毕业设计水利水电工程英文文献翻译

1、外文文献：hydraulicturbinesandhydroelectricpowerAbstractAbstractPower may be developed from water by three fundamental processes ： by of its weight, of its pressure，or of its velocity，or by a combination of any orall three。 In modern practice the Pelton or impulse wheel is the only type whichobtains powe

2、r by a single process the action of one or more high-velocity jets. This type of wheel is usually found in high head developments. Faraday had shown that when a coil is rotated ina magnetic field electricity is generated. Thus, in order toproduce electrical energy, it is necessary that we should pro

3、duce mechanical energy，which can be used to rotate the coil。 The mechanical energy is produced byrunning a prime mover（known as turbine ）by the energy of fuels or flowing water.This mechanical power is converted into electrical power by electric generator which is directly coupled to the shaft of tu

4、rbine and is thus run by turbine. The electricalpower, which is consequently obtained at the terminals of the generator， is thentransited to the area where it is to be used for doing work.he plant or machinery whichisrequiredtoproduceelectricity(i.e。 primemover+electricgenerator)iscollectively known

5、 as power plant。 The building, in which the entire machineryalong with other auxiliary units is installed, is known as power house.Keywordshydraulic turbineshydro-electric power classification of hydel plantshead schemeKeywordsThere has been practically no increase in the efficiency of hydraulic tur

6、binessince about 1925， when maximum efficiencies reached 93% or more。 As far asmaximum efficiency is concerned, the hydraulic turbine has about reached thepracticable limit of development 。 Nevertheless， in recent years, there has been a rapid and marked increase in the physical size and horsepower

7、capacity of individual units.In addition, there has been considerable research into the cause and prevention ofcavitation， which allows the advantages of higher specific speeds to be obtained at higherheadsthanformerlywereconsideredadvisable。The net effect of this progresswith larger units, higher s

8、pecific speed, and simplification and improvements indesign has been to retain for the hydraulic turbine the importantplace which it haslong held at one of the most important prime movers。types of hydraulic turbinesHydraulic turbines may be grouped in two general classes: the impulse typewhich utili

9、zes the kinetic energy of a high-velocity jet which acts upon only a small part of the circumference at any instant, and the reaction type which develops power from the combined action of pressure and velocity of the water that completely fills therunnerandwaterpassages.Thereactiongroupisdividedinto

10、twogeneraltypes： Francis, sometimes called the reaction type，and the propeller type. The propellerclassisalsofurthersubdividedintothefixed-bladepropellertype,andadjustablebladetype of which the Kaplan is representative。impulse wheelsWith the impulse wheel the potential energy of the water in the pen

11、stock istransformed into kinetic energy in a jet issuing from the orifice of a nozzle. This jet discharge freely into the atmosphere inside the wheel housing and strikes against the bowl-shaped buckets of the runner。 At each revolution the bucket enters, passesthrough, and passes out of the jet, dur

12、ing which time it receives the full impact force the jetThis produces a rapid hammer blow upon the bucket. At the same time thebucket is subjected to the centrifugal force tending to separate the bucket from its disk.On account of the stresses so produced and also the scouring effects of the waterfl

13、owing over the working surface of the bowl ， material of high quality of resistanceagainst hydraulic wear and fatigue is required. Only for very low heads can cast iron be employed. Bronze and annealed cast steel are normally used.1。2 Francis runnersWith the Francis type the water enters from a casi

14、ng or flume with a relatively low velocity, passes through guide vanes or gates located around the circumstance，and flows through the runner，from which it discharges into a draft tube sealed belowthe tail-water level。 All the runner passages are completely filled with water, which acts upon the whol

15、e circumference of the runner. Only a portion of the power isderived from the dynamic action due to the velocity of the water, a large part of the power being obtained from the difference in pressure acting on the front and back of The draft tube allows maximum utilization of the available head,both

16、 because of the suction created below the runner by the vertical column of water and because the outlet of he draft tube is larger than the throat just below the runner, thusutilizing a part ofthe kinetic energy ofthe water leaving therunner blades。1。3 propeller runnersnherentlysuitableforlow-headde

17、velopments,thepropeller-typeunithaseffected marked economics within the range of head to which it is adapted. The higherspeed of this type of turbine results in a lower-cost generator and somewhat smaller powerhouse substructure and superstructure. Propellertype runners for low headsand small output

