The velocity of the steam is again increased in the subsequent row of nozzles and then again it is allowed to pass onto another set of velocity compounding that brings about a stagewise reduction of velocity of the steam. Steam turbine compounding of steam turbine mechanicaltutorial. Power plant engineering 2171910 government engineering. Steam turbine 1 content chapter description page i purpose 2 ii steam turbine types 2 2. Difference between velocity compounding turbine and. It is the method of absorbing the jet velocity in stages when the steam. There are several methods of reducing the speed of rotor to lower value. The velocity compounded impulse turbine was first proposed by c g. The steam from the boiler is expanded in a nozzle, resulting in the emission of a high velocity. In steam turbines, the overall transformation of heat energy of steam into. Note that the velocity triangles are drawn for the inlet and outlet of.
Steam with high ke exiting the nozzles works on the first row of moving. Velocity triangles are used to illustrate the flow in the bladings of turbo machinery. Now, let this turbine be made up of parsons stages, for which the velocity triangles are symmetrical. Velocity compounded impulse turbine curtis turbine in velocity compounding, all the pressure drop and hence, enthalpy drop of steam take place in a single row of nozzles and the resultant kinetic energy of steam is absorbed by the wheel in a number of rows of moving blades with guide blades in between two such rows. There is a limit till which you can efficiently expand steam in a single stage. Therefore, for good efficiency the blade velocity should be about one. In all turbines the blade velocity is directly proportional to the.
The pressure compounded impulse turbine has the advantages of reduced blade velocity, reduced steam velocity. Fundamentals of steam turbine systems principles of operation the motive power in a steam turbine is obtained by the rate of change in momentum of a high velocity jet of steam impinging on a curved blade which is free to rotate. A steam turbine is a prime mover in which the potential energy of the. The fixed blades act as nozzles and accelerate the steam to a moderate velocity due to the partial pressure drop. Three main types of compounded impulse turbines are. It is composed of three zones of blades, where the first and third zones are moving, while the middle blade stage is stationary. The jet glides over the inside surface and leaves the blade at d. Pressure velocity compounding curtis turbine curtis turbine pressure velocity compounding.
Now a change in velocity for a given mass flow of steam will produce a force which acts to turn the turbine wheel, i. First, row is developed maximum power in this system. In this type, the total pressure drop expansion of the steam take place only in the first nozzle ring. Steam turbine s k mondals chapter 4 c 2 3 4 1 d 3 1 4 2 ies26. The moving blades are running at horizontal direction with a tangential velocity v and v 2 the absolute velocity of steam leaving of moving blades create an angle. Compounding of steam turbine free download as powerpoint presentation. 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. Steam enters the turbine with a high energy content and leaves after giving up most of it. 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. Later rows are developed very small power rather than first row. Compounding of steam turbines this is done to reduce the rotational speed of the impulse turbine to compounding of steam turbines practical limits. The pressure velocity compounding is a combination of the above two types of compounding. The work done in parsons reaction turbine is twice the work done during expansion in the moving blades.
Compounding of steam turbines is necessary 1 to reduce speed of rotor blades to practical limits. Steam velocity decreases in every moving blade, and remain constant in every fixed blade there will be some frictional losses. The steam velocity is increased by each pressure drop and then decreases again in each row of moving blades, as the velocity graph shows. Rateau turbine pdf pressure compounding is the method in which pressure in a steam turbine is made to. Chapter 1 steam turbine principles and design flashcards. The turbine employing this method of compounding may be said to combine many of the advantages of both pressure and velocity staging by allowing a bigger. Twostage steam turbine under variable operational parameters. The steam turbine can also be classified on the following basis. Pressure velocity compounding velocity compounding there are number of moving blades separated by rings of fixed blades. Because the ratio of blade velocity and steam velocity is not optimum. After that it entering a curved blade and leaving the nozzle at c. Due to moisture entrained in the low pressure steam at the exit of lp turbine.
