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基础设施建设是我国经济建设的重点，给排水工程，特别 是污水处理工程规模浩大包括管道、阀门在内的水处理设备制造业已形成强大的水工业。为阀 门行业的发展，提供了良好契机。我国已进入WTO，全球每年需求阀门约300万吨。要充分利用 阀门业属劳动密集、劳动条件差、我国人均工资低廉，发达国家向发展中国家生产转移等优 势，积极走向世界经济的平台。分几个题目简述给排水阀门的现状与发展。 目前状况 　　现在约有3000家的大小阀门厂，其中温州600家，郑州近200多 家，上海150多家，辽宁250家，江苏、福建各200余家，尽管良莠不齐，但产品品种已达 3000多个型号，近3万个规格。在多品种、密封性能、强度要求、调节功能、动作性能和流 通性能，特别是密封性能，都有了长足的进步，倒退十年前，城镇供水协会的xx人士有句 行业名言说“十阀九漏”，虽然有些夸张，但确是事实。 造成阀门行业存在的众多问题主要是改革开放后，市场急 速扩大，而原有国营阀门企业纷纷关停并转，本来机械工业水平就不高，于是乡镇企业（民营 企业），雨后春笋般迅速发展起来，起点低，技术力量非常薄弱，设备简陋，产品大多数都 是模仿生产，再加上市场混乱，特别是给排水用的低压阀门，问题严重。近十年来，在少数阀门企业的带动下，确有明显进步，有 些品种甚至达到国际先进水平，还有许多企业进行二次创业。但就整体来说，差距还很大，有 很多工作要做。为此，分别作出2010年、2020年技术进步、发展规划有着很重要的意义。 常用的阀门 　　在给排水工程中，中低压阀门广泛应用，特别低压大口径阀门（低压阀门是指公称压力PN≤1.6MPa的阀门），而中压阀门（PN2.5－6.4MPa）较少。而闸阀 、蝶阀是最基本最广泛应用的主导产品。 　　2.1闸阀的现状和发展 　　闸阀使用历史最久，至今世界各国仍在应用，特别是DN300mm 以下，在各类阀门中仍占主导地位。其特征是阀板前后压差使阀板强制压在出口右侧的阀座 上，密封性较好，且全开时，由于阀板不留在流路上，压力损失小。用于切断管道中介质。 　　其缺点是操作力矩大，操作时易使阀体、阀杆损坏，特别 是大口径闸阀。外形尺寸和重量也大，DN1000口径闸阀约3200mm高，需要四个人操作，所以闸阀一 般使用在小口径，即DN500以下使用。 　　闸阀从全开到中间开度，阀门的流阻较小，接近全闭时， 流阻急剧增加。较大的范围内，流阻变化较小，在接近全闭时，流量变化较大，一定不要在阀 门接近关闭时使用，这时很难进行流量的微调。阀门若开度极小，开口处的流速极快，会使 闸板下侧产生气蚀，并伴有激烈的振动和噪声，长时间节流运转，往往会使阀体和闸板的金 属发生气蚀。闸阀工况若处在中间开度，阀板因为是靠两侧的导轨支撑，全闭时配合紧密， 而中间位置时，阀板与导轨间隙大而产生振动。因此，即使在气蚀发生率较低的区域，长时 间使阀门节流运转，导轨也会发生畸形、磨耗或损坏，且由于阀座不是全面接触，而接触部 位表面压力很高，往往会产生咬蚀或粘连，因此，不宜用于流量控制。还要注意，闸阀在小 开度时，流量变化大，如果对阀门紧急启闭，会造成压力急剧上升或产生负压，特别是关阀 门时水锤的产生。 　　在金属密封闸阀基础上，近些年来开发了橡胶软密封闸阀 ，其特点是： 　　（1）法体底部无凹处，流体通过截面呈直线状，不易堆积 和夹杂异物。 　　（2）闸板密封面是压在阀体上进行止水的，关阀力矩小。 　　（3）不因配管的弯曲和拉伸而影响密封性能。 　　（4）整个阀板衬橡胶，耐腐蚀，不出锈水。 　　（5）阀门可在全开通水的同时更换密封材料和O型圈。 　　（6）闸板互换性好。 　　由于功能优越，国际上（特别在欧洲）需求量速增，软密 封闸阀是30年前奥地利人发明，在欧洲每年生产50余万台，几乎100％使用，是硬密封闸阀的替 代产品，其制造口径在欧日为DN500，美国一般用到DN400，而意大利可生产到DN1200。但也有不 足，软密封闸阀是靠对橡胶阀座进行压缩密封的，是否关闭不好判断，要避免关阀过紧 ，不要超过关阀扭矩为好（扭矩在标准上给出）。 　　2.2蝶阀的现状和发展 　　上世纪三十年代，美国发明了蝶阀，上世纪七十年代传入 我国，开发使用。目前世界上一般在DN300mm以上蝶阀已逐渐代替了闸阀。蝶阀与闸阀相比有开 闭时间短，操作力矩小，安装空间小和重量轻等特点。以DN1000为例，蝶阀约2T，而闸阀约3.5 T，且蝶阀易于各种驱动装 置组合，有良好的耐久性和可靠性。 　　橡胶密封蝶阀缺点是作节流使用时，由于使用不当会产生 气蚀，使橡胶座剥落、损伤等情况发生。为此，上世纪七十到八十年代国际上又开发金属密封 蝶阀，耐气蚀、寿命长，近几年我国也开发了金属密封蝶阀，但要注意，阀体、阀座和阀板 。阀座的材质不适组合时，阀座间会产生热咬合，又不能开闭的危险。在国外还开发耐气蚀 、低振动、低噪声的梳齿形蝶阀。由于铸造技术的提高，可使铸铁的阀体、阀板与不锈钢阀 座铸在一起，致使阀座部分的构造简单，导物不积留，耐久性、可靠性大大提高。一般密封座的寿命在正常情况下，橡胶15年以上，不锈钢金 属约80年，综合比较各异。但如何正确选用则要根据工况要求。蝶阀的开度与流量之间的关系，基本上呈线性比例变化。如果阀门处于节流幅度较大状态，阀板的背面容易发生气 蚀，有损坏阀门的可能，一般均在15度以外使用。节流侧阀门下面会产生负压，往往会出现橡 胶密封件脱落。蝶阀操作力矩，因开度及阀门启闭方向不同其值各异，卧 式蝶阀，特别是大口径阀，由于水深，阀轴上、下水头差所产生的力矩也不容忽视。另外，阀 门进口侧装置弯头时，形成偏流，力矩会有增加。 　　2.3排气阀 　　旧式双孔排气阀由于排气能力小等原因，逐渐要被新型高 速进排气阀代替。判定排气阀的性能高低除对阀门的一般要求外有三点至关 重要： 　　（1）在大多压差下大孔口关闭。 　　（2）管道中介质——水，冲上来时是否会把浮球压住，孔 口不能关闭。 　　（3）在低压时（0.02MPa）是否仍在密封不漏水。 　　排气阀口径的选择需要谨慎，特别管内产生负压时，需要 补充，使管内负压不超过0.35kgf/cm2，否则管道会失稳破坏。 停泵水锤防护专用阀门问题 　　3.1水锤种类 　　水锤从不同角度，可分为四种。按关阀历时与水锤相μ的关系分为直接水锤和间接水锤；按水锤成因的外部条件可分为启动水水锤、关阀水锤和停 泵水锤；按水锤水力特性可分为刚性水锤理论和弹性水锤理论两种；按水锤波动的现象分为 水柱连续现象和水柱分离的水锤现象两种。 根据调查统计，在城市给水和工业企业的给水泵 站中，绝大部分水锤事故都属与停泵水锤事故。水锤事故危害性很大，会导致管道和设备的骤然炸破。由于本文只论及停泵水锤的防护，所以水锤的理论问题另做探讨。一般管道末端关阀水锤是先发生高压，后发生低压。泵站 中停泵水锤的特点是先发生低压后发生高压，而且由于水泵电机旋转部分有一定的转动惯量， 在停电后不是立即停止而是转速逐渐降低，仍处于水泵的工作状态，只不过扬程和水量都逐渐下降，当扬程 降至与外部管道压力，流量变为0以后水开始倒流，此时水泵仍在正转受倒流水的作用，而 转速很快下降，此阶段为制动阶段，进一步当水泵转速为0以后受倒流作用，推动水泵倒转， 而开始进入水轮机工作状态，随 后压力才逐渐升起。在整个低压（或负压）水锤波所延续的时间大于正常水锤 波。低压（或负压）波时间，一般可由4、5秒到7、8秒。当水泵出口没有止回阀时，停泵后水可以通过水泵大量倒 流泄水，使正压水锤压力，有效地减小，因此在一定的情况下可以xx水锤，防止水锤事故， 但不能xx拉断水柱的水锤。当水泵出口装有止回阀时或水泵出口阀提早关闭，在水倒 流后水能冲击止回阀迅速关闭，从而产生一个较大的关阀水锤，尤其当发生拉断水柱水锤时， 回流水柱碰到关阀的止回阀上，将产生极大的水锤压力，这是我们主要的防护对象。停泵水锤防护专用阀门要适应这一过程的特点生产制造， 而且在正常运行时水头损失要小，安全可靠。若管道假设为刚体，水锤压力 式中g——重力加速度m/s； 　　a——水锤波传播速度，近似1000m/s； 　　V——流速m/s； 　　L——管道长度m。 　　直接水锤多发生在管道较长，关阀速度较快时，所以关阀 时间T的掌握非常重要，应满足 　　3.2阀门的气蚀问题 　　用气蚀系数δ值，来选定用作控制流量时，选择什么样的阀门结构型式中H1——阀后（出口）压力m； 　　H2——大气压与其温度相对应的饱和蒸气压力之差m； 　　ΔP——阀门前后的压差m； 　　其余符号同前。 　　各种阀门由于构造不同，因此，容许的气蚀系数δ也不同 。如计算的气蚀系数大于容许气蚀系数，则说明可用，不会发生气蚀。如蝶阀容许气蚀系数为 2.5，则： 　　如δ>2.5，则不会发生气蚀。 　　当2.5>δ>1.5时，会发生轻微气蚀。 　　δ<1>

