不同浓度下点火延长时间对煤粉点火能的影响

为评价煤粉爆炸的潜在危险性,掌握使其燃烧所需的最小点火能及其受浓度和点火延长时间的影响,采用垂直哈特曼管研究不同浓度下点火延长时间对煤粉最小点火能的影响。结果表明:对于粒径为54μm的煤粉,随着质量浓度的增加,煤粉最小点火能先减小后增大,最佳点火质量浓度为750 g/m~3;随着时间的延长,煤粉最小点火能先减小后增大继而趋于平缓,最佳点火延长时间为90 ms。     

等离子点火技术在600MW褐煤锅炉上的应用

介绍了等离子点火技术首次应用于600MW直吹式褐煤锅炉上的情况;分析了煤粉浓度、一次风速、二次风量、磨煤机出口温度和煤粉细度等因素对其点火性能的影响;结果表明,等离子点火系统性能稳定,能实现褐煤锅炉少油点火及低负荷稳燃.     

密闭空间煤粉爆炸特性的实验研究

为了探明煤粉在密闭空间中的爆炸特性参数,利用20 L球形爆炸装置进行实验测试,实验研究了不同点火能量对煤粉爆炸行为的影响,对比CaCO_3和Al(OH)_3两种惰性介质的抑爆效果及惰性介质的抑爆效力随点火能量的变化规律进行了重点探讨。结果表明:随着点火能量的增加,爆炸压力随着煤粉浓度的增加呈现先上升后下降的趋势,在同一浓度下,粉尘最大爆炸压力和最大升压速率呈线性上升,在高浓度下,粉尘爆炸压力受点火能量的影响更显著;添加CaCO_3和Al(OH)_3能够降低煤粉的爆炸压力,相对于CaCO_3的物理抑爆而言,Al(OH)_3的物理-化学抑爆效果更佳;惰性介质抑爆效力随点火能量增加而下降,建议采用5~10 k J点火能量考察惰性介质对煤粉爆炸的抑制效力。     

附加散装点火药剂对导爆管点火性能的影响

模拟导爆管雷管点传火结构,利用动态压力测试系统,研究了散装点火药剂对导爆管通过消爆腔引发延期雷管时点火规律的影响.研究结果表明,超细RDX作为点火药剂在消爆腔中可以参与导爆管输出产物的反应,起到点火药的作用.且随RDX量的增大,点火冲量、压力峰值、点火持续时间均呈单调增大的趋势.     

一种适用于煤粉工业锅炉燃烧器的冷态流场特性研究

利用试验和数值模拟的方法对一种适用于煤粉工业锅炉燃烧器的冷态流场特性进行了研究.结果表明,回流区的长度随内二次风旋流强度的增大而明显增大,随钝体阻塞率的减小而缩短;燃烧器回流区内的回流速度随一次风风速的增加略有降低,随内二次风旋流强度的增加而增大,随钝体阻塞率的增加呈先增大后减小的趋势.试验结果为该燃烧器的设计和热态试验提供了一定的指导.     

少油量气化点火在塔里木热电厂应用

塔里木热电厂两台75t/h煤粉锅炉点炉需用轻质柴油2～3吨,每年点火及低负荷用油近100～200吨。针对这一情况2007年6月热电厂自行安装新疆奥科公司少油气化点火设备。经过半年运行,点一次只需用150～200公斤轻质柴油,节油效果非常明显。     

大型煤电机组不同点火方式对锅炉设备的影响

在国家能源发展政策的要求下,高效、节能、环保得到电力行业特别是燃煤电厂的重视,煤粉锅炉的点火方式也从全油、少油点火方式发展到微油、无油点火方式,现今的煤电机组基本都达到了0排放的要求,但是影响锅炉设备安全稳定运行的问题还是时有发生,都需要我们重视、分析和解决。     

点火正时仪测试方法研究探讨

为了保证点火正时仪测试量值的准确和统一,对点火正时仪测试方法进行研究和探讨,并研制出使用精密的集成电路和建立模拟发动机点火控制的标准测试装置,解决目前无法使用高一级标准器对其进行测试的问题.通过标准测试装置对点火正时仪进行测试,并对测试数据进行分析和比对,得出测试方法和结果能满足对点火正时仪测试要求的结论,这是一种新型的测试点火正时仪的标准装置和方法.     

