中文3840字
外文文献：
hydraulicturbines and hydroelectric power
Abstract
Power may be developed from water by three fundamental processes by action of its weight of its pressure or of its velocity or by a combination of any or all three In modern practice the Pelton or impulse wheel is the only type which obtains power by a single process the action of one or more highvelocity jets This type of wheel is usually found in highhead developments Faraday had shown that when a coil is rotated in a magnetic field electricity is generated Thus in order to produce electrical energy it is necessary that we should produce mechanical energy which can be used to rotate the coil’ The mechanical energy is produced by running 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 turbine and is thus run by turbine The electrical power which is consequently obtained at the terminals of the generator is then transited to the area where it is to be used for doing workhe plant or machinery which is required to produce electricity (ie prime mover +electric generator) is collectively known as power plant The building in which the entire machinery along with other auxiliary units is installed is known as power house
Keywords hydraulic turbines hydroelectric power classification of hydel plants
head scheme
There has been practically no increase in the efficiency of hydraulic turbines since about 1925 when maximum efficiencies reached 93 or more As far as maximum efficiency is concerned the hydraulic turbine has about reached the practicable limit of development Nevertheless in recent years there has been a rapid and marked increase in the physical size and horsepower capacity of individual units
In addition there has been considerable research into the cause and prevention of cavitation which allows the advantages of higher specific speeds to be obtained at higher heads than formerly were considered advisable The net effect of this progress with larger units higher specific speed and simplification and improvements in design has been to retain for the hydraulic turbine the important place which it has long held at one of the most important prime movers
1 types of hydraulic turbines
Hydraulic turbines may be grouped in two general classes the impulse type which utilizes the kinetic energy of a highvelocity 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 the runner and water passages The reaction group is divided into two general types the Francis sometimes called the reaction type and the propeller type The propeller class is also further subdivided into the fixedblade propeller type and the adjustableblade type of which the Kaplan is representative
11 impulse wheels
With the impulse wheel the potential energy of the water in the penstock is transformed 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 bowlshaped buckets of the runner At each revolution the bucket enters passes through and passes out of the jet during which time it receives the full impact force of the jet This produces a rapid hammer blow upon the bucket At the same time the bucket 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 water flowing over the working surface of the bowl material of high quality of resistance against hydraulic wear and fatigue is required Only for very low heads can cast iron be employed Bronze and annealed cast steel are normally used
12 Francis runners
With the Francis type the water enters from a casing 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 below the tailwater level All the runner passages are completely filled with water which acts upon the whole circumference of the runner Only a portion of the power is derived 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 runner buckets The draft tube allows maximum utilization of the available head both 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 thus utilizing a part of the kinetic energy of the water leaving the runner blades
