In each stage there is one ring of fixed nozzles and 34 rings of moving blades with fixed blades between them. In simple terms, the velocity compounded curtis type single stage impulse is easier to overspeed, while the reaction turbine is less likely to overspeed. Velocity compounding of the impulse turbine 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 temperature steam. Curtis to solve the problem of single stage impulse turbine for use of high pressure and. The velocity of the steam exiting the nozzles is the major factor in the tendency to accelerate the turbine rotor. Compounded impulse turbine from the impulse principle the blade speed in a single impulse turbine is nearly half the incoming absolute steam velocity. 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. After that it entering a curved blade and leaving the nozzle at c. The inlet angle of the reaction stages are the same as the nozzle angles of the impulse stage 3. When the jet of water strikes at the turbine blade with full of its speed, it generates a large force which used to rotate the turbine. In an impulse turbine, the degree of reaction is zero, meaning that the. 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 temperature steam. 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. Tworows of a velocity compounded impulse turbine have a mean blade speed of 150 ms and nozzle velocity of 675 ms.
This configuration results in velocity reduction as seen in figure 58 and 59. Due to pressure drop in moving blades of reaction turbine they are more prone to leakages. In a twostep pressure velocity compounded turbine, the first pressure drop occurs in the first set of nozzles, the resulting gain in the kinetic energy is absorbed successively in two rows of moving blades before the second pressure drop occurs in the second set of nozzles. 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. To reduce the high speed, more than one set of blades are used.
In an impulse turbine, the degree of reaction is zero. The force is depends on the time interval and velocity of jet strikes the blades. The velocity of steam at inlet to a simple impulse turbine is ms, and the nozzle angle is 20 o. Compounding is achieved by using more than one set of nozzles, blades rotors in a series keyed to a common shaft. Thats why pressure velocity compounded method need less stage as compared to the other method. Pi inlet pressure, pe exit pressure, vi inlet velocity, veexit velocity. Pressure and velocity curve for this turbine is shown in fig. The nozzle angles for the first two impulse turbines are the same. Pressure compounding turbine velocity kinetic energy of steam is converted to useful work in more than one stage. A pressure velocity compounded turbine allows a bigger pressure drop in each stage.
Solving numerical problem in velocity compounded impulse turbine. Curtis to solve the problems of a singlestage impulse turbine for use with high pressure and temperature steam. Various methods of loss calculation were explored in the search for a. Steam expands from boiler pressure to the condenser in one stage. Curtis to solve the problems of a singlestage impulse turbine for use with high pressure and. Compounding of impulse turbine compounding is defined as to reduce more than one set of blades are used,this is called compounding. 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. Apr 25, 2016 impulse turbine works on the basic principle of impulse.
Define blade efficiency and derive an expression for maximum blade efficiency for single stage impulse steam turbine. The degree of reaction of a turbine stage stator nozzles plus rotor blades is the fraction of the fluid static enthalpy drop which occurs in the rotor see section 2. Explain working principle of pressure compounding with neat sketch. The rings of moving blades are separated by rings of fixed blades. Steam turbine compounding of steam turbine mechanicaltutorial. The cylinders are relatively unaware of the existence of the tur. In impulse there is no change in the pressure of the steam as it passes through the moving blades. Pdf power plant lecture notes chapter4 steam turbine. This v r2 can be obtain by subtracting the v and v 2 and it create some angle f 1.
The velocity compounded impulse turbine was first proposed by c g. Difference between velocity compounding turbine and. Classification, single stage impulse turbine, condition for maximum blade efficiency, stage efficiency, need and methods of compounding, multistage impulse turbine, expression for. The pressure velocity compounding is a combination of the above two types of compounding. Compounding of steam turbines this is done to reduce the rotational speed of the impulse turbine to compounding of steam turbines practical limits. Difference between velocity compounding turbine and pressure. The velocity of steam entering a simple impulse turbine is, and the nozzle angle is 20o. The impulse type of turbine is used in hydropower plants for the generation of electricity. Various methods of loss calculation were explored in the search for a method sufficiently accurate to. Pressure energy of steam at turbine input gradually extracted in multiple steps.