电厂锅炉应用等离子点火的技术经济分析

等离子点火技术是一项较为先进的锅炉点火技术,运用该技术能够在锅炉点火、稳燃的过程中减少或取消对燃油的应用,利用等离子直接电弧将煤粉点燃。等离子点火技术的应用,对于电厂来说具有十分重要的意义,能够带来十分理想的经济效益。基于此,本文对等离子点火的系统及原理,实际应用等进行介绍,并对这一技术的应用进行了技术经济分析。     

微小空间点火装置的设计

针对微内燃机燃烧室的尺寸特征和点火形式,对微小空间点火实验装置进行了研究,设计并制作了微小空间内的放电点火装置．设计的硅微燃烧室的尺寸为1mm×1mm×1mm、3mm×3mm×1mm和9mm×9mm×1mm;点火电极位于燃烧室腔体中央,电极间隙在10一,100μm;电极材料为金．本文为微小空间放电点火特性实验研究提供了一种通用装置,也为以微型内燃机为代表的便携式微型高能电源组的微型化和实用化提供了技术支持．     

Optimization of the process of plasma ignition of coal

Results are given of experimental and theoretical investigations of plasma ignition of coal as a result of its thermochemical preparation in application to the processes of firing up a boiler and stabilizing the flame combustion. The experimental test bed with a commercial-scale burner is used for determining the conditions of plasma ignition of low-reactivity high-ash anthracite depending on the concentration of coal in the air mixture and velocity of the latter. The calculations produce an equation (important from the standpoint of practical applications) for determining the energy expenditure for plasma ignition of coal depending on the basic process parameters. The tests reveal the difficulties arising in firing up a boiler with direct delivery of pulverized coal from the mill to furnace. A scheme is suggested, which enables one to reduce the energy expenditure for ignition of coal and improve the reliability of the process of firing up such a boiler. Results are given of calculation of plasma thermochemical preparation of coal under conditions of lower concentration of oxygen in the air mixture.     

纯氧点火技术在300MW机组的应用

纯氧点火技术是利用氧气替代空气作为助燃剂,直接送入燃烧器内部参与燃料点燃的点火技术。通过将原有最下层四只燃烧器改造为装有微油枪加氧点火助燃的煤粉燃烧器以及在炉前加装供氧系统来保证纯氧的安全输送和稳定燃烧。纯氧的投入使燃料得到充分燃烧,加强了燃烧初期的稳定性,提高了燃烧效率,直接使机组在启停以及低负荷稳燃过程中的安全性、经济性、环保性得到较好的提升。     

Investigation of lag on ignition of coal dust clouds under varied experimental conditions

Lag on ignition (LOI) of coal dust cloud greatly influences the initiation and propagation of coal dust explosion. This paper investigates the effects of coal dust particle size, dust concentration, ignition temperature, and dust dispersion pressure on LOI of coal dust clouds using Godbert-Greenwald furnace along with a high-speed camera. LOI of coal dust cloud significantly decreased by 1/13 times from 959 to 77 ms with increase in the ignition temperature from 600 to 1000 °C, demonstrating greatest influence of ignition temperature on LOI. LOI increased by 60% with increase in dust concentration from 500 to 4000 g/m³. Optimum dust dispersion pressure at which LOI was found minimum is determined 70 kPa. Empirical relations are established between LOI of coal dust cloud and particle size, ignition temperature, dust concentration, and dispersion pressure. The results are analysed in terms of the occurring physical processes, which led to a better understanding of the variation of LOI, ignition behavior, and explosion propagation of coal dust clouds at varied experimental conditions.     

升温速率对煤粉燃烧反应动力学的影响

采用热重分析法对不同升温速率(10、20、30℃/min)下的煤粉燃烧特性进行研究,由热重数据进行煤粉燃烧特征参数和动力学参数的计算,分析升温速率对煤粉燃烧特性的影响。结果表明:随着升温速率的升高,着火温度和燃尽温度随之升高。煤粉燃烧出现热滞后现象,反应动力学参数随升温速率的变化而不同。     

Transient ignition on a flat plate

Abstract

In this study, transient ignition on a hot plate is analyzed numerically. In addition to the transient energy and species equations, the transient momentum equation is also considered. A comparison is made between the results of transient velocity field and those of steady velocity field. It is found that the transient velocity field has the effect of increasing the ignition length and ignition time. The effects of wall temperature, Prandtl number and Schmidt number are also studied.     

