energy. The second type is a reaction turbine, which develops power from the combined action of pressure energy and kinetic energy of the water. Reaction turbines can be further divided into several types, of which the principal two are the Francis and the propeller.
水轮机是通过水流动力和压力作用而产生扭矩的机械。它们可以分为两类。一种是冲击式水轮机，它利用高速射流的动能将水能转为机械能。第二种类型是反击式水轮机，它通过水流的压力和动力的综合作用产生动力。反击式水轮机可以进一步被分为几种类型，其中两种基本形式是法兰西斯式水轮机和螺旋桨式水轮机。
9.1 Impulse Turbines 9.1 冲击式水轮机
The impulse turbine is frequently called a Pelton wheel after one of its early developers, Lester Pelton. The potential energy of water flowing from a fore bay through a penstock is transformed into kinetic energy in a jet or jets of water striking the single or double bowl-shaped buckets of the impulse runner. The jet of water strikes the runner tangentially to a circular line of the pitch diameter of the buckets and acts at atmospheric pressure.
冲击式水轮机通常被叫做佩尔顿式水轮机，以其早期开发者之一的Lester Pelton的名字命名。流过压力管道的前池水流的势能被转换为射流的动能，作用在冲击转轮的单个或两个碗状的斗叶上。射流沿着斗叶的节圆直径的圆圈切线防线并以大气压力作用在转轮上。
The water striking the buckets of the runner is regulated through the use of a bulb-shaped needle in a nozzle. The position of the needle determines the quantity of water striking the runner. A deflector arrangement in more sophisticated designs is used to direct the water away from the turbine buckets when there is a load rejection to reduce hydraulic torque on the generator.
作用在转轮斗叶上的水流通过在喷嘴中的灯泡形状的针杆来调控。针杆的位置确定了作用在转轮上的水量。当要发生减少发电机液压扭矩的甩负荷时，要用一个设计更加复杂的偏流器装置将水流从水轮机斗叶处引离。
Impulse turbines are usually high head units and used at locations where heads 1000ft or more. They are also used at lower heads for small-capacity units. The ratio of the wheel diameter to the spouting velocity of the water determines the applicability of an impulse turbine.
反击式水轮机通常是高水头机组，并应用在水头在1000英尺或更高的位置。它们也应用在小容量机组的低水头情况。水轮机直径与射流速度的比值决定了反击式水轮机的适用性。
The impulse or Pelton turbines have advantages for high-head installations, for installations with abrasive matter in the water, and for long-penstock installations where water hammer is critical. Some impulse runners are made with individually bolted buckets and others are solid cast. Double-overhung installations are made with a generator in the center and the runners positioned in the two overhanging ends of a single shaft.
反击式或佩尔顿式水轮机在高水头安装、存在水中磨损问题的安装和在水击很重要的长压力管道安装的情况中有优势。一些反击式水轮机被制作成单独带有螺栓连接的斗叶形式，另外一些则为整体铸造。双悬臂式安装中发电机在中心且转轮定位在单轴两个的突出端。
Another design of an impulse turbine is the Turgo Impulse turbine invented by Eric Crewdson of Gilkes and Co. Ltd. Of England in 1920. The turbine is designed so that the jet of water strikes the buckets at an angle to the face of the runner and the water passes over the buckets in an axial direction before being discharged at the opposite side. The buckets are constrained by a rim on the discharge side of the runner. The advantage claimed for the type of
unit is that a larger jet can be applied, resulting in a higher speed with a comparatively smaller machine.