18、s are sometimes constructed of cast iron. For heads above 20 ft，theyare made of cast steel ， a much more reliable material 。 Large-diameter propellersmay have individual blades fastened to the hub.1.4 adjustable-blade runnersThe adjustableblade propeller type is a development from the fixedblade pro

19、peller wheel. One of the best-known units of this type is the Kaplan unit， in which the blades may be rotated to the most efficient angle by a hydraulic servomotor.A cam on the governor is used to cause the blade angle to change with the gate position so that high efficiency is always obtained at al

20、most any percentage of full load.By reason of its high efficiency at all gate openings， the adjustableblade propeller-type unit is particularly applicable to low-head developments where conditions are such that the units must be operated at varying load and varying head.Capital cost and maintenance

21、for such units are necessarily higher than for fixedblade propellertype units operated at the point of maximum efficiency.thermal and hydropowerAs stated earlier, the turbine blades can be made to run by the energy of fuels or flowing water. When fuel is used to produce steam for running the steam t

22、urbine, thenthe power generated is known as thermal power. The fuel which is to be used forgenerating steam may either be an ordinary fuel such as coal， fuel oil， etc。, oratomicfuel ornuclear fuel。 Coal is simply burnt to produce steam from water and isthesimplest and oldest type of fuel. Diesel oil

23、 ， etc。 may also be used as fuels for producing steam. Atomic fuels such as uranium or thorium may also be used toproduce steam. When conventional type of fuels such s coal, oil， etc。 （calledfossils ） is used to produce steam for running the turbines， the power house isgenerally called an Ordinary t

24、hermal power station or Thermal power station. Butwhen atomic fuel is used to produce steam， the power station, which is essentially athermal power station， is called an atomic power station or nuclear power station 。In an ordinary thermal power station ， steam is produced in a water boiler, while i

25、n the atomic power station； the boiler is replaced y a nuclear reactor and steamgenerator for raising steam. The electric power generated in both these cases is knownas thermal power and the scheme is called thermal power scheme.But, when the energy of the flowing water is used to run the turbines,

26、then the electricity generated is called hydroelectric power. This scheme is known as hydroscheme, and the power house is known as hydel power station or hydroelectric power station. In a hydro scheme, a certain quantity of water ata certain potential head is essentially made to flow through the tur

27、bines. The head causing flow runs the turbine blades,andthusproducingelectricityfromthegeneratorcoupledtoturbine 。 Inthischapterweare concerned withhydel scheme only。classification of hydel plantsHydro-plants may be classified on the basis of hydraulic characteristics as plants storage plantspumped

28、storage plants.tidalplants. they are described below.Runoffriverplants。These plants are those which utilize the minimum flow in a river having noappreciable pondage onits upstream side.A weir ora barrage issometimesconstructedacrossariversimply toraiseandmaintainthewaterlevelatpre-determined level w

29、ithin narrow limits of fluctuations, either solely for the power plants or for some other purpose where the power plant may be incidental. Such ascheme is essentially a low head scheme and may be suitable only on a perennial riverhaving sufficient dry weather flow of such a magnitude as to make the

30、development worthwhile.Run-off river plants generally have a very limited storage capacity, and can use water only when it comes 。 This small storage capacity is provided for meeting the hourly fluctuations of load 。 When the available discharge at site is more than thedemand (during off-peak hours

31、） the excess water is temporarily stored in the pondon the upstream side of the barrage, which is then utilized during the peak hours.he various examples of runoff the river pant are： Ganguwal and Kolta powerhouses located on Nangal Hydel Channel, Mohammad Pur and Pathri power houses onGanga Canal a

32、nd Sarda power house on Sarda Canal。The various stations constructed on irrigation channels at the sites of falls, alsofall under this category of plants。Storage plantsA storage plant is essentially having an upstream storage reservoir of sufficient size so as to permit, sufficient carryover storage

33、 from the monsoon season to the dry summer season, and thus to develop a firm flow substantially more than minimumnatural flow. In this scheme, a dam is constructed across the river and the powerhouse may be located at the foot of the dam ， Rihandprojects etc。 the power house may sometimes be locate

34、d much away from the dam (on the downstream side). In such a case ， the power house is located at the end of tunnelswhich carrywater from thereservoir。The tunnels are connected to the powerhouse machines by meansof pressure pen-stocks which mayeither be underground（as in Mainthon and Koyna projects)

35、 or may be kept exposed （as in Kundahproject).When the power house is located near the dam, as is generally done in the low head installations it is known as concentrated fall hydroelectric development。But when the water is carried to the power house at a considerable distance from the dam or pen-st

