褶型筒式空气过滤器过滤压降的数值模拟

基于计算流体力学（CFD）,采用FLUENT中的多孔介质模型对褶型空气过滤器进行数值模拟研究,通过模拟计算和实验研究得到了空气过滤器的一些阻力性能。结果表明,褶型空气过滤器在过滤气体中的杂质时,过滤器的阻力随着进口风量的增大而增大;而增加过滤器的褶数会增大过滤器的过滤面积,过滤器的过滤面积增大之后过滤器的过滤速度会相应减小,由此可以减小过滤器的阻力。但是增加过滤器的褶数之后会相应的改变过滤器滤芯的褶间距,褶间距的大小会对气流的流动产生影响。气流的流动会影响过滤器的阻力。这些研究可以为过滤器滤芯的设计及应用提供一定的依据。     

我国机动车排放标准及检测方法简述

根据"新车新标准,老车老标准"的原则,双怠速法将是汽油车基本检测方法,简易工况法在全国范围内分步实施,柴油车将逐步采用不透光烟度计的测量方法.同时介绍了国外相关标准及检测方法.     

香港与广州市汽车尾气污染比较

采用较先进自动分析仪器,连续４年在香港九龙青山道及连续９天广州市解放中路,对汽车尾气污染进行监测。结果表明,香港九龙青山道汽车尾气污染较轻,１９８８年和１９８９年基本满足中国国家大气环境质量二级标准的要求。广州市解放中路汽车尾气污染严重。超过国家大气环境质量三级标准,车流组成与行车速度的差异是造成香港与广州市两地汽车气污染差别的主要原因。     

高速公路汽车防碰撞模型仿真研究

随着高速公路的快速建设,交通事故迅猛增长.保证适当的车辆行驶距离是预防高速公路事故的有效手段.论文根据车辆制动规律和运行状态,得出行车安全距离模型,同时对模型中的参数进行了说明和分析.采用MATLAB软件对高速公路车辆的安全距离模型进行仿真分析,得出安全距离随车速和附着系数的变化规律,寻求既保证车辆安全行驶又不影响道路通行能力的合理的安全距离值,为降低高速事故率提供一定的依据.     

在校大学生肩宽及疏散速度的测量研究

为了确定疏散软件中符合中国人的疏散基本参数,采用现场测量的方法对在校男大学生的肩宽及各种情况下的疏散速度进行统计,并对测量结果进行分析。结果表明,在校男大学生平均肩宽为46．5 cm,正常状态下水平行走速度为1．37m／s,上楼速度为0．66m／s,下楼速度为1．36m／s,上坡速度为1．34m／s,下坡速度为1．59 m／s;在无障碍的情况下,紧急状态的疏散速度要比正常状态下的速度快得多,测量得到肩宽和疏散速度的数据,为疏散软件的改进及进一步研究人员疏散问题提供科学依据。     

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...     

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.     

Effect of scale on flame speeds of methane-air

Explosions are the main types of accidents causing casualties in underground coal mines. Research on the mechanisms of gas explosions is needed as a basis for the development of techniques and strategies for explosion prevention, suppression, and mitigation. The prevention of loss in explosion accidents and inquiries into their causes require understanding of the explosion process of methane in air. Because of the high cost and safety issues in full scale experiments, the experiments with small scale ducts have become a key alternative approach. Whether the experimental results at small scales agree with those at full scales needs to be investigated to validate the significance of the experimental results at small scale. Numerical simulation was used to obtain the explosion characteristics of a methane-air mixture in a gallery or duct. If the grid size is too fine in the numerical simulation for a methane-air explosion it is difficult to calculate using the present computer resource. If the grid size is too coarse, the considerable error may result. The effect of grid size on results of calculation depends on the scenario being investigated. The effect of grid sizes on simulation accuracy was analyzed in this work. The overpressure and temperature distributions and the flame propagation for the deflagration of methane-air mixtures in a gallery or duct were obtained by the AutoReaGas code at three different scales. The geometry of investigated objects and the grids in the calculation domain were similar in the three cases. The calculated overpressures vary with the scale. The calculated temperatures do not vary with the scale for the three cases.     

障碍物对油气-空气混合气体泄压爆炸火焰传播特性影响

为了研究障碍物对油气泄压爆炸火焰传播特性的影响规律,进行了不同数量障碍物工况下的对比实验,并利用纹影仪和高速摄影仪记录了火焰传播过程,针对障碍物对火焰形态、火焰锋面位置及火焰传播速度的影响规律进行了研究,结果表明:圆柱体障碍物会导致油气泄压爆炸火焰形态产生褶皱和弯曲变形,诱导层流火焰向湍流火焰转变,加速火焰的传播,对油气泄压爆炸火焰的初始传播形态有显著影响;随着障碍物数量的增多,火焰锋面传播距离点火端的最大距离增大,但到达最远距离的时间减少;障碍物能够增强火焰的传播速度,尤其对障碍物下游火焰影响最为显著,随着障碍物数量的增多,火焰传播的最大速度也随之增大,但达到最大火焰传播速度的时间却随之减少;障碍物的存在增大了油气泄压爆炸过程外部爆炸压力,并且随着障碍物数量的增多,外部爆炸压力峰值增长幅度增大。     

油气浓度对半开口管道爆炸超压特性与火焰行为的影响

为了研究油气浓度对半开口管道爆炸超压特性与火焰行为的影响,建立半开口透明管道实验台架,采用5种不同初始油气浓度,进行了一系列油气爆炸对比实验。研究结果表明:油气浓度对油气爆炸超压峰值以及升压速率有显著影响,二者都呈现随浓度的增加先增大后减小的变化规律;油气浓度对火焰锋面传播速度有着显著影响,在当量浓度比下,火焰锋面的传播速度最大,并且火焰锋面的传播距离也最远;管道内的火焰行为可以分为4个阶段;油气浓度对火焰传播形态以及传播速度有明显的影响,对火焰传播形态的影响主要体现在破坏变形以及管道外爆炸阶段,随着浓度增加,爆炸半径先增大后减小,火焰传播速度呈现相同的变化规律。