火电厂烟道的优化分析

以某电厂2×1 000 MW机组的引增段烟道为例,基于CFD模拟软件开展了烟道系统的优化分析,优化后降低了系统压损122 Pa,年节约运行费用约35万元,投资回收期为0.57 a。优化后的方案较原方案大大降低了系统的磨损及振动,有利于电厂的安全可靠运行。     

管道内瓦斯爆炸温度与压力峰值试验研究

为分析瓦斯爆炸的火焰温度及压力峰值在管道中的传播规律,采用瓦斯管网爆炸测试系统进行试验,通过爆炸压力和爆炸火焰温度采集系统采集数据。在相同点火能量和点火位置的条件下,分析了体积分数对瓦斯爆炸的温度峰值和压力峰值的影响,及温度峰值和压力峰值随管道距离的变化规律。结果表明:当瓦斯体积分数低于9.5%时,温度峰值和压力峰值随瓦斯体积分数增大而增大;同一体积分数下,温度峰值最大值出现在最接近爆源的位置,并呈逐渐下降的趋势,接近爆源的温度峰值下降较明显,随管道延长,温度峰值的下降减慢且趋于平缓;温度峰值与传播距离近似呈三次函数关系;冲击波压力峰值随管道传播呈先上升后下降再上升的波动性变化。     

现役民机客舱热舒适评价

采用修正热舒适评价值(Corrected Predicted Mean Vote,CPMV)模型,针对实测的国内及国际航线数据进行了客舱环境的热舒适评价.结果表明,当客舱内压力满足适航标准要求范围、相对湿度明显低于舒适性要求时,低压和低相对湿度均能导致热舒适评价值(Predieted Mean Vote,PMV)的正偏移,偏移量为0.3～0.4,即低气压和低湿会使乘客感觉更温暖,但这2个参数对乘客热舒适的影响有限.短途航班热舒适性不理想,部分航班出现过热或过冷现象.     

热浮力及室外风压耦合驱动下高层建筑疏散走廊烟气运动网络模拟分析

火灾发生后,火灾烟气主要通过疏散走廊向建筑的其他部位蔓延.有效控制疏散走廊中的烟气,可以阻止其进一步蔓延到楼梯间.了解火灾烟气在疏散走廊中的运动规律,是控制其蔓延扩散的前提.热浮力和室外风压是烟气在走廊中运动的主要驱动力,研究二者耦合作用对走廊中烟气运动的影响,对进一步弄清火灾烟气的流动规律具有较大的意义.采用网络模拟软件CONTAM 3.0模拟疏散走廊中火灾烟气在上述两种驱动力作用下的运动情况.结果表明,随室外风速增大,疏散走廊中火灾烟气的运动速度增大,远大于单纯热浮力作用时烟气的运动速度;当热浮力和室外风压耦合驱动时,室外风压对烟气运动的影响起主要作用.     

本煤层瓦斯抽采渗流模型及数值模拟

在研究煤层瓦斯抽采时,假定煤岩为具有孔隙裂隙的双重介质,在运动方程、连续性方程和辅助方程基础上,以煤岩体应变为耦合媒介建立了考虑裂隙瓦斯渗流、微孔隙吸附瓦斯解吸扩散和煤岩变形的渗流模型.借助多物理场分析软件COMSOL Multiphysics,将模型转化为偏微分方程组,结合沙曲矿24305工作面瓦斯赋存条件进行分析求解.结果表明,进行煤层瓦斯预抽时,抽采初期瓦斯压力下降较快,抽采孔间距对抽采效果影响比较显著,距离抽采孔越远瓦斯压力下降越慢,抽采时瓦斯渗流速度变化可分3个阶段.参考模拟结果现场布置孔距为6m的顺层钻孔,抽采稳定时瓦斯纯量达5～7 m3/min,抽采效果比较理想.     

黄河三角洲海岸带生态承载力综合评价

为全面、深入认识黄河三角洲海岸带的海洋资源和生态环境特征、海洋产业结构及海洋经济发展的优势、劣势条件,选取工业废水排放量、固体废渣排放量、万元GDP能耗、岸线利用率、人均可开发海域面积、人均海岸线长度、海洋初级生产力、污染海域占海域总面积的比例、生物多样性指数、人口密度、人均海洋经济产值、GDP年均增速、科研与开发投入和环境保护支出等压力、状态、响应3类14个指标,采用压力-状态-响应模型对黄河三角洲海岸带生态承载力进行了综合量化评价.结果表明,2006-2010年黄河三角洲海岸带的承载指数和压力指数呈下降趋势,承压比则总体上呈上升趋势.根据评价结果,提出了构建高效生态产业体系、优化黄河三角洲产业空间布局、对传统产业进行生态化改造、发展新兴生态产业、保护黄河三角洲海岸带生态环境、对黄河三角洲海岸带海洋资源进行高效集约利用等提高黄河三角洲海岸带生态承载力的对策.     

