微米级单颗粒铝粉加压着火燃烧特性

为探究压强及氧浓度对铝粉着火燃烧特性的影响,利用自主搭建的基于平面火焰燃烧器的可视化加压携带流台架,结合高速显微摄像方法,对0.1～0.7MPa、20%和30%氧浓度、O₂/CO₂气氛下粒径79μm的离散单颗粒铝粉的微观着火燃烧过程进行了光学诊断。结果表明,铝粉颗粒的燃烧过程可分为4个阶段：预加热缓慢氧化阶段、铝蒸气扩散剧烈燃烧阶段、破碎爆裂旋转加速阶段以及燃尽阶段。当压强每升高0.2MPa,铝粉着火延迟时间缩短约4ms,燃烧持续时间增大约2ms;当氧浓度升高10%,不同压强下铝粉的着火延迟时间缩短约1.5ms,燃烧持续时间增大约0.2ms。随着压强和氧浓度的升高,铝粉颗粒表面的氧分压和氧浓度增大,燃烧更加剧烈,使得铝粉颗粒的总时间缩短,且压强的影响与氧浓度相比更加明显。     

微米铝粉在声场中的振荡燃烧特性

为了解声场中铝粉的燃烧特性,建立了甲烷平面燃烧器,利用外置喇叭产生振荡,进行了微米级铝粉的燃烧实验。研究了铝粉在不同振荡频率下的分布燃烧响应特性及粒径分别为10、20、30μm的3种铝粉颗粒的燃烧特性和产物的阻尼特性。结果表明,振荡频率不同时,铝粉燃烧对振荡压强的增益作用不同,粒径为20μm铝粉燃烧,在振荡频率200Hz和300Hz时增益作用明显。铝粉粒度越大,分布燃烧增益越大。粒径为10μm铝粉对燃烧器高频振荡阻尼最大。随着铝粉粒度增加,燃烧产物颗粒对高频压强振荡的阻尼减小。     

含不同粒度铝粉的铝/冰燃料的燃烧特性

用微米铝粉逐级取代部分纳米铝粉制备铝/冰燃料,采用表面接触法和高速摄影技术研究了不同粒度铝粉改善铝/冰燃料燃烧特性的效果. 结果表明,随微米铝粉取代量增加,铝/冰燃料燃烧反应速率和剧烈程度均先提高后降低,微米铝粉取代量为30%(w)时,铝/冰燃料最高升温速率达6062.24℃/s,是纯纳米铝/冰燃料的3.8倍. 用微米铝粉取代部分纳米铝粉均不同程度提高铝/冰燃料的燃面传播速率,微米铝粉取代量约为20%(w)时燃烧性能最佳,燃面传播速率较纯纳米铝/冰燃料提高57.8%. 在分析实验结果的基础上,建立了铝/冰燃料的燃烧火焰模型.     

高活性微米多孔铝粉的制备与表征

为得到具有高活性多孔铝粉和氢化铝共存的混合体系,在常压下采用格氏试剂法对普通铝粉进行活化,通过半固相反应得到高活性微米多孔铝粉,用红外光谱、X射线衍射、扫描电子显微镜、静态氮吸附等方法对样品进行了表征,通过氧化还原滴定法测试了微米多孔铝粉的活性。结果表明,制备所得样品的主要成分是铝粉,同时还有部分AlH3;样品具有多孔结构,粒径多数分布在30μm左右,不仅具有孔径在2~10nm之间的中孔,还存在孔径分布在1nm以下的部分微孔结构;总孔体积为普通铝粉的5~7倍,比表面积为普通铝粉的2~3倍,样品平均活性含量达到92.83%。这种含有AlH3的高活性微米多孔铝粉混合体系在含能材料领域有很大的应用价值。     

压力对纳米铝粉燃烧性能的影响

基于定容燃烧系统,通过对比火焰结构,燃烧室内温度和动态压力的变化,以及对燃烧产物显微结构及组分分析,研究了不同压力对纳米铝粉燃烧性能的影响。结果表明,纳米铝粉和空气反应生成复杂的氧化铝、氮化铝多型体,随着压力的增大,反应速率不断增大,峰值压力升高,且达到峰值压力的时间缩短,但总放热量大致相同。     

