【作者】 谭满志；

【导师】 郭英男；

【作者基本信息】 吉林大学 ， 动力机械及与工程， 2012， 博士

【摘要】 开发和使用清洁的替代燃料是同时解决能源短缺与大气污染两个全世界亟待解决的关键问题的重要途径，生物柴油和天然气合成柴油两种液体燃料是目前最具潜力的替代燃料，在柴油机结构和参数不做大的变化情况下就可以单独或者掺烧的形式使用。本文在同一柴油机机型上，通过混合燃料理化特性的分析，深入研究生物柴油和天然气合成柴油燃料（GTL）对柴油机燃烧特性、常规排气污染物和排气微粒粒径分布的影响规律，分析排气污染物和排气微粒粒径分布特征和关键影响因素。采用国内通用的先进测试仪器搭建了满足国Ⅳ排放要求的增压中冷高压共轨柴油机的测试平台。开发设计了分流式排气微粒稀释采样系统和两级排气微粒粒径分布测量稀释采样系统，使用TSI EEPS3090型发动机排气粒径谱仪进行排气微粒粒径分布试验时，排气微粒粒径分布测量稀释采样系统的最佳稀释比控制在200～300范围内。测试分析了试验燃料的主要理化特性，总结出生物柴油和天然气合成柴油混合燃料十六烷值、密度、芳烃含量、蒸馏特性温度T90/T95、硫含量、氧含量和黏度等理化特性参数以及天然气合成柴油正构烷烃浓度的变化规律。研究结果表明，对于生物柴油/石化柴油混合燃料，随着生物柴油含量的增加，燃烧特性中最高燃烧压力降低、最大放热率和最大压力升高率增加，但在小负荷时变化规律有所差异。滞燃期略有延长，燃烧持续期缩短。在大负荷工况常规排气污染物的CO、HC、PM和碳烟排放减少，NO_x排放增加。在小负荷工况，PM排放和碳烟排放增加，NO_x排放减少，生物柴油燃料的CO排放和HC排放高于石化柴油。稳态工况时石化柴油的排气微粒粒径分布曲线呈单峰结构，生物柴油呈核态模式和积聚态模式的双峰结构，与石化柴油相比，生物柴油的50nm以下核态微粒排放数量浓度较大，50nm以上积聚态数量浓度少。随着负荷的增加，石化柴油积聚态微粒数量浓度增加的幅度比核态模式微粒大，浓度峰值向大粒径方向偏移；而生物柴油核态微粒数量浓度下降，浓度峰值向小粒径方向偏移，积聚态微粒浓度上升，峰值向大粒径方向偏移。随着生物柴油含量的增加，稳态工况燃料的微粒粒径浓度分布由石化柴油单峰结构逐渐向生物柴油双峰结构过渡，工况不同，过度趋势有所差别。瞬态工况时，石化柴油以积聚态微粒为主，生物柴油以核态微粒为主，其总微粒平均数量浓度要高于石化柴油，核态模式微粒平均浓度要高于积聚态峰值。随着瞬变率变小，两种燃料的核态模式微粒平均浓度均逐渐降低，积聚态模式微粒平均浓度变化不大。随着生物柴油含量的增加，核态模式微粒平均浓度逐渐增加，积聚态微粒平均浓度逐渐减小，核态微粒所占总微粒比例逐渐增加，最高可达97%。生物柴油黏度高，密度大，十六烷值高，氧含量多，芳烃含量少等特点是影响柴油机燃烧特性、常规排气污染物和排气微粒粒径分布的主要因素。对于天然气合成柴油/石化柴油混合燃料，随着混合燃料中GTL含量的增加，燃烧滞燃期缩短，燃烧持续期延长，预混合燃烧量减少，扩散燃烧比增加。最高燃烧压力、最大压力升高率和最大放热率在不同工况变化规律有所差异。常规排气污染物CO、HC、NOx、PM和碳烟排放逐渐减少，只有在10%小负荷工况，NO_x排放略有增加。GTL燃料可以明显改善NO_x-PM的折中关系。石化柴油、GTL以及混合燃料的微粒数量浓度分布曲线在稳态工况均呈单峰结构，分布曲线在25nm左右出现了凹点，峰值区域在50～100nm之间，积聚态模式微粒粒径浓度增加的幅度要比核态模式大。随着GTL含量的增加，不同负荷的25nm以下核态模式微粒数量浓度逐渐减少，25nm以上核态模式微粒数量浓度和50nm以上积聚态模式微粒数量浓度在小负荷工况减少而在中大负荷工况增加。瞬态工况时核态模式微粒数量浓度在增负荷过程前期增加，在中期附近达到峰值，在后期减少。积聚态模式微粒数量浓度在增负荷过程中增加幅度不大。随GTL含量增加，核态模式微粒数量浓度峰值时刻提前，积聚态模式微粒数量浓度增加。使用低含量合成柴油混合燃料，随着合成柴油含量的增加，瞬态工况的核态模式数量浓度逐渐降低，尤其对于大瞬变率工况效果更显著。天然气合成柴油十六烷值高，芳烃含量少，密度小等特点是影响柴油机燃烧特性、常规排气污染物和排气微粒粒径分布的主要因素。更多还原

