卷烟厂粉尘风力收集系统设计与实现

为了解决卷烟生产中烟草粉尘危害的问题,在分析粉尘风力收集原理的基础上,运用流体力学和气力输送的原理,提出具体的粉尘风力收集系统结构设计方案,并对系统压损及风量等主要参数进行计算。同时,对实际应用中的两种不同输送方式进行比较得出,粉尘风力收集系统可以降低粉尘外泄,同时也降低了设备费用及运行费用。     

柴油/碳酸二甲酯燃烧颗粒的微观结构和分形特征

为降低柴油机颗粒物排放,探讨了柴油机燃用柴油/碳酸二甲酯混合燃料燃烧颗粒微观结构和分形特征的变化规律. 采用扫描电镜、透射电镜和SAXS(同步辐射小角X射线散射)相结合的方法,针对DMC(碳酸二甲酯)添加量(以w计)对柴油机燃烧颗粒微观结构和分形特征参数的影响规律进行了研究. 结果表明:与柴油燃烧颗粒相比,D10〔w(DMC)为10%〕、D20〔w(DMC)为10%〕燃烧颗粒的碳粒子平均层面间距分别增加了5.3%、15.1%,弯曲度平均值分别增加了4.0%和10.3%,表明燃烧颗粒的氧化活性增加;与柴油相比,D10、D20燃烧颗粒的质量分形维数分别增加了0.44和0.52,下限均升高了0.2,SAXS与电镜图像对燃烧颗粒的质量分形维数的分析结果相一致,即质量分形维数随DMC添加量的增加而升高,表明燃烧颗粒的团聚程度提高;与柴油燃烧颗粒相比,D10、D20燃烧颗粒表面分形维数的下限分别升高了0.1和0.2,表明其燃烧颗粒表面的粗糙程度和不规则程度提高;与柴油燃烧颗粒相比,D10、D20燃烧颗粒的活化能分别降低了3.9和7.9 kJ/mol,表明燃烧颗粒的氧化活性随着DMC添加量的增加而增强,验证了燃烧颗粒微观尺寸结构和分形特征的研究结果. 研究显示,柴油中添加DMC能够提高燃烧颗粒的氧化活性,燃烧颗粒的氧化活性越强,其在后处理过程中就越易被氧化,有助于降低柴油机的颗粒物排放.      

柴油机EGR氛围颗粒的空间结构与表面形态分析

为揭示EGR(废气再循环)对柴油机颗粒表面形态以及空间结构的影响,针对不同EGR率下产生的柴油机颗粒,采用颗粒粒径分析仪以及X射线小角散射等分析手段,研究了EGR对柴油机排气颗粒粒径、数浓度和质量浓度的影响,分析了颗粒团聚程度、团粒间隙尺寸以及表面形态等参数随EGR率的变化规律.结果表明:随着EGR率从10%增至30%,颗粒数浓度峰值粒径向大粒径方向偏移,粒径在10～50 nm的核模态颗粒数浓度分别降低了14.7%和29.4%;粒径在50～500 nm的积聚态颗粒数浓度分别增加了17.1%和139.4%;总颗粒数浓度也有较大幅度增加,分别增加了4.5%和72.1%.采用EGR后,颗粒的质量分形维数和表面分形维数分别增加了12.1%和18.2%,表明EGR会使颗粒的质量分布不均匀,表面粗糙程度增加.随着EGR率的增加,颗粒的团粒间隙分布有明显差异,EGR率为0时的团粒间隙尺寸主要分布在8～11 nm,EGR率为30%时的团粒间隙尺寸主要分布在4～6 nm,表明EGR可在总体上降低团粒间隙尺寸和数浓度,增加了颗粒的团聚程度和空间结构的紧密程度.研究结果对于拓宽EGR的工况使用范围、提高DPF等后处理装置的工作效率、进一步降低柴油机的NO_x和颗粒排放具有重要意义.      

Research on the effects of diesel engine exhaust transport distance on particulate microstructure