13 propeller runners
nherently suitable for lowhead developments the propellertype unit has effected marked economics within the range of head to which it is adapted The higher speed of this type of turbine results in a lowercost generator and somewhat smaller powerhouse substructure and superstructure Propellertype runners for low heads and small outputs are sometimes constructed of cast iron For heads above 20 ft they are made of cast steel a much more reliable material Largediameter propellers may have individual blades fastened to the hub
14 adjustableblade runners
The adjustableblade propeller type is a development from the fixedblade propeller wheel One of the bestknown 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 almost any percentage of full load
By reason of its high efficiency at all gate openings the adjustableblade propellertype unit is particularly applicable to lowhead developments where conditions are such that the units must be operated at varying load and varying head Capital cost and maintenance for such units are necessarily higher than for fixedblade propellertype units operated at the point of maximum efficiency
2 thermal and hydropower
As 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 turbine then the power generated is known as thermal power The fuel which is to be used for generating steam may either be an ordinary fuel such as coal fuel oil etc or atomic fuel or nuclear fuel Coal is simply burnt to produce steam from water and is the simplest and oldest type of fuel Diesel oil etc may also be used as fuels for producing steam Atomic fuels such as uranium or thorium may also be used to produce steam When conventional type of fuels such s coal oil etc (called fossils ) is used to produce steam for running the turbines the power house is generally called an Ordinary thermal power station or Thermal power station But when atomic fuel is used to produce steam the power station which is essentially a thermal 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 in the atomic power station the boiler is replaced y a nuclear reactor and steam generator for raising steam The electric power generated in both these cases is known as thermal power and the scheme is called thermal power scheme
But when the energy of the flowing water is used to run the turbines then the electricity generated is called hydroelectric power This scheme is known as hydro scheme and the power house is known as hydel power station or hydroelectric power station In a hydro scheme a certain quantity of water at a certain potential head is essentially made to flow through the turbines The head causing flow runs the turbine blades and thus producing electricity from the generator coupled to turbine In this chapter we are concerned with hydel scheme only
3classification of hydel plants
Hydroplants may be classified on the basis of hydraulic characteristics as follow ① runoff river plants ②storage plants③pumped storage plants④tidal plants they are described below
(1) Runoff river plants
These plants are those which utilize the minimum flow in a river having no appreciable pondage on its upstream side A weir or a barrage is sometimes constructed across a river simply to raise and maintain the water level at a predetermined level within narrow limits of fluctuations either solely for the power plants or for some other purpose where the power plant may be incidental Such a scheme is essentially a low head scheme and may be suitable only on a perennial river having sufficient dry weather flow of such a magnitude as to make the development worthwhile
