某楼房的复合定向倾倒爆破

介绍了乌拉特前旗原贵超羊绒衫厂办公楼的拆除爆破,由于该楼东山墙有横向布局的建筑物与之相邻(仅1.8m),简单的定向倾倒或原地坍塌都会影响到周围的建筑物。为此,采用了主体向北倾倒、东山墙部分向西倾倒的复合定向倾倒爆破方案,由于准确地设计了爆破缺口、爆破参数及各段起爆顺序,成功地拆除了该办公楼。     

低压环境下航空电缆材料燃烧特性的研究

在高高原实验室(61 kPa、4 290 m)和广汉实验室(96 kPa、520 m),分别开展常低压条件下FXL型航空电缆的对比燃烧实验。通过热辐射加热箱、烟密度及成分测试仪和氧指数仪等设备,测量点燃时间、烟密度、质量损失速率和CO、CO2及O2等浓度变化。实验结果表明:在96 kPa和61 kPa两种实验环境下,低压下最小点燃时间及温度的数值更大,两者的温度和时间差分别为15℃和4.8 s;烟密度曲线快速升高后趋于平衡,61 kPa条件下的发烟量小于96 kPa;O2体积浓度随着加热时间先下降后升高,而CO2的变化趋势相反。在61 kPa条件下,CO曲线会出现双峰现象且更明显;随着氧浓度增加,质量损失速率加快且呈线性关系;压力因素对燃烧影响减弱且燃烧持续时间差值变小。研究结果揭示了低压环境对航空电缆的燃烧影响,为增强航空安全提供参考。     

甲醇发动机的点火正时和喷射正时优选的试验研究

缸内喷射、火花助燃甲醇发动机是在缸内形成一种层状分布的不均匀混合气，为获得优良的燃烧和排放性能，存在一个最佳的点火和喷射正时。此时着火延迟期最短，缸内混合气浓、稀分布最合理，平均火焰传播速度最快，热效率最高，效率和排放折衷最好。本文详细介绍了点火正时和喷射正时的优选过程及对缸内混合气浓度分布及燃烧过程的影响。     

Ignition kinetics of a homogeneous hydrogen/air mixture using a transient hot jet

The ignition characteristics of a homogenous hydrogen/air mixture using a hot transient jet generated by the combustion of syngas (H₂/CO) with varying CO concentrations from 33% to 95% in a pre-chamber is numerically investigated with particular attention to the chemical kinetics. Detailed reaction mechanism for hydrogen and syngas mixture oxidation with 15 species and 41 reactions is employed. The hot jet ignition delay time is determined by the onset of OH¹ radicals and found to increase with increasing CO molar fractions in the pre-chamber fuel, and this increase is more profound for high CO content. The radicals that formed in the main chamber are examined separately from the radicals within the hot jet. Their temporal evolutions reveal that O and OH radicals in the jet play a crucial role in abstraction of H atoms form ${\text{H}}_2$/air mixture in the main chamber, which initiates ignition. Further analysis of the ${\text{H}}_2{\text{O}}_2$ rate of change identifies two ignition regimes. For high temperature (T > 1000 K) hot jets, ignition is caused by the chain branching reaction $\text{H}+{\text{O}}_2?\text{O}+\text{OH}$ directly, resulting in short ignition delay times (0.14, 0.19, 0.26 ms). For low temperature (T < 1000 K) hot jets, ignition is dominated by the accumulation and decomposition of ${\text{H}}_2{\text{O}}_2$, resulting in long ignition delay times (0.4, 0.67, 1.26 ms). By separating the thermal and chemical effects of the hot jet, it is found that the thermal effects are dominant but composition of the hot jet has little effect on the ignition characteristics.     