冲击式水轮机的另外一种设计是由Gilkes的Eric Crewdson和英格兰公司在1920年发明的Turgo冲击式水轮机。水轮机的设计为射流以与转轮面成某一角度作用在斗叶上，且水流在在对面排出前以轴向通过斗叶。斗叶受到转轮出水侧的边缘的限制。这种形式机组的优点是可以应用一个更大的喷口，从而得到一个更高的速度和一个相对较小的机械。
9.2 Mixed-Flow Reaction Turbines 9.2 混流式反击水轮机
In the operation of reaction turbines, the runner chamber is completely filled with water and a draft tube is used to recover as much of the hydraulic head as possible. Three conditions of flow determine the designs of reaction wheels. If the flow is perpendicular to the axis of rotation, the runner is called a radial-flow turbine. An early type of radial-flow machine was the Fourneyron turbine, in which water flow was radially outward. Many early reaction wheels were radially inward-flow runners. If the water flow is partially radial and partially axial, it is called a mixed-flow turbine. The most common mixed-flow turbine was developed by James B. France and bears his name. Francis turbines have a crown and band enclosing the upper and lower portions of the buckets, while a propeller-type runner has blades projecting from the hub.
在反击式水轮机的运行中，水流完全充满转轮室，且尾水管被用来回收尽可能多的水头。三种水流条件确定了反击式水轮机的设计。如果水流与转动轴向相垂直，那么该转轮被称为径向流动水轮机。径向流动机械的早期类型是Fourneyron水轮机，其中水流径向流出。很多早期的反击式水轮机都是径向入流式水轮机。更常用的混流式水轮机是James B. France开发的并以他的名字命名。弗兰西斯水轮机有一个上冠和下环封装着斗叶的上部和下部部分，而一个螺旋桨式转轮有从轮毂伸出的叶片。
Another type of mixed-flow reaction turbine is the diagonal turbine or Deriaz turbine. The runner blades are set at an angle around the rim of a conical hub. There is no band around the blades. The blades are adjustable and can be feathered about an axis inclined at 45°to the axis of the shaft. The units have been developed for use as reversible pump turbines. They have the advantage of maintaining good efficiency over a wide range of flow, higher-strength attachment of the runner blades to the turbine hub, and the arrangement allows higher permissible operating heads than an axial-flow Kaplan or adjustable blade unit.
另外一种混流式水轮机是斜流式水轮机或Deriaz水轮机。转轮叶片被以一定的角度环绕着锥形轮毂而设置。叶片周围没有带子。叶片可以调整并以与转轴轴线45度的倾角顺桨。该机组已经被开发为可逆式水泵水轮机。它们的优势是在较宽水流范围内保持良好的效率，转轮叶片与水轮机轮毂之间更高强度的连接，并且该设备可以在比轴流Kaplan或可调整叶片机组的更高的水头下运行。
9.3 Axial-Flow Reaction Turbines 9.3 轴流式反击水轮机
The direction of flow for most propeller turbines is axial, parallel to the axis of rotation; thus they are classified as axial-flow turbines. Early developments utilized propeller unit vertical shafts. More recent developments utilize a horizontal shaft. Propeller turbines can have the blades of the runner rigidly attached to the hub; these are called fixed-blade runners. The blades of the runners can also be made adjustable so that the turbine can operate over a wide range of flow
conditions at better efficiencies. A propeller turbine with coordinated adjustable blades and gates is called a Kaplan turbine after its inventor, Viktor Kaplan. A propeller turbine with adjustable blades and fixed gates is sometimes referred to as semi-Kaplan. The automatic coordination of the movement of runner blade and adjustment of the gate positions provides optimum hydraulic performance and has made such units more efficient for variable flow and low-head applications. 大多数螺旋桨式水轮机的水流方向是轴向，与转动轴向方向相平行；因此它们被分类为轴流式水轮机。早期开发利用螺旋桨机组垂直轴。较近的开发使用水平轴。螺旋桨式水轮机可能有刚性地连接到轮毂的转轮叶片；这些被称为固定叶片式转轮。转轮叶片也可以被制成可调式，这样水轮机就可以以更好的小路在一个更宽的水流条件下运行。配有协调可调式叶片和导水叶的螺旋桨式水轮机被以其发明者Viktor Kaplan的名字命名为卡普兰水轮机。配有可调整叶片和固定导水叶的螺旋桨式水轮机被称为半卡普兰式。转轮叶片运动的自动协调和导水叶位置调整提供了最佳水力性能，且对于可变化水流和低水头应用情况使得这样的机组效率更高。
Recent developments utilizing axial-flow runner have included arranging the runners in specialized configurations sometimes referred to as tubular-type turbines. Basically, the units are arranged to minimize the change in direction of flow, to simplify the mounting of the generator, and to provide the best hydraulic characteristics for the water moving through the hydropower plant. TUBE turbine is a registered trademark of the Allis-Chalmers Corporation for a type of unit in which the generator is mounted outside the water passage with direct or gear drive connection to the generator. These units are now being produced in standardized sizes.