Due to surface friction created on the discs of an impulse turbine as the disc rotates in steam atmosphere. Pressure compounding, velocity compounding, pressure velocity compounding, the impulse. Chaplin encyclopedia of life support systems eolss blades some potential energy is converted into kinetic energy but not as much as in the impulse turbine. Please help improve it or discuss these issues on the talk page. Three methods of compounding in steam turbines a media to. There is less of a drop in pressure and consequently a smaller increase in velocity. Large number of stages and it is bulky, require more space. Steam with high ke exiting the nozzles works on the first row of moving. The mean peripheral velocity of blade is 400 ms and the blades are symmetrical. What are the advantages and disadvantages of velocity compounded impulse turbine. The relative velocity w remains unchanged in a pure impulse turbine, except for.
Each stage consists of rings of fixed and moving blades. The velocity coefficient for the rotors and stator is c r 0. As the velocity is absorbed in more than one row of moving blades, the blade speed is less than if the velocity was all absorbed in one row of blades. Difference between impulse turbine and reaction turbine. A velocity compounded impulse turbine is shown in figure onestage velocity compounded impulse turbine curtis turbine the decrease in the absolute velocity of the fluid across the two rotor blade rows r 1 and r 2 is due to the energy transfer. Advantages and disadvantages of velocity compounded impulse. In fact, a series of velocity compounded impulse stages is called a pressure velocity compounded turbine. But for smooth flowing of the steam while existing, it creates an angle of moving blades. The moving blades are keyed to the turbine shaft and the fixed blades are fixed to the casing. Compounding is the splitting up, into two or more stages, of the steam pressure or velocity change through a turbine.
Pressure compounding, velocity compounding, pressure velocity compounding, the impulse reaction turbine, flow of steam through impulse turbine, tangential. Hence in velocity compounded turbines flow passage is from fixed nozzles to multiple rows of moving blades alternating with fixed blades. So, steams pressure drop and it will increase its velocity. Pressure compounding of an impulse turbine is the use of a number of stages of nozzle and blade to reduce progressively the steam pressure. The following particulars refer to a tworow velocity compounded impulse wheel. What is impulse turbine and reaction turbine definition. Velocity compounded impulse turbine pdf squarespace. 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. There is change only in the velocity of the steam flow when the steam strikes the impulse blade through the nozzle inlet. What is velocity and pressure compounding in impulse turbine. The reaction turbine operates on newtons third law of motion. Velocity compound impulse turbine curtic turbine arrangement of velocity compounded impulse turbine is shown in fig. This type of compounding is known as the velocity compounding and the blade and nozzle arrangement for a velocity compounded impulse turbine is shown.
When steam velocity is absorbed in stages, it is called velocity compounding impulse turbine. This high velocity strikes the turbines rotor and the speed of the rotor. The fixed blade angles of the two reaction turbines equal to the given inlet angle. In the compounding method, the steam jet velocity or the steam pressure is absorbed on stages as it flows over the rotor blades. Get answer a two wheel velocity compounded steam turbine. Lets start with impulse turbine first, impulse turbine. Pressure velocity compounding in this lecture we only study about what is advantages and disadvantages of velocity. This results in lower or more acceptable steam flow speeds and a better turbine efficiency. If the steam is to enter the blades without a shock, what will be the blade angles. Advantages and disadvantages of velocity compounded. Understanding and preventing steam turbine overspeeds by. An impulse turbine has fixed nozzles that orient the steam flow into high speed jets.