Runoff 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 the demand (during offpeak hours ) the excess water is temporarily stored in the pond on 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 power houses located on Nangal Hydel Channel Mohammad Pur and Pathri power houses on Ganga Canal and Sarda power house on Sarda Canal
The various stations constructed on irrigation channels at the sites of falls also fall under this category of plants
(2) Storage plants
A storage plant is essentially having an upstream storage reservoir of sufficient size so as to permit sufficient carryover storage from the monsoon season to the dry summer season and thus to develop a firm flow substantially more than minimum natural flow In this scheme a dam is constructed across the river and the power house may be located at the foot of the dam such as in Bhakra Hirakud Rihand projects etc the power house may sometimes be located much away from the dam (on the downstream side) In such a case the power house is located at the end of tunnels which carry water from the reservoir The tunnels are connected to the power house machines by means of pressure penstocks which may either be underground (as in Mainthon and Koyna projects) or may be kept exposed (as in Kundah project)
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 through a canal tunnel or penstock it is known as a divided fall development
(3) Pumped storage plants
A pumped storage plant generates power during peak hours but during the offpeak 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 plant in the system The plant is thus primarily meant for assisting an existing thermal plant or some other hydel plant
During peak hours the water flows from the reservoir to the turbine and electricity is generated During offpeak hours the excess power is available from some other plant and is 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 scheme the same water is utilized again and again and no water is wasted
For heads varying between 15m to 90m reservoir pump turbines have been devised which can function both as a turbine as well as a pump Such reversible turbines 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 generator as well as a motor by reversing the poles The provision of such a scheme helps considerably in improving the load factor of the power system
(4) Tidal plants
Tidal plants for generation of electric power are the recent and modern advancements and essentially work on the principle that there is a rise in seawater during high tide period and a fall during the low ebb period The water rises 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 range ie the difference between high and low tide levels is utilized to generate power This is accomplished by constructing a basin separated from the ocean by a partition wall and installing turbines in opening through this wall
Water passes from the ocean to the basin during high tides and thus running the turbines and generating electric power During low tidethe water from the basin runs back to ocean which can also be utilized to generate electric power provided special turbines which can generate power for either direction of flow are installed 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 of the order of 11 meters This power house contains 9 units of 38000 kW
4Hydroplants or hydroelectric schemes may be classified on the basis of operating head on turbines as follows ① low head scheme (head<15m)②medium head scheme (head varies between 15m to 60 m) ③high head scheme (head>60m) They are described below
(1) Low head scheme
