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水轮机

目录[隐藏]

历史发展
水轮机之最
工作原理
应用


  水轮机是把水流的能量转换为旋转机械能的动力机械,它属于流体机械中的透平机械

历史发展

  
 早在公元前100年前后,中国就出现了水轮机的雏形——水轮,用于提灌和驱动粮食加工器械。现代水轮机则大多数安装在水电站内,用来驱动发电机发电。在水电站中,上游水库中的水经引水管引向水轮机,推动水轮机转轮旋转,带动发电机发电。作完功的水则通过尾水管道排向下游。水头越高、流量越大,水轮机的输出功率也就越大。
  早期的冲击式水轮机的水流在冲击叶片时,动能损失很大,效率不高。1889年,美国工程师佩尔顿发明了水斗式水轮机,它有流线型的收缩喷嘴,能把水流能量高效率地转变为高速射流的动能。

水轮机之最

  20世纪80年代初,世界上单机功率最大的水斗式水轮机装于挪威的悉·西马电站,其单机容量为315兆瓦,水头885米,转速为300转/分,于1980年投入运行。水头最高的水斗式水轮机装于奥地利的赖瑟克山电站,其单机功率为22.8兆瓦,转速750转/分,水头达1763.5米,1959年投入运行。
  80年代,世界上尺寸最大的转桨式水轮机是中国东方电机厂制造的,装在中国长江中游的葛洲坝电站,其单机功率为170兆瓦,水头为18.6米,转速为54.6转/分,转轮直径为11.3米,于1981年投入运行。世界上水头最高的转桨式水轮机装在意大利的那姆比亚电站,其水头为88.4米,单机功率为13.5兆瓦,转速为375转/分,于1959年投入运行。
  世界上水头最高的混流式水轮机装于奥地利的罗斯亥克电站,其水头为672米,单机功率为58.4兆瓦,于1967年投入运行。功率和尺寸最大的混流式水轮机装于美国的大古力第三电站,其单机功率为700兆瓦,转轮直径约9.75米,水头为87米,转速为85.7转/分,于1978年投入运行。
  世界上最大的混流式水泵水轮机装于联邦德国的不来梅蓄能电站。其水轮机水头237.5米,发电机功率660兆瓦,转速125转/分;水泵扬程247.3米,电动机功率700兆瓦,转速125转/分。
  世界上容量最大的斜流式水轮机装于苏联的洁雅电站,单机功率为215兆瓦,水头为78.5米。

