The lower diagram shows the application of the nozzle at the side of a row of impulse blades. Feedwater pumps. Vendor balance heating tanks, comfort heating etc. Where pressure compounding is adopted, the rings of fixed blades are omitted, and for them are substituted sets of nozzles which provide a drop in pressure with an increase of velocity. Expensive. e. Minimum blade clearance. Rows of stationary blades alternating with rows of moving e. One set of nozzles. In its sleek casing, however, the natural laws that govern steam power are turned to good account. In the reciprocating engine steam is prevented from leaking from the cylinder through the piston rod opening by a gland. Thus the pressure p4 at the outlet of the turbine must be lower than the pressure determined at the outlet of the tailwater at the end of the pipe p5. As technologies advanced, higher efficiencies were obtained, and the size of steam turbines increased. WebTo counteract this force, steam is admitted to a dummy (balance) piston chamber at the low-pressure end of the rotor. 104 d. Compensates for steam pressure variations. It is reversible. The rings are also provided with circular knife-edges standing out at right angles from the ring sides that face the flow of steam. Increase steam friction e. 2,3,4, The efficiency of the Rankine cycle (steam plant) that utilizes a steam turbine is: A typical turbine may bleed at 19 bar (275 psi), 9 bar (130 psi), 6 bar (87 psi) and 0.5 bar (7 psi), depending upon the feedwater heating arrangement. A double-regulated Kaplan turbine offers a full discharge at 15%100% efficiency, whereas single-regulated Kaplan turbine shows maximum discharge at 30%100% efficiency [32]. Low level cavitation within condensate pumps may occur. A dummy piston on a steam turbine is used to: Of its high capacity to weight ratio. e. Velocity, kinetic energy. The entrance angle of a reaction blade is: At the top is part of the casing with protruding rings, having sharpened edges that revolve in grooves in the rotor. Topping. d. Rotor. Despite reaction turbines being classified as reaction, there is always a small degree of force imparted due to impulse. The turbine is encapsulated in a spiral-shaped casing having an inlet and an outlet. a. Low rotational speeds are required. On larger turbines the _____ is split in a horizontal direction. May be made up of separate discs and a shaft. 2023 saVRee 3D Interactive Media. Dummy pistons are not always required, however. From the diagram W1 = V2, the angles of both the stationary and rotation blades are identical. To allow for this axial movement, sliding feet, panting beams, plates and/or elongated holes in the holding down bolts are used. As shown in Fig. 
2. 
7 0 obj Residual Steam turbines have been mentioned in history as far back as the 1st century, but the modern steam turbine design was created in 1884 and is accredited to the engineer Charles Parsons. 6.16 into 6.12 and 6.15, we get. b. Dummy piston arrangement on Parsons Turbines&Double Flow Turbines, Problems caused by incorrect warming through, Impulse blading system design & Bull nosed blades. The labyrinth packing, which prevents the leakage of steam, can be seen at either end of the rotor. The section may, perhaps, be described as a lopsided crescent and it may also be likened to the section of an aeroplane wing. Condensers can significantly impact the efficiency of a steam turbine. c. Upper limb The larger flow area is due to the steams reducing pressure and increasing volume as it passes through each stage of the turbine. Electrical generation. Forces are balanced by the drum offering a greater surface area to the low pressure balancing Heat, potential. Nozzle bank 3 will only begin to open if nozzle banks 1 and 2 are fully open, and only if the load on the turbine exceeds the amount of steam available through banks 1 and 2. In the chapter Steam Turbine Engines was traced the story of the turbine over a period of nearly two thousand years. 1. Each diaphragm disc holds a single row of stationary blades and each blade row is referred to as a stage (same terminology as with a turbines rotor). Eng., Ph.D., C.A. A turbine with ahead /XObject << /Im0 8 0 R >> Press fitted. /BitsPerComponent 1 A pipe from some stage in the turbine provides steam to act on the dummy piston which is mounted on the turbine rotor (Figure 6.73). Rings project from the turbine casing into the rotor grooves and the interior of every ring is sharpened to a knife-edge. endobj a. Is found on impulse turbines. Operation at the design temperature. Wiki User 2009-10-20 09:34:55 This answer In a reaction stage there is an enthalpy drop in the rotor blade, so the energy available to the rotor blade is given by, Again, V12=C12+U22C1Ucos1, and Eq. Impulse-reaction turbine schematic and pressure/velocity changes. Centrifugal forces increase with the _____ of the speed. LABYRINTH PACKING to seal the turbine against the atmosphere is indicated here in section. 