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柴油机燃用乙醇-柴油含氧燃料时微粒特性的分析 总被引:12,自引:0,他引:12
研究了一台增压柴油机燃用乙醇一柴油时的微粒总质量排放及粒径分布特性,并对微粒中可溶性有机物(SOF)、干碳烟(DS)和硫酸盐的质量百分比及SOF中的组分进行了分析。结果表明:使用含氧燃料后柴油机排气烟度大幅度降低而微粒总排放量降低幅度要小一些;微粒中DS排放降低;SOF排放增加,与未燃甲酯的产生导致HC排放增加有关;多环芳香烃比例随发动机负荷增大而减小;含氧燃料使得粒径分布在0.2~0.5μm范围内的比重在小负荷时降低,大负荷时升高。 相似文献
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针对风剪切对尾流的影响研究不充分的问题,文章在某风电场进行了风场实验,分析了不同风速下的风剪切现象以及在不同来流条件下的尾流变化特征,并使用了三维尾流模型对垂直尾流剖面进行了验证。结果表明:风速大小对风剪切的影响较为明显,风剪切效应随着风速的增加而加强,风速每增加1 m/s,风剪切指数增加0.05;风剪切效应对尾流的分布有较大影响,风剪切效应越强,尾流的速度沿着高度方向上的梯度越大,尾流的宽度和长度也越大;在轮毂中心线附近的模型预测曲线和尾流实测数据拟合较好,相对误差基本在10%以内,受地形的影响,近地侧预测的相对误差较大。 相似文献
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基于尺寸分布的生物柴油排气微粒组分研究 总被引:1,自引:0,他引:1
使用电子低压撞击仪(ELPI)分级粒径采集了柴油机的排气微粒,应用热重分析(TGA)方法研究了发动机燃用柴油和两种生物柴油时,排气微粒中挥发性物质(VOF)的含量。研究结果表明:燃用生物柴油,排气微粒VOF含量高于纯柴油,排气中小粒径微粒的VOF质量百分比均高于柴油,与总微粒的排放规律相同;超细微粒(d<0.100μm)具有较高的VOF质量百分比。柴油机燃用生物柴油后,总微粒中VOF质量百分比从44.917%上升到70.767%,在0.100μm相似文献
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测量了轻型柴油车在高怠速和低怠速运转的条件下,其尾气烟羽中粒径范围在15nm到30μm的颗粒数量和粒径的分布。利用SMPS和APS测量装置测量尾气烟羽中心线和环境背景条件下的颗粒排放。测量结果表明,测试的柴油车在高怠速运转的条件下会排放出更多的颗粒。然而,在两种怠速条件下,总的颗粒数量浓度由于沉降的作用会随着远离排气管的距离而减少。测量结果还表明,柴油车排放的颗粒主要是粒径小于700nm的颗粒,这些细颗粒比粗颗粒更易长期悬浮于大气中,从而引发局部的颗粒物污染问题。 相似文献
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汽油机颗粒物数量排放及粒径的分布特性 总被引:3,自引:0,他引:3
采用 DMS500快速颗粒取样分析仪对一台气道喷射国Ⅲ汽油机进行了颗粒物粒径分布特性的试验研究.结果表明,汽油机排气中颗粒物以核态为主,仅部分工况存在积聚态.怠速时呈现包括核态和积聚态的双峰分布;低转速时表现为核态的单峰分布;中等转速时粒径分布范围扩大,既存在核态颗粒物,也存在积聚态颗粒物.相同转速下,随负荷的增加核态颗粒物数密度峰值先降低后增加;相同负荷下,随转速的升高核态颗粒物数密度峰值和峰值粒径均降低,积聚态颗粒物数密度峰值有增加的趋势.催化器对核态颗粒物的净化效果较好,对积聚态颗粒物的净化效果较差,对低转速下的粒径分布有明显影响 相似文献
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Carlos A. Echavarria Adel F. Sarofim JoAnn S. Lighty Andrea D’Anna 《Combustion and Flame》2011,(1):98-104
The effect of benzene concentration in the initial fuel on the evolution of soot size distribution in ethylene/air and ethylene/benzene/air flat flames was characterized by experimental measurements and model predictions of size and number concentration within the flames. Experimentally, a scanning mobility particle sizer was used to allow spatially resolved and online measurements of particle concentration and sizes in the nanometer-size range. The model couples a detailed kinetic scheme with a discrete-sectional approach to follow the transition from gas-phase to nascent particles and their coagulation to larger soot particles. The evolution of soot size distribution (experimental and modeled) in pure ethylene and ethylene flames doped with benzene showed a typical nucleation-sized (since particles do not actually nucleate in the classical sense particle inception is often used in place of nucleation) mode close to the burner surface, and a bimodal behavior at greater height above burner (HAB). However, major features were distinguished between the data sets. The growth of nucleation and agglomeration-sized particles was faster for ethylene/benzene/air flames, evidenced by the earlier presence of bimodality in these flames. The most significant changes in size distribution were attributed to an increase in benzene concentration in the initial fuel. However, these changes were more evident for high temperature flames. In agreement with the experimental data, the model also predicted the decrease of nucleation-sized particles in the postflame region for ethylene flames doped with benzene. This behavior was associated with the decrease of soot precursors after the main oxidation zone of the flames. 相似文献
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Particulate Matter size distribution in the exhaust gas of a modern diesel Engine fuelled with a biodiesel blend 总被引:1,自引:0,他引:1
Sathaporn Chuepeng Hongming XuAthanasios Tsolakis Miroslaw WyszynskiPhilip Price 《Biomass & bioenergy》2011,35(10):4280-4289