This study aims to reveal the evolutionary process of particles during the diesel exhaust transport process and to further understand the effects of diesel exhaust transport distance (D_ET) on a particulate microstructure. Specifically, the micromorphological, particle size distribution, and aggregate characteristics of particles as well as the variation of the structural characteristics of elementary carbon particles (ECPs) as D_ET changed were examined using an engine exhaust particle size spectrometer, a high-resolution transmission electron microscopy system, and a small-angle X-ray scattering system. The results show the following: As D_ET increased, the chains gradually lengthened, the extent of accumulation and stacking increased, and a number of clusters gradually rose. The average particle diameter increased from 23.1 nm at 0 m to 92.7 nm at 3 m. In addition, as D_ET increased, the number of accumulation-mode particles, the number of folded, curved carbon layers in the inner core of carbon particles, and the disorderliness of carbon layers in the outer shell of carbon particles all increased. Moreover, the boundary between the inner core and the outer shell became increasingly obscure. As D_ET increased, there was a gradual decrease in the difference in electron density between particles, and the fractal dimensionality of the distribution, average cross-sectional size, radius of gyration, and axial length of pores were, respectively, 33.3%, 40%, 38.2%, and 50.3% less at 3 m than at 0 m. Besides that, the number of small (< 3 nm) pores gradually increased, and the number of large (> 10 nm) pores gradually decreased. Overall, as D_ET increased, pore size and number decreased. There was a gradual increase in the number of folded and curved carbon layers in the inner core of ECPs and an increase in the disorderliness of carbon layers in their outer shell as D_ET increased. Furthermore, the boundary between the inner core and the outer shell became increasingly obscure as D_ET increased. The crystallite size of ECPs decreased from 1.365 nm at 0 m to 1.098 nm at 3 m. This suggests that the number of continuously arranged carbon atoms decreased, the arrangement of carbon atoms was more disorderly, and the degree of graphitization decreased. As D_ET increased, there was a gradual increase in the interlayer spacing and curvature of ECPs. This suggests that increasing D_ET led to a more disorderly distribution of electron orbitals inside the carbon layers, less electron resonance stability in the carbon layers, greater oxidative activity of ECPs, and greater inherent oxidative capacity of particles.

     

废气再循环系统参数对柴油机燃烧特征的影响

为进一步优化柴油机燃烧过程,减少燃烧污染物排放.围绕EGR（exhaust gas recirculation,废气再循环技术）废气组分和废气温度等系统参数对柴油机燃烧特征的影响机制,采用试验与模拟相结合方法,分别研究了通入废气、N₂、CO₂时以及不同EGR废气温度时对柴油机燃烧过程的影响,阐明了燃烧关键中间产物的生成规律.结果表明,①通入CO₂时,柴油机的缸内最大爆发压力和放热率峰值最低,滞燃期最长,燃烧持续期最短,·OH、H₂O₂、CH₂O·和CO等关键中间组分的生成规律与通入N₂时相反.②通入N₂时,柴油机的缸内最大爆发压力和放热率峰值最高,滞燃期最短,燃烧持续期最长并;并且通入N₂时,·OH的峰值最高,形成时刻最早,H₂O₂、CH₂O·以及CO的峰值均有所降低且形成时刻提前.③随着废气温度增加,缸内最大爆发压力降低,放热率曲线由单峰向双峰分布发展,放热率峰值有较大幅度的降低,滞燃期缩短,燃烧持续延长,缸内·OH、H₂O₂、CH₂O·以及CO的峰值均有所降低,并且生成的区域范围变窄.④废气成分中,CO₂对燃烧过程和关键中间产物的影响最大,是阻滞燃烧反应的主要气体成分,通过控制EGR废气成分和温度可以有效改善柴油机燃烧过程,拓宽EGR技术的工况使用范围.研究显示,EGR废气成分对燃烧中间产物的自由基衍化历程影响较大,有必要进一步开展EGR废气成分预处理研究,精确控制EGR废气温度,有助于改善燃烧过程,控制排放污染物中间产物的生成历程和排放量.      

柴油机芳香烃类污染物的测量方法研究

采用活性炭吸附、溶剂解吸和气-质联用(GC-MS)分析的方法,对柴油机尾气中芳香烃污染物进行了定性、定量分析。实验结果表明,该方法能够减少柴油机尾气中其他颗粒相和气相有机成分的干扰,采样快速,灵敏度、准确度高;活性炭吸附管采样效率高,当采样流量为4 L/min、采集时间20 min时,不会出现芳香烃脱附现象;测量方法重复性较好,相对标准偏差低于6.5%,检出限为3~9μg/m3,回收率为87.5%~95.2%;该方法可用于测量柴油机燃用生物柴油和0号柴油尾气中芳香烃污染物。     

山东淄博佛村黄土沉积多指标记录的气候环境演变过程

对山东省淄博市寨里镇佛村黄土剖面(FC剖面)进行粒度、磁化率及色度等沉积学指标分析,结果表明:(1)FC剖面6个光释光样品年龄结果介于3.02±0.45—100.99±13.58 ka,说明FC剖面是末次间冰期以来的沉积物;(2)根据沉积物粒度频率分布曲线和粒度组成特征,并与伊犁黄土、黄土高原黄土对比,可判知FC剖面为风成沉积物;(3)FC剖面磁化率与色度曲线具有相似的变化趋势,较好指示了黄土沉积时的冷暖干湿变化;(4)根据粒度中值粒径(Md)、低频磁化率(χlf)、土壤颜色(L~*,a~*)、环境敏感组分(56.23—112.20μm)等气候代用指标并结合光释光测年结果,将FC剖面划分为5个部分,分别对应于深海同位素MIS1—MIS5时期。1、3、5部分分别对应MIS1、MIS3早期、MIS5阶段,夏季风强盛,气候较暖湿,发育古土壤;2部分对应MIS2和MIS3中晚期阶段,4部分对应MIS4阶段,冬季风强盛,气候较干冷,堆积黄土。