36、ockit is known as a divided fall development。（3） Pumped storage plants。A pumped storage plant generates power during peak hours， but during theoff-peak hours, water is pumped back from the tail water pool to the headwater pool for future use. The pumps are run by some secondary power from some other

37、 plant in the system. The plant is thus primarily meant for assisting an existing thermal plant orsome other hydel plant.During peak hours， the water flows from the reservoir to the turbine andelectricity is generated。 During offpeak hours, the excess power is available fromsome other plant, and is

38、utilized for pumping water from the tail pool to the head pool， this minor plant thus supplements the power of another major plant. In such a schemethe same water is utilized again and again and nowater is wasted.For heads varying between 15m to 90m, reservoir pump turbines have beendevised, which c

39、an function both as a turbine as well as a pump. Such reversibleturbines can work at relatively high efficiencies and can help in reducing the cost of such a plant. Similarly， the same electrical machine can be used both as a generatoras well as a motor by reversing the poles. The provision of such

40、a scheme helpsconsiderablyin improving the load factor of the power system。(4）Tidal plantsTidal plantsforgenerationofelectricpoweraretherecentandadvancements, and essentially work on the principle thatthereis arisein seawaterduring high tide period and a fall during the low ebb period. The water ris

41、es and falls twice a day; each fall cycle occupying about 12 hours and 25 minutes. The advantage of this rise and fall of water is taken in a tidal plant. In other words, the tidal rangeie. the difference between high and low tide levels is utilized to generate power. Thisis accomplished by construc

42、ting a basin separated from the ocean by a partition walland installing turbines in opening through this wall。Water passes from the ocean to the basin during high tides, and thus running theturbinesandgeneratingelectricpower。During low tide,the water from the basin runsback to ocean， which can also

43、be utilized to generate electric power， provided specialturbineswhichcangeneratepowerforeitherdirectionofflowareinstalled 。Such plants are useful at places where tidal range is high. Rance power station in France is an example of this type of power station。 The tidal range at this place is oftheorde

44、rof 11meters. Thispower housecontains 9units of38，000 kW.4。Hydro-plants or hydroelectric schemes may be classified on the basis of operatingheadonturbinesasfollows: lowheadscheme（head15m),mediumhead scheme（head varies between 15m to 60 m) high head scheme They are described below:（1） Low head scheme

45、.A low head scheme is one which uses water head of less than 15 meters or so. Arunoffriverplantisessentiallyalowheadscheme，aweirorabarrageisconstructedto raise the water level, and the power house is constructed either in continuation withthe barrage or at some distance downstream of the barrage ， w

46、here water is taken tothe power house through an intake canal.Medium head schemeA medium head scheme is one which used water head varying between 15 to 60 meters or so. This scheme is thus essentially a dam reservoir scheme， although thedam height is mediocre. This scheme is having features somewher

47、e between low had scheme and high head scheme.Highheadscheme。A high head scheme is one which uses water head of more than 60m or so。 Adam of sufficient height is， therefore， required to be constructed, so as to storewater on the upstream side and to utilize this water throughout the year 。 High head

48、schemes up to heights of 1,800 meters have been developed. The common examples of such a scheme arBhakra dam in（Punjab, Rihand dam in (U.P.and Hoover dam in（。S.A， et。The naturally available high falls can also be developed for generating electric power.ThecommonexamplesofsuchpowerdevelopmentsareJogF

49、allsinIndia，and NiagaraFalls in U。S.A。水轮机和水力发电摘要水的能量可以通过三种基本方法来获得：利用水的重力作用、水的压力作用中，佩尔顿式水轮机或冲击式水轮机是唯一只利用其中一种方法来猎取水能的，.法拉第曾经指出:“线圈”旋转的机械能。用燃料或流水的能动机来实现的，电动机直接连接在涡轮机轴上，由涡轮机驱动。因此，就在发电机的出线端获得电能,然后输送到需要它做功的地区。发电需要的装置或机械(即原动机+发电机统称为动力设备.安置全部机械和其他帮助设施的建筑称为发电厂。关键词水轮机水力发电水电站种类水头系统1925 93或略微高一点就没有再提高了。.然而，在最近几年里，水轮机的大小和单机容量却增长的很快。使得我们能够在高于以前认为的合适水头下获得更高的比转速。更大的机组 ,更高的比转速,以及水轮机的设计上的简化和改进，这几个方面的进步使得水轮机始终以来在作为原动力之一拥有很