共查询到20条相似文献,搜索用时 296 毫秒
1.
以C02为对象,对室内空间气体连续泄漏扩散过程进行试验研究,并对室内CO2气体泄漏扩散的均一质量浓度模型、两厢质量浓度模型和室内半球质量浓度模型进行研究.将理论模型计算值与不同位置测量点的试验数据进行比较分析.3种质量农度模型均表示区域质量浓度的变化,理论模型计算值与试验数据均有些偏差;远离泄漏源处,偏差较小.室内空间不同位置3个模型预测值相对大小会发生变化.对于泄漏源附近及低于泄漏源处,3种质量浓度模型预测结果误差较大;对于高于泄漏源的位置,模型预测结果较好,然而质量浓度均出现振荡不稳定的现象.由于重力沉降作用,下部空间气体质量浓度较大,上部空间气体质量浓度较小.泄漏刚开始阶段,远离泄漏源处,试验测试值与理论模型值相比有一个廷滞期,理论预测值偏差较大. 相似文献
2.
为了实现对有毒推进剂泄漏扩散浓度的快速估算,对液体推进剂偏二甲肼在发射场泄漏蒸发扩散的实际情况进行理论分析,建立扩散模型,并从泄漏源、沉积效应、地面反射、大气稳定度等方面对扩散模型进行完善;应用数值模拟方法进行仿真,将数值模拟结果与实验数据、理论计算结果进行对比分析。研究结果表明:气体扩散模型与数值模拟及实验结果基本一致,但扩散模型计算结果偏小,这是由于推进剂进行了燃烧和氧化反应,扩散区域温度上升,大气稳定度降低,实际浓度更大。 相似文献
3.
液化天然气泄漏扩散模型比较 总被引:4,自引:2,他引:4
重气扩散的SLAB、DEGADIS和Fluent模型被应用于LNG泄漏扩散实验的模拟过程中,以Coyote3和5为例,对各模型模拟的体积分数随时间的变化与实验值进行了对比,结果表明Fluent模拟的结果最为接近实验值,SLAB模拟结果次之,由于模拟假设风速和风向不变致使模拟结果没有实验结果所存在的频繁波动。文中最后对各模型的统计误差FB,MG,VG,MRSE,NMSE以及FAC2进行了计算,分析结果表明三类模型模拟的结果与实验值一致,但结果都偏高,相比较而言,Fluent的结果更准确。 相似文献
4.
重气泄漏扩散实验的计算流体力学(CFD)模拟验证 总被引:7,自引:1,他引:6
运用CFD软件Fluent中的标准双方程湍流模型,对重气瞬时和连续泄漏的扩散进行了模拟以预测重气扩散过程中参数的变化,结果表明重气在垂直高度上的浓度随高度增加而减小,对于重气到达一点处的时间而言,瞬时泄漏的预测时间小于实际到达时间,而且浓度减小到零的时间也要先于实际的时间,连续泄漏的情形则相反,模拟过程假设风速和风向不变导致模拟结果没有实际的波动大.通过将模拟的最大摩尔浓度进行误差统计计算表明:Fluent对于连续泄漏源的扩散模拟结果最为准确.CFD模型能准确预测重气扩散过程中气体浓度的变化,可以应用于实际的风险分析和安全评价中. 相似文献
5.
基于气固两相流理论,采用仿真软件Fluent对热喷涂粉尘的扩散过程进行了数值模拟,分析了热喷涂车间气流速度对粉尘质量浓度分布的影响规律,并通过实验测定了车间呼吸层风速与粉尘质量浓度沿程分布,通过与模拟结果作对比分析,验证了数值模型的可行性。结果表明:粉尘颗粒自尘源处沿径向周围扩散,高质量浓度区域集中在尘源附近;车间气流速度越大,高质量浓度粉尘区域越小,车间粉尘质量浓度越低;当车间出风口风速为12 m/s时,除尘源区域外,呼吸层粉尘质量浓度已明显低于标准限值;通过对比分析,实测数据与数值模拟结果基本吻合,表明采用数值模拟方法研究热喷涂粉尘扩散规律是一种行之有效的方法。 相似文献
6.
在危险化学品泄漏事故中泄漏源强是预测事故后果的主要影响参数,也是事故应急救援决策的基础。为了在化学品泄漏事故过程中快速准确地获取泄漏源强数据,将粒子群优化(PSO)算法应用于危险化学品泄漏源强的反算中。利用高斯烟羽扩散模型和下风向浓度测量数据,将计算浓度与测量浓度的误差平方和作为目标函数,采用粒子群算法来优化,以确定源强并通过模拟的测量浓度数据进行算法有效性验证。结果表明,PSO算法及其参数改进算法不依赖于初值的选择,计算速度快,能满足事故应急响应救援的需要。 相似文献
7.
8.