空气中氮气或氩气浓度对锆粉尘层着火温度的影响

为了探索抑制锆包壳剪切过程中锆粉着火的方法,采用粉尘层最低着火温度测定仪、红外热成像仪、真空手套箱等测定了不同粒径的锆粉尘层在空气和含不同浓度氮气、氩气的空气中的最低着火温度和火焰温度。结果得出:锆粉的中位粒径从2.4 μm升至71.7 μm,粉尘层最低着火温度从200 ℃升至390 ℃,表明粒径越小的锆粉着火敏感性越高;4种粒径的锆粉燃烧火焰最高温度都在1 776～1 913 ℃范围内,锆粉粒径较大时,燃烧的剧烈程度较低;氮气或氩气体积分数从60%～65%升至70% 85%时,锆粉尘层最低着火温度升至400 ℃,表明空气中高浓度的氮气或氩气对锆粉燃烧有抑制作用,且浓度越高,抑制作用越强,锆粉粒径越小,抑制效果越好。氩气的抑制效果强于氮气。     

An investigation of the ignition manner effects on combustion synthesis

The multi-point ignition of combustion synthesizing NiAl compound created by computational means has been analyzed in this article. Since the combustion reaction of Ni and Al is a low exothermic reaction, it has been found that the combustion front hardly propagates in order to complete the reaction. In this study, the reaction is subsequently ignited at different points or it is simultaneously ignited at several points to help the combustion front to propagate completely. The different positions of ignition are found to influence the temperature profiles and an increase in the number of ignition points is noted to increase the propagation velocity. In addition, the effect of a second ignition of the extinguished combustion reaction is also studied. It is noted that the position and time of the second ignition has dramatically influenced on the propagation velocity and combustion temperature, thus resulting in different grades of reactions. The extent of reacting for each double-ignition condition is calculated in order to generate the reacting maps. From the reacting maps generated in this study, the appropriate double-ignition condition can be chosen to synthesize homogeneous products.     

Laser ignition in internal-combustion engines: Sparkless initiation

Laser ignition has been implemented in a single-cylinder internal combustion engine fueled by gasoline. Indicator diagrams (cylinder pressure versus crank angle) were obtained for laser ignition with nano- and microsecond pulses of an Nd:YAG laser. The maximum power of microsecond pulses was below critical for spark initiation, while the radiation wavelength was outside the spectral range of optical absorption by hydrocarbon fuels. Apparently, the ignition starts due to radiation absorption by the oil residues or carbon deposit in the combustion chamber, so that the ability of engine to operate is retained. This initiation of spark-free ignition shows the possibility of using compact semiconductor quantum-cascade lasers operating at wavelengths of about 3.4 μm (for which the optical absorption by fuel mixtures is high) in ignition systems of internal combustion engines.     

粒径对煤粉云最低着火温度特性的影响

为了研究粒径对煤粉云最低着火温度特性的影响,采用粉尘云最低着火温度测试装置测试了不同粒径下煤粉云的最低着火温度,并结合ReaxFF分子动力学对其反应机理进行了微观层面的探讨。结果表明:当煤粉中位径在34 μm时,煤粉云的最佳着火质量浓度为750 g/m³,最低着火温度为550 ℃;随着煤粉粒径的增加,煤粉云最低着火温度逐渐增大,当煤粉中位径达到124 μm,煤粉云最低着火温度上升至650 ℃。通过ReaxFF分子动力学对煤粉热解过程的计算结果表明:随着反应的进行,大分子煤结构逐步分解,芳香环、C—C键、C—O键和C—H键等断裂,产生更小的分子结构,其中,H₂、H₂O、CO₂和CH₂O等小分子产生的数量逐渐增多;H·自由基和OH·自由基在反应初期有明显的数量变化,且其含量对于最终稳定产物有重要影响。