工作原理

  水轮机按工作原理可分为冲击式水轮机和反击式水轮机两大类。冲击式水轮机的转轮受到水流的冲击而旋转,工作过程中水流的压力不变,主要是动能的转换;反击式水轮机的转轮在水中受到水流的反作用力而旋转,工作过程中水流的压力能和动能均有改变,但主要是压力能的转换。
  冲击式水轮机按水流的流向可分为切击式(又称水斗式)和斜击式两类。斜击式水轮机的结构与水斗式水轮机基本相同,只是射流方向有一个倾角,只用于小型机组。
  理论分析证明,当水斗节圆处的圆周速度约为射流速度的一半时,效率最高。这种水轮机在负荷发生变化时,转轮的进水速度方向不变,加之这类水轮机都用于高水头电站,水头变化相对较小,速度变化不大,因而效率受负荷变化的影响较小,效率曲线比较平缓,最高效率超过91%。
  反击式水轮机可分为混流式、轴流式、斜流式和贯流式。在混流式水轮机中,水流径向进入导水机构,轴向流出转轮;在轴流式水轮机中,水流径向进入导叶,轴向进入和流出转轮;在斜流式水轮机中,水流径向进入导叶而以倾斜于主轴某一角度的方向流进转轮,或以倾斜于主轴的方向流进导叶和转轮;在贯流式水轮机中,水流沿轴向流进导叶和转轮。
  轴流式、贯流式和斜流式水轮机按其结构还可分为定桨式和转桨式。定桨式的转轮叶片是固定的;转桨式的转轮叶片可以在运行中绕叶片轴转动,以适应水头和负荷的变化。
  各种类型的反击式水轮机都设有进水装置,大、中型立轴反击式水轮机的进水装置一般由蜗壳、固定导叶和活动导叶组成。蜗壳的作用是把水流均匀分布到转轮周围。当水头在40米以下时,水轮机的蜗壳常用钢筋混凝土在现场浇注而成;水头高于40米时,则常采用拼焊或整铸的金属蜗壳。
  在反击式水轮机中,水流充满整个转轮流道,全部叶片同时受到水流的作用,所以在同样的水头下,转轮直径小于冲击式水轮机。它们的最高效率也高于冲击式水轮机,但当负荷变化时,水轮机的效率受到不同程度的影响。
  反击式水轮机都设有尾水管,其作用是:回收转轮出口处水流的动能;把水流排向下游;当转轮的安装位置高于下游水位时,将此位能转化为压力能予以回收。对于低水头大流量的水轮机,转轮的出口动能相对较大,尾水管的回收性能对水轮机的效率有显著影响。
  轴流式水轮机适用于较低水头的电站。在相同水头下,其比转数较混流式水轮机为高。轴流定桨式水轮机的叶片固定在转轮体上,叶片安放角不能在运行中改变,效率曲线较陡,适用于负荷变化小或可以用调整机组运行台数来适应负荷变化的电站。
  轴流转桨式水轮机是奥地利工程师卡普兰在1920年发明的,故又称卡普兰水轮机。其转轮叶片一般由装在转轮体内的油压接力器操作,可按水头和负荷变化作相应转动,以保持活动导叶转角和叶片转角间的最优配合,从而提高平均效率,这类水轮机的最高效率有的已超过94%。
  贯流式水轮机的导叶和转轮间的水流基本上无变向流动,加上采用直锥形尾水管,排流不必在尾水管中转弯,所以效率高,过流能力大,比转数高,特别适用于水头为3~20米的低水头电站。这种水轮机装在潮汐电站内还可以实现双向发电。这种水轮机有多种结构,使用最多的是灯泡式水轮机。
  灯泡式机组的发电机装在水密的灯泡体内。其转轮既可以设计成定桨式,也可以设计成转桨式。世界上最大的灯泡式水轮机(转桨式)装在美国的罗克岛第二电站,水头12.1米,转速为85.7转/分,转轮直径为7.4米,单机功率为54兆瓦,于1978年投入运行。
  混流式水轮机是世界上使用最广泛的一种水轮机,由美国工程师弗朗西斯于1849年发明,故又称弗朗西斯水轮机。与轴流转桨式相比,其结构较简单,最高效率也比轴流式的高,但在水头和负荷变化大时,平均效率比轴流转桨式的低,这类水轮机的最高效率有的已超过95%。混流式水轮机适用的水头范围很宽,为5~700米,但采用最多的是40~300米。
  混流式的转轮一般用低碳钢或低合金钢铸件,或者采用铸焊结构。为提高抗汽蚀和抗泥沙磨损性能,可在易气蚀部位堆焊不锈钢,或采用不锈钢叶片,有时也可整个转轮采用不锈钢。采用铸焊结构能降低成本,并使流道尺寸更精确,流道表面更光滑,有利于提高水轮机的效率,还可以分别用不同材料制造叶片、上冠和下环。
  斜流式水轮机是瑞士工程师德里亚于1956年发明,故又称德里亚水轮机。其叶片倾斜的装在转轮体上,随着水头和负荷的变化,转轮体内的油压接力器操作叶片绕其轴线相应转动。它的最高效率稍低于混流式水轮机,但平均效率大大高于混流式水轮机;与轴流转桨水轮机相比,抗气蚀性能较好,飞逸转速较低,适用于40~120米水头。
  由于斜流式水轮机结构复杂、造价高,一般只在不宜使用混流式或轴流式水轮机,或不够理想时才采用。这种水轮机还可用作可逆式水泵水轮机。当它在水泵工况启动时,转轮叶片可关闭成近于封闭的圆锥因而能减小电动机的启动负荷。

