【作者】 吕晓辉；

【导师】 孙俊； 李格升；

【作者基本信息】 武汉理工大学 ， 轮机工程， 2011， 硕士

【摘要】 21世纪能源及车用燃料的多元化,开发及应用生物质能等可再生能源及清洁替代燃料,是净化空气保护环境、解决矿产燃料不足的必然趋势。乙醇和氢气都是良好的内燃机代用燃料,能有效的改善现有内燃机的燃烧和排放性能,在乙醇中掺烧少量氢气能达到良好的燃料互补作用。由于含水酒精重整燃料中含有乙醇及氢气,故本文创新性地整合了乙醇-氢气混合气的化学反应机理,通过实验与数值计算重点研究了乙醇-氢气混合气的预混层流燃烧特性。通过乙醇-氢气混合气的定容燃烧弹实验,得到了不同当量比、不同氢气比例的混合气的火焰传播速率、层流燃烧速率、马克斯坦长度、火焰厚度、火焰前锋面结构、质量燃烧流量等参数,研究结果表明：随着氢气比例的增大,乙醇-氢气混合气的火焰传播速率(拉伸、无拉伸)、层流燃烧速率(拉伸、无拉伸)、质量燃烧流量(其增加率略小于层流燃烧速率的增加率)亦逐渐增大,马克斯坦长度则逐渐降低。而在当量比1.2时,火焰传播速率、层流燃烧速率等达到峰值,偏离该当量比后,速率均降低。在低氢气比例条件下(低于40%),马克斯坦长度随当量比的增大,呈现逐渐降低的趋势；高氢气比例(高于60%)时则相反。燃烧产物的生成速率随着拉伸率的增加而增加,燃气的消耗速率随着拉伸率的增加而减小。另外,容弹内燃烧压力的变化表明容弹中的燃烧是在近似绝热条件下进行的。而通过火焰的纹影图片,观察到了3种火焰的不稳定性。同时拟合了乙醇-氢气混合气的无拉伸层流燃烧速率的经验公式。探索了乙醇-氢气混合气的稀燃极限,发现掺氢能拓宽燃料的稀燃极限。对乙醇和氢气的化学反应机理进行了整合,在乙醇的反应机理中,添加氢气机理中包含的H2O2+O2=HO2+HO2基元反应以及O组分、O2组分的热力学数据,形成了新的乙醇-氢气混合气的反应机理,并通过敏感性分析和反应速率分析法对整合后机理进行了详细分析。同时,为了预测NO的排放,在新的乙醇-氢气混合机理中添加了泽利多维奇机理。在上述机理的基础上,运用CHEMKIN软件计算了不同初始条件下的乙醇-氢气混合气的火焰传播速率、层流燃烧速率、绝热火焰温度、CO和NO排放以及火焰结构等,为实验研究起到了辅助作用。通过数值计算结果和实验结果的层流燃烧速率和火焰传播速率的对比,发现对比结果具有良好的吻合性,表明本文中整合的机理适用于计算不同氢气比例下的稀混合气和化学计量比附近乙醇-氢气混合气的燃烧和化学反应过程。更多还原

【Abstract】 The diversification of energy and vehicle fuels in the 21st century, developments and applications of bio-energy and other renewable and clean alternative fuels are the inevitable trends towards purifying air, protecting the environment and solving the problem of mineral fuel shortage. As being good alternative fuels, both ethanol and hydrogen can improve effectively the performance of combustion and reduce emissions. The mixture of ethanol with small quantities of hydrogen can achieve good complementary actions.Based on the reformed hydrated alcohol fuels containing ethanol and hydrogen, this paper has studied the premixed laminar combustion properties of ethanol-hydrogen mixtures through experiment and numerical calculation and integrated the chemical reaction mechanism of ethanol-hydrogen mixtures.The flame speed、laminar burning velocity、Markstein length、flame thickness、flame front surface structure and the burning flux are obtained by the experimental study of ethanol-hydrogen mixtures at different equivalent ratios and hydrogen proportions on the constant volume combustion bomb. The results show that:with the increase of the hydrogen proportion, the flame speed (stretched and unstretched)、laminar burning velocity(stretched and unstretched) and the burning flux increase gradually (the increase rate of the burning flux is slightly less than the laminar burning velocity), Markstein length decreases. While the flame speed and the laminar burning velocity achieve peaks at an equivalent ratio equal to 1.2 and decrease after deviating from this value. Markstein length decreases with the increase of the equivalent ratio in low hydrogen proportions (less than 40%) and the opposite happens when hydrogen proportion is more than 60%. The generation rate of combustion products increases with the increase of the stretched ratio whereas the gas consumption rate decreases when the stretched ratio is increased. Besides the change of the pressure shows that the combustion in the constant volume combustion bomb is carried out under conditions similar to adiabatic conditions. Three kinds of flame instabilities are observed in flame pictures. Meanwhile fit the empirical formula of the unstretched laminar burning velocities of ethanol-hydrogen mixtures. Explore the lean burn limit of ethanol-hydrogen mixtures, and hydrogen enhancement in ethanol can extend the lean burn limit.Through adding the basic element reaction H2O2+O2=HO2+HO2 and thermodynamic datum of O and O2 which are contained in the hydrogen mechanism to the ethanol mechanism, the chemical reaction mechanism of ethanol-hydrogen is integrated. By the methods of sensitivity and ROP, the consumption rates of ethanol and hydrogen are analyzed in details. Meanwhile in order to predict NO emissions, Zeldovich mechanism is added to the new ethanol-hydrogen mechanism. Based on the above mechanism, the flame speed、laminar burning velocity、adiabatic flame temperature、CO/NO emissions and the flame structure of ethanol-hydrogen mixtures in different initial conductions are calculated using CHEMKIN software, and this calculation plays a key role in the experimental study.Comparison shows good agreements between numerical calculation and experimental results of burning velocity and flame speed, and this means that the integrated mechanism of this paper can be used to calculate the combustion process of ethanol-hydrogen mixtures with different hydrogen proportions at conditions which are stoichiometric ratio and lean mixture.更多还原