共查询到20条相似文献,搜索用时 62 毫秒
1.
基于密封圈O形圈的密封原理,分析了橡塑弹性体在油缸密封中的静密封作用和动密封作用,阐述了橡塑弹性体弹性变形是弹性体在往复运动密封中运用的基本原理,在设计各类油缸密封中起着重要作用。 相似文献
2.
简述螺旋密封的工作原理、结构及性能特点。对螺旋密封应用中的难点——停车密封,作了较为详细的论述。介绍一例螺旋密封的应用实例,为此密封设计了简便、实用、安全可靠的停车密封装置,对螺旋密封的应用推广有一定的参考价值。 相似文献
3.
4.
组合密封在活塞密封中的应用 总被引:1,自引:0,他引:1
针对某装置的活塞和缸体间存在着摩擦而易使密封失效的问题,介绍了几种常用于动密封的密封机理与密封结构形式,采用组合密封结构密封性能良好。组合密封结构中的导向环起定位和导向作用,挡圈起支承和定位作用,弹性橡胶圈提供预紧力并补偿密封环的磨损,密封环与油缸内孔形成配合而对偶面产生密封效果,因此组合密封结构能够满足使用要求。 相似文献
5.
6.
磁流体密封结构 总被引:6,自引:1,他引:5
磁流体密封是60年代末产生的一种新型的密封技术,经过20多年的发展现已达到较高的技术水平,并已在工业中应用。目前磁流体密封气体,其承压能力达3.43MPa,密封真空其真空度达1.332×10~(-6)Pa,主要用于动态密封和隔绝密封。在动态密封方面,磁流体密封已应用于半导体生产,纤维光学,激光技术,质普仪,X射线仪,真空热处理炉等。在隔绝密封方面,磁流体密封已应用于保护精密机械,仪器仪表,免受环境污染。在纺织工业中,用磁流体密封马达轴承,防止周围环境中的纤维物污染轴承。在计算机外围设中用磁流体密封硬盘驱动轴,保护磁盘和磁头,防止环境中的微粒进入磁盘和磁头的间隙中。此外,磁流体密封还以其完全无泄漏的特点应用于有腐蚀性和有放射性泄漏会对环境和人体形成危险的气体的密封。总之,磁流体密封正以其独特的性能在机械和化学工业中应用越来越广,本文介绍磁流体密封的一些典型结构,供各位同行参考。 1 磁流体密封原理和特点 磁流体密封从它问世以来之所以发展迅速,是因为它具有许多独特的性能,优于传统密封。我们知道传统密封可分为接触式密封和非接触式密封两大类,它们都存在一定的不足。 相似文献
7.
8.
9.
介绍一种应用于振动筛中的密封装置,该装置由迷宫密封和接触式密封组合而成,既能阻止润滑油外漏,又能防止灰尘侵入. 相似文献
10.
分析了高抗冲聚苯乙烯引进装置中的VIKING泵机械密封的结构特点以及常见故障,介绍了该泵机械密封改为螺旋密封的有关计算及其实际使用效果。 相似文献
11.
12.
A theoretical analysis of load and flow characteristics of a capillary compensated oil-lubricated externally pressurized journal bearing having four rectangular recesses is presented. The analysis is based on an exact solution of the pressure distribution over the bearing sill area and has been made for two configurations of loading, through the centre of any recess and through the centre of the circumferential sill between any two recesses. The influence of circumferential sill length and intensity of compensation on the load carrying capacity and the flow requirement is shown. Theoretical analysis and experimental results are compared. 相似文献
13.
14.
The Carboniferous sediments of northern England have formed the context for an optical study of the effects of differing geothermal history on the included organic material. In the north of the area, the Northumbrian Trough contains 5000 m of cyclothemic Carboniferous sediments with frequent coals and is probably underlain by Old Red Sandstone rocks. To the south, the Alston Block comprises 1500 m of basically similar Carboniferous sediments underlain by highly metamorphosed Silurian slates and a Caledonoid granite. The contrasting nature of the basements has produced variable geothermal gradients and consequently varying coal rank throughout the Carboniferous succession. Alteration of the coals and dispersed organic matter in the sediments by the intrusion of a quartz dolerite sill, the Whin Sill, during Stephanian times has been closely examined. The optical changes induced by the thermal metamorphism depend on the initial rank of the sediments. It has been possible to deduce rank profiles through the succession at the time of intrusion; these can be closely related to the character of the basement. The area was subsequently subjected to hydrothermal (lead, zinc) mineralization. 相似文献
15.