铝/乙醇基纳米浆体燃料的着火燃烧特性研究

为了明确纳米铝粉从低浓度到高浓度变化对液体碳氢燃料着火燃烧特性的影响,采用液滴悬挂法研究了不同温度下(700~800℃)乙醇液滴和添加不同浓度(2.5wt%, 10wt%, 15wt%和20wt%)纳米铝粉的铝/乙醇基纳米浆体燃料液滴的着火燃烧特性。利用高速摄影系统捕捉了液滴整个燃烧过程,分析了其液滴寿命。通过热电偶对液滴附近气相温度的测量,获得了其着火性能参数。结果表明,添加纳米铝粉可以改善乙醇液滴的着火性能。不同铝粉浓度改善效果不同,低浓度时效果较好,着火延迟时间显著缩短,点火温度明显降低。随温度升高,乙醇及添加纳米铝粉的铝/乙醇基纳米浆体燃料液滴着火延迟时间及着火温度均明显降低。纳米铝粉(S2)对乙醇(S1)着火延迟时间和液滴寿命的降幅在750℃最大,其降幅分别达42.20%和18.43%。纳米铝粉(S3)着火温度降低,其最大降低幅度也出现在750℃,相对于乙醇(S1)降低幅度达28.57%。一定铝粉浓度范围内,液滴微爆炸程度和微爆炸时长随铝粉浓度升高而增大,但铝粉浓度超过10wt%后趋势变得平稳。     

低温烘焙提质对褐煤着火燃烧特性的影响

褐煤高水分和高挥发分不利于运输和储存,且会降低锅炉燃烧效率,低温烘焙提质作为一种褐煤提质常用技术,能有效降低燃料中水分并提升燃料品质,显著改变褐煤燃烧特性。为研究低温烘焙提质对褐煤着火特性的影响,利用平面火焰燃烧系统并结合CMOS相机研究了不同热协流温度(1 473、1 673和1 873 K)和O₂体积分数(5%、10%和20%)下低温烘焙预处理(200、250和300℃)对褐煤着火燃烧特性的影响,并分析低温烘焙提质对着火延迟距离和火焰亮度的影响。结果表明,经低温烘焙预处理的褐煤颗粒在相同热协流温度和O₂浓度条件下的着火延迟距离稍大于原始褐煤颗粒;O₂体积分数为5%时,200℃烘焙褐煤的着火延迟距离在热协流温度1 473、1 673和1 873 K时较原始褐煤颗粒分别增加了0.24、0.28和0.13 cm;此外,不同烘焙温度下煤粉颗粒的着火位置较褐煤均有所延迟,且升高烘焙温度会降低褐煤着火距离,在1 673 K、O₂体积分数5%下,烘焙温度200、250和300℃时对应的着火延迟距离较褐煤的增加...     

超细铝粉燃烧性能研究

研究了四种粒度的铝粉在四组元（ＨＴＰＢ／ＨＭＸ／ＡＰ／Ａｌ）推进剂中的燃烧特性。实验结果表明，超细铝粉可减轻在燃面的凝聚程度，其燃烧性能明显优于粗铝粉。因此，在推进剂中合理使用超细铝粉，可以提高燃烧效率，对配方研制具有十分重要的意义     

固体推进剂中铝粉氧化过程及其燃烧效率影响因素

在对铝粉氧化过程和单颗粒燃烧过程分析的基础上,总结了导致铝粉团聚的主要因素,讨论了不同因素对铝粉燃烧效率的影响规律.这些因素包括铝粉粒度及含量、氧化剂种类、氧化剂粒度及级配和环境压力.随着铝粉粒度和含量的提高,铝粉燃烧效率降低;而随着氧化剂热值的提高,气相区的温度随之提高,铝粉的燃烧效率相对较高.对细AP而言,随着粒度...     

AP和铝粉对AP-CMDB推进剂燃烧性能的影响

通过测定推进剂不同压强下的燃速和压强指数,研究了高氯酸铵(AP)和铝粉的粒度及含量对AP-CMDB推进剂燃烧性能的影响.结果表明,减小AP粒度和增大铝粉粒度均能有效提高AP-CDMB推进剂的燃速,推进剂在10～20 MPa压强范围内的燃速压强指数随AP和铝粉粒度的减小而明显增大;铝粉的质量分数低于14%时,调节不同比例的AP和铝粉含量对AP-CMDB推进剂的燃烧性能影响不明显,铝粉的质量分数高于14%时,由于铝粉燃烧不完全导致推进剂的燃速降低.     

