The theory is given for a singlestage impulse turbine and velocity compounded impulse turbine. Impulse turbine works on the basic principle of impulse. 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 shape of the moving blades however is not the same for impulse and reaction turbines. In the case of 50% reaction parsons turbine the enthalpy drop is the same for both fixed and. Velocity compounded impulse turbine when the velocity energy produced by one set of fixed nozzles is unable to be efficiently converted into rotational motion by one set of moving blades then it is common to install a series of blades as shown in figure. The example of velocity compounded impulse turbine is the curtis turbine named after its designer. After what condition, is the cause of large temperature and pressure drops in the firststage nozzles of a combination impulse and reaction turbine. The moving blades of impulse turbines do not have a change in flow area. A velocitycompounded impulse, also known as curtis, stage at the high pressure end of the turbine followed by reaction blading.
Pressure compounding or rateau stage in a pressure. How to solve numericals on impulse turbine part 1 youtube. Each set of rings of moving blades is separated by a single ring of fixed blades. The curtis stage turbine, as it came to be called, is composed of one stage of. In the impulse turbine pressure drops and the velocity increases as the steam passes through the nozzles. A turbine is a device that extracts the energy from a fluid flow and converts it to useful work. 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. The pressurevelocity compounding is a combination of the above two types of compounding. The force is depends on the time interval and velocity of jet strikes the blades. The mean peripheral velocity of blade is 400 ms and the blades are symmetrical. The hp turbine is a pressurevelocity compounded, single axial flow, noncondensing impulse turbine. It is the most renowned example of impulse turbine. In the impulsereaction turbine the fixed and moving blades are of similar form, consisting of converging passages to give a pressure drop in each case. Velocity compounded impulse turbine contd velocity compounded impulse turbine from me 430 at the city college of new york, cuny.
The velocity of the steam exiting the nozzles is the major factor in the tendency to accelerate the turbine rotor. Impulse stages may be either pressurecompounded, velocitycompounded, or pressurevelocity compounded. What is the velocity and pressure compounding in a turbine. Steam velocity at nozzle exit 600 ms nozzle angle 16 o mean blade velocity 120 ms exit angles. Neglecting the friction effects on the blades, calculate the tangential. Impulse and reaction turbine animation explain youtube. The fixed blade angles of the two reaction turbines equal to the given inlet angle. There are two basic types of turbines according to the mode of steam. A curtis turbine is an example of pressure velocity compounded impulse turbine. The inlet angle of the reaction stages are the same as the nozzle angles of the impulse stage 3. The following section consists of steam nozzles and turbines questions on physics.
In fact, a series of velocitycompounded impulse stages is called a. Steam expands from boiler pressure to the condenser in one stage. Between the moving blades are fitted guide blades which are connected to the turbine casing. Classification pressure compounded impulse turbine velocity compounded.
Three main types of compounded impulse turbines are. It is composed of one stage of nozzles, as the single stage turbine, followed by two rows of moving blades instead of one. Turbines a turbine is a rotary engine that exerts energy from a fluid flow and converts it into useful work. The curtis stage turbine, as it came to be called, is composed of one stage of nozzles as the singlestage turbine, followed by two rows of moving blades instead of one. One of the most popular example of impulse turbine is pelton wheel. The high pressure hp turbine see figure 1 is the first main engine turbine to receive steam from the main steam system. In a simple impulse turbine, high velocity steam is allowed to flow through one row of moving blades, it produces a rotor speed of about 30k rpm which is too high for practical use. Pressure compounding, velocity compounding, pressurevelocity.
Pi inlet pressure, pe exit pressure, vi inlet velocity, veexit velocity. This is why we call this type of turbine as impulse turbines. The velocitycompounded impulse turbine was first proposed by c. 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.
Pressurevelocity compounded impulse turbine it is a combination of the above two types of compounding. There is less of a drop in pressure and consequently a smaller increase in velocity. It may be noted that the diameter of the turbine is increased at each stage to allow the increasing volume of steam at the lower pressures. For a steam turbine, steam is the driving source of the energy. When the steam passes through the moving blades the velocity drops but the pressure remains the same. Thus a steam turbine could be viewed as a complex series of windmilllike arrangements, all assembled on the same shaft.
