Influence Of Fuel Injection On Combustion Characteristics Of A Dual Fuel Engine With Micro Injection Ignition

Energy shortage and environmental pollution are the concerns of the whole world at this stage.With the increasingly stringent regulations on energy efficiency and emission of ships,the requirement for their economy and pollutant emission control is becoming higher and higher,forcing the transformation of marine engines to new energy sources.Natural gas,as an alternative clean energy with abundant reserves,receives people’s attention.However,natural gas engine has some problems,such as low inflation efficiency and slow flame propagation in cylinder,which results in its power density being lower than that of traditional diesel engine.Diesel/natural gas dual fuel engine has higher power density and lower fuel consumption,and can realize redundancy and backup of the mode.It can significantly reduce engine emissions while ensuring the safe and reliable operation of the engine.It is the most realistic technological way for current realization of ships to save energy and reduce emissions.In micro-injection ignited dual-fuel engine,the change of excess air coefficient and ignited diesel injection parameters will change the mixture concentration,ignition energy and ignition time in cylinder,and then affect the combustion process of fuel in cylinder.Therefore,in order to organize combustion in cylinder reasonably to optimize the power and emission of dual fuel engine,it is very important to study the influence of fuel injection parameters(micro-injection amount,micro-injection timing)on the combustion characteristics of dual fuel engine under different excess air coefficients.In this paper,FIRE software is used to simulate and calculate the 6K dual fuel engine at 1800r/min,100% load,1607N*m torque and 303 kw power.The excess air coefficients are 2.1,2.3,the micro-injection quantity is 1%,2.5%,5%,10%,and the injection timing is 715°CA,710°CA,707.5°CA and 705°CA,respectively.To analyzed and summarized the effect of the change about micro-injection quantity and micro-injection timing under different excess air coefficients in cylinder on the combustion characteristics of the engine.To provide guidance for the optimization of the engine performance.The results show that,in the range of research,the increase of micro-injection quantity and the advance of micro-injection timing will increase the peak value of in-cylinder pressure,temperature and heat release rate,accelerate the combustion process,shorten the combustion duration of in-cylinder fuel,improve engine power and thermal efficiency,reduce engine unburned hydrocarbon emissions and increase engine NO emissions.But the ignition delay of fuel in cylinder will be shortened with the increase of micro-injection quantity and increase with the advance of the micro-injection timing.Cause the combustion noise will be reduced with the increase of micro-injection quantity and increase with the advance of micro-injection timing.When the micro-injection quantity is 2.5% and the micro-injection timing is 707.5°CA,the fuel economy of engine is the highest and the emission is the best.When the excess air coefficient increases from 2.1 to 2.3,the cylinder pressure,fuel combustion duration,engine unburned hydrocarbon emissions will increase,while the peak temperature,heat release rate and engine NO emissions will decrease significantly.When the average pressure and temperature in the engine cylinder are higher,properly increasing the excess air coefficient in the cylinder can further improve the engine power performance and significantly reduce the engine NO emission on the basis of a small increase in the engine unburned hydrocarbon emissions.