【Abstract】 The world faces two critical problems of energy shortage and air pollution. Developmentand utilization of clean alternative fuels is an effective solution. At present, biodiesel andgas-to-liquids (GTL) are most promising alternatives. They can be mono-fuel or blendedwith few diesel engine structure modification and parameters tuning. On the same dieselengine, this paper analyzes the physical and chemical characteristics of biodiesel andGTL blended fuel, their effects on combustion process, exhaust gas pollutants and PMsize distribution, and finding the key factors.The advanced test platform is established for high pressure common rail diesel enginewith advanced measurement facilities. Two partial flow dilution sampling systems aredesigned for PM mass and PM size measurement. Accroding to the requirement for theengine exhaust particle size spectrometer of TSI EEPS3090, the optimal dilution ratio isset in200~300.Seven physical and chemical properties of biodiesel and GTL blended fuel, aresummarized, as well as cetane number, density, aromatic content, distillationcharacteristic temperature T90/T95, sulfur content, oxygen content, viscosity, n-alkanesconcentration of GTL base on measurement.The results show that the peak pressure decreases, the maximum rate of heat releaseand the maximum pressure rising rate increases with more biodiesel. But, the case iscomparably different under low load. However ignition delay period increases slightlyand combustion duration decreases. Under high load, more biodiesel blended content,less CO, HC, PM and soot emission concentration, while more NOx. Under low load, PMand soot increases, NOxdecreases. CO and HC resulting from biodiesel B100arehigher than those of diesel. NOxand PM trade-off relationship are not obviouslyimproved.The particle size distribution curve of diesel is unimodal at steady operating conditions,while that of biodiesel is bimodal with nuclei mode and accumulation mode. Thenumber density of nuclei mode particle from biodiesel is higher than that of diesel,however, that of accumulation mode is less. Under higher load, the number densityrising rate of accumulation mode from diesel is bigger than that of nuclei mode, and thepeak shifts to the big size. The number density of nuclei mode from biodiesel decreasesand the peak shifts to the small size, while that of the accumulation mode rises and thepeak shifts to the big size. With more blended biodiesel under steady operatingconditions, particle distribution gradually changes from unimodal of diesel fuel tobimodal of biodiesel, but the transition trend is distinct under different operating condition. The particle size distribution from diesel dominates with50nm accumulationmode under transient operating conditions, and that of below50nm nuclei mode. Theaverage number density of biodiesel is higher than that of diesel, while that of nucleimode is higher than that of accumulation mode. With the transient rate decreases, theaverage number density of nuclei mode decreases, while that of accumulation is muchsmall. The average number density of nuclei mode gradually increases with moreblended biodiesel, while that of accumulation mode gradually decreases, the highestcan amount to97%.The biodiesel is of higher viscosity, cetane number, oxygen content and lower aromaticcontent, density. They have great effect on combustion，exhaust gases pollutants andPM size distribution.With more blended GTL, the shorter ignition delay period and longer combustionduration. At the same time pre-mixing combustion quantity decreases and diffusioncombustion ratio increases. The peak pressure, maximum pressure rise rate and themaximum rate of heat release are distinct under different operating condition. CO, HC,NOx, PM and soot emissions gradually decrease, but NOx increases slightly at10%lowload, GTL can significantly improve the NOxand PM trade-off relationship.Under steady operating conditions, PM number density distribution from diesel, GTL andblended fuel take on unimodal. At about25nm, the number density is the smallest. Thepeak area lies between50~100nm. That of accumulation mode from GTL is biggerthan that of nuclei mode. With more blended GTL，that of nuclei mode below25nmgradually decreases under different load, that of nuclei mode above25nm and that ofaccumulation mode above50nm decreases under low load decrease, however theyincrease at medium and higher load. Under transient operating conditions, the numberdensity of small particle size of nuclei mode increases under higher load at early stage,peak near interim and reduce in the later. That of accumulation mode change very smallunder higher load. With more blended GTL, the peak number density of nuclei modeadvances and that of large particle size of accumulation mode increases. With lessblended GTL, the peak number density of nuclei mode gradually decreases with moreblended GTL, especially for large transient rate condition better effect.The GTL is of higher cetane number, lower aromatic content, less density which hasgreat effects on combustion, exhaust pollutants and PM size distribution.更多还原