等离子体催化铁系金属催化剂氨分解制氢研究进展

氢能作为一种零碳二次能源被广泛应用于各种工业领域.氨作为一种储氢载体,具有储氢量高(17.6 wt%)、能量密度高和易液化等特点,其分解产物只有氢气和氮气,符合国家“碳达峰,碳中和”的战略发展方向.但是氨分解的活化能高,反应条件较为苛刻.因此,开发安全、高效、低成本的氨分解制氢技术对于氢能发展具有重要意义.文章首先阐明了氨分解反应的基本原理,介绍了铁系金属催化剂催化NH₃分解制氢的研究进展, Fe,Co和Ni基催化剂的NH₃分解活性较高,因为其金属-氮的结合能适中,之后从调控活性金属中心出发,通过加入第二金属、调控形貌、缺陷/掺杂、构建金属-载体相互作用等方面设计提高氨分解的活性,并采用多种表征方法揭示催化剂的构效关系.除铁系催化剂外,还重点介绍了提高氨分解效率的等离子体技术,回顾了等离子体的原理、种类、作用机制以及在辅助催化氨制氢方面的协同效应.文章综述了催化NH₃分解的反应机理,介绍了目前氨分解制氢催化剂设计的最新进展,总结了提高NH₃分解制氢的策略,强调了等离子体在辅助催化NH₃     

不同晶型CL-20热分解反应机理计算分析

基于反应力场,采用NPT、NVT系综和Berendsen方法,对ε-、β-和γ-CL-20超晶胞在不同温度下的热分解反应过程进行分子动力学计算。结果表明:3种晶型CL-20的初始分解路径均是五元环和六元环中的N-NO₂键断裂生成·NO₂自由基,生成的主产物包括N₂、H₂O、CO、CO₂、NO₂、NO₃、HNO₂、HNO₃、N₂O₅、N₂O₂和NO等。相同晶型的CL-20发生热分解生成的主产物的反应速率常数随温度的升高而增大。     

Granulation by spray coating aqueous solution of ammonium sulfate to produce large spherical granules in a fluidized bed

Spherical 2-4mm granules of ammonium sulfate（NH₄）₂SO₄ are promising fertilizer for practical use,though only much smaller grains are being produced in industry.This work used coating granulation to produce large spherical granules of（NH₄）₂SO₄ in a fluidized bed by spraying its aqueous solution onto0.9-1.6 mm（NH₄）₂SO₄ core particles.However,the overall coating efficiency was only 58%due to loss as dust by attrition of（NH₄）₂SO₄ in the vent gas.By adding CaCO₃ or SiO₂ particles into the feed solution,the coating efficiency was increased to over 90%.This increase in coating efficiency was due to a change in the crystallization mechanism of（NH₄）₂SO₄.The added CaCO₃ or SiO₂ particles provided a heterogeneous surface that induced（NH₄）₂SO₄ to crystallize uniformly to form a more compact structure less susceptible to attrition.     

Chemical composition and source apportionment of the ambient PM2.5in Hangzhou,China

