| The development of shipping industry not only brings great economic benefits,but also causes a certain degree of pollution to the atmospheric environment.In recent years,with the increasingly strict regulations on ship exhaust gas emission,mixing of oxygencontaining fuel and diesel has become one of the important ways to effectively solve the emission problem of Marine diesel engine.N-pentanol fuel has attracted wide attention in the field of alternative fuels due to its high energy density,high cetane number,high carbon content,and good inter-solubility with diesel.In this paper,n-pentanol was mixed into heavy diesel to explore the possibility of its introduction to improve the combustion quality of Marine diesel engine and reduce emission generation.This study has some potential significance for improving fuel combustion efficiency and economy.The combustion chamber of 6210ZLC-1 Marine medium-speed diesel engine was modeled and mesh-divided by using AVL FIRE software,the combustion parameters were determined,and the rationality of the combustion model was verified.Four fuel schemes were selected: heavy diesel(DP0 fuel),heavy diesel mixed with 10% volume fraction n-pentanol(D90P10 fuel),heavy diesel mixed with 20% volume fraction npentanol(D80P20 fuel),and heavy diesel mixed with 30% volume fraction n-pentanol(D70P30 fuel).The combustion characteristics and emission characteristics of mixed fuels with different proportions of n-pentanol were studied.DP0 and D80P20 fuels were used to study the effects of different inlet pressure,different injection advance angle and different EGR rate on the combustion and emission characteristics of the Marine diesel engine.And drew the following conclusions:With the mixing ratio of n-pentanol increases,the oxygen content and ignition delay of the mixed fuel increase,and the low calorific value and viscosity decrease gradually,thus improving the atomization performance of the mixed fuel,making the oil and gas mix more evenly and combustion more fully.Compared with DP0 fuel,the introduction of n-pentanol significantly increased the average pressure,average temperature,heat release rate and cumulative heat release of combustion in the cylinder.Under the condition of high temperature and rich oxygen,the amount of NO increased gradually and the amount of Soot decreased obviously.With the increase of intake pressure,the oxygen content in the cylinder increases continuously and the combustion rate is accelerated.At the same time,with the increase of inlet pressure,the working medium doing work in the cylinder increases obviously,resulting in the increase of specific heat capacity of mixture.These factors eventually lead to the increase of the average combustion pressure in the cylinder,the decrease of the average temperature and the combustion heat release rate,and the increase of the cumulative heat release.Soot generation and Soot generation can decrease by 8.91% and34.58% in DP0 fuel combustion process.NO and Soot generation of D80P20 fuel decreased by 12.41% and 40.77% respectively.With the increase of fuel injection advance angle lengthens the fuel’s ignition delay period in the cylinder,which leads to more uniform oil and gas mixing and more sufficient fuel combustion.The average pressure,average temperature and heat release rate of the two fuels in the cylinder significantly increase,but the impact of fuel injection advance angle on the cumulative heat release is not obvious.With the increase of injection advance angle,NO generation of DP0 fuel increases gradually,and NO generation of D80P20 shows a trend of increasing first and then decreasing.The increase of fuel injection angle is beneficial to Soot emission reduction.The maximum reduction of Soot emission from DP0 and D80P20 fuels is 11.61% and 9.96%,respectively.With the increase of EGR rate,the proportion of waste gas entering the cylinder keeps increasing,resulting in the decrease of oxygen content in the cylinder,and the specific heat capacity of the mixture in the cylinder keeps increasing.The introduction of EGR resulted in the deterioration of the combustion quality of both fuels,resulting in a significant decrease in the average pressure,average temperature,heat release rate,and cumulative heat release of in-cylinder combustion.At the same time,the amount of NO decreased significantly,and the amount of Soot did not change much.Among them,the maximum emission reduction of NO of DP0 and D80P20 fuel decreased by 84.71% and84.55% respectively. |
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