尾气余热制氢柴油机的燃烧特性分析

设计了一种利用发动机尾气余热制取氢气的装置,该装置可以利用发动机余热,将乙醇水溶液催化反应为富含氢气的重整气。该重整气通入发动机供其燃烧使用,可以有效的提高发动机的燃烧效率。主要考虑该重整气对柴油燃烧的影响,依据美国加州劳伦斯利弗莫尔国家实验室反应机理,通过Chemkin软件计算该装置生成的重整气加入发动机以后对发动机燃烧特性的影响,分析了不同重整气掺混比例下的火焰传播速度,研究了柴油燃烧和柴油混合重整气燃烧的区别,总结了重整气在改善发动机燃烧方面所发挥的作用。     

爆炸法回收废旧轮胎实验研究

利用爆破法处理废旧轮胎,通过观察测量废旧轮胎爆破后的橡胶碎片量,考察了不同炸药对轮胎回收效果的影响。通过测量加入不同比例消焰剂的TNT爆破回收量,确定了最佳配比范围。研究表明,在TNT中加入消焰剂可有效提高轮胎爆破回收效果,消焰剂加入量10%~15%时效果最佳。     

Experimental and LES investigation of premixed methane/air flame propagating in a chamber for three obstacle BR configurations

The paper aims at revealing the effect of blockage ratio (BR) on the flame acceleration process and the flame-vortex mechanism in an obstructed chamber based essentially on the experimental and numerical methods. In the experiments, high-speed video photography and pressure transducer are used to study the flame shape changes and pressure dynamics. In the numerical simulations, large eddy simulation (LES) with the flame surface density (FSD) model is applied to investigate the interaction between the moving flame and vortices induced by obstacle. The results demonstrate that the flame propagation process can be divided into four stages, namely spherical flame, finger-shaped flame, jet flame and volute flame for three obstacle BR configurations, and a small recirculation zone is observed above the obstacle only for BR = 0.5. The peak of flame tip speed and pressure growth rate increases with the blockage ratio. The generation and evolution of the vortex behind the obstacle can be attributed to the initial flame acceleration, while the subsequent flame deceleration is due to the flame-vortex interaction. In addition, the transition from a “thin reaction zones” to a “broken reaction zones” is also observed in the simulation.     

管道压力对天然气射流火热辐射灾害的影响

天然气管道时常受到破坏,并诱发巨大的射流火焰,可能引燃周围建构物体。系统地分析了管道压力对天然气射流火热辐射灾害的影响,以建立天然气射流火热辐射灾害的系统定量分析方法。基于压力管道小孔泄漏模型和权重-多点源热辐射计算模型,建立了目标物体最大入射热辐射通量、管道压力和目标物与泄漏小孔水平距离的定量关系式。进而选定10 k W/m~2和31.5 k W/m~2作为城镇建筑物遭受引燃和机械破坏的热辐射通量阈值,得到了不同管道压力下天然气射流火热辐射灾害范围。计算结果表明,GB 50028—2006《城镇燃气设计规范》依据管道压力所规定的燃气管道与建筑物的安全间距不能完全满足天然气管道破坏时射流火焰的安全要求,与某武汉天然气管道射流火事故后果一致。     

PHB/V in Extrusion Coating of Paper and Paperboard: Part I: Study of Functional Properties

Extrusion-coating experiments were carried out in the pilot line at Tampere Univesity of Technology (Institute of Paper Converting). Typical paper and paperboard substrates were coated with commercially produced 3-hydroxybutyrate/3-hydroxyvalerate. The resulting physical properties of extrusion-coated composite structures were studied. Adhesion between PHB/V and a fiber-based substrate was rather poor, regardless of typically used pretreatments (corona and flame). On the other hand, adhesion was sufficient (mode of failure was fiber tear as the materials were separated) when the substrate was primed with an acrylic-based primer. The surface energy and polarity of PHB/V were much higher than the respective ones of LDPE. Curling of PHB/V was reduced by the addition of wax or tall oil rosin into the base polymer.     

柱形连通容器内预混气体爆炸过程的火焰传播模拟

为研究连通容器内气体爆炸规律,采用Fluent(经典流体动力学软件)对柱形连通容器内预混气体爆炸过程进行模拟,模拟了不同点火位置和火焰传播方向条件下连通容器内火焰传播过程和压力变化,并分析了连通容器内不同时刻的速度场.结果表明:火焰面在传播过程中并非完全对称,当火焰到达传爆容器后,湍流燃烧剧烈,火焰不规则变形显著;端面点火后在传爆容器内产生的压力峰值和压力波动比中心点火时更大;当起爆容器为大容器时,传爆容器内气体预压缩程度更大,压力峰值更高.     