Velocity compound impulse turbine can increase stage power even more using velocity compounding multiple nozzlerotors in series example, tworow compounded impulse turbine all p in 1st nozzle 1st rotor exits with high. 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. Velocity of steam is low when compared to velocity compound turbine. The curtis turbine is a compound impulse turbine, the com pounding being both for pressure and velocity.
Compounding is done to reduce the rotational speed of the impulse turbine to. Another impulse turbine is the pressure compound or ratteau turbine. Impulse turbine efficiency calculation methods with organic. Velocity drop is arranged in many small drops through many.
The project was based on an existing impulse turbine, a onestage turbine set in an organic rankine cycle with the working fluid being r245fa. Other impulse turbines are known as curtis, zoelly and. Fewer number stages, and hence the turbine length is short, require less space. Simple indicates an elementary turbine without complications such as velocity compounding.
The velocity compounding of the impulse turbine the velocity compounded impulse turbine was first proposed by c. In a delaval turbine, steam issues from the nozzle with a velocity of 1200msec, the nozzle angle is 200, the mean blade velocity is 400msec and the inlet and outlet of angles are equal. If high velocity of steam is allowed to flow through one row of moving blades, it produces a rotor speed of about 30000 rpm. If the flow of steam through the nozzles and moving blades of a turbine.
Draw the velocity diagram of impulse turbine and find the work done on the blade, blade efficiency derive the expression for condition for maximum efficiency of an impulse turbine. Steam velocity at nozzle exit 600 ms nozzle angle 16 o mean blade velocity 120 ms exit angles. This turbine used to rotate the generator, which produces electric power. Velocity compounded impulse turbine numerical problem. Impulse turbine efficiency calculation methods with. Constructional details, compounding of steam turbines 02 hour. A two wheel velocity compounded steam turbine has the. In this type, the total pressure drop expansion of the steam take place only in the first nozzle ring. It is composed of three zones of blades, where the first and third zones are moving, while the middle blade stage is stationary. Since the kinetic energy gained in each step is absorbed completely before the next pressure drop, the turbine is pressure compounded and as well as velocity compounded.
More detailed discussions of these basic design factors of steam. The turbo compound uses this high velocity gas to drive an impulse turbine wheel which does work by absorbing some of the velocity energy of the gas without imposing back pressure on the cylinders. Thermalengineeringbyrkrajput chapter19 steam turbine. The reaction principle, the impulse turbine, compounding of impulse turbine. A curtis turbine is an example of pressure velocity compounded method.
The jet glides over the inside surface and leaves the blade at d. Pressure compounding, velocity compounding, pressure velocity compounding. 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. A two wheel velocity compounded steam turbine has the nozzle angle a 2 67. Curtis to solve the problems of a singlestage impulse turbine. This divides the velocity drop across the stage into several smaller drops. In modern plants the turbine velocity is very high which is beyond the safety limits due to centrifugal stresses on the rotor material. Velocity compounded impulse turbine numerical problem prof. Introduction to turbine turbine classical mechanics. The impulse wheel carries two or three rows of moving blades. Neglecting the friction effects on the blades, calculate the tangential. Velocitycompounded impulse turbine this turbine is also termed as curtis turbine. The exist angles of first row of moving blades, fixed blades and second row of moving blades are 25,25 and 30o respectively. If the exit velocity from the second wheel is axial, what is the inlet velocity to the first wheel.
Dec 10, 2015 the first stage of an impulse turbine is compounded for velocity and has two rows ofmouing blades and one ring affixed mada. An impulse turbine is a turbine in which the high velocity of water strikes the bucket directly. The velocity compounded impulse turbine was first proposed by c. Nov 24, 2014 pressure velocity compounding in a reaction turbine compounding can be achieved only by pressure compounding. A turbine was investigated by various methods of calculating its efficiency. Chapter 1 thermal power plant darshan institute of. 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. In velocity compounded turbines velocity drop is maintained in stages and hence reducing velocity loses. Each set of rings of moving blades is separated by a single ring of fixed nozzles.
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