The effect of vent size and concentration in vented gasoline-air explosions

Experimental data from vented explosion tests using gasoline-air mixtures with concentrations from 0.88 to 2.41% vol. are presented. A 2L vessel was used for the tests with vent sizes of 25 cm², 50 cm² and 100 cm². The tests were focused on the effect of gasoline vapor concentration and vent size on the pressure development and the flame behavior inside and outside the vessel. It was found that the inner flame propagation speed was mainly dependent on the initial concentration, while the maximum flame spreading distance was mainly influenced by the vent size. The external flame speed and duration could be influenced by the combination of the two properties. The internal pressure increases gradually with the flame propagated inside the vessel and decreased sharply when the vent failed. High-pressure durations containing pressure peaks were recorded by transducers in front of the vent and oscillations could be observed besides the vent. At any measure point, the maximum external pressures for A = 25 cm² or 50 cm² were significantly larger than those for A = 100 cm².     

火源功率对竖井负压控烟效果影响的实验研究

基于竖井的烟囱效应原理,利用小尺寸实验台开展了一系列实验,通过改变油盘的尺寸,对竖井内的烟气温度、压力、速度以及通风口处的压力、气流速度进行测量,研究了火源功率对房间利用竖井进行负压控烟效果的影响。实验结果表明:一方面随着火源功率的增大,室内温度升高,热烟气形成的热压增大,使烟气向外膨胀;另一方面,竖井底部的烟气温度升高,竖井底部的负压值增大,烟囱效应增强,排烟速度增大,新鲜空气补入的速度增大,逐渐抑制住烟气从通风口向外溢出,达到了负压控烟的效果。     

Bioaccumulation of Hg, Cu, and Zn in the Azores triple junction hydrothermal vent fields food web

In this work, mercury (Hg), copper (Cu) and zinc (Zn) concentrations and tissue distribution are determined in seven benthic invertebrates species (the key species) from the Mid Atlantic Ridge (MAR) hydrothermal vent fields. The samples were collected from three hydrothermal vent fields – Menez Gwen, 840 m; Lucky Strike, 1700 m and Rainbow, 2300 m – near the Azores Triple Junction. These fields are characterized by different depths, geological context and chemical composition of the hydrothermal fluid, particularly the metal content, which is reflected by the metal concentrations in the organisms. Indeed, our results show that organisms from Menez Gwen presented the highest Hg concentrations, while those from Lucky Strike and Rainbow were richer in Cu and Zn. The potential transfer of these metals through two trophic links are also evaluated and include (1) the mussel Bathymodiolus azoricus and the commensal worm Branchipolynoe seepensis, and (2) three different species of shrimps and the crab Segonzacia mesatlantica. No evidence of Hg biomagnification in either of the vent food chains is clearly observed but an increase in Hg accumulation from prey to predator in the crustacean food chain. The same pattern was observed for Cu and Zn, even though these metals are not known to be generally biomagnified in food chains.     

SEQUENT PEAK PROCEDURE: MINIMUM RESERVOIR CAPACITY SUBJECT TO CONSTRAINT ON FINAL STORAGE1

ABSTRACT: When the sequent peak procedure is used to size a reservoir, two cycles of inflows and drafts are analyzed. The use of two cycles results in the identification of the minimum reservoir capacity which, when simulated with the design inflows and drafts, will not only meet demands, but will also result in a final storage which equals or exceeds the initial storage. Demonstration of optimality follows from consideration of a method which is equivalent to the sequent peak procedure.     

Vent sizing for gas-generating runaway reactions

Exothermic runaway reactions that generate non-condensible gas as the temperature increases, as is typical of decompositions for example, can reach extremely high rates of pressure rise necessitating emergency relief of the process vessel containing the reactant. Sizing of a relief device using presently recommended methods (e.g. DIERS) frequently leads to extremely large and expensive vents. This paper presents a methodology that leads to a simple but much improved method for vent sizing, fully allowing for two-phase release of the gas—liquid mixture. A number of examples are presented which lead to interesting conclusions about the influence of plant variables.     

Experimental study of the venting characteristics of dust explosion through a vent duct

To further understand the dynamic mechanism of dust explosion through a vent duct, we designed a small-scale cylindrical vessel connected with a vent duct and performed a dust explosion venting experiment under different opening pressures using corn starch as the explosive medium in this study. The results show that weakening effect of duct on venting is positively correlated with the opening pressure. The explosion pressure in the duct presents a three-peak-structure with time, successively caused by the membrane breaking shock wave, the secondary explosion in the tube, and the continuous combustion, and decreases gradually with the propagation distance. Meanwhile, the three pressure peaks are positively correlated with the opening pressure, while the time interval between them goes to contrary. The increase of opening pressure leads to the increase of secondary explosion intensity and reverse flow in the vessel, further accelerates the reaction rate in the vessel, and then shortens the duration of combustion in the vessel until the phenomenon of flame reignition in the vessel disappears.     

Some observations on explosion development in process pipelines and implications for the selection and testing of explosion protection devices

In recent years there has been continuing interest in the potential hazards from detonations in pipelines. The interest has arisen in several instances due to the introduction of vapour recover systems, as part of measures to limit environmental emissions. These environmental pressures initially coincided with the preparation of new European-wide test procedures for explosion arrester devices and, more recently, moves to develop a new international ISO standard for the certification and approval of detonation arrester devices. It is an opportune time therefore to review current understanding of explosion development in pipelines and to consider the implications for plant design and explosion arrester selection and testing.     

矩形定径式喉口的设计与应用

针对双文氏管湿法除尘系统一级文氏管喉口存在的问题,开发设计了矩形定径式喉口.该工艺运行周期长,不存在调节翻板卡死问题,不存在溢流盆堵塞问题,喉口使用寿命长,效果良好.     

微电解/A/O工艺处理浆纱废水的试验研究

研究采用微电解/A/O工艺处理浆纱废水。试验结果表明:经过微电解处理后的废水可生化性得到明显改善;经过系统处理后,出水COD和BOD5浓度分别为126 mg/L和42 mg/L,COD和BOD5的总去除率分别达到94.5%和73.8%,出水符合国家污水综合排放标准。     

碳纤维上浆技术对其可织性能的影响

碳纤维具有优良的力学性能,被誉为21世纪的新型材料。因其具有模量高、强度大、比重小、耐高温、抗疲劳、抗腐蚀等一系列优异的性能,其与先进树脂形成的复合材料在现代航空航天尖端技术领域及民用领域有着广泛的应用。为了提高其加工界面性能及可织造性,本文对碳纤维上浆情况,特别是对碳纤维的上浆剂、上浆工艺、表面处理的情况进行了介绍,旨在为读者提供有关碳纤维上浆技术的有关技术信息。