中国大陆地区年最大平均风速的概率密度函数

根据中国大陆地区1951-2002年的实测风速数据资料，采用密度演化方法进行了各站点年最大平均风速的概率密度函数估计，给出了大陆地区年最大平均风速均值和标准差的等值线分布图。与常用的基于拟合优度检验的概率密度函数估计和统计量分析不同，所提方法不需要进行先验分布类型的假定，可以通过直接计算给出与基本数据经验分布函数符合得较好的概率密度函数与概率分布函数。对比研究表明，该方法给出的统计结果是可信的，具有工程实用参考价值。     

被动采集大气颗粒物样品的粒径分布特征

在可同时采集气态与颗粒态大气污染物的被动采样装置中放置涂有薄层凡士林的载玻片,用于采集大气悬浮颗粒物,利用粒度粒形仪分析样品粒径分布特征,并深入探讨风速以及采样罐外壁添加300目滤网(孔径50μm)对样品粒径分布的影响.结果表明,在室内静风与室外相对封闭的条件下,添加滤网可有效阻止50μm的粗颗粒组分进入采样罐;而在室外有风的条件下,添加滤网后仍有粗颗粒进入采样罐中,但进入概率与风速大小之间无关.观察粒径10μm以下颗粒的分布曲线,室内静风条件下得到的分布曲线与主动采样得到的结果极为类似.而在有风条件下,3～5μm的颗粒组分比重有所减少,6～9μm颗粒组分比重明显增加.上述问题在被动采样器的使用中需予以考虑,结合样点具体情况判断是否添加滤网.     

Impacts of environmental factors on urban heating

This study investigated the impact of important environmental variables (i.e.,wind speed,solar radiation and cloud cover) on urban heating.Meteorological parameters for fifteen years (from 1990 to 2005),collected at a well developed and densely populated commercial area (Tsim Sha Tsui,Hong Kong),were analyzed in details.Urban heat island intensity (UHII),a well known indicator of urban heating,has been determined as the spatially averaged air-temperature difference between Tsim Sha Tsui and Ta Kwu Ling (a thinly populated rural area with lush vegetation).Results showed that the UHII and cloud cover have increased by around 9.3% and 4%,respectively,whereas the wind speed and solar radiation have decreased by around 24% and 8.5%,respectively.The month of December experienced the highest UHII (10.2°C) but the lowest wind speed (2.6 m/sec) and cloud cover (3.8 oktas).Conversely,the month of April observed the highest increases in the UHII (over 100%) and the highest decreases in wind speed (over 40 %) over fifteen years.Notably,the increases in the UHII and reductions in the wind speed were the highest during the night-time and early morning.Conversely,the intensity of solar radiation reduced while the intensity of urban cool island (UCII) increased during solar noon-time.Results demonstrated strong negative correlation between the UHII and wind speed (coefficient of determination,R2=0.8) but no negative correlation between UCII and solar radiation attenuation.A possible negative correlation between UHII and cloud cover was investigated but could not be substantiated.     

青岛华威风电场风能资源分析

根据华威风电场2008年4月1日-2009年3月31日一整年的测风仪测风资料,对风电场的风能资源各参数进行了详细地计算和分析,对风电场的风能资源进行评价,为当地的风能开发提供分析基础。     

复合式厌氧氨氧化反应器脱氮性能研究

采用低速机械搅拌装置,以无纺布作为固定床的填料,把搅拌床与固定床的优点有机结合起来,设计一种复合式厌氧氨氧化反应器.在反应器中,生物滞留量相对较高,微生物的性状由接种时的碎絮状很快转变成颗粒状,短期内反应器系统的脱氮性能迅速提高,启动时间大为缩短.仅用38d,反应器中总氮去除速率稳定增长至1.9kg·m·-3d-1.随...     

油包水型乳化液水击波速的分析

水击驻波场处理油包水型乳化液是一门新兴工艺,稳定驻波场的存在是破乳的关键,而水击压力波波速在驻波场形成中起着重要的作用。因此,为了更精确的求解水击波速,从W/O型乳化液两相流产生水击现象的特点出发,根据流体力学的连续性原理,推导其水击波波速的表达式,并与经典单相流水击波波速公式进行对比,通过MATLAB仿真分析与对比验...     