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原文：
As the national economy growth and the demand for electric power industry, Shanghai has become the world's modern manufacturing base and processing center, as China's power equipment manufacturing of large enterprises, the company introduced UG NX2 system, using its powerful features, superior performance, sound technology, using information technology to stimulate industrialization of advanced design methods and manufacturing levels and advanced computer CAD / CAE / CAM combined permeate all aspects of design and manufacture of steam turbines, so that product development, design and manufacturing cycles are significantly reduced, thus lower production costs, strong participation in international market competition. UG NX2 that this is on the main steam valve in the steam turbine design for specific description. 1. Introduction The long-term sustainable development of the national economy is bound to have a greater demand for the power industry into the 20th century, China's power equipment industry has ushered in a spring, as China's power equipment manufacturing of large enterprises, must adapt to new demands, open a new situation, using information technology to stimulate industrialization, enabling businesses to the needs of the moment according to the market changes, timely feedback, adjust product performance, in the shortest possible time to maximize meet customer needs, enhance product competitiveness, Shanghai Turbine Co., Ltd. (STC) was introduced into the United States in the 95 Westinghouse design and development of technology, based on large-scale steam turbines since 2001, establishment of project design and development platform, an advanced design methods and manufacturing levels and advanced computer CAD / CAE / CAM integration, through the in all aspects of design and manufacture of steam turbines, so that product development cycles shorten design and manufacturing, product performance and quality constantly improving, changing the past 3 to 4 years of developing a new product for enterprises to create considerable economic benefits and social benefits. Unigraphics (abbreviated UG) is a CAD / CAE / CAM integrated 3D parametric software is the world's most advanced computer-aided design, analysis and manufacturing software, widely used in aviation, aerospace, automotive, shipbuilding, general machinery and electronics industrial fields. Primarily for automotive and transportation, aerospace, consumer goods, general machinery, and electronics industry and other fields through its virtual product development (VPD) to provide multi-level concept-oriented, integrated, enterprise-class products and services, including software, including complete MCAD solutions. Since my company has been the introduction of UG NX, with its advanced theory, a strong engineering background, perfect functionality and professional technical service well received by the engineers and professional and technical personnel of the favorite, and its maximum extent into practice development, research and manufacturing in order to enable my company's technology to align with international standards, continuing to improve the new product design cycle and design quality, and enable our company to produce high-quality low-cost turbine become a reality, a strong participation in the international marketplace in competition. 