A low head scheme is one which uses water head of less than 15 meters or so A run off river plant is essentially a low head scheme a weir or a barrage is constructed to raise the water level and the power house is constructed either in continuation with the barrage or at some distance downstream of the barrage where water is taken to the power house through an intake canal
(2) Medium head scheme
A 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 the dam height is mediocre This scheme is having features somewhere between low had scheme and high head scheme
(3) High head scheme
A high head scheme is one which uses water head of more than 60m or so A dam of sufficient height is therefore required to be constructed so as to store water on the upstream side and to utilize this water throughout the year High head schemes up to heights of 1800 meters have been developed The common examples of such a scheme are Bhakra dam in (Punjab) Rihand dam in (UP) and Hoover dam in (USA) etc
The naturally available high falls can also be developed for generating electric power The common examples of such power developments are Jog Falls in India and Niagara Falls in USA
水轮机水力发电
摘
水量通三种基方法获：利水重力作水压力作水流速作者中意两种全部三种作组合实际应中佩尔顿式水轮机击式水轮机唯利中种方法获取水利束者束高速水流作获量种水轮机种类型水轮机通常应高水头电站法拉第指出：线圈磁场中旋转产生电获电必须产生线圈旋转机械燃料流水量带动原动机（称涡轮机）产生机械种机械转换成电通电动机实现电动机直接连接涡轮机轴涡轮机驱动发电机出线端获电然输送需做功区发电需装置机械（原动机+发电机）统称动力设备安置机械辅助设施建筑称发电厂
关键词水轮机水力发电水电站种类水头系统
1925年开始水轮机高效率达93稍微高点没提高效率言水轮机水利率已达实际发展极限然年里水轮机单机容量增长快
外引起空蚀原样预防空蚀做研究研究够高前认合适水头获更高转速更机组更高转速水轮机设计简化改进方面进步水轮机直作原动力拥重位
1水轮机类型
水轮机分两类：击式水轮机——利高速水流击水轮机部分时产生动反击式水轮机——利充满转轮水道水流拥水压力流速两者相结合获动力反击式系列分成两种通型式：弗朗西斯式（时称作反击式）旋桨式旋桨式进步分定轮叶式水轮机卡普兰式代表转叶式水轮机
11击式水轮机
击式水轮机压力钢中水喷嘴孔口中射出时水势转换成动射流射入水轮室空气中撞击转轮碗状戽斗戽斗旋转周进入射流射流转出次段时间戽斗承受着射流全部击力种击力产生高速锤击戽斗时戽斗受离心力作脱离座盘趋势产生应力水流戽斗碗状工作面刷作需选抵御水力磨损疲劳高质量材料般采青铜韧化铸钢水头低时铸铁
12弗朗西斯式转轮
弗朗西斯式水轮机说蜗壳水槽流速较低水通位转轮周围导叶闸门然流转轮转轮泄入安置尾水位气相通尾水水充满水道作转轮整周围仅部分动力水流速引起动力作部分动力通作转轮叶片前工作面压力差取尾水利水头充分利方面转轮面垂直水柱产生吸出作方面尾水出口面积紧接转轮喉面积水流离开转轮叶片时部分动利
13旋桨式转轮
旋桨式机组适低水头电站适水头范围已产生显著济效果种水轮机转速较高致发电机价格较低发电厂房水结构水结构尺寸较低水头功率旋桨式转轮时铸铁制造水头高20英寸时种更材料──铸钢制造直径螺旋桨单叶片固定轮毂制成
14转叶式水轮机
转叶旋桨式水轮机定轮叶旋桨式水轮机发展成卡普兰式水轮机类水轮机中熟悉种叶片液压伺服器调整效率角度利伺服器凸轮叶片角度阀门开启位置变化种满负载百分率情况保持高效率
转叶旋桨式水轮机组闸门种开度情况效率高特适必须变负载变水头条件运行低水头电站然种机组投资费维护费高效率点运行定轮叶旋桨式水轮机组
2火电水电
述涡轮机叶片燃料流水量带动燃料产生蒸汽驱动蒸汽涡轮机时产生电称火电产生蒸汽燃料般燃料煤燃料油等原子燃料核燃料直接燃烧煤产生水蒸气煤简便古老种燃料柴油等作产生蒸汽燃料原子燃料铀钍产生蒸汽传统燃料煤燃料油等（称矿物燃料）产生蒸汽带动水轮机时种发电厂般称普通火力发电厂热电厂原子燃料产生蒸汽时种发电厂（基属火力发电厂）称原子发电厂核电厂般火力发电厂锅炉产生蒸汽原子发电站核反应堆蒸汽发生器代锅炉产生蒸汽两种情况产生电称火电该系统称火力发电系统
然流水量驱动水轮机时产生电称水电种系统称水力发电系统发电厂称水力发电厂水电站水电系统中必须具定势定数量水流流水轮机势水流动驱动水轮机叶片样水轮机连接发电机发出电章涉水力发电系统容
3水力发电站种类
根水力特性水力发电站分列种：①径流式电站②蓄水式电站③抽水蓄电站④潮汐电站类电站分述：
(1)径流式电站
类电站河流游适宜水库情况利河流流量电站时修建拦河堰坝水位提高保持预定数值允许范围变化单独电站服务者目标服务兼顾电站种方案基种低水头方案仅适枯水季流量值开发常年性河流
径流式电站通常具蓄水库容径流时方利蓄水库容满足时负荷变化设立河道水流量发电需时（非峰荷期间）余水量暂时蓄存拦河建筑物游水库中供峰荷期间
径流式电站诸例子：楠加尔•海德尔运河冈古瓦尔科拉水电站恒河默罕默德•普尔帕特里水电站萨尔达运河萨尔达水电站
灌溉渠道跌水处修建电站属径流式水电站
(2)蓄水式电站
蓄水式电站基足够游蓄水库贮存季风季节干旱夏季径流量提供枯季流量稳定流量种设计方案中水坝拦河修筑电站布置脚巴克拉希陶库德里亨工程等电站位坝游远方种情况电站位水库输水隧道末端输水隧道助压力水电站机械装置连接压力水（迈吞高勒工程）（孔达工程）
电站位坝附时般采低水头发电装置种电站称集中落差式水力发电工程水流坝渠道隧道压力水长距离输送电站时称分散落差式水力发电工程
(3)抽水蓄电站
抽水蓄电站峰荷期间发电非峰荷期间水尾水池抽回蓄水前池供抽水机该系统电站辅助电力驱动类抽水蓄电站协调现火电站水电站
峰荷期间水水库流入水轮机产生电非峰荷期间利电站剩余电尾水池抽水前池较电站较电站补充电样系统中样水量次次重复利没浪费
利15～90米间变化水头已制造出种逆式水泵──水轮机作水轮机作水泵种逆式水轮机高效率运转助减少类电站投资样种电力设备做发电机通电极互换作马达系统中设备非常助提高电力系统负载系数
(4)潮汐电站
潮汐电站发电现代成根海水高潮期升落潮期降原理工作海水日涨落两次次涨潮周期约12时25分潮汐电站利水位涨落效益换言利高低潮间水位差进行发电修建水池隔墙海隔开关隔墙孔洞里安装水轮机发电
高潮期间海水流入水池驱动水轮机发电落潮期间水水池流回海洋安装种两水流方发电特种水轮机组利流回海洋水流进行发电类电站潮差方法国朗斯电站类电站例子里达11米该站拥九台机组装机容量38000千瓦
4根水轮机工作水头水电站（水电系统）分列种：①低水头系统（落差15米）②中水头系统（落差变化15～60米）③高水头系统（落差60米）现分述：
(1)低水头系统
低水头系统水头15米左右径流式电站基属低水头电站该系统中修建拦河坝提高水位电站建拦河坝端建坝游离拦河坝定距离方通引水渠水送电站
(2)中水头系统
中水头系统水头变化15米60米左右该系统基种坝水库系统坝高度低水头高水头系统间该系统某方优点
(3)高水头系统
高水头系统水头60米游蓄水全年水求建造足够高度坝已发展高水头系统坝高已达1800米该系统常见例子印度旁遮普省巴克拉坝印度北方邦里亨坝美国胡佛坝等
高度较天然落差发电类动力开发般例子印度乔喀瀑布美国尼拉瀑布
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外文文献：