小风条件下大气扩散模式发展回顾研究

由于小风对污染事件的潜在影响,以及与中等风速和大风条件相比边界层结构、湍流和扩散的特殊性,常规的稳态高斯烟流模式在这种条件下具有局限性,建立适用于小风条件的大气扩散模式具有重要的理论和实际意义。本文回顾了近年来小风条件下大气扩散模式的建立和发展,从较简单的解析模式到复杂的数值模式,并对不同模式的参数化方案、与示踪物实验的比较结果、适用性和不足之处进行了总结。综合考虑不同模式的优劣,在应用方面有利于根据实际情况选择合适的模式,在模式开发方面,有助于建立更加完备的大气扩散模式。     

Improved electrospray design for aerosol generation and flame propagation analysis

Although the hazards of aerosol fires and explosions have been studied for decades the data for aerosol flame propagation is still scarce. Additionally there is a lack of standard techniques and measurement apparatus, which impedes the development of optimal aerosol hazard mitigation measures. The focus of this study is development of an improved aerosol electrospray device for the generation of high quality aerosol data. The goal is achieved through higher nozzle packing, precise nozzle and mesh hole alignment and adding two ground meshes. In addition to a flat ground mesh, the utilization of a cylindrical ground mesh demonstrated improved confinement and guidance of droplets. Duratherm 600, heat transfer fluid, was examined to demonstrate the modified electrospray device capabilities as compared to previous design. Results show the modified electrospray can produce more uniform droplets, more even test chamber dispersion, smaller droplet size and higher concentration aerosol, which is essential to study aerosol flame propagation. Accordingly, the results of aerosol flame speed tests for the improved design were more reproducible. Moreover, it was found that a traditional propane pilot flame was unable to ignite the smaller aerosol droplet size due to the strong turbulence generated by the open flame. However, by careful modification of the pilot flame length, the turbulence decreased dramatically and the small droplet size aerosol can be tested.     

Experimental Study on the Influence of Rotational Speed on the Performance of a Single-screw Expander with a 175 mm Screw Diameter

A single-screw expander has been designed and manufactured independently. Based on this prototype, testing system has been built and performance experiment has been made. In this article, compressed air was used as working fluid and performance test for the prototype was finished at conditions including different rotational speed and different inlet pressure.

From the experimental data, it is shown that when inlet pressure less than 0.8MPa the output power increases with the increase of rotational speed because of not enough expansion; when inlet pressure more than 0.8MPa, the every biggest output power is appeared in the condition of rotational speed 2600 rpm. The test results also show that the total efficiency is influenced by rotational speed obviously, and the highest total efficiency of this machine is 69.64% in the condition of 3000 rpm and 15 bar.     

Effects of vent layout and vent area on dynamic characteristics of premixed methane-air explosion in a tube with two side-vented ducts

To further elucidate the influence mechanism of side vents on the dynamic characteristics of gas explosions in tubes is helpful to design more reasonable vent layouts. In this paper, 9.5% methane-air explosion experiments were conducted in a tube with two side-vented ducts, and the effects of vent layouts and vent areas on the dynamic characteristics of explosion overpressure and flame propagation speed were investigated. The results demonstrate that under the same condition with a single vent area of 100 mm × 100 mm, when only the end vent is open, the maximum explosion overpressure and the maximum flame propagation speed are the highest among the five vent layouts. When the side vents 1 and 2 and the end vent are open, the maximum explosion overpressure is the lowest, and an unusual discovery is that the flame front changes into a hemispherical shape, finger shape, quasi-plane shape, tulip shape and wrinkled structure. When only side vent 1 is open, a unique Helmholtz oscillation occurs, and a new discovery is that there is a consistent oscillation relationship among the overpressure, flame propagation speed and flame structure. Helmholtz oscillation occurs only when a single vent area is 100 mm × 100 mm–60 mm × 60 mm, and the oscillation degree decreases with decreasing vent area. During the vent failure stage, the maximum explosion overpressure is generated, the flame front begins to appear irregular shape, and the flame propagation speed shows a prominent characteristic peak. After the vent failure stage, the driving effect of the end vent on the flame is higher than that of the side vent on the flame. Furthermore, the correlation equations of the mathematical relationships among the maximum explosion overpressure P_red, the static activation pressure P_stat and the vent coefficient K_v under four vent layouts are established, respectively.