Pdf power plant lecture notes chapter2 steam power plant. The exit steam from one turbine is made to enter the nozzle of the succeeding turbine. The energy available at inlet of turbine is partially kinetic energy and partially pressure energy. In fact, a series of velocitycompounded impulse stages is called a pressurevelocity.
The steam from the boiler passes through the first nozzle ring where its pressure drops and velocity increases. These jets contain significant kinetic energy, which is converted into shaft rotation by the bucketlike shaped rotor blades. The leaving velocity and exhaust loss from a steam turbine may be likened to the tailrace loss of a water wheel. Unit iii steam nozzles and turbines flow of steam through nozzles, shapes of nozzles, effect of friction, critical pressure ratio,supersaturated flow. There are several methods of reducing the speed of rotor to lower value. Each of the simple impulse turbines would then be termed a stage of the turbine. Applications of steam turbines power generation transport 4. Difference between velocity compounding turbine and.
The expansion takes place through a series of fixed blades nozzles, that orient the steam flow into high speed jets. Compounding of steam turbines is the method in which energy from the steam is extracted in a number of stages rather than a single stage in a turbine. Impulse turbines are simple devices where the steam expands in or through the nozzle, and the heat released through the pressure drop associated with the nozzle or comparable device imparts velocity to the steam. In general, a steam turbine is a rotary heat engine that converts thermal energy contained in the steam to mechanical energy or to electrical energy. Compounding of steam turbines is the strategy in which energy from the steam is extracted in a.
A multiple system of rotors are connected in series keyed to a common shaft and the steam pressure or velocity is absorbed in stages as it flows over the blades. The impulse turbine is the simplest type of turbine. The steam velocity is increased by each pressure drop and then decreases again in each row of moving blades, as the velocity graph shows. There are two classical types of turbine stage designs. The rotor is turned by steam impinging against attached vanes or blades on which it exerts a force in the tangential direction. Oct 28, 2016 velocity compounding of steam turbinesquickly. A steam turbine consists of a rotor resting on bearings and enclosed in a cylindrical casing. This is a combination of pressurevelocity compounding. Steam turbines their construction, selection and operation pdf. Steam turbine working principle and types of steam turbine. Therefore, for good efficiency the blade velocity should be about one. Neglect initial velocity of steam and assume isentropic expansion in the nozzle. Rocket turbine design emphasizes power density, because of the overriding concern for mass saving.
Its modern manifestation was invented by charles parsons in 1884 the steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency from the use of multiple stages in the expansion of the steam, which results. The velocity of steam entering a simple impulse turbine is, and the nozzle angle is 20o. It is designed to efficiently extract work out of high pressure steam. The chance of steam leakage will be more when compared to velocity compounded turbine. In a steam turbine, highpressure steam from the boiler expands in a set of stationary blades or vanes or nozzles. This highvelocity strikes the turbines rotor and the speed of the rotor. Cross compound steam turbine arrangement compounding is the splitting up, into two or more stages, of the steam pressure or velocity change through a turbine. Only a small fraction of the overall pressure drop available in a turbine can be extracted in a single stage consisting of a set of stationary nozzles or vanes and moving blades or buckets. Steam velocity decreases in every moving blade, and remain constant in every fixed blade there will be some frictional losses velocity of steam increase in every nozzle fixed blade. The high pressure hp turbine see figure 1 is the first main engine turbine to receive steam from the main steam system. Also, it is hard to design and fabricate blades which can tolerate such high velocities. Rateau turbine pdf pressure compounding is the method in which pressure in a steam turbine is made to. In order for the steam to give up all its kinetic energy to the moving blades in an impulse turbine, it should leave the blades at zero absolute velocity. Pressure compounding, velocity compounding, pressurevelocity compounding, the impulse.
In its simplest form, a steam turbine consist of a boiler steam generator, turbine, condenser, feed pump and a variety of auxiliary devices. This is done to protect the casing and rotor from higher pressure and temperature conditions. Impulse stages may be either pressurecompounded, velocity compounded, or pressure velocity compounded. Pressure compounding it is used to solve the issues of high blade velocity in the single stage impulse turbine. It is the process by which rotor speed come to its desired value. Difference between velocity compounding turbine and pressure compounding turbine mecholic no comments. With this background, now calculate the generation of velocity in each stage. Now, let this turbine be made up of parsons stages, for which the velocity triangles are symmetrical. Power plant lecture notes chapter2 steam power plant cycles. It is the method of absorbing the jet velocity in stages when the steam flows over moving blades. In all turbines the blade velocity is directly proportional to. Division of steam flow indicates whether the steam flows in just one direction or if it flows in more than one direction. A steam turbine is a device that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft.