Ignition hazard evaluation on A2L refrigerants in situations of service and maintenance

To restrict the progress of the global warming, A2L refrigerants such as 2,3,3,3-tetrafluoroprop-1-ene (R1234yf), (Z/E)-1,3,3,3-tetrafluoroprop-1-ene (R1234ze), and difluoromethane (R32) have been expected of alternatives to the standard refrigerants currently in use. The ignition hazard of A2L refrigerants under plausible accident situations in service and maintenance was examined experimentally for two cases: leakage of an A2L refrigerant from a pinhole in a pipe or hose (Scenario 1), and leakage of an A2L refrigerant into an item of equipment used for service and maintenance, such as a collection device (Scenario 2). In Scenario 1, the location of the flammable zone and the possibility of a jet flame being formed instantaneously on contact with an ignition source were examined. Even when R1234yf leaked from a 4 mmϕ pinhole (corresponding to breakage of a pipe), the flammable zone extended only about 10 cm from the pinhole in the downstream region. In an ignition test with a continuous spark as the ignition source, a pale emission appeared only near the spark, and the flame did not propagate to the rest of the refrigerant jet. In Scenario 2, the accumulation and ignition behaviors of A2L refrigerants in a model collection device were examined experimentally. Ignition and flame propagation occurred in a test on a model collection device lacking slits, whereas when slits wider than 20 mm were present, ignition and flame propagation did not occur. Even if R1234yf leaked into the model collection device, provided that slits of an effective width were present, the R1234yf could diffuse through slits and barely accumulated, and no ignition or flame propagation occurred.     

Theoretical estimation of the lower flammability limit of fuel-air mixtures at elevated temperatures and pressures

We present an approach for predicting the lower flammability limits of combustible gas in air. The influence of initial pressure and temperature on lower flammability limit has been examined in this study. The lower flammability limits of methane, ethylene and propane in air are estimated numerically at the pressure from one to 100 bar and the temperature from ambient to 1200 K. It was found that the predicted LFLs of methane, ethylene and propane decrease slightly with the elevated pressure at the high temperature. The LFLs variation for methane-air mixture is 0.17, 0.18, 0.18 volume% with the initial pressure from one to 100  bar at the initial temperature of 800 K, 1000 K and 1200 K respectively, which is significantly higher than that at lower temperature. And the LFL of methane-air mixture at 1200 K and 100 bar reaches 1.03 volume% which is much lower than that at 1 bar and ambient temperature. On the other hand, the LFLs variation is 0.11–0.12 volume% for ethylene-air mixture and 0.06–0.07 volume% for propane-air mixture with the initial temperature from 800 K to 1200 K at the same range of pressure. The LFL values at high temperatures and pressures represent higher risk of explosion.     

Extinguishment of hydrogen laminar diffusion flames by water vapor in a cup burner apparatus

Transient computations with full hydrogen chemistry were performed to reveal the flame structure and extinguishment process of co-flow, hydrogen diffusion flame suppressed by water vapor. As the concentration of water vapor was increased, the flame detached away from the burner brim and formed an edge flame at the flame base. Water vapor showed larger chemical inhibition effect than nitrogen when extinguishing hydrogen flame, which was attributed to its enhanced third body effect in the reaction H + O₂ + M = HO₂ + M. The minimum extinguishing concentration (MEC) of water vapor and nitrogen was predicted by Senecal formula and perfectly stirred reactor (PSR) model respectively. The MECs predicted by PSR model agree with the MECs calculated by Fluent, which shows that 1) the flame extinction is controlled by the flame base, and 2) radiation absorption is negligible. The measured MECs are in a reasonable agreement with the values calculated by Fluent, which demonstrates the accuracy of the CFD model. A simple model was used to investigate the relative importance of extinguishing mechanisms of water vapor. The results show that in a co-flow configuration the thermal cooling and chemical inhibition effect are the main extinguishing mechanisms in suppressing hydrogen diffusion cup burner flame.     

利用主成分分析法简化甲烷/空气层流预混火焰的反应机理

利用主成分分析(Principal Component Analysis)的方法对甲烷/空气氧化的详细化学反应机理进行了简化，在低压层流预混火焰条件下进行了计算，计算结果与详细机理的计算结果及实验值进行了比较。结果表明简化机理与详细机理吻合较好，简化机理的规模和计算时间有所减少。