There is change in both pressure and velocity as the steam flows through the moving blades. So what we do is we split the expansion process in a series of turbines. Three methods of compounding in steam turbines a media to. Velocity compounded impulse turbine pdf squarespace. Necessity the steam produced in the boiler has sufficiently high enthalpy when superheated. In the compounding method, the steam jet velocity or the steam pressure is absorbed on stages as it flows over the rotor blades. Steam turbine project gutenberg selfpublishing ebooks. Pressure velocity compounding steam turbine youtube. Rateau 4 condensing turbine 5 required condition 6 normal rated 7 steam flow available tonhr 51 8 n rpm 6000 9 pi bar a 42 10 ti c 400 11 po bar a 0. The impulse turbine, compounding of impulse turbine. With this background, now calculate the generation of velocity in each stage. 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. But for smooth flowing of the steam while existing, it creates an angle of moving blades. The rand woodbury illusionworks pdf pressure compounded impulse turbine is.
Steam turbine free download as powerpoint presentation. Pressure compounding, velocity compounding, pressure. Steam expands from boiler pressure to the condenser in one stage. Oct 28, 2014 methods of reducing rotor speed advantages velocity compounding 1 the arrangement has less number of stages and hence less initial cost 2 the arrangement requires less space 3 the system is reliable and easy to operate 4 the fall of pressure in the nozzle is considerable, so the turbine itself need not work in high pressure surroundings and the turbine housing need not be very strong disadvantages 1 more friction losses due to very high velocity in the nozzles 2 less efficiency. A steam turbine converts the energy of highpressure, high temperature steam. Changes in the flow direction and velocity are easy to understand with the help of the velocity triangles. In this turbine compounding is done for velocity of steam only. Velocity compound impulse turbine curtic turbine arrangement of velocity compounded impulse turbine is shown in fig. In a two stage velocity compounding impulsive turbine cutis turbine, moving and fixed blades are placed alternately. To reduce the high speed, more than one set of blades are used. 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.
This divides the velocity drop across the stage into several smaller drops. Only a portion of the high velocity of steam jet is absorbed by this blade. The chance of steam leakage will be more when compared to velocity compounded turbine. This high velocity strikes the turbines rotor and the speed of the rotor. The invention of parsons steam turbine made cheap and plentiful electricity possible and revolutionized marine transport and naval warfare. Compounding and governing of steam turbines with methods. Now, if the entire energy of the steam is extracted in. Steam is expanded in the nozzle from the boiler pressure to condenser pressure, to a high velocity. Steam turbines their construction, selection and operation pdf. When the steam passed through the nozzles where it is expanded to condenser pressure. The pressure compounded impulse turbine has the advantages of reduced blade velocity, reduced steam velocity friction and equal work among the stages. In this type of turbine steam expands in a set of nozzle from the boiler pressure upto the condenser pressure which converts its pressure energy into kinetic energy. It is the method of absorbing the jet velocity in stages when the steam flows over moving blades.
Explain the necessity of compounding in steam turbine and. Its modern manifestation was invented by sir charles parsons in 1884. Pdf power plant lecture notes chapter4 steam turbine. Pdf steam turbine find, read and cite all the research you need on researchgate.
Compounding of steam turbine mechanics rotating machines. Compounding of steam turbines is the strategies in which energy from the steam is extracted in a number of stages rather than a single stage in a turbine. A velocity compounded impulse stage consist of a row of fixed nozzles followed by two or more rows of moving blades and fixed blades without expansion. The steam turbine is a device for obtaining mechanical work from the energy stored in steam. Change of pressure and velocity ratio in individual stages is studied.
