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为了研究边界滑移对上游泵送机械密封性能的影响,建立液膜三维几何模型和计算模型,基于 Navier 线性滑移模型对液膜壁面边界条件进行修正,采用商用软件 Fluent 的 SIMPLEC 算法及层流模型求解三维 Navier －Stokes 方程,并分析相对滑移量对液膜静压分布、开启力、摩擦扭矩、泄漏量的影响规律。结果表明：相对于边界滑移发生的位置,滑移速度的大小对密封性能的影响更大;当相对滑移量较小时,存在边界滑移与无滑移的模拟结果无明显区别,能很好地解释宏观无滑移边界假设的应用,当相对滑移量较大时液膜动压效应随滑移的增加而减弱,开启力、摩擦扭矩、泄漏量都随边界滑移的增加而减小;相对于开启力的降低,边界滑移的减阻和降低泄漏的效果更为明显;当开启力较小,应避免边界滑移发生;当开启力足够大时,加工成超疏水表面形成边界滑移,可极大地减少摩擦扭矩,降低能耗。 相似文献
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T. J. Carter G. J. Pierce J. R. G. Hislop J. A. Houseman & P. R. Boyle 《Fisheries Management and Ecology》2001,8(3):207-225
Detailed observations of the behaviour of harbour seals, Phoca vitulina L., at sites within the estuaries of the Rivers Dee and Don, in north-eastern Scotland, were made over two full years between 1993 and 1996. Small numbers of grey seals, Halichoerus grypus Fab., were also present. The presence of seals within the estuaries was strongly related to season, with maximum numbers observed in winter and early spring; seals were virtually absent in June and July. The River Don was used largely as a haul-out site, while the River Dee was used predominantly as a foraging site, although it was not possible to determine whether the same seals were using the two estuaries. More seals were hauled-out on the River Don during twilight and dark than in daylight. The seals were observed to eat mostly salmonids, Salmo salar L. and S. trutta L., unidentified roundfish and flounder, Pleuronectes flesus L. The otoliths identified in scats collected at the mouth of the River Don belonged to marine species indicating that the seals were also feeding outside the estuaries. A minimum estimate is given of the numbers of large salmonids eaten in each river during the course of the year. Although no information was available on the numbers of salmonids using the rivers or the reproductive status of the fish eaten by the seals, as a cause of mortality, seal predation on large salmonids in estuaries is apparently an order of magnitude less important than mortality caused by angling within the river. 相似文献
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为研究中温高黏度介质双端面机械密封主密封的传热和变形规律以及冲洗液的压力和温度对其影响,从而为密封性能改进和冲洗液的高效控制提供依据.以乳液输送设备双端面机械密封(AR201)为研究对象,建立传热计算模型,采用有限元法分析主密封温度场,研究了密封环温度和变形量随冲洗液压力和温度的变化规律.研究表明:密封环端面的最高温处于动静环接触面靠近密封腔位置处,在冲洗液的作用下,动静环内径侧温度明显低于外径侧,动静环温度自接触面开始沿轴向至环外侧逐渐降低;端面最高温度和最大变形量随冲洗液温度和压力的升高而增大,最大变形量的大小和随冲洗液参数变化的波动幅度与密封材料有关;合理选择冲洗液压力和温度是有效改善主密封性能的措施,对于AR201机械密封,将冲洗液压力控制在0.80~0.85 MPa和较低的温度能减少端面磨损现象. 相似文献
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为了避免中高压往复泵的密封件因摩擦温升而快速磨损或破坏,在选择和设计往复泵密封件时要对其摩擦温升进行分析计算,保证摩擦面最高温度不超过密封材料的许用温度.摩擦面最高温度主要由环境温度、摩擦接触体温升、摩擦面温升3个因素决定.考虑以上因素,推导了往复泵接触体温升计算公式,并在经典摩擦面温升解析计算公式的基础上,提出了1种基于摩擦面温升的往复泵密封件设计校验简洁公式.通过与试验结果对比,验证了校验式的适用性.研究结果从摩擦温升角度为往复运动密封件的选择与设计提供了参考. 相似文献