《中国安全科学学报》2016,(8)
为减少工业氨气泄漏造成的环境污染、人员伤害及财产损失,建立适用于工业氨气泄漏的气体扩散高斯模型,提出氨气泄漏源的定位方法,并研制出一套基于Zig Bee无线传感网的氨气泄漏无线监测系统,其主要包括检测节点、网络协调器以及上位机。试验模拟不同浓度下的氨气泄漏定位,实测的相对定位误差约为12%。试验结果表明:通过简化后的气体扩散高斯模型检测空气中的氨气浓度,并对泄漏源定位,结果与实际情况相符,测量精度符合国家标准;增加氨气传感器的数量可降低定位误差,提高救援抢险效率。 相似文献
9.
针对受限空间内气体扩散问题,为研究不同湍流模型对气体扩散仿真结果的影响
,选取FLUENT软件中工程应用较为广泛的湍流模型为研究对象,以相关气体扩散实验为
参考,构建数值仿真模型,在初始和边界条件相同的情况下采用不同的湍流模型对实验
过程进行数值模拟。在对模拟结果定量化分析方面,采用了Hanna等人提出的广泛应用
于重气扩散模型评价的误差分析方法,并结合了chang等人提出的有关模拟效果的统计
误差评判标准,通过计算模拟值与实验值之间的统计误差对比分析了各模型模拟效果。
结果表明,所选的5种Reynolds平均湍流模型模拟结果的统计误差指标均符合有效性评
判标准,模拟值总体上要高于实验值,并且Realizable k-ε模型的模拟效果要优于其
他模型。湍流模型的选用会对受限空间内气体扩散仿真结果产生影响,选择合适的湍流
模型有助于提高数值仿真的精度。 相似文献
10.
为了研究埋地燃气管道泄漏燃气在非稳态泄漏条件下的扩散行为,基于燃气管道非稳态泄漏大孔模型,应用CFD分别求解土壤和大气扩散方程,通过丙烷地面扩散通量耦合了土壤和大气环境,进行了泄漏扩散的数值模拟,所得模拟计算结果与地上泄漏扩散数值模拟结果进行了对比分析。研究结果表明:耦合模拟条件下,风速仍是影响丙烷扩散距离和高度的主要因素;温度和相对湿度对丙烷扩散有相对较小的影响;与埋地泄漏相比,不同条件下地上泄漏的扩散距离和扩散高度均有误差,水平扩散距离误差普遍较大,扩散高度个别情况下误差较大;地上泄漏条件下的模拟结果数值偏大,对事故的预测和评估准确性会产生显著影响。 相似文献
11.
平地型铀尾矿库氡大气扩散数值模拟及环境效应分析 总被引:2,自引:0,他引:2
以平地型铀尾矿库为研究对象,采用数值模拟方法,分析了铀尾矿库下风向的氡扩散和浓度分布,并预测了该地区常年主导风向下氡对公众所致的年有效剂量。结果表明,风速从0.5 m/s变化到2.0m/s时,氡在尾矿库下风向的积聚范围由5 000 m缩减为2 500 m,尾矿库下风向2 500 m距离以内的氡浓度降低较快,随着距离的增大,近地面区域氡浓度不断降低,5 000 m外氡浓度变化渐趋平缓。U10=0.5m/s时尾矿库下风向地区的氡浓度比其他风速下最高高出近43%。对照公众个人的年有效剂量标准,考虑风频风速影响,对氡的环境效应分析表明,低风速下现行标准中铀尾矿库防护距离的规定值偏小,应进行适当调整。 相似文献
12.
Toxic gas leakage in a tank area can have catastrophic consequences. Storage tank leakage location (particularly for high leakage) and downwind storage tanks potentially influence gas diffusion in tank areas. In this study, we developed a numerical and experimental method to investigate the impact of a high leakage location and downwind storage tank on gas diffusion based on three (1.05H, 0.90H, and 0.77H, H was the tank height, 22m) leakage field experiments on the leeward side of storage tank, which have been not conducted before. The experiments revealed an unexpected phenomenon: the maximum ground concentration first decreased and then increased with increasing leakage height. The simulations illustrated that the differences in micrometeorological conditions caused the maximum ground concentration of gas emitted from the roof to be higher than that emitted from the tank wall near the storage tank height. The downwind storage tank 1) had little influence on the entire diffusion direction but altered the local diffusion pattern; 2) reduced the maximum ground concentration (∼18.7%) and the distance from the emission source (approximately a storage tank diameter); and 3) had strong influences on the concentration, velocity, turbulence, and pressure on the leeward side. The concentration negatively correlated with the velocity, pressure, and turbulence in the middle of the two storage tanks on wind centerline. Our results can improve understanding of gas dispersion in tank areas and provide references for mitigating loss and protecting lives during emergency response processes. 相似文献
13.