The purpose of compounding in a steam turbine is to. What is steam turbine description and characteristics. Compounding is achieved by using more than one set of nozzles, blades rotors in a series keyed to a common shaft. In the reaction turbine however the stage pressure drop is spread across both the fixed and moving blades. Curtis to solve the problem of single stage impulse turbine for use of high pressure and. In fact, a series of velocity compounded impulse stages is called a pressure velocity compounded turbine. Now, let this turbine be made up of parsons stages, for which the velocity. Steam pressure inside the turbine is literally equal to the atmospheric pressure so there will be no problem of steam leakage. Friction loss is high due to high velocity of steam of nozzle. This steam then impinges upon the moving blades and imparts some energy to. It may be defined as the process of arranging the expansion of steam or the utilization of kinetic energy or both in several rings. Steam turbine is a type of turbomachine which is an assembly of nozzles and. If the steam is expanded only in a single stage from the boiler pressure to the exhaust pressure, its velocity must be extremely high.
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. Unit iii unit iii steam nozzles and turbines flow of steam. Impulse stages may be either pressurecompounded, velocity compounded, or pressure velocity compounded. The steam turbine is used for operating the load which fluctuates with time and the steam turbine is subjected to varying load conditions. Thermalengineeringbyrkrajput chapter19 steam turbine. To study the working of impulse and reaction steam turbine. This method of pressure velocity compounding is used in the curtis turbine. Reaction turbine 2 iii steam turbine operating range 2 3. The method in which energy from steam is extracted in more than single stage is called compounding. If high velocity of steam is allowed to flow through one row of moving blades, it produces a rotor speed of about 30000 rpm. The high velocity steam coming out of the nozzles impinges on the blades. The steam would expand for any pressure ratio you like the problem is with the efficiency. When steam velocity is absorbed in stages, it is called velocity compounding impulse turbine. The modern steam turbine was invented in 1884 by charles parsons, whose first model was connected to a dynamo that generated 7.
These turbines are geared to the crankshaft and utilize the velocity energy of the exhaust gas, which is normally wasted. 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 a reaction turbine compounding can be achieved only by pressure compounding. Compounding of steam turbine turbine turbomachinery scribd.
Velocity drop is arranged in many small drops through many rows of moving blades. Compounding of steam turbines is the strategies in which energy from the steam is extracted in. The compounding is the way of reducing the wheel or rotor speed of the turbine to optimum value. The steam from the boiler is expanded in a nozzle, resulting in the emission of a high velocity jet. It is the combination of the internal energy and the flow. The net result of pressure velocity compounding of steam. The steam is fed through one or several nozzles which do not extended completely.
It is the combination of velocity compounding and pressure compounding. What is velocity and pressure compounding in impulse turbine. Dec 04, 2020 necessity of compounding in steam turbine. Difference between velocity compounding turbine and pressure. This configuration results in velocity reduction as seen in figure 58 and 59. The highpressure steam from the boiler is expanded in nozzles to create a high velocity jet of steam. This is the operating principle of all steam turbines, although the. In all turbines the blade velocity is directly proportional to the velocity of the steam passing over the blade.
In the case of the turbo compound, the highly developed and dependable basic 18 cylinder cyclone engine has been supplemented with a second power producer, consisting of three interchangeable blowdown turbines. When turbine blade velocity is equal to one half the steam velocity, then exiting steam. The impulse wheel carries two or three rows of moving blades. In all turbines the rotating blade velocity is proportional to the steam velocity passing over the blade. This v r2 can be obtain by subtracting the v and v 2 and it create some angle f 1. The axial velocity of the steam at exit from the blades is 164 ms and the blades are symmetrical.
Velocity kinetic energy of steam is converted to useful work in more than one stage. So, steam s pressure drop and it will increase its velocity. Learn easily about velocity compounding and pressure compounding of steam turbines. In velocity compounding of an impulse turbine the expansion of steam takes place in a nozzle or a set of nozzles from the boiler pressure to the condenser pressure. Assume, it creates at an angle a to the tangent of the wheel with a velocity v 1 which is the absolute velocity of steam.
Impulse turbines, reaction turbines, the impulse principle, the reaction principle, the impulse turbine, compounding of impulse turbine. Steam is expanded through a stationary nozzle from the boiler or. This condition will exist if the blade velocity is equal to one half of the steam velocity. Thus the inlet steam velocities to each stage are equal and due to a reduced h as shown in figure 511.
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