Study On The Influence Of C2-C4 Low-carbon Alcohol Fuel Molecular Structure Changes On The Combustion And Emission Characteristics Of RCCI

Energy shortages and increasingly serious environmental pollution problems have promoted the development of internal combustion engines to efficient and clean combustion.Scholars have proposed measures such as the use of renewable fuels and advanced combustion methods.Alcohol fuels are used in internal combustion engines due to their many advantages and have made great contributions to energy conservation and emission reduction.The molecular structure of alcohol fuels,such as the length of the carbon chain of the fuel molecule and increasing the branched chain structure,all have a greater impact on the combustion and emission process.At the same time,new combustion modes are also constantly developing.Reactivity Controlled Compression Ignition(RCCI)is a very potential combustion method.The combination of RCCI mode and alcohol fuel has been confirmed by scholars to have great development prospects.Therefore,in order to explore the combustion and emission laws of alcohol fuel in RCCI mode,this article uses alcohol fuel as low-reactivity fuel and diesel as high-reactivity fuel on a six-cylinder heavy-duty diesel engine to organize RCCI combustion.Under the conditions of a total cycle energy of 2000J and an engine speed of 1500r/min,ensure that the oxygen ratio(Ro)is 8% and 12% and the energy premix ratio(RP)is 0.3 and 0.5,respectively,next under three kinds of start of injection(SOI),the effect of the increase in carbon chain length and adding branched chain structure of alcohol fuels molecules on the combustion and emission performance of RCCI was studied.The results showed that: Under the same working conditions,the increase in carbon chain length and adding branched chain structure of alcohol fuels molecules have a small effect on the combustion characteristics of RCCI,especially under the same conditions of ensuring Ro,no mat ter what kind of molecular structure changes,almost all combustion characteristic parameters have only slight changes.Under the two control parameters of Ro and RP,the increase in carbon chain length and adding branched chain structure have different effects on the combustion characteristic parameters such as the peak heat release rate and the ignition delay.The impact of the two molecular structures on the emission characteristics of RCCI is more obvious.Under all Ro and RP,CO and HC emissions show an increasing trend with the increase in carbon chain length and adding branched chain structure,while the change in NO_x emissions is very small.When ensuring the same Ro,the increase in carbon chain length reduces the overall soot emission,and the overall concentration of particulate matter increases first and then decreases.Adding branched chain structure makes the soot emission decrease first and then increase,and the concentration of particulate matter will decrease as a whole;while ensuring the same RP,the increase in carbon chain length will increase the total emission of soot,and the concentration of particulate matter will first increase and then decrease,the change range is reduced under large RP.Adding branched chain structure increases the soot emission and the concentration of particulate matter as a whole.