Changes in nitrogen budget and potential risk to the environment over 20 years (1990–2010) in the agroecosystems of the Haihe Basin,China

The nitrogen balance can serve as an indicator of the risk to the environment of nitrogen loss from agricultural land. To investigate the temporal and spatial changes in agricultural nitrogen application and its potential threat to the environment of the Haihe Basin in China, we used a database of county-level agricultural statistics to calculate agricultural nitrogen input, output, surplus intensity, and use efficiency. Chemical fertilizer nitrogen input increased by 51.7% from 1990 to 2000 and by 37.2% from 2000 to 2010, concomitant with increasing crop yields. Simultaneously, the nitrogen surplus intensity increased by 53.5% from 1990 to 2000 and by 16.5% from 2000 to 2010, presenting a continuously increased environmental risk. Nitrogen use efficiency decreased from 0.46 in 1990 to 0.42 in 2000 and remained constant at 0.42 in 2010, partly due to fertilizer composition and type improvement. This level indicates that more than half of nitrogen inputs are lost in agroecosystems. Our results suggest that although the improvement in fertilizer composition and types has partially offset the decrease in nitrogen use efficiency, the environmental risk has still increased gradually over the past 20 years, along with the increase in crop yields and nitrogen application. It is important to achieve a better nitrogen balance through more effective management to significantly reduce the environmental risk, decrease nitrogen surplus intensity, and increase nitrogen use efficiency without sacrificing crop yields.     

Potential application of high pressure carbon dioxide in treated wastewater and water disinfection: Recent overview and further trends

Recently emerging disadvantages in conventional disinfection have heightened the need for finding a new solution. Developments in the use of high pressure carbon dioxide for food preservation and sterilization have led to a renewed interest in its applicability in wastewater treatment and water disinfection. Pressurized CO₂ is one of the most investigated methods of antibacterial treatment and has been used extensively for decades to inhibit pathogens in dried food and liquid products. This study reviews the literature concerning the utility of CO₂ as a disinfecting agent, and the pathogen inactivation mechanism of CO₂ treatment is evaluated based on all available research. In this paper, it will be argued that the successful application and high effectiveness of CO₂ treatment in liquid foods open a potential opportunity for its use in wastewater treatment and water disinfection. The findings from models with different operating conditions (pressure, temperature, microorganism, water content, media …) suggest that most microorganisms are successfully inhibited under CO₂ treatment. It will also be shown that the bacterial deaths under CO₂ treatment can be explained by many different mechanisms. Moreover, the findings in this study can help to address the recently emerging problems in water disinfection, such as disinfection by-products (resulting from chlorination or ozone treatment).     

Space-time analysis of the changing patterns of population pressure on the ecological environment in China

This paper examines the temporal change and spatial variation of population pressure on the ecological environment in China. We have collected sufficient data from the statistical yearbooks of 31 provincial administrative areas in 1990, 1995, 2000, 2005, and 2010. Using a geographic information system (GIS) and relevant models, we analyzed the trend of the population pressure on ecological environment and the change of the gravity center of ecological environment quality. We conclude that: (1) generally, population pressure on the ecological environment in China was becoming higher during 1990–2010, especially in some areas where the population and environment were in serious imbalance and the ecological environment experienced severe pollution; (2) during a certain period, population pressure on the ecological environment was becoming lower in some areas, but the ecological environment was getting worse; (3) the areas with super-high population pressure on the ecological environment were Beijing, Tianjin, and Shanghai; (4) the gravity center of population pressure on the ecological environment and the center of ecological environment quality move differently during the study time period, but the general trend was similar – both of them were moving from west to east. Based on the analysis, this paper also provides some policy suggestions on the control of ecological environment quality.     

Effect of working time on environmental pressures: empirical evidence from EU-15, 1970–2010

There is growing interest in the correlation between working time and environmental pressures, but prior empirical studies mostly focused on static methodologies. This article used dynamic panel regression approaches to examine and compare the relationship among western, southern, and northern European countries over the period 1970–2010, and proved the existence of strongly significant relationships in all models. Furthermore, this article detected the relationship between working hours and environmental indicators (carbon emission and energy use) at different phases. We contribute to a further understanding of the environmental effects of the working time reduction policy by comparing the differences among various periods and country groups in a system generalized method of moments (GMM) dynamic framework.