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本文对油罐本安型阻油切水阀研制过程中的几个技术关键之一￣二次启动进行了较详细的力学分析，研究了阻油切水阀的启动过程，分析了启动过程中液体在静止和流动两种情况下对浮球工作的影响，提出了启动机构方案。 相似文献
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严寒寒冷地区装配式蒙古包冬季供能多采用生物质燃烧、电加热等方式,无法满足分布式绿色低碳可持续供能的要求。为解决上述问题,该研究提出一种用于装配式蒙古包的新型太阳能多曲面聚光集热供能技术,其具有太阳辐射“接力”供能、热输运阻力小、集热装置与蒙古包围护合而为一、正浮力梯度传热等特点,介绍了技术运行原理及所用多曲面聚光器结构参数,利用光学仿真软件TracePro对聚光器光学性能随时间的变化规律进行了分析,对比研究了实际天气条件下正浮力梯度传热与负浮力梯度传热对聚光器内空气进出口温度、集热量等热性能的影响。结果表明,当径向入射偏角为15°时,聚光器光线接收率约为89.50%,当轴向入射偏角为30°时,聚光器光线接收率为83.47%,相邻不同朝向聚光器在10:30和13:30左右聚光效率复合;在冬季晴天,采用正浮力梯度传热方式的聚光器最大出口温度与最大集热量分别为21.3℃和787.29 W,分别比采用负浮力梯度传热方式的聚光器提升了9.3℃和59.30%。此外,聚光器采用正浮力梯度传热与负浮力梯度传热时的光热转化效率分别为46.81%和35.71%,研究结果可以为装配式蒙古包供能用聚光器集成提... 相似文献
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Valeria Hidalgo-Ruz Guillermo Luna-Jorquera Marcus Eriksen Hanna Frick Diego Miranda-Urbina Matias Portflitt-Toro Marcelo M. Rivadeneira Christopher J.R. Robertson R. Paul Scofield Juan Serratosa Cristián G. Suazo Martin Thiel 《水产资源保护:海洋与淡水生态系统》2021,31(2):389-407
- While floating near the sea surface plastic debris interacts with a number of external factors, including many different organisms. Seabirds have the most extensive documented history of interactions with plastics, through ingestion, entanglement, and nest construction.
- In the present study, eight seabird species from the South Pacific Ocean were used as a proxy to determine potential patterns of removal of marine plastic debris, and three hypotheses were tested in relation to their feeding habits and nesting areas.
- Plastics from abiotic compartments (Chilean continental coast, South Pacific Gyre, and Rapa Nui beaches) and biotic compartments (surface-feeding seabirds, diving seabirds, and nesting areas) were compared, according to their type, colour, shape, and density.
- Continental beaches had a relatively wide range of colours and shapes, with many non-buoyant plastics. Samples from the South Pacific Gyre (SPG) and Rapa Nui (Easter Island) beaches comprised mainly hard, rounded, buoyant, and white/grey plastics.
- These results indicate that the composition of floating plastics from terrestrial sources changes during transport with oceanic currents, reducing the proportion of prey-like plastics present in the subtropical gyres.
- The stomach contents of surface-feeding and diving seabirds were dominated by hard, white/grey, and round plastic items, similar to plastics from the SPG, suggesting non-selective (accidental or secondary) ingestion.
- Nesting areas had a more variable composition of brightly coloured plastics, suggesting a pattern of selective removal of plastics by seabirds, probably from oceanic sources.
- The present study reveals extensive interactions of seabirds with plastics on a broader scale, which is highly relevant given that the impacts of plastics on seabirds are increasing worldwide, compromising their efficient conservation.
