共查询到20条相似文献,搜索用时 140 毫秒
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以燃料电池客船“Water-Go-Round”号为对象,利用FLUENT软件模拟燃料电池客船舱内管道发生氢气泄漏并引发爆炸的情况,研究不同舱室氢气点火爆炸事故的影响规律。结果表明:可燃氢气云被点燃后,爆炸超压波自点火位置向四周迅速传播,点火位置对超压波的分布影响较大;控制舱爆炸时,超压强度最大,对船体超压危害最大;乘客舱爆炸强度最小,但超压中心分布在乘客舱,超压对乘客造成的危害最大;船舶舱室燃烧火焰温度主要由可燃氢气云的分布决定,燃料电池舱的火焰衰减趋势基本相同;乘客舱受到的高温危害较低,船艏舱无燃烧火焰的高温危害。 相似文献
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1.前言火花点火层状充气发动机是燃烧室内混合气的浓度分布发生层状变化,用装在可燃混合气层的火花塞点火,而后火焰沿着扩散形成的可燃层向混合气传播的方式工作的发动机。采用这种方式,总空燃比虽然很稀,已超过了可燃极限,但在局部却可形成可燃混合气层。因而不同于供给相同浓度混合气的普通汽油机,部分负荷时无需节流进气。 相似文献
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采用大涡模拟的方法对一台燃用压缩天然气(CNG)/CO2混合气体燃料的火花点火发动机缸内湍流涡团与火焰面的相互作用过程开展了模拟计算研究.基于OpenFOAM开源CFD程序包建立了AKTIMEuler点火模型和PaSR-LES燃烧模型,并采用耦合多面体顶点运动与梅斯基特算法的求解方法构建了发动机动网格.经过对计算结果的分析可知:随着可燃气体中惰性气体组分的增加,湍流火焰传播速率下降,涡对结构对火焰面皱褶的作用减弱,火焰面在达到相同皱褶度的时间向后推迟,其皱褶度的升高率也随之下降;随着发动机转速的增大,火焰面受到涡团卷吸与拉伸的作用增大,局部容易形成环形火焰面的现象. 相似文献
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Fires caused by accidental spillage of flammable liquids have been a major safety concern in industries and urban areas. There has been a recent surge of interest in the research concerning the combustion and flame spread over an inert porous media soaked with flammable liquid. This interest has been driven by the need to better understand fire and its behaviour under these conditions and improve the relevant fire safety and prevention technologies. A review of key studies in this subject area has been conducted and summarised, focussing mainly on the theory plus a notable experimental findings about combustion and the flame spread phenomena of fuel-soaked porous media. The review covers topics such as flame spread behaviour, physical flame propagation aspects, heat transfer, temperature distribution; and fuel consumption over inert porous media. The review concludes with some practical safety and environmental considerations for decontamination of land soaked with flammable liquid. 相似文献
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IntroductionIn the matter of internal combustion engine, thesimultaneous reduction of fuel consumption andpollutant emission are required. Pedial premixedcombustion is expected to be a combustion method torealize this. The combustion method has both theadvantage of premixed combustion (low environmentalpollution ) and that of diffusive combustion (highefficiency ). The method is already used in the directinjection gasoline engine and in diesel engine with twostage injection or spray atomizatio… 相似文献
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Bo Ling Zhongqian Ling Min Kuang Xianyang Zeng Xiaojin Li Yang Xu Yangxi Chen 《国际能源研究杂志》2019,43(2):970-982
A porous burner stacked in turn with 3‐ and 9‐mm alumina pellets was established to perform C2H4 combustion experiments by acquiring the flammable limits, temperature variation characteristics, combustion wave velocity, pollutant emissions, and treatment efficiency. The burner operated well at equivalence ratios within 0.3 to 0.7. Larger alumina pellets widened the burner's lower flammable limit. As the flame propagated downstream, the higher premixed gas flow velocity and larger alumina pellets, the higher combustion wave velocity, whereas the circumstances were opposite as the flame spread upstream. The combustion temperature increased with the equivalence ratio and premixed gas flow velocity. In response to the effect of the alumina pellet dimension, 3‐mm alumina pellets corresponded to higher combustion temperatures, lower CO emissions, and higher treatment efficiency than those less than 9‐mm conditions. 相似文献
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J. L. Consalvi B. Porterie J. C. Loraud 《Numerical Heat Transfer, Part B: Fundamentals》2013,63(5):419-441
ABSTRACT A finite-volume blocked-off-region procedure is developed to represent internal flammable targets in fire-spread scenarios. In this procedure, the computational domain includes both gas and solid regions. The standard numerical scheme is modified to render hydrodynamically inactive the solid regions and to match the interface conditions at the burning solid surface correctly. A two-grid refinement procedure is used to solve the conjugate heat and mass transfer problem accurately. The first large-scale scenario concerns the flame spread over a vertical panel exposed to a burner flame. Second, the procedure is used to simulate cone calorimeter tests of particle board. For the latter application, the predicted mass loss rates are in qualitative agreement with experimental data. 相似文献