二. Turbine Throttle Valve Components Overview Main steam valve components are most critical of modern steam turbine, one of the most important components is the steam turbine into the door of the safe operation of steam turbines, play a role in the last line of defense to protect one, that is, when required to play Emergency block into the role of steam, while in the turbine starts to control the turbine speed. A steam turbine consists of two main steam valve - adjustable steam valve components, respectively, in the high-pressure cylinder mounted on both sides. Each component has a main steam valve and two adjustable steam valve, main steam valve and adjust the steam valve in the combination of a whole casting. The opening and closing of these valves are used hydraulic pressure to open, spring closed, DEH and controlled manner, that is installed in the valve by the respective implementing agency under the control of. The main steam valve for the horizontal structure, the main valve in an internal bypass valve, both single-seat non-balanced plate valve. When the valve in the closed position when the steam pressure and the compression spring into the load will be two valves at the same time pressed its seat on the disc. The main steam valve steam into the mouth, with two-story strainer - permanent and temporary mesh strainer to prevent foreign matter into the flow section. Turbine first time up and running after a certain time, installed in the outer layer of the temporary filter can be removed. Regulating valve for the vertical structure, each headed by an oil-motivated control. Oil motive directly mounted on the upper end of valve. Oil motive piston moving up steam when you open the regulating valve is closed when the move down. Regulating steam valve stem sleeve, there are two steam leakage interfaces, high-pressure port connected to the high-pressure cylinder exhaust steam, low pressure port is connected to the steam seal coolers. Main steam valve - control valve components of land-pin screw through the bracket fixed on the basis, as a fixed dead. This bracket can withstand the force the user channel, and can maintain the location of the steam room and adapt to the thermal expansion of components of their own. 三. UG NX in the turbine main steam valve design Modern turbine design methods from the design of a single power unit into power in a certain building blocks within the design method, there is a high technological content of the main steam valve components as turbine design, one of the important building blocks, there are hundreds of a composition of various shapes of parts, parts of a large number of structural forms of complex, high processing technology, the traditional use of computer graphics instead of drawing board drawing two-dimensional CAD design techniques are obviously not well positioned to meet this new design approach and the use of advanced UG NX powerful features, superior performance to achieve design automation, to ensure the reasonableness and accuracy of the design, greatly reducing the design work, shorten production cycle.

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