Synthesis of aluminum nanoparticles as additive to enhance ignition and combustion of high energy density fuels

High energy density fuels are critical for hypersonic aerospace propulsion but suffer from difficulties of ignition delay and incomplete combustion. This research reports aluminum nanoparticles (Al NPs) assisted ignition and combustion of high energy density JP-10 fuel. Al NPs with a size of 16 nm were fabricated through a mild and simple method by decomposing AlH₃·Et₂O with the addition of a surfactant ligand. The uniform size distribution, nanoscaled size and surface ligand make Al NPs stably suspend in JP-10, with 80% NPs being dispersed in the liquid fuel after six months. A shock tube test shows that the presence of 1 wt-% Al NPs can significantly shorten ignition delay time at temperature of 1500 to 1750 K, promote the combustion, and enhance energy release of JP-10. This work demonstrates the potential of Al NPs as ignition and combustion additive for high energy density fuel in hypersonic applications.

Open image in new window

     

Experimental study on ignition and combustion characteristics of typical oils

The impact of radiant heat flux on ignition and combustion behavior of typical oils (diesel, lubricating oil, and aviation kerosene) was conducted in a cone calorimeter. A circular steel pan with a diameter of 10 cm was used to contain diesel, lubricating oil, and aviation kerosene without water sublayer. Using the standard oxygen consumption method, we obtained ignition time, heat release rate, mass loss rate, extinction coefficient, CO, and CO₂ yield, and average specific extinction area was calculated from the extinction coefficient. Janssens' method was adopted in this study to deal with ignition time and radiant heat flux under a 0.55 power rule. Results show that the fitting through Janssens' method is good for ignition time of diesel, lubricating oil, and aviation kerosene and radiant heat flux. Moreover, heat release rate, mass loss rate, and CO/CO₂ ratio appear to positively correlate with radiant heat flux, whereas average specific extinction area varies in a certain range. Copyright © 2013 John Wiley & Sons, Ltd.     

铝–油酸/正庚烷基纳米浆体燃料液滴着火燃烧特性

采用液滴悬挂法研究了正庚烷液滴、油酸/正庚烷混合燃料液滴、含20wt%纳米铝粉的铝–油酸/正庚烷基纳米浆体燃料液滴在不同温度下(600~800℃)的着火燃烧特性。用高速摄像机观测液滴进入管式电阻炉后的着火燃烧过程,使用热电偶记录液滴周围的气相温度变化,同时通过对应的温度曲线计算液滴的着火延迟时间。结果表明,纳米铝粉和油酸的添加均能降低正庚烷液滴的着火延迟时间。随温度升高,正庚烷、油酸/正庚烷混合燃料、铝–油酸/正庚烷基纳米浆体燃料液滴的着火延迟时间显著降低,但变化趋势逐渐趋于平缓。铝–油酸/正庚烷基纳米浆体燃料液滴的着火延迟时间与环境温度满足阿累尼乌斯方程。与纯正庚烷、油酸/正庚烷混合液滴的燃烧过程相比,铝–油酸/正庚烷基浆体燃料液滴的燃烧过程有显著差异,其燃烧经历3个阶段：正庚烷稳定燃烧阶段、正庚烷微爆炸阶段和表面活性剂微爆炸阶段。铝–油酸/正庚烷基浆体燃料液滴燃烧时间延长,火焰熄灭后又复燃,且燃烧过程中发生剧烈的火焰形变和铝颗粒溅射现象,大部分铝以团聚体形式在第三阶段完成氧化还原反应。     

Ignition, combustion, and agglomeration of encapsulated aluminum particles in a composite solid propellant. I. Theoretical study of the ignition and combustion of aluminum with fluorine-containing coatings

This paper gives a brief review of methods for modifying metallic fuels for composite solid propellants, including the application of coatings onto aluminum particles (encapsulation). Requirements for the coating material are formulated. By means of thermodynamic calculations, it is shown that some fluorine-containing coatings reduce the content of the condensed phase in the propellant combustion products without decreasing the specific impulse. A mathematical model for the ignition of a single encapsulated particle is proposed. Calculations show a decrease in the ignition time of an aluminum particle with a fluorine-containing coating. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 5, pp. 46–55, September–October, 2006.     