hydraulicturbines and hydroelectric power
Abstract
Power may be developed from water by three fundamental processes by action of its weight of its pressure or of its velocity or by a combination of any or all three In modern practice the Pelton or impulse wheel is the only type which obtains power by a single process the action of one or more highvelocity jets This type of wheel is usually found in highhead developments Faraday had shown that when a coil is rotated in a magnetic field electricity is generated Thus in order to produce electrical energy it is necessary that we should produce mechanical energy which can be used to rotate the coil’ The mechanical energy is produced by running 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 turbine and is thus run by turbine The electrical power which is consequently obtained at the terminals of the generator is then transited to the area where it is to be used for doing workhe plant or machinery which is required to produce electricity (ie prime mover +electric generator) is collectively known as power plant The building in which the entire machinery along with other auxiliary units is installed is known as power house
Keywords hydraulic turbines hydroelectric power classification of hydel plants
head scheme
There has been practically no increase in the efficiency of hydraulic turbines since about 1925 when maximum efficiencies reached 93 or more As far as maximum efficiency is concerned the hydraulic turbine has about reached the practicable limit of development Nevertheless in recent years there has been a rapid and marked increase in the physical size and horsepower capacity of individual units
In addition there has been considerable research into the cause and prevention of cavitation which allows the advantages of higher specific speeds to be obtained at higher heads than formerly were considered advisable The net effect of this progress with larger units higher specific speed and simplification and improvements in design has been to retain for the hydraulic turbine the important place which it has long held at one of the most important prime movers
1 types of hydraulic turbines
Hydraulic turbines may be grouped in two general classes the impulse type which utilizes the kinetic energy of a highvelocity 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 the runner and water passages The reaction group is divided into two general types the Francis sometimes called the reaction type and the propeller type The propeller class is also further subdivided into the fixedblade propeller type and the adjustableblade type of which the Kaplan is representative
11 impulse wheels
With the impulse wheel the potential energy of the water in the penstock is transformed 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 bowlshaped buckets of the runner At each revolution the bucket enters passes through and passes out of the jet during which time it receives the full impact force of the jet This produces a rapid hammer blow upon the bucket At the same time the bucket 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 water flowing over the working surface of the bowl material of high quality of resistance against hydraulic wear and fatigue is required Only for very low heads can cast iron be employed Bronze and annealed cast steel are normally used
12 Francis runners
With the Francis type the water enters from a casing 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 below the tailwater level All the runner passages are completely filled with water which acts upon the whole circumference of the runner Only a portion of the power is derived 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 runner buckets The draft tube allows maximum utilization of the available head both 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 thus utilizing a part of the kinetic energy of the water leaving the runner blades
