Experimental Study On Butanol-diesel Compound Combustion Mode

Under the pressure of increasingly serious energy crisis and environment pollution,the research of clean alternative fuel and combustion technology have been the hot topic in the field of internal combustion engine.In this thesis,some experiments were done based on a refitted diesel engine with compound combustion mode which used the port-fuel-injection of n-butanol and direct-injection of diesel oil.Firstly,the effect of the butanol substitution on engine property under different DI injection timing and different engine load was investigated.Secondly,the effect of the butanol concentration on engine properties under different quantity of diesel oil and different injection timing was investigated.Lastly,the diesel injection parameters was investigated in the twice-injection mode under a chosen butanol concentration atmosphere.Results showed that: under medium engine load condition,the max pressure in-cylinder decreased in the late injection timing and increased in the early injection timing with the increasing of substitution ratio of n-butanol,the combustion retard period increased and the combustion duration period shorted with the increasing of substitution ratio of n-butanol,the indicated thermal efficiency reached its max value when the substitution ratio of butanol was in the range of 25%-30%.NOx and Soot emissions were decreased while THC emissions increased and CO firstly went up then went down with the increasing of substation ratio of butanol,and the changing trend of THC and CO enlarged with earlier injection timing.In the case of early injection timing conditions,with the increasing of n-butanol substitution ratio: the Pmax increased and the increase rate was higher when the engine load was higher,the pressure increase rate increased rapidly.The indicated thermal efficiency,CO and THC emissions were higher than the low load condition,NOx emissions and Soot emissions decreased and the downward trend was significantly greater than that under the low load condition.With the increasing of n-butanol concentration,the heat release velocity at the initial stage of combustion firstly decreased and then increased,and with the delaying of injection timing and the increasing of diesel oil,the decreasing trend of heat release velocity decreased.Under the condition of each diesel fuel,the emissions of NOx and Soot decreased with the increasing of butanol concentration,but the NOx emissions increased and Soot emission decreased when injection timing got earlier.With the increasing of butanol concentration,the emissions of CO and THC firstly increased and then decreased,and was lower when the injection timing was earlier.With the increasing of the proportion of the main fuel injection,the maximum burst pressure in-cylinder increased,the pressure rise rate firstly increased then decreased,the maximum pressure rise rate was high and not affected by the proportion of main fuel injection when the injection timing was too early.The thermal efficiency increased slowly with the increasing of the proportion of the main fuel injection when the injection timing was earlier,and the thermal efficiency decreased slowly with the increasing of the main spray ratio when the injection timing was late;With the increasing of the proportion of fuel injection,NOx emissions decreased,Soot emissions firstly increased then decreased,the CO and THC emissions increased and was higher when the injection timing was later.