高海拔对煤粉燃烧特性的影响研究

为掌握高海拔低气压环境下煤粉燃烧特性,指导高海拔地区大型燃煤锅炉设计,在试验台上模拟高海拔低气压环境,利用一维火焰炉、着火炉研究了煤粉在不同海拔高度下的着火、燃烬及NO_x排放特性。结果显示随着海拔的升高,煤粉的着火温度升高,燃烬性能有一定下降,而NO_x生成量变化不大。与低海拔地区类似,试验煤样煤粉变粗会使着火温度升高,但对燃烬率影响较小,氧含量对燃烬率和NO_x影响较大。综合考虑,高海拔地区锅炉设计应采用较细的煤粉细度、适当提高燃烬空间。     

铝粉对红棕色降温涂料性能的影响

有较高反射率的金属是热隐身涂料最常用和最重要的颜料种类.在实际应用中,多选用性能优异、价格低廉的铝粉.在前期实验的基础上,向3种基本组成相同而复色浆不同的红棕色涂料中加入定量的铝粉,研究了加入铝粉前、后涂层的表面发射率以及在指定波段内的反射率.结果发现,加入一定量的铝粉后,可提高涂料在380～2 500 nm波段尤其是可见光区的反射率:加入一定量的铝粉后,涂层在8.0～13.5 μm波段内的表面发射率均小于未加铝粉的涂层.     

The catalytic effect of the Na and Ca-rich industrial wastes on the thermal ignition of coal combustion

The catalytic effects of four industrial wastes, namely, the soap residue (SR), brine sludge (BS), calcium carbide residue (CCR), and white lime mud (WLM), on coal thermal ignition were investigated. The acidity of palmitate anion associated with Na⁺ in SR was lower than that of chloride anion combined with Na⁺ in BS, which resulted in an improved the combustion of SR. The acidity of OH^- anion combined with Ca²⁺ in CCR was lower than that of CO₃^2- anion combined with Ca²⁺ in WLM, resulting in CCR exhibiting a better catalytic effect on coal ignition. The alkaline metal Na had lower initial ionisation energy than the alkaline earth metal Ca. Therefore, the Na-rich SR exhibited higher catalytic activity on coal ignition than Ca-rich CCR. The ignition temperature of coal with 0.5% SR decreased from 544 to 503℃.     

铝粉爆炸危险性实验研究

利用水平管道式实验装置,对不同粒度的铝粉爆炸极限进行实验研究和分析。实验结果表明,粒度越小,其爆炸范围越大,爆炸的可能性也越大,需要防护的力度也要加大。为预防和减少铝粉爆炸的损害提供了理论依据。     

Condensed combustion products of aluminized propellants. IV. Effect of the nature of nitramines on aluminum agglomeration and combustion efficiency

The condensed combustion products of two model propellants consisting of ammonium perchlorate, aluminum, nitramine, and an energetic binder were studied by a sampling method. One of the propellants contained HMX with a particle size D ₁₀ ≈ 490 μm, and the other RDX with a particle size _{D 10} ≈ 380 μm. The particle-size distribution and the content of metallic aluminum in particles of condensed combustion products with a particle size of 1.2 μm to the maximum particle size in the pressure range of 0.1–6.5 MPa were determined with variation in the particle quenching distance from the burning surface to 100 mm. For agglomerates, dependences of the incompleteness of aluminum combustion on the residence time in the propellant flame were obtained. The RDX-based propellant is characterized by more severe agglomeration than the HMX-based propellant — the agglomerate size and mass are larger and the aluminum burnout proceeds more slowly. The ratio of the mass of the oxide accumulated on the agglomerates to the total mass of the oxide formed is determined. The agglomerate size is shown to be the main physical factor that governs the accumulation of the oxide on the burning agglomerate. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 4, pp. 78–92, July–August, 2006.