Removal of Contaminants from Underground Spaces by Induced Ventilation

The present paper introduces induced airflow as an effective means for removal of contaminants from underground enclosed spaces. The airflow is caused by natural convection in a vertical duct which absorbs solar irradiation outside the building. Experimental studies and three-dimensional numerical simulations have been performed in a scaled-down laboratory model. The experiments included temperature and velocity measurements and flow visualization. The results obtained from the simulations are fully supported by the experimental results, indicating that effective ventilation by the proposed method is achievable. For real-size structures, three-dimensional computer simulations have been performed using a standard k-ε turbulence model. The results yield a detailed flow field inside the enclosure for various configurations of the ducts and partitions. Rate of air change is calculated both for the whole enclosure, and for the regions above the floor where contaminants like radon tend to accumulate. By adjustment of openings in the basement, the ceiling may be cleared of contaminants as well. It is shown that a properly designed structure, even at low solar fluxes, can provide adequate ventilation of a real-size underground enclosure.     

湖南宝山矿深部开采井下通风系统网络优化及应用

文章针对宝山矿井下通风外部漏风点多、漏风量大、内部风流短路、有效风量率低的问题,提出了相应的改进措施,改善了井下作业环境,取得了良好的通风效果.     

复杂采空区条件下井下通风系统模拟仿真与优化

庙岭金矿井下采空区规模庞大,大量的废弃巷道和未处理采空区,导致井下通风风流紊乱、漏风量大、通风效果差、主扇运转效率低。基于变权重与可变模糊集耦合模型对现有复杂采空区进行了稳定性风险评估,通过对安全风险较大的采空区进行充填治理、对风险一般的采空区和废弃巷道进行封闭,大大减少了漏风和串风现象。增设459 m平硐作进风通道,将原单翼对角式通风系统优化为双翼对角式通风系统,大大缩短了通风线路,改善了进风质量。基于Ventsim的矿井通风网络模拟与仿真,解算了容易时期和困难时期机械通风所需的风压。在充分利用现有风机和新增少量采掘工程的基础上,有效改善了风流质量,保障了通风效果,节约了系统改造投资成本。     

Antiproliferative therapy with 5-fluorouracil in erbium:YAG laser sclerostomy ab externo

In the United States debate continues about the necessity of ventilation during CPR because of fear of contracting infectious diseases. Three questions will be considered in this article. First, is ventilation necessary for the treatment of cardiac arrest? Second, is mouth-to-mouth ventilation any better than no ventilation at all? Third, are other techniques of ventilation as effective or more effective than mouth-to-mouth ventilation during basic life support CPR? Although research is still inconclusive with regard to the need for ventilation during CPR, recent findings have clarified the effect of ventilation during low blood flow states and how ventilation influences resuscitation. Ventilation affects oxygenation, carbon dioxide elimination, and pH during times of low rates of blood flow. Ventilation may be unnecessary during the first few minutes of CPR. Under conditions of prolonged, untreated cardiac arrest, ventilation during CPR affects return of spontaneous circulation. Isolated hypoxemia and hypercarbia independently have adverse effects on survival of cardiac arrest. Because ventilation with exhaled gas contains as much as 4% CO2 and less oxygen than air, it may have adverse effects during CPR. Spontaneous gasping may provide sufficient ventilation during CPR. Chest compression alone provides some pulmonary ventilation and gas exchange. Active chest compression-decompression may improve gas exchange better than does standard chest compression. Other forms of manual ventilation may also have a role in CPR.     

三鑫金铜矿深井复杂通风系统方案优化改造实践

三鑫金铜矿原采用多级机站通风,随着生产中段下延及增多,存在矿井总风量不足、风机运行效率低、部分中段风流反风及通风困难等问题。通过对总需风量进行校核,有针对性地提出了3种通风系统优化方案,利用Ventsim三维动态仿真模拟软件解算和定量定性分析比较,选择了前期井下集中+后期多级机站接力的通风系统方案。按照优选方案组织改造实施后,经过通风测定,总风量、进回风风速都达到了设计要求,有效风量率达81. 33%,主扇运行效率达85%以上,处于高效率区运行,通风效果明显改善。     

配备辅助通风的高温矿井采掘区温度分布数值模拟

巷道高温是制约深部开采的一个重要因素。为了更好地发挥辅助通风设施的作用,提高短距离高温矿井的通风降温效果,采用数值模拟方法研究辅助通风设施对巷道降温效果。通过建立数值模型,设置有无辅助通风设施、不同辅助通风设施长度、不同辅助通风设施与墙壁之间的距离以及不同进气道风速等条件,分析掘进巷道的冷却情况。结果表明:无辅助通风设施的巷道仅靠增加进气道风速无法获得显著的冷却效果;在增加辅助通风设施的情况下,随着辅助通风设施长度的增加,掘进巷道的冷却效果越来越好,当辅助通风设施长度增加到一定程度后通风降温效果开始下降;增加辅助通风设施与墙壁之间的距离可显著提高通风降温效果;在辅助通风设施长度和辅助通风设施与墙壁之间距离固定的前提下,增加进气道风速可改善冷却效果,但随着风速增加,冷却效果改善越来越不明显。     