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Experimental investigations on flame spread along a droplet array have been conducted at elevated pressures up to supercritical pressures of the fuel droplet under normal gravity and microgravity. The flame spread rate is measured using high‐speed chemiluminescence images of OH radicals and direct visualization is employed to observe the images of the vaporizing fuel around the unburnt droplet. The mode of flame spread is categorized into two: a continuous mode and an intermittent one. There exist a limit droplet spacing and a limit ambient pressure in normal gravity, above which flame spread does not occur. It is seen that flame spread rate is dependent upon the relative position of flame to droplet spacing. In microgravity, the limit droplet spacing of flame spread and the droplet spacing of maximum flame spread rate are larger than those in normal gravity. In microgravity, the flame spread rate with ambient pressure decreases initially, shows a minimum, and then decreases again after taking a maximum. Flame spread time is determined by competing effects between the increased transfer time of the thermal boundary layer due to reduced flame diameter and the decreased ignition delay time in terms of the increase of ambient pressure. In normal gravity, the flame spread rate with ambient pressure decreases monotonically and there exists a limit ambient pressure, except at small droplet spacing, under which flame spread extends to the range of supercritical pressures of fuel. This is because natural convection induces the upward flow of hot gases into a plume above the burning droplets and limits the lateral transfer of thermal boundary layer. Consequently, it is found that flame spread behaviour under microgravity is considerably different from that under normal gravity due to the absence of natural convection. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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Tzung-Hsien Lin 《Numerical Heat Transfer, Part A: Applications》2013,63(8):841-859
A time-dependent model was developed and solved numerically to study a purely buoyant downward flame spread over a thermally thin solid fuel in various gravity environments. According to the specified burn-out solid density and no retained ash, the flame propagation behavior over a thin solid fuel surface could be simulated. At ignition, the flame is premixed. After several transition burnouts the flame transitions into a self-sustained steady spread diffusion flame. When the gravity level was varied, the Damkohler number effects were verified. An unstable flame spread was noted near the extinction limit at which the flame spread rate decelerated. Blow-off extinction was predicted after the flame spread a short distance. The ignition delay time increased with increasing gravity level. Compared with the experimental measurements, the predicted blow-off extinction limit was closer than that predicted by the steady combustion model. 相似文献
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《International Journal of Hydrogen Energy》2022,47(84):35928-35939
The transportation and utilization of hydrogen blended natural gas have received extensive attention. The dangerous characteristics of hydrogen such as high diffusivity and wide flammability/explosion limit also increase the leakage risk of hydrogen blended natural gas. In this paper, a numerical model is established for the leakage and diffusion of hydrogen blended natural gas in a closed container. The evolution of the distribution, diffusion law and flammable area of different proportions of hydrogen blended natural gas after leaking into a closed container is investigated. The results show that the flammable area with low hydrogen ratios (20% and below) will disappear within 2.7 s–11.1 s after the leakage, which is relatively safer, while the high hydrogen ratio (80% and above) reaches 3875 s–4555 s with a significant increase in risk duration. After the 50% hydrogen ratio leakage, the thickness of the flammable area is higher than 15.67% for the 80% hydrogen ratio and 30.25% higher than pure hydrogen at 120 s after leakage, and the risk is higher in a short time. Due to the difference in the diffusion rates between methane and hydrogen, hydrogen diffuses to the middle and lower part of the enclosed container faster, and the risk in the middle and lower part also deserves attention. 相似文献
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An experimental study was conducted to explore the flame spread mechanism over thin solid fuel sheets. Flame spread rates over paper at various inclined angles were measured, and Schlieren photography was used to qualitatively assess heat transfer to the unburnt material in front of the pyrolysis zone. Two different types of flame spread were observed. One is te downward flame spread observed in the range of ?90 to ?30 deg from the horizontal. In this region, flame spread rate was almost constant with time, although it increased slightly with increasing angle. The other type of spread observed was the accelerative upward flame spread at angles of zero to 90 deg. Flame spread at angles from ?30 deg to zero seemed unsatable and increased by repetitive acceleration and deceleration In the range of inclined angles from ?90 to ?30 deg, heat transfer from the flame zone to the unburnt material seemed to take place mainly through the gas phase in the region 0.2 ~ 0.4 cm in front of the pyrolysis zone. In this case, the direction of the gas stream could be considered to oppose that of the flame spread. In the case of upward flame spread, the unburnt material in front of the pyrolysis zone seemed to be heated by convection of the bottom side, where the direction of the gas stream was obviously parallel with that of flame spread. 相似文献
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针对内燃机高温排气与ORC工质的匹配问题,提出了一组安全且环保的烷烃/CO_2混合工质。为了解决混合工质泄漏后可燃的问题,按照美国ASTME681-2009标准提出测量异丁烷-二氧化碳混合工质可燃区域的实验手段。实验结果表明,异丁烷的可燃下限随阻燃剂二氧化碳的加入基本不变,可燃上限随着阻燃剂的加入迅速减小。并基于临界火焰温度理论建立了预测异丁烷-二氧化碳混合工质可燃极限的模型,与试验值相比较表明,预测模型可以较好地预测异丁烷的可燃下限,上限预测误差较大。 相似文献