生物柴油/DMF混合燃料对柴油机低温燃烧的影响

Effect of Biodiesel/DMF Blended Fuel on Low Temperature Combustion in a Diesel Engine

在生物柴油中分别掺入体积分数20%和50%,的2,5-二甲基呋喃(DMF)组成DMF20和DMF50混合燃料,在一台单缸柴油机上对柴油、生物柴油和生物柴油/DMF混合燃料开展低温燃烧试验研究.结果表明,生物柴油和柴油燃烧特性相近,生物柴油含氧特性在一定程度上可以改善低温燃烧的碳烟排放;增大生物柴油中DMF掺混比例,混合燃料十六烷值降低,滞燃期延长,燃烧速率加快,预混放热峰值升高,最大压力升高率增大,DMF50即使在高负荷下也呈现典型的预混单峰放热.在低负荷时,掺混燃料热效率并没有优势,随负荷增大,掺混燃料在热效率方面逐渐表现出优势,特别是DMF50在高负荷时优势明显,指示热效率提高到46.5%(此时柴油和生物柴油分别为43%和43.3%).掺混DMF对碳烟改善明显,在高负荷、低温燃烧、低氧浓度条件下DMF50仍可基本实现无碳烟排放,同时提高DMF掺混比例对改善高负荷低温燃烧的CO和HC排放作用显著.

Low temperature combustions of diesel,biodiesel and biodiesel/DMF blends were investigated on asingle-cylinder diesel engine.Blended fuels including DMF20and DMF50were formulated by blending DMF withbiodiesel at20%,and50%,volume ratios,separately.The results show that the combustion characteristic of biodieselis similar to that of diesel and its fuel oxygen can improve the soot emission of low temperature combustionto some extent.With the increase of blending ratio,the cetane number of blended fuel is reduced and the ignitiondelay is prolonged,which results in higher burning rate and higher premixed heat release rate,and the maximumpressure rise rate is also increased.For DMF50,the typical premixed mono-peak heat release is presented evenunder high load condition.At low load,no advantage in thermal efficiency is shown for fuel blends,while as loadincreases,the fuel blends gradually show the advantage in thermal efficiency.And at high load,the indicatedthermal efficiency can be increased up to46.5%,for DMF50,while the indicated thermal efficiency of diesel andbiodiesel are43%,and43.3%,,respectively.The soot emission can be obviously improved by the fuel blends andsmoke-free operation can still be realized for DMF50even under high load low temperature combustion conditionwith relatively low oxygen concentration.Meanwhile,the CO and HC emissions of low temperature combustionat high load can also be significantly improved by increasing the blending ratio of DMF.