To identify and apportion the sources of the ambient PM_2.5 in the urban area of Hangzhou,China,PM_2.5samples were collected at three sites in the city from April 2004 to March 2005.Water-soluble ions,metal elements,and total carbon（TC） in PM_2.5 samples were analyzed.The results indicated that the 24-h mean concentrations of PM_2.5 ranged from 17.1 to 267.0 μg/m³,with an annual average value of 108.2 μg/m³.Moreover,the seasonal mean values for PM_2.5 in spring,summer,autumn,and winter were 116,73.1,114.2,and 136.0 μg/m³.respectively.According to the Chinese ambient quality standard,at least 70% of the monitoring data exceeded the limit value.The total contribution of water-soluble ions,including F^-,Cl^-,NO₃^-,SO₄^2-.NH₄⁺,K⁺,and Na⁺.to PM_2.5 mass varied from 32.3% to 36.7%.SO₄^2-,NO₃^-,and NH₄⁺were the main constituents of the ions,with contributions to PM_2.5 varying from 14.1% to 14.7%,6.0%to 7.8%,and 6.4% to 7.7%,respectively.In addition,the annual mean mass fraction of TC in PM_2.5 was27.8%.The annual average total contribution of the group of elements of Zn,Pb,Cu,Mn,Cr,Ni,Se,Mo.Cd,Sb,and Ag to the aerosol was in the range of 1.7-2.0%.Furthermore,positive matrix factorization was applied to analyze the PM_2.5 data collected from the central area,and five factors were identified.The factor contributions to PM_2.5 mass were 12.8%,31.9%,10.1%,17.2%,and 27.9%,respectively.Iron/steel manufacturing and secondary aerosol were the main sources for the fine particles.These findings may have significance for controlling the atmospheric contamination in the city.     

掺氢比对甲烷-氧气爆轰特性的影响

含氢多组分燃料由于其优良的燃烧特性逐渐成为研究关注的重点。为了对掺氢燃料的爆轰特性作进一步的研究，设计了长3 000 mm、管径30 mm的圆柱形半封闭燃烧室，对不同初压下的CH₄-2O₂、6CH₄-H₂-12.5O₂、3CH₄-H₂-6.5O₂（掺氢比分别为0%、5.1%、9.5%）3种预混合气的爆轰特性进行了实验研究，并采用烟熏膜、离子探针和压力传感器分别探测胞格结构、火焰位置和内部压力。结果表明，甲烷/氧气掺氢后可以有效提高爆轰波的传播速度，且掺氢浓度越高，传播速度越快；同时，氢气的掺入可减少管道出口处的速度亏损并在初始压力较低时加速火焰和激波的耦合，降低胞格尺寸，提高爆轰敏感性。     

爆轰法合成纳米CeO粉末*2

爆轰合成过程中采用Ce(NO₃)₃·6H₂O制备的可爆药剂,并利用X射线衍射仪(XRD)和透射电子显微镜(TEM)对合成的纳米CeO₂粉末进行了检测,研究了起爆方式对于合成产物结晶化度、粒径和形貌的影响。结果表明,采用Ce(NO₃)₃·6H₂O制备的可爆药剂,可以合成立方晶系的球形纳米CeO₂; 提高可爆药剂的爆速,可有效降低纳米CeO₂的粒径,得到球形化更好的纳米粒子。     

低稀释度条件下乙烯点火特性的激波管研究

在激波管中利用反射激波后高温环境加热燃料,以燃料点火过程中氢氧自由基特征发射光谱强度的急剧变化作为点火发生的标志,在温度范围800 1 650K,压力0.2MPa, 0.7MPa, 1.2MPa,化学当量比为0.5, 1, 2,O₂ 浓度为空气含量20% 的条件下,进行了C₂H₄/O₂/Ar 混合气在低稀释度条件下点火特性的实验研究. 获得了乙烯点火延时随温度、压力、化学当量比、燃料以及氧化剂浓度等参数变化的拟合关系式. 对乙烯点火转爆轰现象进行了初步观察,考察了初始温度对乙烯点火特性以及点火转爆轰的影响.      

低稀释度条件下乙烯点火特性的激波管研究简

在激波管中利用反射激波后高温环境加热燃料,以燃料点火过程中氢氧自由基特征发射光谱强度的急剧变化作为点火发生的标志,在温度范围800 1 650K,压力0.2MPa, 0.7MPa, 1.2MPa,化学当量比为0.5, 1, 2,O₂ 浓度为空气含量20% 的条件下,进行了C₂H₄/O₂/Ar 混合气在低稀释度条件下点火特性的实验研究. 获得了乙烯点火延时随温度、压力、化学当量比、燃料以及氧化剂浓度等参数变化的拟合关系式. 对乙烯点火转爆轰现象进行了初步观察,考察了初始温度对乙烯点火特性以及点火转爆轰的影响.     

