The Study Of Surrogate Fuel And Emission Control Technology In A Low-speed Two Stroke Diesel Engine

With the strengthening of people’s awareness of environmental protection,the control of harmful pollutants in the environment has been increasingly strengthened.Ship transportation has a vital role in the development of society.Two-stroke marine engines play an important role in ship transportation due to the high thermal efficiency,wide power range,and simple maintenance,but the marine diesel engine produces more emissions.With the implementation of Tier III regulations,marine engine pollutants need to be decreased.The combustion process of fuel is closely related to the produce of emissions.The improvement of the combustion process can effectively reduce the emissions.This article focuses on the study of combustion to reduce emissions from marine diesel engines.The chemical kinetic mechanisms of surrogate fuels were researched in this article.The coupling of chemical kinetics with three-dimensional simulations can better describe the combustion process of the fuel and make the simulation results closer to the real situation.First,the differences between the performance of alkane fuels were analyzed,including n-heptane,n-dodecane,n-tetradecane,and n-hexadecane.Then,the comparisions of different surrogate fuels and combustion models on the performance of two-stroke marine engines were analyzed.Based on the results,n-tetradecane was selected as the basic surrogate fuel for marine diesel fuel,and the chemical kinetic mechanism of n-tetradecane was developed.The aromatic compounds have large influence on soot precursors,the chemical kinetic mechanism of n-tetradecane-toluene was developed.Then,the effect of toluene content on the performance of marine diesel engines was studied,and the composition of the components that were most optimal as an surrogate fuel for marine diesel was obtained.Second,by testing the chemical composition of heavy fuel oil used in ships,the component with a large proportion of heavy oil was found.According to the results,the chemical kinetic mechanism of heavy fuel oil was constructed.This mechanism contains eight components.Then,the simulated and experimental values of the heat release rate of the heavy fuel oil were compared using six different component ratios of mechanisms.The optimal surrogate fuel of the heavy fuel oil was selected according the results.On this basis,the chemical kinetic mechanism of heavy fuel oil including sulfur component was developed,and the influence of sulfur content on the performance of marine engines was analyzed.Finally,the chemical kinetics mechanism coupled with three-dimensional simulations are used to simulated the technical route to reduce NO_x emissions from marine heavy-oil engines.First,the potential for single technology measures was analyzed to reduce NO_x emissions,such as exhaust gas recirculation,humid air motor,miller cycle,and injection timing.Then,the technical route based on exhaust gas recirculation and humid air motor was analyzed.By comparing NO_x emissions and economic,the optimal technical route for marine engine emissions reductions was proposed.