On this channel you can get education and knowledge for general issues and topics. A steam turbine consists of a rotor resting on bearings and enclosed in a cylindrical casing. It is designed to efficiently extract work out of high pressure steam. Impulse turbine or turbine stages, which are simple, singlerotor or multirotor. Each stage consists of rings of fixed and moving blades. Pressurevelocity compounded impulse turbine this is a combination of pressurevelocity compounding. Basics of impulse turbine in impulse turbine, steam coming out through a fixed nozzle at a very high velocity strikes the blades fixed on the periphery of a rotor. The impulse generated in this procedure is used to provide the momentum to the blades. This is also known as a rateau turbine, after its inventor. The velocity of steam entering a simple impulse turbine is, and the nozzle angle is 20o. So, steams pressure drop and it will increase its velocity.
Velocity compounded impulse turbine the velocity compounded turbine was first proposed by c. Steam turbines their construction, selection and operation pdf. In impulse turbine all hydraulic energy is converted into kinetic energy by a nozzle and it is is the jet so produced which strikes the runner blades. Pressure compounding or rateau stage in a pressure compounded impulse turbine, called as rateau stage, the pressure drop is divided among different stages one single rateau stage consists of. The method in which energy from steam is extracted in more than single stage is called compounding. Impulse turbine and reaction turbineprinciple, working. The alternator is used in power plants which converts a. What is velocity and pressure compounding in impulse turbine.
Compounding of steam turbines is the strategy in which energy from the steam is extracted in a. It has the advantage of reduced blade velocities, reduced steam velocities and equal work among stages, or equal work distribution among the stages as desired by the designer. 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. The nozzle angles for the first two impulse turbines are the same. A pelton turbine develops 2000 kw under a head of 100 m and with an overall efficiency of 85%. Impulse turbine efficiency calculation methods with. The project was based on an existing impulse turbine, a onestage turbine set in an organic rankine cycle with the working fluid being r245fa. The first stage of a steam turbine is a two row velocity compounded impulse wheel. If the steam is to enter the blades without a shock, what will be the blade angles. In this type, the total pressure drop expansion of the steam take place only in the first nozzle ring. 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. Other impulse turbines are known as curtis, zoelly and. Curtis to solve the problems of a singlestage impulse turbine for use with high pressure and temperature steam. Comparison between impulse turbine and reaction turbine.
This highvelocity strikes the turbines rotor and the speed. Pdf power plant lecture notes chapter4 steam 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. The rotor is turned by steam impinging against attached vanes or blades on which it exerts a force in the tangential direction. These two rows are separated by one row of fixed blades which has the function of redirecting the steam leaving the first. Impulse and reaction principles, compounding, velocity diagrams for simple and multistage turbines, speed regulationsgovernors and nozzle governors. Velocity compounding of an impulse turbine is the use of a single nozzle with an arrangement of several moving blades on a single disc. The optimum rotational speed of the turbine was in. The blades change the direction of steam flow without changing its pressure.
This divides the velocity drop across the stage into several smaller drops. In the impulsereaction turbine the fixed and moving blades are of similar form consisting of converging passages to give a pressure drop in each case. Impulsereaction turbine this utilizes the principle of impulse and reaction. The total pressure drop of the steam is divided into a number of stages. This turbine used to rotate the generator, which produces electric power. A pressurecompounded impulse stage is a row of fixed nozzles followed by a row of moving blades, with multiple stages for compounding.
The shape of the fixed blades in both impulse and reaction turbines is such as to reduce the flow area and increase the velocity. Multiple choice questions on steam nozzles and turbines. A turbine was investigated by various methods of calculating its efficiency. The force due to change of momentum causes the rotation of the turbine shaft. Various methods of loss calculation were explored in the search for a method sufficiently accurate to. A velocitycompounded impulse stage consist of a row of fixed nozzles followed by two or more rows of moving blades and fixed blades without expansion.
June 2018 443 diagram of absolute steam velocities c, relative steam velocities w, rotor rotational velocity u, axial forces f x, and thrust forces f y over the stages in one curtis wheel steam turbine. There are a number of rows of moving blades attached to the rotor and an equal. Before describing compounding, understanding of the steam turbine is necessary. Steam turbine a steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into useful mechanical work. The fact that the pressure does not drop across the moving blades is the distinguishing feature of the impulse. Steam is a vapour used as a working substance in the operation of steam turbine. More detailed discussions of these basic design factors of steam. Reaction turbine impulse turbines an impulse turbine uses the impact force of the steam jet on the blades to turn the shaft. The velocity compounded turbines are used n m g m g m lost velocity. The following are chief methods for reducing the rotor speed. The following particulars refer to a tworow velocity compounded impulse wheel.
277 781 253 177 628 665 108 843 771 748 896 1123 464 1489 721 1396 110 307 1297 1144 106 8 269 70 895 1182 1179 1340 597 498 351 1491 1096 1050 991 586 744 970 635 1492 1045 1011