13 propeller runners
nherently suitable for lowhead developments the propellertype unit has effected marked economics within the range of head to which it is adapted The higher speed of this type of turbine results in a lowercost generator and somewhat smaller powerhouse substructure and superstructure Propellertype runners for low heads and small outputs are sometimes constructed of cast iron For heads above 20 ft they are made of cast steel a much more reliable material Largediameter propellers may have individual blades fastened to the hub
14 adjustableblade runners
The adjustableblade propeller type is a development from the fixedblade propeller wheel One of the bestknown 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 almost any percentage of full load
By reason of its high efficiency at all gate openings the adjustableblade propellertype unit is particularly applicable to lowhead developments where conditions are such that the units must be operated at varying load and varying head Capital cost and maintenance for such units are necessarily higher than for fixedblade propellertype units operated at the point of maximum efficiency
2 thermal and hydropower
As 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 turbine then the power generated is known as thermal power The fuel which is to be used for generating steam may either be an ordinary fuel such as coal fuel oil etc or atomic fuel or nuclear fuel Coal is simply burnt to produce steam from water and is the simplest and oldest type of fuel Diesel oil etc may also be used as fuels for producing steam Atomic fuels such as uranium or thorium may also be used to produce steam When conventional type of fuels such s coal oil etc (called fossils ) is used to produce steam for running the turbines the power house is generally called an Ordinary thermal power station or Thermal power station But when atomic fuel is used to produce steam the power station which is essentially a thermal 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 in the atomic power station the boiler is replaced y a nuclear reactor and steam generator for raising steam The electric power generated in both these cases is known as thermal power and the scheme is called thermal power scheme
But when the energy of the flowing water is used to run the turbines then the electricity generated is called hydroelectric power This scheme is known as hydro scheme and the power house is known as hydel power station or hydroelectric power station In a hydro scheme a certain quantity of water at a certain potential head is essentially made to flow through the turbines The head causing flow runs the turbine blades and thus producing electricity from the generator coupled to turbine In this chapter we are concerned with hydel scheme only
3classification of hydel plants
Hydroplants may be classified on the basis of hydraulic characteristics as follow ① runoff river plants ②storage plants③pumped storage plants④tidal plants they are described below
(1) Runoff river plants
These plants are those which utilize the minimum flow in a river having no appreciable pondage on its upstream side A weir or a barrage is sometimes constructed across a river simply to raise and maintain the water level at a predetermined level within narrow limits of fluctuations either solely for the power plants or for some other purpose where the power plant may be incidental Such a scheme is essentially a low head scheme and may be suitable only on a perennial river having sufficient dry weather flow of such a magnitude as to make the development worthwhile