1,3,5 The dummy piston causes an equal opposing force to that created by the rotor thrust; thus, the two opposing forces cancel each other out. Each course has aquiz,handbook, and you will receive acertificatewhen you finish the course. d. Impulse. a. Axial. b. However, due to varying load conditions, it is not possible to leave steam throttle valves permanently open, and the valves must at some point be throttled (moved to a position between fully open and fully closed). The emergency trip valve is held open by the hydraulic control oil pressure. High rotational speeds are required. Steam turbine with a dummy piston and wet steam blockage Abstract The steam turbine has a high pressure flow channel arranged between a rotatably supported a. a. Condensing. nitric acid plants. d. Press fitted and welded. A typical marine steam turbine will operate at 65 bar (943 psi) and 515C (959F) at the HP turbine inlet. The curved passage ways between the blades are approximately parallel and the steam rushes through without any change in pressure. Make grooves for diaphragms. a. LP turbines operate at lower pressures and temperatures than IP and HP turbines. c. Kinetic, mechanical. Due to their shape, they are referred to as cylinders as well as casings. The work produced in an impulse turbine with a single stage running at the same blade speed is twice that of a reaction turbine. As the velocity of the steam is directly proportional to the amount of energy transferred to the rotor, the velocity of the steam is increased using nozzles prior to it impinging upon the rotor blades. Francis turbine coupled with an electrical generator. a. Nozzles and moving blades. impulse turbine blade? b. WebThe modern marine steam turbine has been developed from the two main principles, reaction type and impulse type, invented respectively by Hero of Alexandria about AD 50 When steam leaves the moving blades at zero absolute velocity: 3. Velocity diagram of a reaction stage. 1 0 obj Give confidence to the operator. 4. c. Leftover Nozzle boxes increase the velocity of steam prior to its entry to the first stage of a HP turbine. c. Load. If using a steam turbine to drive/rotate a ships propeller, there needs to be some way of driving it astern (reverse direction). Minimum seal clearance. However, non-condensing turbines are cheaper. 1. Fully balanced. Steam turbines can also be used to reduce the pressure of a steam system to a lower pressure and temperature. 4. High level - in extreme cases, condensate may enter the low-pressure turbine(s); this is more a problem for condensers installed on an axial plane with the turbine, not for turbines which have the condenser installed beneath them. a. Increase steam velocity This type of combination leads to an excellent compromise: an all-impulse turbine would have a very low efficiency and an all-reaction turbine would have an excessive number of stages. The steam is redirected by the rows of fixed blades (F) and so passes from moving to fixed blades in turn. The casing forms the largest pressure boundary of the steam turbine. /Length 5 0 R Register to licenses this file for a specified project. e. Polytropic process. The Parsons reaction turbine is thus pressure-compounded, but in some recent designs the machines have been built with the high-pressure stages arranged on the velocity-compounded impulse principle and with later stages operated on the pressure-compounded reaction system. An early turbine of the impulse type was designed by Dr. C. Gustav P. de Laval in 1889. The front edge of the shrouding is sharpened, and is brought close to the roots of the next ring of blades. a. e. 1, 4. Another name for the rotor is the rotor assembly. c. Condensing-bleeder. Bearing lubrication oil is maintained at approximately 40C (104F) as this is an optimum temperature for the oil. e. Topping. _____ turbines are large turbines consisting of two or more turbines in series coupled together as one shaft and applied to one generator. Steam flow is controlled by hydraulic valves equipped with stellite discs/plugs and seats; the stellite layer lends the plugs and seats very hard erosion resistant properties. The most important use of the Michell bearing in marine work is to carry the propeller shaft and transmit the thrust of the screw to the ship. the moving c. Too expensive to maintain. WebA dummy piston and cylinder at the turbine inlet end Rotor axial thrust developed in a reaction turbine is the result of a steam pressure drop across __________. d. Level. b. Adjust the thrust generated by the turbine. Generally, this type of turbine is called the Parsons reaction turbine, and is characterized by low steam velocity and popular acceptance worldwide. Are nozzle shaped. endstream e. Are located in the rotor. Dummy piston arrangement on Parsons Turbines&Doubl End thrust is balanced removing need for dummy pistons or cylinders on reaction turbines . Support the dummy piston. e. 50-55%. WebWhy do power plants use steam turbines instead of piston engines. When the exit pressure of a steam turbine nozzle is less than _____ times the inlet pressure then a _____ nozzle will be used. In reaction turbine designs, where each blade row produces high thrust, the inlet end steam steel diameter is raised to function as a balance drum. b. Usually, the reaction turbines use a draft tube to improve the use of head. 
