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排序方式: 共有120条查询结果,搜索用时 328 毫秒
31.
A study of explosions in several elongated cylindrical vessels with length to diameter L/D = 2.4–20.7 and ignition at vessel's bottom is reported. Ethylene–air mixtures with variable concentration between 3.0 and 10.0 vol% and pressures between 0.30 and 1.80 bara were experimentally investigated at ambient initial temperature. For the whole range of ethylene concentration, several characteristic stages of flame propagation were observed. The height and rate of pressure rise in these stages were found to depend on ethylene concentration, on volume and asymmetry ratio L/D of each vessel. High rates of pressure rise were found in the early stage; in later stages lower rates of pressure rise were observed due to the increase of heat losses. The peak explosion pressures and the maximum rates of pressure rise differ strongly from those measured in centrally ignited explosions, in all examined vessels. In elongated vessels, smooth p(t) records have been obtained for the explosions of lean C2H4–air mixtures. In stoichiometric and rich mixtures, pressure oscillations appear even at initial pressures below ambient, resulting in significant overpressures as compared to compact vessels. In the stoichiometric mixture, the frequency of the oscillations was close to the fundamental characteristic frequency of the tube. 相似文献
32.
在役压力容器的动态检测技术与研究进展 总被引:3,自引:0,他引:3
根据笔者多年声发射检测与评价技术的研究成果并综合分析不同发展阶段的有关文献,论述了压力容器结构完整性检测与综合评估的意义,分析其合理性和难度,并对这种动态检测技术在评价压力容器结构完整性方面的研究进展作了较全面的评述 相似文献
33.
The difference between fishermen's fishing catch and the optimal fishing catch is the basic reason for the transaction of marine fishing rights (TMFR). The effects of productive cost, non-productive cost, use-cost, transaction cost, productive revenue and non-productive revenue on the TMFR and the optimal fishing catch are analyzed. This paper draws following conclu- sions: the non-productive revenue has a positive effect on the TMFR, and other factors, such as non-productive cost, usecost and transaction cost, have a negative effect; the TMFR will promote the resource allocation; the high transaction cost may affect the implementation of TMFR. 相似文献
34.
对甲烷-空气预混气体在球形容器和球形管道连通容器内的泄爆过程进行实验研究,根据实验结果得出在较小的泄压面积时,与密闭容器爆炸实验比较,不能降低容器内的最大压力,反而会增大容器内的最大压力。通过实验结果分析,泄爆口安装在远离点火源的位置,当发生预混气体爆炸时能较好地降低容器内的最大压力,起到保护容器的作用。 相似文献
35.
S. Radandt Jianye Shi A. Vogl X. F. Deng S. J. Zhong 《Journal of Loss Prevention in the Process Industries》2001,14(6):495-502
Height to diameter (H/D) ratio is one of the important parameters affecting premixed particle–air combustion characteristics. This paper focuses on the behavior of cornstarch combustion in closed vessels with changed H/D ratios and fixed volumes; and a combustion model is employed to simulate the experiments. An Eulerian–Lagrangian approach for two-phase flows was used in the model and conservation equations of unsteady turbulent two-phase reacting flows were solved in two-dimensional domains. Heat loss to the vessel walls was taken into consideration in the model. The simulation results have a good agreement with those of experiments. Further simulations were carried out for higher H/D ratios from 8 to 15. These results show that H/D=8 is a changing point. When H/D<8, the maximum pressure and the rate of maximum pressure rise decrease with increasing H/D ratios. While H/D>8, the both have an increasing tendency with increasing H/D ratios. 相似文献
36.
H. Weimerskirch D.P. Filippi J. Collet S.M. Waugh S.C. Patrick 《Conservation biology》2018,32(1):240-245
Despite international waters covering over 60% of the world's oceans, understanding of how fisheries in these regions shape ecosystem processes is surprisingly poor. Seabirds forage at fishing vessels, which has potentially deleterious effects for their population, but the extent of overlap and behavior in relation to ships is poorly known. Using novel biologging devices, which detect radar emissions and record the position of boats and seabirds, we measured the true extent of the overlap between seabirds and fishing vessels and generated estimates of the intensity of fishing and distribution of vessels in international waters. During breeding, wandering albatrosses (Diomedea exulans) from the Crozet Islands patrolled an area of over 10 million km2 at distances up to 2500 km from the colony. Up to 79.5% of loggers attached to birds detected vessels. The extent of overlap between albatrosses and fisheries has widespread implications for bycatch risk in seabirds and reveals the areas of intense fishing throughout the ocean. We suggest that seabirds equipped with radar detectors are excellent monitors of the presence of vessels in the Southern Ocean and offer a new way to monitor the presence of illegal fisheries and to better understand the impact of fisheries on seabirds. 相似文献
37.
38.
根据人-机系统中人的操作行为具有时序性和差错可纠正性的特点,结合船舶舱室行为形成主因子,开展船舶舱室人因可靠性研究。以人因失误的时序性和差错纠正参数为基础,建立人-机系统中操作者行为模式和人因失误事件树模型。通过对人的差错纠正能力的分析,开展人因可靠性量化模型纠正理论研究。最后,以船舶舱室操作台的监控任务人因可靠性为例进行量化计算,定量评估操作人员执行任务的可靠度。 相似文献
39.
通过对容积为504.94m3的某型号压力容器出厂前水压试验的声发射检测,分析了其在升压和保压过程中的声发射信号特征及其来源。结合AE信号参数、波形及定位图分析,对该容器进行了声发射活性评价,确定需要后续复检的强活性区域。文章为压力容器的声发射检测和安全评价提供了理论指导和参考数据。 相似文献
40.
The purpose of this study was a refinement of knowledge on predicting the ejection velocities of fragments generated by explosions of cylindrical horizontal pressure vessels. A procedure is proposed for assessing these velocities by means of the stochastic simulation. The procedure is used to quantify uncertainties related to the ejection velocities and to carry out a simulation-based sensitivity analysis. The main finding is that the currently available information on phenomena related to the vessel fragmentation is sparse and, therefore, predicting ejection velocities will require a substantial amount of subjective judgement. It was found that ejection velocities are functions of a relatively large number of random input variables, many of which must be modelled subjectively. The study revealed also the need to choose subjectively between several alternative mathematical models used to specify input variables that influence the ejection velocities. The most critical choice must be made between several models used for an assessment of the energy liberated during vessel explosions. Results of the sensitivity analysis indicate that the ejection velocities are influenced mainly by input variables used to express energies involved in the prediction problem. Increased sensitivity to filling ratio of a two-phase pressure vessel was also detected. Results of the study can be used for an improvement of estimation of fragment impact probabilities and design of protective barriers that are built close to the pressure vessels posing explosion hazard. 相似文献