Runoff 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 the demand (during offpeak hours ) the excess water is temporarily stored in the pond on 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 power houses located on Nangal Hydel Channel Mohammad Pur and Pathri power houses on Ganga Canal and Sarda power house on Sarda Canal
The various stations constructed on irrigation channels at the sites of falls also fall under this category of plants
(2) Storage plants
A storage plant is essentially having an upstream storage reservoir of sufficient size so as to permit sufficient carryover storage from the monsoon season to the dry summer season and thus to develop a firm flow substantially more than minimum natural flow In this scheme a dam is constructed across the river and the power house may be located at the foot of the dam such as in Bhakra Hirakud Rihand projects etc the power house may sometimes be located much away from the dam (on the downstream side) In such a case the power house is located at the end of tunnels which carry water from the reservoir The tunnels are connected to the power house machines by means of pressure penstocks which may either be underground (as in Mainthon and Koyna projects) or may be kept exposed (as in Kundah project)
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 through a canal tunnel or penstock it is known as a divided fall development
(3) Pumped storage plants
A pumped storage plant generates power during peak hours but during the offpeak 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 plant in the system The plant is thus primarily meant for assisting an existing thermal plant or some other hydel plant
During peak hours the water flows from the reservoir to the turbine and electricity is generated During offpeak hours the excess power is available from some other plant and is 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 scheme the same water is utilized again and again and no water is wasted
For heads varying between 15m to 90m reservoir pump turbines have been devised which can function both as a turbine as well as a pump Such reversible turbines 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 generator as well as a motor by reversing the poles The provision of such a scheme helps considerably in improving the load factor of the power system
(4) Tidal plants
Tidal plants for generation of electric power are the recent and modern advancements and essentially work on the principle that there is a rise in seawater during high tide period and a fall during the low ebb period The water rises 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 range ie the difference between high and low tide levels is utilized to generate power This is accomplished by constructing a basin separated from the ocean by a partition wall and installing turbines in opening through this wall
Water passes from the ocean to the basin during high tides and thus running the turbines and generating electric power During low tidethe water from the basin runs back to ocean which can also be utilized to generate electric power provided special turbines which can generate power for either direction of flow are installed 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 of the order of 11 meters This power house contains 9 units of 38000 kW
4Hydroplants or hydroelectric schemes may be classified on the basis of operating head on turbines as follows ① low head scheme (head<15m)②medium head scheme (head varies between 15m to 60 m) ③high head scheme (head>60m) They are described below
(1) Low head scheme