Lyall F 《Microscopy research and technique》2003,60(4):402-411
It is now well known that in order to establish human hemochorial placentation and to provide a progressive increase in blood supply to the growing fetus, the uterine spiral arteries must undergo considerable alterations. This physiological modification is thought to be brought about by the interaction of invasive cytotrophoblast with the spiral artery vessel wall. Despite intensive research our understanding of the mechanisms that control human trophoblast invasion in normal, let alone abnormal pregnancy, are sill poorly understood. This is partly due to difficulties in obtaining "true" placental bed biopsies and most investigators have relied on in vitro models of trophoblast invasion. This article describes the morphological changes that occur within the placental bed throughout human pregnancy along with a review of the various studies which have attempted to sample the placental bed. Thereafter, follows a review of the evidence that invasive trophoblast can release the vasoactive agents nitric oxide and/or carbon monoxide which, in turn, could contribute to early physiological changes in spiral arteries prior to destruction of the smooth muscle within the vessel wall. Current evidence supports the idea that trophoblast-derived carbon monoxide may contribute to spiral artery modification. In contrast there is no evidence for a similar role by nitric oxide. 相似文献
16.
The powerful method of Group Method of Data Handling (GMDH) was used for estimating the discharge coefficient of a rectangular side orifice. First, the existing equations for calculating the discharge coefficient were studied making use of experimental results. On the first hand, the factors affecting the discharge coefficient were determined, then five models were constructed in order to analyze the sensitivity in achieving accuracy by using different parameters. The results, obtained using statistical indexes (MARE=0.021 and RMSE=0.017), showed that one model out of the five models, on estimation using the dimensionless parameters of the ratio of depth of flow in main channel to width of rectangular orifice (Ym/L), Froude number (Fr), the ratio of sill height to width of rectangular orifice (W/L) and width of main channel to width of rectangular orifice (B/L), presented the best results. 相似文献
17.
18.
INTEGRAL EQUATION METHOD'S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES 总被引:1,自引:0,他引:1
LI Cheng ZHENG Yanping 《机械工程学报(英文版)》2008,21(6):115-118
The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value. 相似文献
19.
EXPERIMENTAL RESEARCH AND DESIGN ON HEAT TRANSFER OF EVAPORATOR USED IN THE LARGE QUICK FREEZE PLANT
ZHENG Chuanxiang ZHUO Chuanmin 《机械工程学报(英文版)》2007,20(6):18-23
The evaporator is the main part of a quick-freeze equipment. There are many factors influencing the heat transfer coefficient of an evaporator. The most important factors among them are the fin shape, tube diameter, distance of fin space, frost, and velocity of air flow etc. They mainly influence the thermal efficiency of an evaporator, and therefore its thermal efficiency has direct relationship with the whole efficiency of the quick freeze plant. Evaporators with different structural types have different heat transfer efficiency. In order to obtain high efficiency structure of evaporator, 8 evaporator models with different fin shape, tube diameter and tube arrangement are analyzed and compared. The calculation results show that the integral waved fins, equilateral-triangle arranged small diameter tubes and varying fin-spacing has the highest heat transfer coefficient. The experimental result also shows that the evaporator with this type of structure has better thermal efficiency. The experimental result is in good agreement with the calculation result. It can instruct engineering design for usual designer. A real quick-freeze equipment is designed and put into production. The result shows that, compared with traditional domestic quick-freeze equipments, this equipment decreases by 40% in size and by 20% in energy consumption. 相似文献
20.
《Measurement》2016
This article describes designing, implementation and tuning processes of multiple-tapped-delay-line (MTDL). Obtained MTDL can be implemented in various field-programmable-logic-devices (FPGA) devices and applied for time-to-digital-converters (TDC) construction. The task of tuning process is the tapped-delay-line (TDL) linearisation, and consists of two stages. The first stage depends on selecting an appropriate configurable-logic-block (CLB) for particular delay-segment realization and selecting proper connection between these blocks. The second tuning stage, that is essential from this article viewpoint, depends on inter CLBs connecting wires delay regulation realized directly by load regulation. The Load regulation depends on connecting an appropriate number of unused three-state-buffers or CLB inputs to the wire which delay is adjusted. Depending on the number of inputs connected to the wire its capacitance changes that influences its time-constant and finally changes its time-delay.The MTDL mathematical model, obtained characteristics and results of time-interval (TI) measurements are also presented. The derived TDL model provides information about how the particular wire delay should be changed and in which order the changes should be executed. This makes the designing process predictable and easy to carry out. Presented characteristics confirm the proper operation of presented linearisation technique. The proper operation of the whole measuring module is confirmed by obtained TIs histograms presentation. 相似文献