控制循环风流新方法研究

随着开采深度的增加,通风系统变得更加复杂,工作面位置距离地表主扇越来越远,地表主扇供风方式对深部通风的控制力微乎其微,因此有必要将风机安装在井下。风机安装在井下后,极易出现循环风流,要实现高效通风,必须控制循环风问题。复杂矿井循环风流本质是矿井存在漏风,通过分析循环风形成的本质,提出控制通风系统内部循环风流的评价指标,应用自主开发的软件VentNetLab分析得出有效的控制措施,并对极其复杂的通风网络进行实证研究,指导矿山进行整改。     

海沟金矿采空区漏风调查及治理

矿井通风系统的优劣,直接影响矿山的安全生产和经济效益,而采空区漏风直接降低了矿井的有效风量率,严重干扰通风系统的高效运行。针对海沟金矿采空区漏风实际,采用过风断面风量分段标定技术对采空区漏风情况进行调查分析,开展了采空区漏风模式研究,提出了喷浆+锚杆支护、多刚性风筒并联通风以及负压通风等漏风治理方法。实施效果表明,漏风治理方法合理有效,提高了通风系统的稳定性,保证了矿山的安全生产。     

加强通风管理 确保生产安全

针对矿井通风系统存在上部回风道中的行人和中部的反风等问题,山东金岭铁矿采取重新设计矿井通风系统,加强矿井通风系统检测和管理等措施,使召口、侯庄两矿的有效风量率由59.6%、62%分别提高到83%、74.6%,风机效率由52%提高到65%以上,满足了井下生产用风的需要。     

改善局部通风方法节省通风能耗

本文从正确选择局部通风装置和采用有部分循环同流的通风方法两上方面，论述了在压抽混合式局部通风中的节能问题。     

Experimental changes in the alveolo-capillary barrier induced by artificial ventilation

Mechanical ventilation can have deleterious effects on the lungs. Extra-alveolar escape of air, such as pneumothorax or subcutaneous emphysema, are complications which have long been known. New experimental studies have clearly shown that mechanical ventilation can also result in pathologic changes to the air/blood barrier. Mechanical ventilation with high end-inspiratory pressure and high volume causes lung edema in whose origin abnormal permeability of the alveolo-capillary barrier plays a major role. The abnormalities are in fact the result of pulmonary distention and not of elevated air pressure; this justifies the term "volume traumatism". The presence of a previous acute pulmonary injury considerably increases the deleterious effects of mechanical ventilation on the lungs. Although the clinical implications of these experimental studies are difficult to assess, they have nevertheless resulted in major changes in ventilation strategy for acute lung diseases such as the acute respiratory distress syndrome of the adult.     

基于Ventsim的深井线性热源对有效通风量的影响分析

随着矿产资源开采深度的日益增加,深井通风因其通风网络规模大、环境复杂等,面临着成本及能耗高的问题。考虑到深井高温环境具有大量且便利的热能,基于对深井温差能可利用性的理论分析,通过在回风井深部设置线性热源,运用Ventsim数值模拟的方法,研究了线性热源作用下温差能对矿井有效通风量的影响。结果表明：在矿井巷道干球温度处于25~48 ℃的范围内,线性热源的温度提升与矿井有效风量的提高呈正相关,且回风井内二者呈近似线性相关,但对于矿井底部风量基础值较小的水平巷道,回风井内线性热源对其有效风量的提升不明显;在线性热源作用下,不同的温度递增设置方案对于有效风量的提升也有一定影响,在线性热源温差范围相同的情况下,对温差间隔进行小幅度、多区间的合理设置,有利于提高温差能的利用率。     

高温深井通风降温技术的适用条件研究

随着矿山开采深度的不断增加,“三高一扰动”恶劣开采环境问题日益突出,给矿井通风降温工作带来极大困难。对于深井矿山,仅采用通风降温难以满足深部开采的需要,系统研究高温深井矿山通风降温技术的适用性问题,对矿山深部开采具有重要的理论意义和工程适用价值。首先从热力学角度,揭示风流在通风线路中的热交换规律;其次利用差分法原理计算深井筒风流温度,并依此推导出巷道和回采工作面风流温度变化趋势;然后结合采场安全生产允许温度进行反推,最终获取通风降温条件下的可采极限深度计算公式,并选取广西铜坑矿锌多金属矿体作为工程应用试验区进行论证分析。结果表明：基于风流的热交换模型可以推导出风流在井筒、巷道及工作面的温度计算公式,该公式与低温梯度、风流流经路径长度有关;假定工作面温度达到安全开采允许最高温度,可反推出该条件下矿山可采极限深度和巷道通风极限长度（仅采用通风降温措施时）;基于铜坑矿区锌多金属矿的实际条件,代入相关数据,验证计算所得极限开采深度符合实际,即所推导公式是可行的。     

