【作者】 谭满志；

【导师】 郭英男；

【作者基本信息】 吉林大学 ， 动力机械及工程， 2004， 硕士

【摘要】 由于能源问题是世界大多数国家共同面临的困难，对石油替代能源的研究早已在世界各国进行，代用燃料中最具潜力之一的乙醇燃料已成为国内外研究的重点。由于柴油和乙醇理化性质差异加大，两者混合时表现出较差的相溶性，易分层，不易形成稳定的乳化液，应用助溶剂解决了柴油和乙醇相溶性问题，使用助溶剂配制的柴油醇样品，实现了凝固点温度以上时不分层，稳定期超过三个月。柴油醇燃料的部分主要理化性质数值可由经验公式估算。柴油醇的密度、十六烷值、低热值、闪点都低于柴油，而汽化潜热却高于柴油，且随柴油醇中乙醇含量的增加，这种规律变化的越大，这将对压燃式发动机燃用柴油醇的发动机各项性能产生影响。在增压中冷压燃式发动机的结构和参数不作任何调整条件下，进行了发动机分别燃用柴油（E0）及E10、E15和E20柴油醇的试验研究。从发动机外特性试验结果看：随着燃料中乙醇含量的增加，发动机最大扭矩和额定功率逐渐降低；从发动机负荷特性试验结果看，随着燃料中乙醇含量的增加，发动机燃油消耗率逐渐增加，小负荷增加幅度较大；能量消耗率在发动机中、高负荷相差不大，小负荷受乙醇高汽化潜热影响还是有所增加；负荷特性烟度逐渐降低；CO浓度排放在中、高负荷变化不大，在小负荷，尤其在低转速的小负荷有一定程度的增加；HC浓度排放在所有负荷都增加，小负荷增加幅度较大；NOx浓度排放在小负荷和大负荷有所降低，在中等负荷有所增加。从发动机十三工况排放试验看：随着燃料中乙醇含量的增加，除DS比排放量有所降低，其他污染物CO、HC、NOx、PM和SOF的比排放量都有所增加，功率的降低造成比排放量与同工况浓度排放的规律差异。 <WP=65>从发动机燃烧特性试验结果看：随着燃料中乙醇含量的增加，缸内最高压力逐渐降低，压力升高率逐渐增加，工作过程有所粗暴；滞燃期的总体趋势逐渐延长，燃烧持续期总体趋势逐渐缩短；小负荷的放热率峰值逐渐降低，中高负荷的最大放热率逐渐增加。对试验结果分析可知乙醇热值低、汽化潜热高、十六烷值低等特点对本试验用增压中冷压燃式发动机燃用柴油醇性能影响非常大，是各项性能降低的主要因素。在增压中冷压燃式发动机结构不作变化和调整情况下燃用柴油醇，柴油醇中乙醇的体积含量不应超过10%。燃用E10柴油醇，发动机额定功率降低了5.9%，最大扭矩降低了5.2%；燃油消耗率和HC排放有所增加，尤其是小负荷工况增加较大；烟度普遍降低，其他排放物有增有减，变化幅度不大。根据以上发动机试验结果总结出的趋势和规律，调整发动机相关参数，如提高进气温度、调整供油提前角等，或采用其他方法，如应用着火促进剂、降低乙醇掺烧比例等，进行了提高和改善增压中冷压燃式发动机燃用柴油醇各项性能的试验研究。提高进气温度，可以增加乙醇汽化所需热量，提高缸内温度，从而降低中小负荷大多数排气污染物的比排放量，只是由于温度增加，NOx排放有所增加；应用着火促进剂有助于柴油醇燃料的着火，从而降低CO 和HC排放，但NOx排放有所增加；由于乙醇的热值较低、汽化潜热较高，发动机燃用柴油醇，若保证发动机的动力性和经济性，应在原供油提前角的基础上适当提前，但发动机的排放会有所变化，烟度和CO排放减少，HC和NOx排放增加，尤其NOx排放增加幅度较大；燃用E5柴油醇，发动机的动力性、经济性及排放性能都要好于燃用E10柴油醇，但与燃用柴油相比还是有所下降。更多还原

【Abstract】 The study of alternative energy sources had already been developed all over the world because of energy sources problem. Ethanol as one of the most potential alternative fuels has became the study emphasis.The physical and chemical characteristics of ethanol are different from that of diesel. The mutual dissolubility of ethanol and diesel is very poor so as to bring delamination and the steady emulsion isn’t produced. A solublizer was added to the blend of diesel and ethanol to improve their mutual dissolubility and to prepare diesohol fuel. The diesohol didn’t bring delamination above freezing point temperature and the stabilization time exceeded three month.The main physical and chemical characteristics of diesohol were simply calculated using experience formula. The density, the cetane number, the low heat value and the flash point of diesohol are lower than diesel, but the vaporization heat is higher. The rule changes evidently when the volume concentration of ethanol is increased. These will affect the performance of engine fueled with diesohol.Without any configuration modification of a turbocharged intercooled CI engine, and keeping same volume supply delivery of different fuels at the same mode, extensive experiments were carried out on a engine fueled with diesel and three kinds of diesohol fuels (E10, E15 and E20).The results of engine full-load characteristic show that the power output of engine decreases as the ethanol volume concentration of diesohol fuel increases. The results of engine constant speed characteristic show that the brake specific fuel consumption (bsfc) increases, especially at the low load while the brake specific energy consumption (bsec) <WP=67>using diesohol increases at the low load and is equivalent at the moderate and high load range in comparison with that of the diesel fuel. The smoke emission decrease obviously, CO concentration emission increases at the low load of the low speed conditions while is equivalent at the moderate and high load, HC concentration emission increases gradually, especially at the low load, and NOx concentration emission decreases at the low and high load while increases at the middle load.The results of exhaust emission characteristics according to ECE R49 13-mode show that the brake specific emissions of CO, HC, NOx, PM and SOF fueled with disohol are higher than those of the diesel fuel operation, while brake specific emissions of DS are lower as the ethanol volume concentration of diesohol fuel increases. The rule of brake specific emission and concentration emission is different owing to decreasing of power output.The results of combustion characteristics show that the pressure in the cylinder gradually decreases as the ethanol volume concentration of diesohol fuel increases while the ratio of pressure rise gradually increases and the working process becomes rude. The periods of ignition delay prolong in collectivity trend, and the combustion duration is shortened. The maximum value of heat release gradually decreases at the low load, but it increases at the moderate and high load.The experiment results were analyzed, the low heat value, high vaporization heat and low cetane number of ethanol badly affect the performance of the turbocharged intercooled CI engine fueled with diesohol and they are the main reason of the performance decreasing. Without any adjustment for a turbocharged intercooler CI engine fueled with diesohol, the ethanol volume concentration of diesohol doesn’t exceed 10%. Fueled with E10 diesohol, the brake power of engine decreases 5.9% and the maximum torque decreases 5.2% while the specific fuel consumption and HC emission increase, <WP=68>especially at the low load. Smoke decreases evidently and other emissions change few.According to the trend and rule of above experiment results, the experiments were carried out on a engine fueled with E10 diesohol to improve engine performance by increasing the inlet temperature, adjustment fuel supply advance angle, using ignition improver and decreasing ethanol vo更多还原