生物柴油同分异构替代燃料丁酸甲酯和丙酸乙酯预混燃烧对比研究

Comparative Study on Premixed Combustion of Biodiesel Isomeric Surrogate Fuels Methyl Butanoate and Ethyl Propanoate

在CO_2/O2/Ar气氛下对生物柴油两种同分异构替代燃料丁酸甲酯和丙酸乙酯的预混燃烧(当量比为0.8)进行了对比研究,重点分析了生物柴油替代燃料的同分异构化对燃烧主要产物、稳定中间产物以及自由基的影响,同时揭示CO_2对两种同分异构替代燃料燃烧的化学作用,给出了潜在典型污染物的生成趋势和规律。结果表明,CO_2的加入对两种燃料中重要的烟黑前驱物C2H2和C3H3具有抑制作用。CO_2的稀释和热作用对C2H2生成的抑制作用在丙酸乙酯火焰中更加显著,而对C3H3的抑制作用在丁酸甲酯火焰中更加明显,并且CO_2的化学作用可进一步加强对两种火焰中C2H2和C3H3生成的抑制。同时,CO_2的存在可有效降低两种燃料非常规污染物醛酮类产物的浓度,其中CH2O和CH3CHO的浓度在丙酸乙酯火焰中的减小更为显著。两种火焰中抑制CH2O生成的主要作用是CO_2的稀释和热作用,而CO_2的化学作用则是抑制CH3CHO生成的主导作用。由产物消耗速率分析得知,对丁酸甲酯消耗影响最大的化学反应是脱氢反应MB+H=H2+MB2J,而对丙酸乙酯消耗影响最大的则是分解反应EP=C2H5COOH+C2H4。

A comparative study on premixed combustion (equivalence ratios are 0.8) of two biodiesel isomeric alternativefuels methyl butanoate and ethyl propanoate is investigated under the CO2/O2/Ar atmosphere. The isomerization effects ofbiodiesel alternative fuels on main products, intermediates and radicals are analyzed with particular emphasis on thechemical effects of CO2 addition on two alternative fuels combustion. An analysis of potential pollutants formations iscarried out. The results show that, CO2 addition suppresses formations of the precursors of soot e.g. acetylene andpropargyl in two flames. The dilution and thermal effects of CO2 addition are more significant on inhibiting the formationof C2H2 in ethyl propanoate flame, while in methyl butanoate are more considerable on reducing C3H3 mole fraction.Moreover, the chemical effects of CO2 addition make a further suppression on C2H2 and C3H3. Furthermore, the addition ofCO2 leads to a decrease in the unconventional emissions aldehydes and ketones in the alternative fuels, especiallysignificant for formaldehyde and acetaldehyde in ethyl propanoate flame. In the two flames, the decrease in CH2O is due tothe dilution and thermal effects of CO2 addition, while the chemical effects of CO2 addition are the dominant factor onsuppressing CH3CHO. Known from product consumption rate analysis, the main reaction responsible for methyl butanoateconsumption is dehydrogenation reaction MB+H=H2+MB2J, while the main reaction responsible for ethyl propanoateis decomposition reaction EP=C2H5COOH+C2H4.