Experimental investigation on the self-acceleration of 10%H2/90%CO/air turbulent expanding premixed flame

The self-acceleration characteristics of a syngas/air mixture turbulent premixed flame were experimentally evaluated using a 10% H₂/90% CO/air mixture turbulent premixed flame by varying the turbulence intensity and equivalence ratio at atmospheric pressure and temperature. The propagation characteristics of the turbulent premixed flame including the variation in the flame propagation speed and turbulent burning velocity of the syngas/air mixture turbulent premixed flame were evaluated. In addition, the effect of the self-acceleration characteristics of the turbulent premixed flame was also evaluated. The results show that turbulence gradually changes the radius of the premixed flame from linear growth to nonlinear growth. With the increase of turbulence intensity, the formation of a cellular structure of the flame front accelerated, increasing the flame propagation speed and burning speed. In the transition stage, the acceleration exponent and fractal excess of the turbulent premixed flame decreased with increasing equivalence ratio and increased with increasing turbulence intensity at an equivalence ratio of 0.6. The acceleration exponent was always greater than 1.5.     

含火烧煤层露天矿边坡变形破裂过程FEPG模拟研究

露天矿开采过程中边坡变形破裂过程一直是岩土工程领域研究的难点,尤其考虑含火烧煤层露天矿开采过程中的边坡稳定使得研究问题更加复杂。采用FEPG数值模拟的研究方法,对露天矿某边坡KT3剖面进行了破裂过程分析,得到了含火烧煤层露天矿边坡变形破裂规律,研究结果表明,边坡火烧砂岩的顶部首先出现拉张裂缝,边坡以压剪破坏为主,压剪破坏又促使拉张破坏,二者相互影响,最终导致边坡发生失稳破坏。     

Environmental aspects of thermal power equipment operation modes optimization

The article deals with development of methods for improving the efficiency of power generation in thermal power plants by means of main equipment operating mode optimization. The technique for efficient load distribution between cogeneration turbines for cogeneration of heat and electricity is introduced. The calculated fuel consumption corresponds to the optimal operating modes of turbines. The environmental aspects of optimization method have been considered. The economic effect from implementation of proposed technical solutions has been calculated. For more significant reduction of toxic compounds, generated in boiler furnace, the use of thermal effect from combustion of the hydrogen formed during the decomposition of the damp water, metered into the combustion chamber at temperature 1100 °C is introduced. The use of hydrogen additive as a source of additional stored energy due to combustion in the combustion device, expands the scope of its application in a power system significantly and provides normal emissions of toxic compounds into the air. The use of hydrogen additive in combustion refers to the best available techniques, implementation of which allows increasing the competitiveness of Russian energy production.     

Associations between indoor environment in residential buildings in wet and dry seasons and health of students in upper northern Thailand

We performed a repeated questionnaire study on home environment and health (six medical symptoms) in 1159 junior high school students (age 12.8 ± 0.7 years) in upper northern Thailand in wet and dry seasons. Data on outdoor temperature, relative humidity (RH), and air pollution were collected from nearest monitoring station. Odds ratios (OR) were calculated by multi-level logistic regression. Most common symptoms were rhinitis (62.5%), headache (49.8%), throat (42.8%), and ocular symptoms (42.5%). Ocular symptoms were more common at lower RH and rhinitis more common in dry season. Water leakage (28.2%), indoor mold (7.1%), mold odor (4.1%), and windowpane condensation (13.6%) were associated with all six symptoms (ORs: 1.3–3.5). Other risk factors included cat keeping, environmental tobacco smoke (ETS), other odor than mold odor, gas cooking, and cooking with biomass fire. Biomass burning inside and outside the home for other reasons than cooking was associated with all six symptoms (ORs: 1.5–2.6). Associations between home environment exposure and rhinitis were stronger in wet season. In conclusion, dampness-related exposure, windowpane condensation, cat keeping, ETS, gas cooking, and biomass burning can impair adolescent health in upper northern Thailand. In subtropical areas, environmental health effects should be investigated in wet and dry seasons.     

Hydrogen permeation across super‐thin membrane and the burning limitation in low‐temperature proton exchange membrane fuel cell

Hydrogen permeation across the membrane is unavoidable in proton exchange membrane fuel cells, especially for super‐thin membranes, which lowers the open‐circuit voltage and could even be a safety concern. In this paper, hydrogen permeation across two membranes (25‐um‐thick Nafion^® 211 and 18‐um‐thick reinforced composite membrane) are evaluated at various temperatures, relative humidity (RH), and gas pressure differences between the anode and cathode. The results indicate that the hydrogen permeation rate in both membranes increases almost exponentially with temperature and linearly with pressure differences. Compared with RH, the effects of temperature and pressure differences are more crucial to hydrogen permeability. However, the effect of RH on the hydrogen permeation is quite complicated. The permeability exhibits a minimum value at intermediate RH (approximately 40% RH) for both applied membranes. The permeability of Nafion^® 211 appears more sensitive to RH than that of reinforced composite membrane at elevated temperature. Copyright © 2013 John Wiley & Sons, Ltd.     

Advantages and challenges with using hypoxic air venting as fire protection

The use of hypoxic air venting system as fire protection is increasing and is sometimes used to replace traditional extinguishing systems. An oxygen level of 15% is generally used because a lower concentration could pose serious health risks. On the request of the Swedish Radiation Safety Authority, a literature review was conducted to determine advantages and challenges with the system and further research needs. The main advantages with a reduced oxygen environment are the reduced probability of ignition and lowered heat release rate. However, at 15% oxygen level, risk for fire still exists, and the system cannot be seen as an alternative to extinguishing systems. Reduced oxygen environment also results in higher production rates of soot and smoke, and there is limited knowledge regarding the effect of fuel configuration and fire behavior of products. In addition, a first evaluation of the test method specified in the hypoxic air venting standards was carried out through testing. The testing showed that the particleboard passed the test criteria at normal atmosphere even though it is commonly known that a particleboard burns in normal air. It is concluded that the test method has deficiencies, and there is clearly a need for development of the test method to guarantee safety levels. © 2013 The Authors. Fire and Materials published by John Wiley & Sons, Ltd.     

Applications of ground source heat pump systems in different temperature zones in China

An analysis of the application of ground source heat pump (GSHP) systems to different temperature zones in China is presented in this paper. According to the climate characteristics, China is divided into six different temperature zones: the tropical zone, the subtropical zone, the warm temperate zone, the mid temperate zone, the cold temperate zone, and Qinghai-Tibet Plateau vertical temperature zone. Six representative cities corresponding to the six temperature zones are chosen and their different climate and soil characteristics are studied. The results show that a GSHP system can be applied to the first four temperature zones above, but not the cold temperate zone and the Qinghai-Tibet Plateau vertical temperature zone. However, in different temperature zones, different GSHP systems should be designed and built.     

弹性聚酯复合纤维的定性方法研究

通过燃烧法、显微镜观察法、差示扫描量热仪法研究了弹性聚酯复合纤维的外观形态及物理特征,确定了弹性聚酯复合纤维的定性鉴别方法。