使用轴流式转轮的近期开发已经包括了在专门构型中的转轮，有时被称为贯流式水轮机。基本上，这样的机组布置尽量减少水流方向的变化，简化发电机的安装，使水流流过电厂时具有最好的水力特性。贯流式水轮机是Allis-Chalmers有限公司的机组类型的注册商标，其中发电机被安装在流道外，流道与发电机直接或通过齿轮传动相连。这些机组现在正以标准化型号生产。
Bulb hydropower units include propeller turbines that drive a generator encapsulated and sealed to operate within the water passage. The generator design is such that all mechanisms are compressed into a diameter that is approximately equal to the propeller diameter. The very compact nature tends to provide some advantages in powerhouse design and in pattern of water flow. It does require special cooling and air circulation within the generator bulb. This type of unit is being manufactured by several companies.
灯泡水电机组包括封装并在流道内运行的驱动发电机的螺旋桨水轮机。发电机被设计成所有的机械的直径都被压缩成与螺旋桨直径大致相等。这样非常紧凑的特性在厂房设计和水流形式中较有优势。它确实需要在发电机灯泡室内特殊的冷却和空气循环。有几家公司可以制造这种机组。
10. Turbine Cases 10. 水轮机蜗壳
A turbine case may be defined as a water passage surrounding a turbine. Its primary function is to distribute uniformly the water around the stay ring, the wicket gates, and the runner. To vertical-shaft turbines the water is conveyed from one side, so their cases are made
spiral in shape with the outer wall completely or partially embracing the staying ring. Quite appropriately, turbine cases of this configuration have come to be known as spiral cases. The basic parameter of a spiral case is the volute angle Фvol made by the planes passed through the throat and the small end.
水轮机蜗壳可以被定义为环绕水轮机的流道。其首要功能是均匀地分配环绕座环、导水叶和转轮的水流。对于垂直轴水轮机，水流从一侧传输，因此其蜗壳被制成螺旋状且其外墙完全或部分地环抱着座环。这样配置的蜗壳很合适地被称作螺旋型蜗壳。螺旋型蜗壳的基本参数是蜗壳的包角Фvol，即从蜗壳进口到蜗壳末端的平面角度。
There exist two basic types of spiral cases, namely concrete cases with a volute angle of 180°to 270° and metal cases with a volute angle of 345° to 360°. Concrete spiral cases are used under heads up to 80m. They may be symmetrical in radial cross section or have an extended lower or upper portion. When the head on the turbine exceeds 50m, concrete cases are lined with metal. As a rule, concrete cases are used for adjustable-blade propeller (Kaplan) turbines, although, on some rare occasions, they are employed for low-head Francis turbines.
螺旋型蜗壳有两种基本类型，即角度为180°到 270°的混凝土蜗壳，以及角度为345°到 360°的金属蜗壳。混凝土螺旋型蜗壳应用于水头低于80米的情况。它们可以是径向横截面对称的或有一个延长下部或上部结构。当水轮机水头超过50米时，混凝土蜗壳就用钢板做内衬。按规定，混凝土蜗壳被用于可调整叶片式螺旋桨（卡普兰）水轮机，尽管在很少的情况下，它们也用于低水头的弗兰西斯水轮机。
For large vertical-axis turbines, semi-spiral or reinforced concrete spiral cases are used. The advantage of the semi-spiral case is lower head loss. The head loss is also lower for an open-flume arrangement than for more sophisticated spiral casings. For large-, medium-, and high-head turbines the spiral case is usually fabricated from steel plate. Older installations sometimes had cast steel or cast iron spiral cases. The water passageways are different for various types of turbines.