Spatiotemporal variations of PM2.5 and PM10 concentrations between31 Chinese cities and their relationships with SO2,NO2,CO and O3

The variations of mass concentrations of PM_2.5,PM₁₀,SO₂,NO₂,CO,and O₃ in 31 Chinese provincial capital cities were analyzed based on data from 286 monitoring sites obtained between March 22,2013 and March 31,2014.By comparing the pollutant concentrations over this length of time,the characteristics of the monthly variations of mass concentrations of air pollutants were determined.We used the Pearson correlation coefficient to establish the relationship between PM_2.5,PM₁₀,and the gas pollutants.The results revealed significant differences in the concentration levels of air pollutants and in the variations between the different cities.The Pearson correlation coefficients between PMs and NO₂ and SO₂ were either high or moderate(PM_2.5 with NO₂:r=0.256-0.688,mean r=0.498;PM₁₀ with NO₂:r = 0.169-0.713,mean r = 0.493;PM2.5 with SO₂:r= 0.232-0.693,mean r=0.449;PM₁₀ with SO₂:r = 0.131-0.669,mean r=0.403).The correlation between PMs and CO was diverse(PM_2.5:r = 0.156-0.721,mean r=0.437;PM₁₀:r=0.06-0.67,mean r= 0.380).The correlation between PMs and O₃ was either weak or uncorrelated(PM_2.5:r--0.35 to 0.089,mean r=-0.164;PM₁₀:r=-0.279 to 0.078,mean r=-0.127),except in Haikou(PM2.5:r=0.500;PM₁₀:r-0.509).     

Impacts of aerosol chemical compositions on optical properties in urban Beijing,China

The optical properties of aerosols and their chemical composition,including water-soluble ions,organic carbon（OC）,and elemental carbon（EC） in PM_2.5 and PM₁₀,were measured from 26 May to 30 June of 2012 at an urban site in Beijing.The daily average concentrations of PM_2.5 and PM₁₀ were 103.2 and 159.6 μg/m³,respectively.On average,the OC and EC contributed 20.1% and 4.3% ,respectively,to PM_2.5 and 16.3% and3.9% ,respectively,to PM₁₀.Secondary ions(SO₄^2-,NO₃^-,and NH₄⁺) dominated the water-soluble ions and accounted for 57.9% and 62.6% of PM_2.5 and PM₁₀,respectively.The wind dependence of PM_2.5,OC,SO₄^2-,and NO₃^- implied that the pollution sources mainly came from south and southeast of Beijing during the summer.The monthly mean values of the scattering coefficient(σ_sc) and absorption coefficient(σ_ab) at525 nm were 312.9 and 28.7 Mm^-1,respectively,and the mean single-scattering albedo（ω） was 0.85.The wind dependence of σ_sc revealed that this value was mainly influenced by regional transport during the summer,and the relationship between σ_ab and wind indicated that a high σ_ab resulted from the joint effects of local emissions and regional transport.The reconstructed σ_sc that was derived from the revised IMPROVE equation agreed well with the observations.The contribution of different chemical species toσ_sc was investigated under different pollution levels,and it was found that secondary inorganic aerosols accounted for a large part of σ_sc during pollution episodes（35.7% ）,while organic matter was the main contributor to σ_sc under clean conditions（33.6% ）.     

湍流强度对预混燃烧影响的大涡模拟研究

本文对甲烷和空气在突扩燃烧室内的预混燃烧进行了大涡模拟(LES)研究,主要关注于预混燃料的湍流强度对甲烷-空气预混燃烧效率的影响.LES数值模拟给出了不同入口湍流强度的条件下燃烧室内湍流预混燃烧反应流场的速度场,温度场和浓度场分布.分析的结果表明:随着预混燃料入口湍流强度的增大,燃烧反应更加剧烈,燃烧效率提高,火焰长度也随之变短,同时,一氧化碳的生成区域明显变小,整体生成量减少.研究的结果对有效地提高燃气轮机的燃烧效率和减少污染物的排放提供一定的参考依据.     