In 1924 krupp built the steam turbine locomotive t18 001, operational in 1929, for deutsche reichsbahn. Turbine classification in order to better understand turbine operation, five basic classifications are discussed. A steam turbine locomotive engine is a steam locomotive driven by a steam turbine. The thermal energy contained in the steam is converted to the mechanical energy by expansion through the turbine. Efficiency, while clearly a consideration, takes a less prominent role than in aircraft turbine design. To improve the thermal efficiency of any power plant, generally high pressure near about 120 to 140 bar, high temperature and high velocity steam is used. Cross compound steam turbine arrangement for marine use.
A highvelocity steam is coming from the nozzles and it strikes the rotating blades which are fitted on a disc mounted on a shaft. So, steams pressure drop and it will increase its velocity. The impulse turbine, compounding of impulse turbine. Thus a steam turbine could be viewed as a complex series of windmilllike arrangements, all assembled on the same shaft. Three main types of compounded impulse turbines are. Following figures show steam process in steam turbine.
The first hp stage of a turbine, where it is desired to give a large pressure drop to the first row of nozzles, sometimes incorporates two impulse stages on the same wheel. Compounding of steam turbine mechanics rotating machines. The energy available at inlet of turbine is kinetic energy. Pressure velocity compounding curtis turbine curtis turbine pressure velocity compounding. The pressure velocity compounding is a combination of the above two types of compounding. The steam produced in the boiler has got very high enthalpy. The mean peripheral velocity of blade is 400 ms and the blades are symmetrical. Steam turbines velocity compound has a few disadvantages which include high friction losses due to high steam velocity. As a velocity compounded stage uses approximately the same heat drop as four impulse stages, it is used to provide a shorter and cheaper turbine, although with some sacrifice in efficiency.
In a twostage velocitycompounded impulse turbine, the steam issues from the nozzles at a speed of 800 msec. Steam turbines are mainly classified into two types. Pressure compounding of an impulse turbine is the use of a number of stages of nozzle and blade to reduce progressively the steam pressure. Impulse and reaction principles, compounding, velocity diagrams for simple and multistage turbines, speed regulationsgovernors and nozzle governors. In the reaction turbine however the stage pressure drop is spread across both the fixed and moving blades. If the steam is to enter the blades without a shock, what will be the blade angles. It is the combination of the internal energy and the flow. Also, if you observe, the moving buckets in impulse turbine are designed to get pushed by the steam. If the tailrace runs downhill, there is a corresponding loss of headthe wheel setting should have been lower. It may be defined as the process of arranging the expansion of steam or the utilization of kinetic energy or both in several rings. A multiple system of rotors are connected in series keyed to a common shaft and the steam pressure or velocity is absorbed in stages as it flows over. Now, let this turbine be made up of parsons stages. Unlike with reciprocating engines, for instance, compression, heating and expansion are. The first steam turbine rail locomotive was built in 1908 for the officine meccaniche miani silvestri grodona comi, milan, italy.
Steam turbine convert a part of the energy of the steam evidenced by high temperature and. A high velocity steam is coming from the nozzles and it strikes the rotating blades which are fitted on a disc mounted on a shaft. The compounding is the way of reducing the wheel or rotor speed of the turbine to optimum value. Pdf compounding of steam turbine lecture slide 04 md. A steam turbine is a device that extracts thermal energy from pressurized steam and uses it to one of the founders of the modern theory of steam and gas turbines was aurel stodola, a slovak physicist and engineer and professor a major challenge facing turbine design is reducing the creep experienced by the blades. This tends to favor low reaction turbines and when multistaging, velocity compounding over pressure compounding. In steam turbine compounding there are three major forms. In all turbines the rotating blade velocity is proportional to the steam velocity passing over the blade. Are you a person willing to work in industrial sectors then logon to steam turbine is a device that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft. Steam turbine is a mechanical device, which is used for converting thermal energy of steam to mechanical energy. Thermal engineering pdf of rk rajput for mechanical.
Impulse stages may be either pressurecompounded, velocitycompounded, or pressurevelocity compounded. Pdf power plant lecture notes chapter2 steam power. This tends to favor low reaction turbines and when multistaging. There is a reduced amount of work performed in the lowpressure stages. Difference between velocity compounding turbine and pressure. Are you a person with a degree in mechanical or technical engineering. The rand woodbury illusionworks pdf pressure compounded impulse turbine is also called as rateau turbine, after its.