对于大型垂直轴水轮机，要使用半螺旋或钢筋混凝土螺旋型蜗壳。半螺旋型蜗壳的优点是低水头损失。开放式水槽装置比更加复杂的螺旋型蜗壳的水头损失也更低。对于大型、中型和高水头的水轮机，螺旋型蜗壳通常用钢板制就。早期的安装有时用铸钢或铸铁螺旋型蜗壳。该流道不同于很多型式的水轮机。
Metal spiral cases are an excellent choice for Francis and high-head Kaplan turbines operating under heads ranging from 40 to 500 m. They are traditionally circular in cross section throughout, and are made of welded plate steel, or under higher heads, of cast iron or cast steel. 对于在在40到500米之间水头下运行的弗兰西斯和高水头卡普兰水轮机来说，金属螺旋型蜗壳是一个非常好的选择。它们通常在全断面上都是圆形，并用焊接钢板制就，或者在更高的水头下用铸铁或铸钢制就。
Water velocities and uniformity of flow are primary engineering concerns. Water velocities in the spiral casing as a rule of thumb, according to Brown (1970), should, for low-specific-speed turbines, be approximately
??=0.14 2???? （1）
and for high-specific-speed turbines,
??=0.20 2???? （2）
where v= water velocity at cross sections normal to the radius and at entrance to spiral case, ft/sec; h=design net head, ft.
水流速度和均匀度是设计的首要考量。根据Brown (1970)的经验，对于低比转速的水轮
机，在螺旋型蜗壳内的水流速度应大致为：
??=0.14 2???? （1）
且对高比转速水轮机：
??=0.20 2???? （2）
其中v=垂直径向断面及螺旋型蜗壳进口处的水流速度，英尺/秒；h=净设计水头，英尺。
Generally, there should be no deceleration of water as it flows from the penstock to and through the spiral case. Special requirements as to shape, dimensioning, and velocity are needed for different kinds of turbines.
通常来说，当水流从压力管道流向并通过螺旋型蜗壳时，水流速度不应该减小。对于不同类型的水轮机来说，其所需的形状、尺寸和速度都有特殊需求。
11. Draft Tubes 11. 尾水管
Draft tubes are the final components of the water passages of hydropower plants. A draft tube may serve the double purpose of (1) allowing the turbine to be set above tailwater level, without loss of head, to facilitate inspection and maintenance, and (2) regaining, by diffuser action, the major portion of the kinetic energy delivered to it from the reaction-turbine runner.
尾水管是水电站水流通道的最后部分。尾水管可以起到双重目的（1）允许将水轮机设置在尾水位之上，不产生水头损失，以便于检修和维护，以及（2）通过扩散作用重新获得从反击式水轮机转轮传到其中的大部分动能。
Draft tubes usually consists of steel sections which change shape from circular to rectangular in cross section. The sections expand in cross-sectional area to decrease the water velocity with a minimum occurrence of vortexes and maintain a nearly uniform velocity at any section. The draft tube is usually formed in reinforced concrete. The principal engineering problems are determining the water velocity at the exit to the draft tube and determining the controlling dimensions of the draft tube.
尾水管通常包括钢结构，其横截面形状从圆形变为矩形。该面积在横截面扩大，以减小水流速度并将涡流发生降至最低，并在任意断面维持一个接近均匀的速度。尾水管通常用钢筋混凝土制成。主要的设计问题是确定出口进入尾水管处的水流速度，以及确认尾水管的控制尺寸。
As regards the shape of a draft tube, the best performance could be obtained with the conical tube. Unfortunately, its length would be great in terms of throat diameter, and therefore, for large machines it would require a considerable amount of excavation. For this reason, it is used only relatively small machines, the draft tube for large vertical-shaft turbines being mostly of the elbow construction. In fact, the elbow type of tube is now used with most turbine installations. With this type, the vertical portion begin with a conical section which gradually flattens in the elbow section of elaborate shape and then discharges horizontally through substantially rectangular diffuser section to the tailrace. One or two vertical piers are placed in the horizontal portion of the tube for structural reasons. The basic dimension of any draft tube is the height h. Obviously, the greater the height of the draft tube, the better the turbine