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简要分析了多环芳烃(PAHs)的危害及水泵橡胶密封件中PAHs的来源,首次采用了水泵密封件中多环芳烃的超声萃取气相色谱-质谱(GC-MS)联用的测定方法.优化了超声萃取条件,确定了16种PAHs的分离和测定条件.样品经过超声波萃取,采用选择离子监测模式(SIM)定性和定量检测水泵密封件中多环芳烃,用内标法对PAHs进行定量分析.用加标回收方法试验确定方法的准确度.结果表明:16种PAHs平均回收率为80.9%～103.8%, RSD为4.80%～15.7%,该方法可满足水泵密封件多环芳烃的检测要求. 相似文献
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针对输送含颗粒介质柱塞泵的柱塞、填料寿命问题,从接触型往复密封的摩擦学机理出发,通过优化匹配柱塞直径、行程及泵速各参数,合理控制柱塞的线速度,降低摩擦速度,对柱塞填料密封进行优化设计;通过求解间隙中的流体力学层流运动问题,合理控制冲洗液的压力,保证全压密封系统中接触区的液膜处在混合润滑状态下工作,使密封副有良好的润滑;提出了两种填料函方案,并和采用不同表面处理工艺的柱塞及多种填料搭配组合进行试验.试验结果表明,密封累计运行了4 455 h后,组合1和组合2柱塞的磨损仅为0.03 mm和0.05 mm;在生产实际中,改进后的密封设计,使柱塞及填料的使用寿命从原来的1 500 h提高到4 500 h以上. 相似文献
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为了揭示工作参数对螺旋密封性能和内部流动的影响机理,获得螺旋密封工作参数的选取范围和相互关系,将摩擦因数作为螺旋密封性能的量纲一评价因子.首先,建立了包括离心泵和螺旋密封的耦合三维模型和块结构化网格模型,基于RANS雷诺时均方法和RNG k-ε模型,选择螺旋角、相对槽宽和相对槽深等工作参数,基于Fluent软件预测了轴向雷诺数和螺旋密封摩擦因数的特性曲线,并对螺旋密封内部流场分布特性进行数值分析.结果表明:不同螺旋密封模型的摩擦因数随着轴向雷诺数增大而减小,且减小幅度越来越小;在其他影响因素一致,而仅改变螺旋角、相对槽宽和相对槽深中的某一参数的情况下,当螺旋角α=21.05°或相对槽宽r=0.5时,摩擦因数达到最大值,密封性能最优;当相对槽深H=3时,密封性能最优.为螺旋密封的设计和选型提供理论依据. 相似文献
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A. J. Ribbink 《African Zoology》2013,48(1):45-73
Some anatomical, adult shell and larval features of Unto coffer Krauss are described and compared to those reported in previous accounts of this and other species. The findings necessitate the removal of U. caffer from the nominal genus Cafferia Simpson, for which it is the type species, and its return to the genus Unio Pbilipsson, in the Unionidae: Unioninae. Cafferia consequently becomes a junior subjective synonym of Unto.Unio caffer is characterized in part by zigzag beak sculpture, dimorphic septal spacing between the marsupial, outer (comparatively dense) and the non-marsupial, inner (more distant) demibranchs and also within the marsupial demibranchs, the presence of perforated marsupial septa and imperforate non-marsupial septa, the occurrence of hermaphrodites in some but apparently not all populations, production of subtriangular glochidia with a hook at the ventral margin of each valve, short-term incubation of larvae in the marsupial demibranchs, and by its disjunct occurrence in the southern Ethiopian region (other Unio occurring only in the Palearctic).These adult shell and anatomical features relate this species to those of several nominal genera in the Oriental region, although the latter are distinguished from it by the production of subovate, hookless glochidia. 相似文献
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《African Zoology》2013,48(1):129-130
During a survey of seals in September and October 2009 at Gough Island, South Atlantic Ocean, we recorded goose barnacles (Lepas australis) attached to the pelage of two of the 12 elephant seals (Mirounga leonina) inspected and one of the seven vagrant Antarctic fur seals (Arctocephalus gazella) which were found amongst the resident Subantarctic fur seals (A. tropicalis). We also recorded a goose barnacle attached to a Northern rockhopper penguin (Eudyptes chrysocome moseleyi). 相似文献