic rate constant,which reduce the deviation caused by traditional theory.Through comparing the harmonic and anharmonic rate constant,the anharmonic effect on each reaction is discussed.Meanwhile,the rate constant calculated is compared with the experimental data,which could prove the importance of anharmonic effect on reaction.In order to describe the calculation results accurately,this research obtains the kinetics and thermodynamic parameters of reaction mechanism,which are fitted by the calculating data base on the least-square method.For each reaction in the N20 system studied in this paper,the harmonic and anharmonic rate constant in all channels increase as temperature growing,and the difference between the harmonic and anharmonic rate constant of most reactions is also increasing as temperature growing.In addition,especially in the high temperature range,the anharmonic rate constant is more consistent with the experimental value.When temperature is 2500 K,the rate constants of the reaction that generates N2O directly are greater than 108 orders of magnitude,which is consistent with the conclusions of previous experiments.Besides,the rate constants of the reaction that decomposes N2O are also greater than 108 orders of magnitude,and those reactions are capable of producing Nitric oxide(NO),which is consistent with the fact that the NO content is high and the N2O content is low in the NOx emissions from ships.