Characterization of summer PM2.5 aerosols from four forest areas in Sichuan,SW China

Aerosol samples were collected over 24 and 12 h to represent day/night aerosol characteristics in forest areas at Ya’an Baima Spring Scenic Area（BM）,Panzhihua Cycas National Nature Reserve（PZ）,Gongga Mountain National Nature Reserve（GG）,and Wolong National Nature Reserve（WL）,during the summers of 2010-2012.Mass and chemical component concentrations,including organic carbon,elemental carbon,and inorganic ions(F^-,Cl^-,NO₂^-,NO₃^-,SO₄^2-,C₂O₄^2-,PO₄^3-,K⁺,Na⁺,Ca²⁺,Mg²⁺,and NH₄⁺),of PM_2.5 aerosols were measured.The average PM2.5 concentrations for 24 h were 72.42,104.89,20.55,and29.19 μg/m³ at BM,PZ,GG,and WL,respectively.Organic matter accounted for 38.0-49.3%,while elemental carbon accounted for 2.0-5.7%of PM2.5 mass.The sum concentrations of SO₄^2-,NH₄⁺,and NO₃^-accounted for 23.0%,17.4%,22.1%,and 30.5%of PM2.5 mass at BM,PZ,GG,and WL,respectively.Soil dust was also an important source of PM2.5,accounting for 6.3%,17.0%,10.4%,and 19.1%of PM2.5 mass at BM,PZ,GG,and WL,respectively.These reconstructed masses accounted for 75.9-102.0%of PM2.5 mass from the four forest areas of SW China.     

气/固/液三相混合物燃烧转爆轰过程实验研究

利用多相燃烧爆炸实验系统,通过高压喷粉/喷雾以及高能点火等过程,对化学当量比条件下3种 典型燃料空气炸药,即硝基甲烷/铝粉/空气、硝酸异丙酯/铝粉/空气、乙醚/铝粉/空气三相混合物的燃烧转爆 轰过程进行了实验研究,同时根据实验结果对比了3种三相混合物的燃爆性能。得到了三相悬浮混合物燃烧 转爆轰过程的宏观规律以及三相混合物燃爆性能随质量浓度变化的规律。     

Chemical characteristics of PM2.5 during dust storms and air pollution events in Chengdu,China

Daily fine particulate(PM_2.5) samples were collected in Chengdu from April 2009 to February 2010 to investigate their chemical profiles during dust storms（DSs） and several types of pollution events, including haze（HDs）,biomass burning（BBs）,and fireworks displays（FDs）.The highest PM_2.5 mass concentrations were found during DSs（283.3μg/m³）,followed by FDs（212.7μg/m³）,HDs（187.3μg/m³）,and BBs（130.1μg/m³）.The concentrations of most elements were elevated during DSs and pollution events, except for BBs.Secondary inorganic ions(NO₃^-,SO₄^2-,and NH₄⁺) were enriched during HDs,while PM_2.5 from BBs showed high K⁺ but low SO₄^2-.FDs caused increases in K⁺ and enrichment in SO₄^2-.Ca²⁺ was abundant in DS samples.Ion-balance calculations indicated that PM_2.5 from HDs and FDs was more acidic than on normal days,but DS and BB particles were alkaline.The highest organic carbon（OC） concentration was 26.1μg/m³ during FDs,followed by BBs（23.6μg/m³）,HDs（19.6μg/m³）,and DSs（18.8μg/m³）. In contrast,elemental carbon（EC） concentration was more abundant during HDs（10.6μg/m³） and FDs （9.5μg/m³） than during BBs（6.2μg/m³） and DSs（6.0μg/m³）.The highest OC/EC ratios were obtained during BBs,with the lowest during HDs.SO₄^2-/K⁺ and TCA/SO₄^2- ratios proved to be effective indicators for differentiating pollution events.Mass balance showed that organic matter,SO₄^2-,and NO₃^- were the dominant chemical components during pollution events,while soil dust was dominant during DSs.     