Biao Sun Ranjeet P. Utikar Vishnu K. Pareek Kaihua Guo 《Journal of Loss Prevention in the Process Industries》2013,26(1):117-128
Computational fluid dynamics (CFD) simulations have been conducted for dense gas dispersion of liquefied natural gas (LNG). The simulations have taken into account the effects of gravity, time-dependent downwind and crosswind dispersion, and terrain. Experimental data from the Burro series field tests, and results from integral model (DEGADIS) have been used to assess the validity of simulation results, which were found to compare better with experimental data than the commonly used integral model DEGADIS. The average relative error in maximum downwind gas concentration between CFD predictions and experimental data was 19.62%.The validated CFD model was then used to perform risk assessment for most-likely-spill scenario at LNG stations as described in the standard of NFPA 59A (2009) “Standard for the Production, Storage and Handling of Liquefied Natural Gas”. Simulations were conducted to calculate the gas dispersion behaviour in the presence of obstacles (dikes walls). Interestingly for spill at a higher elevation, e.g., tank top, the effect of impounding dikes on the affected area was minimal. However, the impoundment zone did affect the wind velocity field in general, and generated a swirl inside it, which then played an important function in confining the dispersion cloud inside the dike. For most cases, almost 75% of the dispersed vapour was retained inside the impoundment zone. The finding and analysis presented here will provide an important tool for designing LNG plant layout and site selection. 相似文献
14.
15.
The frequent occurrence of LNG leakage accidents has caused serious economic loss and environmental damage. Experiments and simulations can be combined to obtain the transient process of LNG leakage and diffusion. This paper analyzed LNG leakage diffusion rules with experiment results obtained by depleting 1.4t LNG. The vapor clouds and LNG concentration are measured, which can be a comparison with the simulation results. Computational fluid dynamics and gas diffusion theory were chosen as the theoretical basis, simulating the transient process of LNG gasification to obtain the diffusion concentration rules. The simulation of LNG diffusion is divided into two parts: LNG leakage at the source and atmospheric diffusion. The maximum concentration of methane in the experiment was 4.1%, and the maximum concentration in the simulation was 4.6%. The results show good agreement of the deviation statistics, which fall in the standard recommendation value range. Then we make a prediction of the dangerous concentration area and the flammability hazard zone of LNG leakage accident. The simulation results show that the range of the lower wind direction danger area firstly increases and then decreases, and the maximum distance of IDLH increases firstly and arrived at the peak of 52 m at 300s. 相似文献
16.
A new and simple method for locating emission source was proposed in this work based on gas dynamic dispersion information. The simulation of the unsteady state dispersion of leakage gas emission from the geosequestration project showed that the transportation process of emission gases in the atmosphere is similar to wave propagation, and the time parameter of the dispersion wave is linearly related to the downwind distance. Therefore, monitoring the dispersion wave at different downwind positions can be used to estimate the leakage source position. An estimation formula for locating emission sources was derived. First, an estimation formula for locating emission sources was derived under some initial assumptions. Then, the deviation of the location formula was investigated using a computational fluid dynamics (CFD) model and analytic solution to get the offset distance under different conditions. The results showed that the average distance is stable for a certain atmosphere and terrestrial conditions. This method needs no more than 3 sensors’ dynamic information to locate the emission source, and hence it is highly useful for conditions with limited sensors. A numerical test demonstrated that the absolute error of the source estimation is within the range of 1–30 m. Finally, experimental tests were conducted to verify the feasibility of the source location with dispersion waves. Therefore, the dispersion wave monitor is a potentially simple and feasible way to estimate the source location for gas emission event management with limited sensors in the process industries. 相似文献
17.
18.
为探究煤尘质量浓度对甲烷煤尘耦合爆炸传播特性及伤害距离的影响,自制长15 m的爆炸管道系统,用体积分数为7%甲烷分别与质量浓度为0、50、100和200 g/m3的煤尘进行耦合爆炸试验,并根据质量、动量和能量守恒理论推导出最大压力计算公式.结果 表明:不同质量浓度煤尘与甲烷耦合爆炸时,最大压力均随与爆源距离的增加呈现出... 相似文献
19.
20.
为了分析不同通风条件对柴油池火燃烧特性及引燃特性的影响,进行205 mm带水垫层柴油池火的引燃实验,通过对池火燃料的质量损失速率、火焰高度、温度及热辐射等的监测,分析通风环境中柴油池火的热传递规律。结果表明:当风速为0.5 m/s时,火灾进入旺盛阶段的时间提前,火焰平均温度最高;当风速为1 m/s时,风速的增加导致油池火的质量损失速率增加,位于主火源下风向的待引燃火源获得的热辐射通量增大,火灾旺盛阶段火焰的平均温度降低,火焰高度降低,下风向相邻油盘引燃的时间提前;1 m/s情况下,205 mm带水垫层柴油池火的安全间距需增加到1D以上;通风环境对池火发展及蔓延的影响是显著的,应适当加大下风向可燃物的安全间距,合理选择通风排烟风速,优化火灾应急救援策略。 相似文献