应用

  水泵水轮机主要用于抽水蓄能电站。在电力系统负荷低于基本负荷时,它可用作水泵,利用多余发电能力,从下游水库抽水到上游水库,以位能形式蓄存能量;在系统负荷高于基本负荷时,可用作水轮机,发出电力以调节高峰负荷。因此,纯抽水蓄能电站并不能增加电力系统的电量,但可以改善火力发电机组的运行经济性,提高电力系统的总效率。50年代以来,抽水蓄能机组在世界各国受到普遍重视并获得迅速发展。
  早期发展的或水头很高的抽水蓄能机组大多采用三机式,即由发电电动机、水轮机和水泵串联组成。它的优点是水轮机和水泵分别设计,可各自具有较高效率,而且发电和抽水时机组的旋转方向相同,可以迅速从发电转换为抽水,或从抽水转换为发电。同时,可以利用水轮机来启动机组。它的缺点是造价高,电站投资大。
  斜流式水泵水轮机转轮的叶片可以转动,在水头和负荷变化时仍有良好的运行性能,但受水力特性和材料强度的限制,到80年代初,它的最高水头只用到136.2米(日本的高根第一电站)。对于更高的水头,需要采用混流式水泵水轮机。
  抽水蓄能电站设有上、下两个水库。在蓄存相同能量的条件下,提高扬程可以缩小库容、提高机组转速、降低工程造价。因此,300米以上的高水头蓄能电站发展很快。世界上水头最高的混流式水泵水轮机装于南斯拉夫的巴伊纳巴什塔电站,其单机功率为315兆瓦,水轮机水头为600.3米;水泵扬程为623.1米,转速为428.6转/分,于1977年投入运行。
  20世纪以来,水电机组一直向高参数、大容量方向发展。随着电力系统中火电容量的增加和核电的发展,为解决合理调峰问题,世界各国除在主要水系大力开发或扩建大型电站外,正在积极兴建抽水蓄能电站,水泵水轮机因而得到迅速发展。
  为了充分利用各种水力资源,潮汐、落差很低的平原河流甚至波浪等也引起普遍重视,从而使贯流式水轮机和其他小型机组迅速发展。

水轮

金轮,水轮,风轮

  器世间是物质的世间,即是众生居住的世界,其产生是:刚开始形成的时候,先有风轮,然后有水轮,接下来有金轮,最后出现大地。经典还说,金轮在水轮上,水轮在风轮上;地球正是如此,风轮是地心核爆,水轮是岩浆,金轮是地壳。虽然大地出现,但是还没有众生,即是还没有有情世间。这个有情世间的众生是某些天的众生堕落到人间,那时候没有畜生、饿鬼、地狱的众生。即是当器世间刚圆满形成时,没有地狱的众生,后来人心越来越险恶,人就堕落做畜生,接着有人堕落做饿鬼,最后就有地狱的众生。出现了第一个地狱的众生后,整个三千大千世界的有情世间才圆满,此世间的形成才算完成,接着随有缘的众生的共业继续变化。

四轮持世界

  四轮持世界[出佛祖统纪] 轮取持载之义。华严经云。三千大千世界。依于水轮风轮空轮。不言金轮者。文略也。(三千者。小千。中千。大千也。今言三千大千者。总别兼称也。)一金轮大地之下有金轮。起世因本经云。水上有风。吹转此水。于上成金。如熟酥生膏。是名金轮。二水轮金轮之下有水轮。菩萨藏经云。最上风轮。为水轮之所依止。其水量高六十八百千由旬。(梵语由旬。华言限量。)三风轮水轮之下有风轮。菩萨藏经云。风轮量高六万八千俱胝。(梵语俱胝。华言百亿。)四空轮风轮之下有空轮。华严经云。空无所依。虽无所依。然由众生业感。世界次第安住。

医学

  水轮,人体部位名,系眼的五轮之一。见《秘传眼科龙木论》。又名冰轮。《银海精微》认为:“肾属水,曰水轮,在眼为瞳人。”即瞳神。其疾患多与肾、膀胱有关。详见条。

Ezine Advertising Strategy Exposed

In my opinion, Electronic Magazine (Ezine) advertising is the greatest, untapped source of online advertising available today. The reason: Ezine Advertising (EA) matches your product or idea to people with similar interests.

Example: who better to sell your health product to than a large group of people subscribed to a health newsletter? Or, you could pitch a business opportunity to a group already subscribed to another ezine about MLM and Biz Ops!

The idea of EA is fairly simple - but to make yours a success, you have to first determine which ezines or newsletters produce results, and which ones to avoid. After a year and a half of EA, I've created a formula that produces increasing profit because I've learned how to avoid poor performing ezines and rip offs, while revealing the gems.

Strategy for Profit

I used to get ripped off about once for every 2 or 3 ezines I advertised in. They either took my money without running my ad (and ignored my subsequent emails), or my proven ads did too poorly for the money I paid.

The reasons ranged from abandoned ezines with working payment links, unethical newsletter owners, to a lot of ignorance and impatience on my part. If you follow my proven strategy, you'll discover the best sources of ezines to advertise in - no matter who your target group is. And, you should see positive results every time.

This article outlines the steps to making your EA a successful return on investment (ROI). Writing Your Ad

I won't go into details about ad writing, but if your ad is poorly written or untested, you should start with the cheapest ezines first. If you're really unsure of your writing abilities, I further suggest hiring a professional to write your ad for you.

Because you can run your ad as many times as you want, your investment in a professional will more than pay for itself in the end.