Morphology and optical absorption of Bi2Fe4O9 crystals via mineralizer-assisted hydrothermal synthesis

Submicron-sized Bi₂Fe₄O₉ crystals were successfully synthesized via the hydrothermal method,while micron-sized Bi₂Fe₄O₉ crystals with rod-like morphologies were obtained in the presence of the mineralizer KNO₃.X-ray diffraction,scanning electron microscopy and transmission electron microscopy were employed to characterize the products.According to a series of time-dependent experiments,it was concluded that the likeliest formation mechanism for the microrods was the Ostwald ripening process.It was proposed that the blocking effect of NO₃^- contributed to the formation of the rod-like powders.Moreover,the optical absorption of the prepared Bi₂Fe₄O₉ crystals was measured using an UV-vis spectrophotometer,indicating that Bi₂Fe₄O₉ powders can be used as effective photocatalysts under visible light.     

开口阻塞比对粉体抑制甲烷爆炸的影响研究

为了研究开口阻塞比φ对粉体抑爆特性的影响，采用质量浓度C为0、80、160、240 g/m3的Al (OH)₃和NaHCO₃粉体，分别抑制具有不同φ（0、0.2、0.4、0.6、0.7、1.0）值的5 L管道内甲烷/空气预混气爆炸。实验结果表明:火焰的破碎度随粉体抑爆效率的增大而增大；最大超压峰值p_max、爆燃指数K_st由燃烧速率和泄爆速率共同决定。φ=0.7是每条爆炸特征参数曲线的拐点。随着φ值增加，超压峰值下降率δ先增大后减小，在0.4和0.6之间达到最大；总体上，Al (OH)₃和NaHCO₃两种粉体的抑爆效率相近。但在某些阻塞比下，阻塞比引起的低湍流影响着粉体颗粒的沉降行为，使得Al (OH)₃抑爆效率优于NaHCO₃。当粉体质量浓度从80 g/m3增加到240 g/m3时，热阻增加，火焰的热量不能扩散到粒子云的中心，不利于内部粒子的吸热分解，致使浓度效应越来越弱。     

RP-3航空煤油点火特性研究

在预加热到135℃的激波管反射激波后5区,以点火过程中OH自由基在306.5nm处特征发射光谱强度的急剧变化作为点火发生的标志,进行了RP-3航空煤油点火特性的实验研究.实验温度范围为800～1450K,当量比为0.5,1,1.5,压力为0.05,0.1,0.2MPa,O₂的摩尔浓度为空气含量20%.实验获得了低压条件下（0.05,0.1,0.2MPa）RP-3航空煤油点火延时与点火温度﹑压力﹑当量比以及煤油和氧气浓度的依赖关系.将低压实验结果与高压（0.55,1.1,2.2MPa）条件下煤油点火特性进行了对比.结果显示,当量比对煤油点火特性的影响存在一个临界温度.在临界温度以上的高温区,煤油点火延时随当量比增加而增长;在临界温度以下的低温区,煤油点火延时随当量比增加而缩短;这一临界温度随点火压力的降低而升高.采用3种煤油燃烧反应动力学机理对煤油点火过程进行了动力学数值模拟,并与实验结果进行了对比.结果显示,Honnet等提出的煤油反应机理在高压（2.2MPa）下与实验结果吻合得很好,而在低压下有一些差异.对不同压力条件下的点火过程进行敏感度分析表明,三体反应H+O₂+M=HO₂+M在高压时对煤油点火起轻微抑制作用,而在低压时对煤油点火起促进作用.      