What is velocity and pressure compounding in impulse turbine. This is a combination of pressure velocity compounding. As the steam turbine spins the generator spins and creates electricity. Fewer number stages, and hence the turbine length is short, require less space. Compounding of steam turbine is used to reduce the rotor speed. Steam turbine turbine steam free 30day trial scribd. Steam process in steam turbine steam entrance to turbine through governor valv e to control steam capacity and therefore to control turbine speed. In fact, a series of velocity compounded impulse stages is called a pressure velocity compounded turbine. In contrast to water turbines where the total head is extracted in a single runner see above, the steam velocities obtained from the enthalpy drop between steam. This high velocity steam produces dynamic pressure on the blades in which blades and shaft both start to rotate in the same direction. Each stage comprises its ring of nozzle and blades. Pressure compounding, velocity compounding, pressure velocity compounding, the impulse. The method in which energy from steam is extracted in more than single stage is called compounding.
Boyce, in combined cycle systems for nearzero emission power generation, 2012. Lecture series on steam and gas power systems by prof. The pressurevelocity compounding is a combination of the above two types of compounding. Figure 4 shows steam process in enthalpy against entropy diagram of curtis and single row rateau turbine. Feb 19, 2017 lecture series on steam and gas power systems by prof. What is steam turbine description and characteristics. To improve the thermal efficiency of any power plant, generally high pressure near about 120 to 140 bar, high temperature and highvelocity steam is used. The hp turbine is a pressure velocity compounded, single axial flow, noncondensing impulse turbine. Steam turbine compounding of steam turbine mechanicaltutorial. Therefore, for good efficiency the blade velocity should be about. Steam expands from boiler pressure to the condenser in one stage.
This condition will exist if the blade velocity is equal to one half of the steam velocity. Let this be the entry velocity of steam in a given stage refer to comment no. Neglecting the friction effects on the blades, calculate the tangential. Three methods of compounding in steam turbines a media to. If the tailrace runs level there is the loss of velocity head only, which may be small if the crosssectional area is gen.
This highvelocity steam produces dynamic pressure on the blades in which blades and shaft both start to rotate in the same direction. Velocity compounding is accomplished in the first two stages by two rows of moving blades between which is placed a row of stationary blades that reverses the direction of steam flow as it passes from the first to the second row of moving blades. The fixed blades act as nozzles and accelerate the steam to a moderate velocity due to the partial pressure drop. Compounding is achieved by using more than one set of nozzles, blades, rotors, in a series, keyed to a common shaft. Working principle of steam turbine depends on the dynamic action of steam. The velocity compounded impulse turbine was first proposed by c g curtis to solve the problem of single stage impulse turbine for use of high pressure and. Lets say you have superheated steam coming out of the boiler at 70 bar, which is suppose to drive a steam turbine. Pressure compounding, velocity compounding, pressurevelocity. Pdf power plant lecture notes chapter4 steam turbine. In noncondensing turbines or backpressure turbines, steam exhausts at a pressure greater than. Definition a steam turbine is a prime mover in which the potential energy of the steam is transformed into kinetic energy and later in its turn is transformed into the mechanical energy of rotation of the turbine shaft. Design, applications, and rerating model steam turbines. Difference between the impulse and reaction turbine.
Steam turbine free download as powerpoint presentation. Velocity of steam is low when compared to velocity compound turbine. Type of compounding refers to the use of blading which causes a series of pressure drops, a series of velocity drops, or a combination of the two. A turbine that expands the steam in two or more sets of nozzles in series, each set having velocity compounded blades to recieve the steam issuing from the nozzles is called. This high velocity strikes the turbines rotor and the speed of the rotor. Pressurevelocity compounding curtis turbine curtis turbine pressurevelocity compounding. Simple impulse turbine that if the expansion of steam from the boiler pressure to condenser pressure takes place. When the steam passes through the moving blades of steam turbine the velocity drops but the pressure remains the same when the steam exhaust outside the steam turbine the fact that the pressure does not drop across the moving blades of steam turbine, it is. This steam then impinges upon the moving blades and imparts some energy to. So, steam s pressure drop and it will increase its velocity.544 733 426 562 506 1373 1226 177 689 1469 744 262 8 642 1514 663 1544 1167 1414 1465 1497 1061 800 1359 47 1065 959 586 1538 1129 828 508 192 672 172 871 1442 977 285 850 1299 1349 652 275 1158 340