Chemical kinetic study of a novel lignocellulosic biofuel: Di-n-butyl ether oxidation in a laminar flow reactor and flames

The combustion characteristics of promising alternative fuels have been studied extensively in the recent years. Nevertheless, the pyrolysis and oxidation kinetics for many oxygenated fuels are not well characterized compared to those of hydrocarbons. In the present investigation, the first chemical kinetic study of a long-chain linear symmetric ether, di-n-butyl ether (DBE), is presented and a detailed reaction model is developed. DBE has been identified recently as a candidate biofuel produced from lignocellulosic biomass. The model includes both high temperature and low temperature reaction pathways with reaction rates generated using appropriate rate rules. In addition, experimental studies on fundamental combustion characteristics, such as ignition delay times and laminar flame speeds have been performed. A laminar flow reactor was used to determine the ignition delay times of lean and stoichiometric DBE/air mixtures. The laminar flame speeds of DBE/air mixtures were measured in the stagnation flame configuration for a wide rage of equivalence ratios at atmospheric pressure and an unburned reactant temperature of 373 K. All experimental data were modeled using the present kinetic model. The agreement between measured and computed results is satisfactory, and the model was used to elucidate the oxidation pathways of DBE. The dissociation of keto-hydroperoxides, leading to radical chain branching was found to dominate the ignition of DBE in the low temperature regime. The results of the present numerical and experimental study of the oxidation of di-n-butyl ether provide a good basis for further investigation of long chain linear and branched ethers.     

Effects of buffer gas composition on low temperature ignition of iso-octane and n-heptane

Experimental and numerical studies have been performed on the thermal and chemical effects of buffer gas composition on low temperature ignition of iso-octane and n-heptane. Experiments were conducted using a recently developed rapid compression machine in the temperature range of 600–850 K. Three buffer gases were studied including nitrogen (N₂), argon (Ar), and a mixture of Ar and carbon dioxide (CO₂) at a mole ratio of 65.1%/34.9%. Iso-octane was studied at 20 bar, ? = 1, and a dilution level of buffer gas to O₂ of 3.76:1 (mole ratio). n-Heptane was studied at 9 bar, ? = 1, and a dilution level of buffer gas to O₂ of 5.63:1 (mole ratio). For experiments where two-stage ignition was observed, the buffer gas composition had no impact on the first-stage ignition time but, as expected, it caused differences in the total heat release, pressure and temperature rise after the first-stage ignition. As a consequence, significant differences were observed for the total ignition delay time as a function of the buffer gas composition, with up to 40% and 42.5% faster total ignition time for iso-octane and n-heptane, respectively, by using Ar instead of N₂. The chemical effects of the buffer gas composition were studied experimentally by comparing the results of the N₂ and Ar/CO₂ (65.1%/34.9%) mixtures, recognizing that while the Ar/CO₂ mixture has the same heat capacity as N₂, its predicted combined third-body collision efficiency is about 76% higher than N₂. The experimental results showed negligible chemical effects on the first-stage and total ignition delay times. Numerical simulations were carried out over a wider range of temperatures for pure N₂, Ar, and CO₂ as buffer gases. Results showed that thermal effects are very pronounced and dominated at the negative temperature coefficient and two-stage ignition conditions, which is consistent with the experimental results and previous studies in the literature. However, the simulation results also showed at temperatures higher than 850 K, the chemical effects of CO₂ became more important than the thermal effects.     

Induction-heating ignition of pulverized coal stream

Induction-heating ignition burner for the pulverized coal fired boiler is introduced. Some experiments were conducted on an experimental set-up, which includes alternative current power system, induction-heating system, pulverized coal and air supplier system, and measurement system to study the ignition process of coal powder and air mixture stream. Some results are presented. An industrial induction-heating burner for a 220 t/h boiler, which was designed on the basis of a series of researches, is described. This kind of oil-free ignition burner is characterized by its stable operation performances, and the lower cost in its maintenance.     

火烧油层点火方式研究

点火是决定火烧油层成败的关键因素,文章对目前火烧油层所采取的主要点火方式的适用条件进行研究分析,结合现阶段研究人员室内一系列先导试验及现场总结出的有价值的经验公式,研究分析各个相关因素(地层温度、电点火注气速率、孔隙度等因素)对点火的影响程度,总结出各因素的变化与点火时间的关系,对相关因素的影响进行进一步的整合、推导,考虑多因素前提下总结出一套可以服务于点火施工的设计方案。     

化学沉积点火药制备机理及应用研究

介绍了多组分(3组分以上)化学液相沉积点火药制备的新技术,通过组合点火管产品点火性能试验,验证了化学液相沉积点火药点火性能稳定性和可靠性。同时提出该项新技术推广应用的前景。