纳米疏水性SiO2协同作用抑制丁烷爆炸速度与压力的耦合分析

为研究纳米疏水性SiO₂粉末作为阻燃剂和流动增强剂作用下丁烷爆炸速度与压力的耦合规律,在自行设计并搭建的基于LabVIEW控制系统的爆炸测试平台上开展了实验,通过休止角测试、SEM（scanning electron microscope）和EDS（energy dispersive spectrometer）分析了粉末团聚情况,分析了混合粉末抑制爆炸的机理,同时,实验了不同比例和不同浓度下纳米疏水性SiO₂改善CaCO₃粉末流动性并协同其抑制丁烷爆炸的效果,对爆炸火焰速度和压力的耦合关系进行了分析。结果表明,添加疏水性SiO₂可以使混合粉末的休止角降低,流动性增强,改善粉末的扩散效果和贮存能力,改变混合粉末的比例和浓度对燃烧反应有着显著的影响,在一定浓度范围内,粉末通过较大的比表面积和热解结合燃烧区域的自由基,使火焰传播速度和爆炸超压显著下降,但过大的粉末浓度会促进初期的爆炸,并且两种粉末协同对爆炸的抑制效果优于单一粉末。在混合粉末的抑制作用下,爆炸压力达到最大值时速度几乎降至最低,压力波形由持续上升变为单峰曲线。此外,在SiO₂和CaCO₃两种粉末质量比为1∶1混合、粉末质量浓度为106 g/m3时,对丁烷体积分数为4.20%的丁烷-空气混合气体爆炸的抑制效果最佳,火焰传播平均速度和最大爆炸超压的衰减率分别为85.5%和59.6%。     

STUDIES ON THE AUTOIGNITION CHARACTERISTICS OF RP-3 AVIATION KEROSENE

在预加热到135℃的激波管反射激波后5区,以点火过程中OH自由基在306.5nm处特征发射光谱强度的急剧变化作为点火发生的标志,进行了RP-3航空煤油点火特性的实验研究.实验温度范围为800～1450K,当量比为0.5,1,1.5,压力为0.05,0.1,0.2MPa,O₂的摩尔浓度为空气含量20%.实验获得了低压条件下（0.05,0.1,0.2MPa）RP-3航空煤油点火延时与点火温度﹑压力﹑当量比以及煤油和氧气浓度的依赖关系.将低压实验结果与高压（0.55,1.1,2.2MPa）条件下煤油点火特性进行了对比.结果显示,当量比对煤油点火特性的影响存在一个临界温度.在临界温度以上的高温区,煤油点火延时随当量比增加而增长;在临界温度以下的低温区,煤油点火延时随当量比增加而缩短;这一临界温度随点火压力的降低而升高.采用3种煤油燃烧反应动力学机理对煤油点火过程进行了动力学数值模拟,并与实验结果进行了对比.结果显示,Honnet等提出的煤油反应机理在高压（2.2MPa）下与实验结果吻合得很好,而在低压下有一些差异.对不同压力条件下的点火过程进行敏感度分析表明,三体反应H+O₂+M=HO₂+M在高压时对煤油点火起轻微抑制作用,而在低压时对煤油点火起促进作用.     

增强型喷射器对爆轰波DDT过程的影响

在激波、火焰及射流同时存在的流场中，组织燃烧转爆轰过程是脉冲爆震发动机实现点火、起爆的关键问题。设计一类喷射器，采用C₂H₂/O₂/Ar反应，数值验证了该喷射器能增强爆震室燃料燃烧转爆轰的可行性，并讨论了流场中热点的点火机制。结果显示:该装置在流场中可激发不稳定性，产生漩涡，加速能量、质量的交换。流场产生热点，促进火焰速度加快，追赶前导激波。喷射器位置影响前导激波的运动速度。在一定范围内，前导激波速度越大，碰撞产生的热点越容易激发燃烧转爆轰过程。