To reduce these losses, most condensers are of the regenerative type. endobj 2. Sometimes, if a single casing LP turbine design is not possible, two smaller double flow LP turbines may be used. 4.31). Kaplan turbine is a complete reaction turbine that works based on the lift force generated on the impeller blades due to its aerofoil shape [29]. Steam turbines are now powering some of the worlds largest electrical generators. e. Set at 45 degrees to the nozzle angle. d. 1, 3. e. Increase. 4. However, a gradual turbine stop would require a large amount of oil and a correspondingly large gravity tank. d. Heat, kinetic. WebThe main method for steam turbine unit efficiency improvement is the increase in the initial steam parameters temperature and pressure. Note that back-pressure steam turbines are a type of non-condensing turbine. The blades are bucket-shaped in section and in general appearance resemble a woodworkers gouge. The sizes of the exhaust ports and passage-ways of a reciprocating engine are necessarily limited, and they are periodically closed by the slide valves. Steam pressure acting on an enlarged section of the rotor creates the geometry of a piston. The boilers provide the necessary steam for the steam turbine(s). Medium to large turbine designs utilise plain white metal bearings and tilting pad bearings (Michell Bearings). Have discs whose bore is 0.01 mm smaller than the shaft. Creep e. Feed-water heating. Finally, the LP turbine will exhaust to the condenser, which is held at around 720mm Hg (-0.95 bar/-13.77 psi) vacuum. c. Condensing-bleeder >> 36 The blade root e.g. Figure2.39 shows a schematic view of a reaction turbine. d. 1,2,4 Steam turbine rotors are often mechanically coupled together to drive a large generator within a power station; this configuration is referred to as Tandem and these types of turbine are directly coupled together (they rotate at the same speed). So far as velocity of steam is concerned, it accelerates through the stator and decelerates through the rotor, with practically no net change in steam velocity across the stage but with a decrease in both pressure and temperature, reflecting the work performed in the spinning action of the rotor. Pressure staging ensures that the volume and velocity of the steam is accounted for as the steam passes through each row of turbine rotor blades. Rows of stationary nozzles and moving blades. Some typical monitored parameters may include: Measured values will have associated alarms and trips depending upon their criticality. c. Sectional. Condensing steam turbines expand the steam from full boiler pressure down to a vacuum in order to harness the largest amount of heat energy possible from the steam. For this reason, a gearbox represents an additional potential failure mode. c. Permits higher steam pressure use. a. Reaction turbine blades (moving): c. Almost 90 degrees. Another method of overcoming end thrust is to use a Michell thrust bearing on the shaft. Muhammad Asif Hanif, Umer Rashid, in Renewable and Alternative Energy Resources, 2022. a. Frictional losses are maximized. Although steam turbines can be used as prime movers to drive pumps and other small/medium sized machinery items, they are most commonly associated with the power generation industry, where they are used to provide mechanical power to a generator, thus producing electricity. The shaft itself forms the bearing journal surface upon which the plain bearings are mated. b. Instead of piston, seal strips are also used to duplicate a piston's counter force. On the shaft itself forms the largest pressure boundary of the nozzle at the blade... Emergency trip valve is held at around 720mm Hg ( -0.95 bar/-13.77 psi ) and 515C ( 959F at... In its sleek casing, however, a gearbox represents an additional potential failure mode edge of shrouding... 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