平焰燃烧湍流场的冷热态比较

 应用粒子成像测速技术(PIV)对平焰燃烧湍流场及其对应的冷态流场进行了测量,对热态流场与相应冷态流场进行了对比分析。结果表明,与冷态流场相比,燃烧状况下流场的回流区宽度增加,回流速度明显增大;附壁射流区厚度变薄,附壁射流区内的径向速度持续增加。实验表明,在湍流燃烧中冷态流场模拟与实际燃烧过程的流动存在较大差异。由于燃烧使气体温度升高体积膨胀产生的推力对流场有很大影响,是不能忽略的。     

柏杖子金矿通风系统改造工程设计及应用

矿山通风系统的建立和完善是实现矿山安全生产的重要条件之一。针对柏杖子金矿开采深度不断延伸,通风线路增长、新鲜风流不足等问题,对原有通风系统进行优化改造,形成了原竖井和新混合井作为进风井,两翼对角抽出式通风系统,并详细介绍了通风系统优化改造工程设计过程,工程应用取得了良好的效果。     

太阳能通风塔辅助通风的可行性探讨

自然通风具有无能耗、无污染等优点,通过对流体力学及矿井自然通风规律的研究,提出一种新的矿井辅助通风设备——太阳能通风塔,利用太阳能对安装于出风井处的太阳能通风塔内空气进行加热,使矿井进、出风井产生空气压力差,形成自然风流,辅助矿井通风,减少矿井通风机的使用频率,达到节约能源的目的。     

茶山矿南矿段通风系统改造研究

为解决茶山矿南矿段自然通风系统通风能力不足、井下通风困难等现状,详细分析了通风系统存在的问题,通过现场实测数据论述了通风系统改造的必要性,并结合矿井的实际情况和生产计划的具体要求提出了针对性的改造方案。改造完成后,对通风系统的实际效果进行测定,结果表明:改造后的矿井通风系统已符合有关规程的规定,井下温度已全部降到28℃以下,矿井有效风量率达到90.98%,工作环境得到大大改善,保障了矿井的安全高效生产。     

Theory of gas exchange in the avian parabronchus

To understand the distribution of oxygen and carbon dioxide in the avian lung, a theoretical treatment of gas exchange in the parabronchus of the avian lung is described. The model is modified after Zeuthen (1942). In addition to bulk flow through the parabronchial lumen, diffusion through the air spaces of both the parabronchial lumen and air capillaries is treated. The relationship of PO2 and PCO2 within the blood capillaries, air capillaries, and parabronchial lumen to parabronchial blood flow and ventilation is graphically shown. The results indicate that the variations of PO2 and PCO2 along an air capillary are less than one torr under resting conditions. Removal of diffusion resistance within the air space of the air capillaries increases calculated parabronchial gas exchange by less than 0.1% at rest. At high or resting ventilation rates the partial pressure profile along the parabronchial lumen calculated considering bulk flow only agrees well with the profile calculated considering bulk flow and axial diffusion, but as the ventilation rate decreases there is increasingly large disagreement. Forward diffusion of O2 toward the parabronchus reduces pre-parabronchial PO2 and backward diffusion of CO2 from the parabronchus increases PCO2. Neglecting diffusion within the air spaces of both the lumen and the air capillaries increases calculated parabronchial gas exchange by less than 2% (CO2) or 6% (O2) at rest.     

Resection of stenotic trachea: a case presentation

Tracheal stenosis is usually a complication of prolonged mechanical ventilation. If the narrowing is severe it will greatly obstruct the air flow. Resection of the damaged trachea is a life saving procedure. The anesthetic management of the resection of an "ice cream cone narrowing" of the trachea (3 mm diameter) 4 cm above the carina is reported. A forced vital capacity loop (expiration-inspiration) of air flow versus volume revealed preoperatively little difference in the flow during the forced (F-V) and resting ventilation (Vt), thus confirming a diagnosis of severe upper airway obstruction. A total obstruction of the air flow was encountered during the skeletonization of the trachea and the surgeon was allowed to work for not more than 60 seconds at a time. Perfect cooperation between the surgeon and the anesthetsia team is necessary for the successful completion of this type of surgery.     

High-volume aspiration as a supplemental scavenging method for reducing ambient nitrous oxide levels in the operatory: a laboratory study

Occupational exposure to low levels of nitrous oxide (N2O) have been associated with adverse health effects. The National Institute for Occupational Safety and Health has established a threshold guideline of 25 ppm N2O. The purpose of this laboratory study was to determine the effectiveness of a high-volume dental aspirator as a supplemental device to reduce ambient N2O levels in the operatory. The investigation evaluated four experimental groups that were assigned based on whether or not the aspirator was used and on the rate at which operatory ventilation was established (5 or 10 room air exchanges per hour). Ambient N2O levels were monitored at 30 cm from the nasal hood using an infrared spectrophotometer. The room air exchange rate was measured with a flow hood and then manipulated to the desired ventilation rate. N2O levels were detected with a spectrophotometer and data were recorded with a microprocessor that continuously collected data. The results demonstrated that both utilization of supplemental oral aspiration and increased operatory ventilation significantly reduced ambient N2O levels. It was concluded that a high-volume aspirator, when used in conjunction with the normal scavenging system, can significantly reduce ambient N2O levels to within the guidelines established by the National Institute for Occupational Safety and Health.