The characteristics of particulate mater size distribution in the exhaust gas of an automotive diesel engine have been studied for a biodiesel blend of 30% rapeseed methyl ester (RME) and 70% ultra low sulphur diesel (ULSD) by volume (B30). The engine, a twin-turbo charged V6 equipped with a common rail fuel injection system, was operated on 16 steady-state points extracted from a corresponding New European Driving Cycle test with no engine system modification and a fast differential mobility spectrometer was used to determine the particulate number concentration and distribution. It is shown that the number-size distribution is dependent on engine operating conditions including the rate of exhaust gas recirculation (EGR). Compared with ULSD, B30 leads to a 41% smaller average size of the particles with EGR but gives rise to a higher number concentration under certain engine operating conditions, with the differences varying between nucleation and accumulation mode. The calculated particle total mass for B30 combustion aerosol is lower than the value with ULSD for all the engine operating conditions tested. The average B30 aerosol was 28% smaller in size on mass basis, compared to ULSD aerosol. For both fuels, the relationship between the particle total number and total mass has been found to be directly correlated and both the number and the mass of particles increase when the mean diameters of particles increase. 相似文献
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直喷式柴油机排放微粒尺寸分布特性 总被引:4,自引:0,他引:4
在一台单缸柴油机上用SMPS微粒测量装置测量了不同运转条件(如转速、负荷变动、怠速运行、燃油喷射定时等)下柴油机排放微粒尺寸与浓度分布,分析了柴油机微粒排放尺寸分布和数量浓度的特征及其主要影响因素.结果表明,发动机负荷变化对微粒排放的影响较大,在各种负荷下大部分排放微粒都是碳核模式的超细或纳米尺寸微粒,而质量上以累积模式颗粒占主要部分,发动机冷机起动和怠速运行时产生的大部分排放微粒是碳核模式粒子,喷油提前角对排放微粒浓度和尺寸分布有显著影响. 相似文献
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凝并作用下火灾烟颗粒粒径分布及变化 总被引:1,自引:0,他引:1
预测火灾烟颗粒粒径分布特征参数的动态变化可实现探测系统对环境参数响应的动态模拟.顶棚烟气输运中,烟颗粒的布朗凝并是改变粒径分布的主要过程,应用矩方法求解布朗凝并作用下对数正态颗粒粒径分布的烟颗粒非线性凝并方程,得到随燃烧变化的凝并速率下粒径分布特征参数随时间的计算结果.正庚烷试验火烟颗粒分布的计算预测值与实验测量值相近,结果表明,在烟雾浓度快速上升阶段,烟颗粒凝并造成颗粒浓度损失不明显,几何平均粒径变化很小,而燃烧基本结束后,烟颗粒数密度衰减很快. 相似文献
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对柴油机颗粒过滤器(diesel particulate filter,DPF)进行了颗粒物(particulate matter,PM)在线捕集试验。通过发动机废气排放颗粒物粒径谱仪EEPS-3090分析了DPF对不同粒径PM的捕集特性;通过扫描电镜仪和热重分析仪探究了DPF前后端PM的堆积形貌及氧化特性。研究结果表明:DPF对大粒径颗粒物的捕集效果优于小粒径颗粒物,聚集态颗粒物基本被DPF完全拦截;DPF孔道过滤壁面的深层碳烟减小了微孔孔径,随着采样时间的增加,DPF对PM的捕集率升高。柴油机排气流经DPF后,逃逸出少量PM,以核态颗粒物为主。与DPF前端相比,后端PM的挥发性组分含量升高,元素碳的含量下降,氧化活性增强。 相似文献
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We measured particle size distributions of total and singly charged nanoparticles in premixed flames with different flame stoichiometry and temperature to investigate particle inception.Particle charging in flames occurs by diffusion charging involving ions formed by chemi-ionization reactions in the flame front. It can be described by a Boltzmann charge fraction distribution evaluated at the local flame temperature where the particles interact with the chemi-ions. As the particles coagulate in the post flame zone, their charge fraction is reduced. The charge distribution of the coagulated aerosol again results in a Boltzmann curve, this time evaluated at the local post flame gas temperature where the particles had their last coagulation event. Particle nucleation in the post flame zone, where chemi-ions are drastically reduced, produces uncharged particles.Considering the above charging processes, the charge fraction of the nucleation mode contains information on the location within the flame these particles were formed. The results show that in flames near the particle inception threshold, particles are charged close to the flame front and remain charged even late in the post flame zone. Furthermore, smaller particles undergo less charge neutralization by coagulation as they travel through the post flame zone than larger particles. A different scenario is observed in richer flames; the smaller particles eventually become uncharged, indicating that significant amounts of freshly nucleated particles in these flames are formed in the post flame zone. Whether nucleation preferentially occurs close to the flame front or persists into the post flame zone also depends on flame temperature. 相似文献
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介绍了以四甲基硅烷为原料,采用气相燃烧的方法制备超细白炭黑的新工艺。探讨了火焰构型、四甲基硅烷给气速率、甲烷给气速率、氧气给气速率、载气(氮气)通气速率等反应条件对产物的理化特性的影响。结果表明,前驱体浓度、初级颗粒在火焰中停留时间和火焰温度是影响白炭黑颗粒粒径大小的主要因素,前驱体浓度大、火焰中停留时间长、火焰温度高、产物粒子粒径越大。通过调节适量载气,可以很好地控制白炭黑粒径大小,使其粒径分布更均匀,成功制取粒径为9.46nm的超细白炭黑。并指出二氧化硅纳米颗粒在扩散火焰中经历化学反应、成核、凝并及团聚等几个主要过程。 相似文献