Target your advertising

If you leap into EA without first researching your target group, you'll end up wasting a lot of time and money. Plus, you probably miss some of the best ezines available.

To determine who your prospect is, take the time to list the possible keywords that directly relate to your product and do keyword searches for ezines, newsletters, and ezine directories. For example, if you sell herbs, a good keyword search would include: herbs, health, nutrition, supplements, etc.

Avoid Co-ops

While doing your ezine research, you will probably stumble upon the offer to use Co-op (bulk) advertising as the means for your EA.

To be blunt, you should never pay to use Co-ops for your EA because they are too difficult to track and usually contain untargeted ezines. Worse still, you'd find that most never run your ad. Subscribe

Now that you've found your ezine target group, you'll want to know whether the ezines you found are a good option (i.e. profitable) for your EA.

I've found the best strategy for making this determination is to subscribe to the targeted ezines. To keep the subscriptions readily available for further research, I recommend creating a separate folder to store your subscription data. And because you'll need to subscribe to quite a few ezines, I also suggest creating separate email accounts dedicated to your ezine subscriptions. Double Opt-In Subscriptions In the process of subscribing, you'll quickly determine possible ezines to avoid. When you subscribe and get a notice that you must confirm your subscription, the ezine is referred to as 'double opt-in'.

Double opt-in ezines indicates a better quality of subscribers with a lower risk of bulk email addresses. For you and me, this means better ad responses (yeah!). Solo Ads

Within the first week of your new ezine subscription, you should see solo ads from other advertisers. If not, the ezine may be too new, or worse, no one is advertising because of poor results. Worse yet, the ezine took the advertiser's money and failed to run the ad.

On the other hand, if you see two or more solo ads a day, their list is probably burned out due to over advertising. You're looking for no more than one ad a day, or a minimum of one ad a week. Keep watching! Subject Line

Does the ezine put the advertiser's subject line in the subject of the email or do they just say something like "Solo ad from xyz ezine"?

Your subject line is the most important part of your ad and definitely should be in the subject of the email.No subject line equals no response. Advertiser Response

Repeat (or regular) advertisers in an ezine is a very good sign that the subscribers are responsive. To further test responsiveness, I recommend looking through the ezine's online archives (if available).

Archives are previous email publications that the publisher has posted to their website for visitors to view. The archive search is not only quick and easy, but archives can also provide an extra trickle of visitors when your ad gets archived.

Testimonial Page

After passing the above steps, see if your prospective ezine has a testimonial page. If the ezine has gotten this far, chances are it will. Waiting Period

Another indicator of responsive subscribers is the waiting period to run an ad in the chosen ezine. If the waiting period is a month or more, this indicates a very popular ezine with responsive readers. You've uncovered a real gem! Web Forms

I've found that the better ezines have web forms that get your ad to the publisher's inbox and usually send auto confirmation of receipt. If there is no web form, try emailing the publisher a question first, like when the next ad run date is.

No response may indicate a poor choice in the ezine, or your email was filtered or blocked as spam. Wait at least 2 days and try emailing again using a different email account.

If your emails still don't get through, neither will your ad. (Ironically, your payment always go through). Trust me, if they fail to communicate, save your money and time and move on. Free Classifieds

If the ezine offers free classifieds, this is another good place to run your ad. Since classifieds usually don't produce responses, any activity from your ad here would further indicate an active readership. Ad Tracking

Never advertise without using an ad tracker. You can purchase one or better, use one of the many available online for free. Ad trackers give you a url that you use in place of your website address.

The new url gives you important information like how many visitors you had, where they came from, and some list the number of sales per visitor.

This tracking information is crucial to the direction of your ad campaign because you'll learn of the need to change your ad and/or the sales page. More importantly, you'll know for certain whether the ezine produced enough visitors for the advertising price you paid. Run Your Ad Twice If your ad produced a great response, wait a week or two and run the ad again in the same ezine. I've found you'll probably get as good if not better results the second time around.

I would advise against running the ad a third time in a row because most of your prospects will be found in the first two runs.

Rotating Ads

Once your ad has been tested and you have a base of 5-10 solid, performing ezines, start rotating your ad between your ezines.

For optimal results, make sure 2-3 months have passed before running your ad in the same publication. Keep building your base and watch your profits grow!

About the author: Greg Root has been using ezine advertising almost exclusively since 2003 and owns and

maintains 'The Ezine Ad Tester©' at http://www.maxprofitpro.com/. See the results of his

ezine advertising campaigns to find the best ezine marketing resources on the internet.

Author: Greg Root

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