| In the face of severe energy crisis and environmental crisis,actively seeking and reasonably using alternative fuels is one of the main ways to alleviate energy shortage and environmental pollution.Alcohol fuel is a promising alternative fuel,which is not only widely sourced,clean and renewable,easy to store and transport,but also can be directly burned in the cylinder of a diesel engine.Methanol is a clean fuel known as liquid sunlight.Methanol has high octane number,high latent heat of vaporization,and good lean combustion characteristics,which can improve engine combustion and emission characteristics.However,methanol and diesel fuel have significant differences in polarity and poor mutual solubility,while n-butanol is more soluble in diesel than methanol.Therefore,taking n-butanol as the cosolvent of diesel/methanol blended fuels to form a ternary blended fuel,experimental and simulation investigations on the combustion,performance,and emission characteristics of diesel/methanol/n-butanol blended fuels engine.It is helpful to provide a theoretical basis and rationale for the application and promotion of diesel engine alternative fuel.The main work and results of this paper are as follows:Firstly,using one-dimensional simulation software AVL-BOOST,the effects of different diesel/methanol blended fuels on combustion characteristics,performance,and emission of the diesel engine were studied.On this basis,the effects of different diesel/methanol blended fuels on combustion characteristics,performance,and emissions of the diesel engine were studied.The results showed that with the increase of methanol ratio in the blended fuel,the in-cylinder pressure increased and the in-cylinder combustion temperature decreased;the fuel consumption of the diesel engine increased,and the torque and power decreased,which made the power characteristics of the diesel engine worse.In addition,due to the oxygen content of methanol,the fuel was fully combusted,and the fuel burns well,resulting in reduced soot,NO_x,and CO emissions.However,due to the reduction of combustion temperature in the cylinder,the quenching effect was increased,and HC emission was increased.Secondly,using the three-dimensional simulation software CONVERGE,the effects of n-butanol blending on the spray,combustion,and emission characteristics of diesel/methanol blended fuels the diesel engine were studied.The results showed that compared with diesel,the diesel/methanol/n-butanol blended fuel improved the combustion characteristics of the diesel engine,increased the cylinder pressure,and reduced the in-cylinder combustion temperature.However,it would increase fuel consumption,reduce power,and deteriorate the economic characteristics of the diesel engine.In addition,the use of methanol and n-butanol as alternative fuels to diesel resulted in reduced NO_x,CO,Soot,and HC emissions in the diesel engine.Through the analysis of the results,it is concluded that the best blending ratio of the blended fuel was 70%diesel+20%methanol+10%n-butanol(D70M20B10).Finally,the effects of the pre-injection strategies on the combustion,performance,and emission of the diesel engine were studied using the optimal blending ratio D70M20B10 as fuel.The results showed that the cylinder pressure of the diesel engine has increased by about 9.8%to 14.57%.However,the in-cylinder combustion temperature was reduced and the ignition delay and combustion duration were shortened.In addition,the use of the pre-injection strategies reduced diesel engine pollutant emissions,with NO_x emission reduced by approximately 46.43%to 87.18%and HC emission reduced by approximately 24.05%to 38.03%,but fuel consumption increased.The optimum pre-injection timing and pre-injection fuel mass ratio were obtained by orthogonal test design optimization at-45°CA and 0.3.At this point the peak cylinder pressure was 8.83 MPa,fuel consumption was 304.46 g/(kW·h)and NO_xemission was 168.74 ppm. |
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