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西部管道乌鲁木齐输油首站成品油主泵启输及运行中多次出现机械密封泄漏油气油烟的过热失效现象。针对该问题,通过对机械密封失效现象的观察、气阻机理的探讨以及对气阻和杂质堵塞致机械密封失效的现象和原因进行对比分析,确定了气阻是导致机械密封过热失效泄漏油气油烟的主因。同时,提出了机械密封过热失效的解决方法,包括：启泵前需要反复多次对泵腔灌泵以充分排气;运行过程中若发现机械密封压盖及冲洗冷却循环管路快速升温发烫,则应立即在不停泵的状态下缓开泵腔排气阀排气。相关经验可为输油站现场避免发生此类问题提供实践依据。（图2,参6） 相似文献
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在我国西部地质、气候条件恶劣的沼泽地建设管道，其稳定方法是一个技术关键。在沼泽地的管道，除钢管自重，输送介质重量、回填土重量外，还有浮力、如果前三种力之和小于管道所受的浮力。管道将会上浮，相反，管道则会下沉，详细介绍了几种常用的管道稳定方法，并做了初步比较。指出，在沼泽地区管道的稳定不仅关系到管道的安全性，稳定性，同时也会影响到沼泽地区管道建设的投资。 相似文献
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二八灰土回填地下粮仓浮力预警试验研究 总被引：2，自引：2，他引：0
地下结构的浮力多以阿基米德定律为基础进行计算,未考虑周围回填土体。该文以某地下粮仓为研究对象,考虑周围回填二八灰土的实际工况,分别进行直径为400(模型筒A)、500(模型筒B)、600 mm(模型筒C)的室内缩尺模型试验。试验包含纯水试验和回填二八灰土试验。纯水试验结果表明,以阿基米德定律计算的实际浮力与模型筒自重(包含模型筒上部约束反力所折算自重)的理论浮力基本一致,模型筒A、B、C的实际浮力与理论浮力的误差分别为0.03%、1%、3%。在回填二八灰土试验中,通过缓慢注水,利用位移计、压力传感器监测模型筒位移及模型筒上部的约束反力,分析了模型筒整个上浮过程中位移和约束反力的变化情况。位移突变值滞后于约束反力突变值,压力传感器读数发生明显变化而位移计读数未发生明显变化所测量的水位为警戒水位,压力传感器与位移计读数均发生明显变化所测量的水位为实际起浮水位。以警戒水位和实际起浮水位作为理论计算依据,得出警戒水位和实际起浮水位时模型筒自重(包含模型筒上部约束反力所折算自重)作用下理论抵抗浮力及计算所得的实际抵抗浮力。警戒水位时模型筒A、B、C实际抵抗浮力为理论抵抗浮力的1.93、2.43、1.66倍。实际起浮水位时模型筒A、B、C实际抵抗浮力为理论抵抗浮力的2.15、3.36、2.96倍。从安全储备方面综合考虑,回填工况地下粮仓在预警水位时实际抵抗浮力为理论抵抗浮力的1.5倍,实际起浮水位时抵抗浮力为理论抵抗浮力的2倍,研究结果为今后地下粮仓及其他地下结构的抗浮设计提供参考。 相似文献
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The thermal radiation is the main factor affecting internal thermal flow field in a tunnel. This paper studies on two open ends of a channel inclined with angles of 10°, 20° and 30° by experiments and numerical simulations. The experimental data agree well with the predicted results by using Large Eddy Simulation (LES) to solve N-S equations driven by the buoyancy flow. And the influence of thermal radiation on thermal flow field of tunnel with inclination angles from 10° to 30° at same heat source is obtained by comparing the experiment results and numerical resolutions of coupled with radiation model and without radiation model. Thermal radiation makes temperature near the upper wall of tunnel drop, and the influence of thermal radiation on bottom end of tunnel declines with the inclination angle increasing. However, the inclination angle has a little effect on temperature near the ceiling of the top end of tunnel. Simultaneously, the higher temperature zone leaning to the top end due to the thermal radiation is obtained, and the temperature at the bottom of the upper part of the tunnel increases. The findings of the study are important references for theory research of thermal flow field in inclined tunnels. 相似文献
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饥饿状态下真鲷仔鱼早期阶段的高温,低盐耐力和浮力 总被引：3，自引：1，他引：3
（１）真鲷初孵仔鱼的高温和低盐耐力分别为３０℃和３．８‰，随饥饿程度加剧，耐力逐渐下降至２７℃和６．５‰，投饵仔鱼随着发育推进，耐高温能力增强，耐低盐耐力出现波动。（２）真鲷早期仔鱼的低盐耐力和浮力变化与仔鱼体内水分含量有关。（３）开口后３日龄和ＰＮＲ是真鲷仔鱼对外界环境的敏感期，其对高温和低盐耐力很低。 相似文献
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【目的】研究曝气池中气泡浮力羽流的动力特性,为提高深层曝气方式的污水处理效率提供依据。【方法】分别采用欧拉双流体模型和混合模型结合标准κ-ε紊流模型,对气泡浮力羽流进行数值模拟,讨论了这2种模型计算流场的精确性和边界条件的适应性,并使用压力隐式算子分裂PISO(Pressure-Implicit with splitting of operators)算法进行了速度与压力耦合求解。【结果】通过模拟得到了气泡羽流的瞬时性及其尾部的摆动规律等流动特性,模拟的速度矢量沿水深方向呈增加趋势,但表现并不稳定,在上部区域气泡羽流出现了摆动,而在下部区域气泡羽流的摆动不明显,但这一部分的速度相对较大。【结论】欧拉双流体模型结合标准κ-ε紊流模型模拟气泡浮力羽流动力特性优于混合模型。 相似文献