A low head scheme is one which uses water head of less than 15 meters or so A run off river plant is essentially a low head scheme a weir or a barrage is constructed to raise the water level and the power house is constructed either in continuation with the barrage or at some distance downstream of the barrage where water is taken to the power house through an intake canal
(2) Medium head scheme
A 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 the dam height is mediocre This scheme is having features somewhere between low had scheme and high head scheme
(3) High head scheme
A high head scheme is one which uses water head of more than 60m or so A dam of sufficient height is therefore required to be constructed so as to store water on the upstream side and to utilize this water throughout the year High head schemes up to heights of 1800 meters have been developed The common examples of such a scheme are Bhakra dam in (Punjab) Rihand dam in (UP) and Hoover dam in (USA) etc
The naturally available high falls can also be developed for generating electric power The common examples of such power developments are Jog Falls in India and Niagara Falls in USA
水轮机水力发电
摘
水量通三种基方法获：利水重力作水压力作水流速作者中意两种全部三种作组合实际应中佩尔顿式水轮机击式水轮机唯利中种方法获取水利束者束高速水流作获量种水轮机种类型水轮机通常应高水头电站法拉第指出：线圈磁场中旋转产生电获电必须产生线圈旋转机械燃料流水量带动原动机（称涡轮机）产生机械种机械转换成电通电动机实现电动机直接连接涡轮机轴涡轮机驱动发电机出线端获电然输送需做功区发电需装置机械（原动机+发电机）统称动力设备安置机械辅助设施建筑称发电厂
关键词水轮机水力发电水电站种类水头系统
1925年开始水轮机高效率达93稍微高点没提高效率言水轮机水利率已达实际发展极限然年里水轮机单机容量增长快
外引起空蚀原样预防空蚀做研究研究够高前认合适水头获更高转速更机组更高转速水轮机设计简化改进方面进步水轮机直作原动力拥重位
1水轮机类型
水轮机分两类：击式水轮机——利高速水流击水轮机部分时产生动反击式水轮机——利充满转轮水道水流拥水压力流速两者相结合获动力反击式系列分成两种通型式：弗朗西斯式（时称作反击式）旋桨式旋桨式进步分定轮叶式水轮机卡普兰式代表转叶式水轮机
11击式水轮机
击式水轮机压力钢中水喷嘴孔口中射出时水势转换成动射流射入水轮室空气中撞击转轮碗状戽斗戽斗旋转周进入射流射流转出次段时间戽斗承受着射流全部击力种击力产生高速锤击戽斗时戽斗受离心力作脱离座盘趋势产生应力水流戽斗碗状工作面刷作需选抵御水力磨损疲劳高质量材料般采青铜韧化铸钢水头低时铸铁
12弗朗西斯式转轮
弗朗西斯式水轮机说蜗壳水槽流速较低水通位转轮周围导叶闸门然流转轮转轮泄入安置尾水位气相通尾水水充满水道作转轮整周围仅部分动力水流速引起动力作部分动力通作转轮叶片前工作面压力差取尾水利水头充分利方面转轮面垂直水柱产生吸出作方面尾水出口面积紧接转轮喉面积水流离开转轮叶片时部分动利
13旋桨式转轮
旋桨式机组适低水头电站适水头范围已产生显著济效果种水轮机转速较高致发电机价格较低发电厂房水结构水结构尺寸较低水头功率旋桨式转轮时铸铁制造水头高20英寸时种更材料──铸钢制造直径螺旋桨单叶片固定轮毂制成
14转叶式水轮机
转叶旋桨式水轮机定轮叶旋桨式水轮机发展成卡普兰式水轮机类水轮机中熟悉种叶片液压伺服器调整效率角度利伺服器凸轮叶片角度阀门开启位置变化种满负载百分率情况保持高效率
转叶旋桨式水轮机组闸门种开度情况效率高特适必须变负载变水头条件运行低水头电站然种机组投资费维护费高效率点运行定轮叶旋桨式水轮机组
2火电水电
述涡轮机叶片燃料流水量带动燃料产生蒸汽驱动蒸汽涡轮机时产生电称火电产生蒸汽燃料般燃料煤燃料油等原子燃料核燃料直接燃烧煤产生水蒸气煤简便古老种燃料柴油等作产生蒸汽燃料原子燃料铀钍产生蒸汽传统燃料煤燃料油等（称矿物燃料）产生蒸汽带动水轮机时种发电厂般称普通火力发电厂热电厂原子燃料产生蒸汽时种发电厂（基属火力发电厂）称原子发电厂核电厂般火力发电厂锅炉产生蒸汽原子发电站核反应堆蒸汽发生器代锅炉产生蒸汽两种情况产生电称火电该系统称火力发电系统
然流水量驱动水轮机时产生电称水电种系统称水力发电系统发电厂称水力发电厂水电站水电系统中必须具定势定数量水流流水轮机势水流动驱动水轮机叶片样水轮机连接发电机发出电章涉水力发电系统容
3水力发电站种类
根水力特性水力发电站分列种：①径流式电站②蓄水式电站③抽水蓄电站④潮汐电站类电站分述：
(1)径流式电站
类电站河流游适宜水库情况利河流流量电站时修建拦河堰坝水位提高保持预定数值允许范围变化单独电站服务者目标服务兼顾电站种方案基种低水头方案仅适枯水季流量值开发常年性河流
径流式电站通常具蓄水库容径流时方利蓄水库容满足时负荷变化设立河道水流量发电需时（非峰荷期间）余水量暂时蓄存拦河建筑物游水库中供峰荷期间
径流式电站诸例子：楠加尔•海德尔运河冈古瓦尔科拉水电站恒河默罕默德•普尔帕特里水电站萨尔达运河萨尔达水电站
灌溉渠道跌水处修建电站属径流式水电站
(2)蓄水式电站
蓄水式电站基足够游蓄水库贮存季风季节干旱夏季径流量提供枯季流量稳定流量种设计方案中水坝拦河修筑电站布置脚巴克拉希陶库德里亨工程等电站位坝游远方种情况电站位水库输水隧道末端输水隧道助压力水电站机械装置连接压力水（迈吞高勒工程）（孔达工程）
电站位坝附时般采低水头发电装置种电站称集中落差式水力发电工程水流坝渠道隧道压力水长距离输送电站时称分散落差式水力发电工程
(3)抽水蓄电站
抽水蓄电站峰荷期间发电非峰荷期间水尾水池抽回蓄水前池供抽水机该系统电站辅助电力驱动类抽水蓄电站协调现火电站水电站
峰荷期间水水库流入水轮机产生电非峰荷期间利电站剩余电尾水池抽水前池较电站较电站补充电样系统中样水量次次重复利没浪费
利15～90米间变化水头已制造出种逆式水泵──水轮机作水轮机作水泵种逆式水轮机高效率运转助减少类电站投资样种电力设备做发电机通电极互换作马达系统中设备非常助提高电力系统负载系数
(4)潮汐电站
潮汐电站发电现代成根海水高潮期升落潮期降原理工作海水日涨落两次次涨潮周期约12时25分潮汐电站利水位涨落效益换言利高低潮间水位差进行发电修建水池隔墙海隔开关隔墙孔洞里安装水轮机发电
高潮期间海水流入水池驱动水轮机发电落潮期间水水池流回海洋安装种两水流方发电特种水轮机组利流回海洋水流进行发电类电站潮差方法国朗斯电站类电站例子里达11米该站拥九台机组装机容量38000千瓦
4根水轮机工作水头水电站（水电系统）分列种：①低水头系统（落差15米）②中水头系统（落差变化15～60米）③高水头系统（落差60米）现分述：
(1)低水头系统
低水头系统水头15米左右径流式电站基属低水头电站该系统中修建拦河坝提高水位电站建拦河坝端建坝游离拦河坝定距离方通引水渠水送电站
(2)中水头系统
中水头系统水头变化15米60米左右该系统基种坝水库系统坝高度低水头高水头系统间该系统某方优点
(3)高水头系统
高水头系统水头60米游蓄水全年水求建造足够高度坝已发展高水头系统坝高已达1800米该系统常见例子印度旁遮普省巴克拉坝印度北方邦里亨坝美国胡佛坝等
高度较天然落差发电类动力开发般例子印度乔喀瀑布美国尼拉瀑布
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