dummy piston in steam turbinedummy piston in steam turbine

d. Diaphragms. c. 2,3,5 c. 1, 3, 4 Parsonss original design was inefficient, running at 18,000 rpm and producing 7.5 kilowattsabout the power of a small household backup generator today.

Low rotational speed Constant supervision The power to rotate the DC pumps is taken from batteries (flooded lead acid type typically), which operate independently of the main electrical bus board; this ensures the pumps will operate even if a power outage occurs. can operate at high speeds, the associated turbine normally connects to the load via a reduction gearbox. Reaction turbines are placed in the water stream where the water enters the casing tangentially. WebIn pressure compound steam turbines: 1. A reaction turbine has: In a reaction turbine the steam pressure drops across both the fixed and moving blades while the steam's _____ velocity rises in the fixed blades and drops in the moving blades. Figure 6.73.

Simpler, fewer moving parts, more RPMs, More efficient, no reciprocating mass, far less vibration, quieter, fewer 1. May be made from a solid forging. d. Lower limb b. Steam is then exhausted from the LP turbine into the condenser at 720mm Hg (-0.95 bar/-13.77 psi) vacuum and very low steam temperatures. c. 1,4 d. 40-45% d. 4th Double Flow LP Turbine (shown on the right). What is the pH\mathrm{pH}pH at the equivalence point ? A hollow drum rotor, for good balance, is machined both outside and inside thus the drum must be open at one end. b. The kinetic energy is regained by the conversion of water into suction head, thereby increasing the total pressure difference on the runner. 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. ______ Mastoid process. This axial clearance, as it is known, is made adjustable by a micrometer collar on the end of the turbine shaft. 1st Pulp mill. This system of end-tightening, as it is called, prevents leakage of steam past the blade tips, and is adopted because it is impossible to provide sufficiently small clearances between the fixed and moving parts of the turbine. c. Fluctuates. e. A velocity drop in the stationary blades. THE DE LAVAL NOZZLE is shown in detail in the top diagram. 2,3,5. This pressure drop gives rise to a reaction in the opposite direction to that of added velocity. a. Latent High rotational speeds are required.

a. Khan, in Advances in Clean Energy Technologies, 2021. 2nd d. Moving. d. 2,3 5 0 obj These figures show differences of only one inch of vacuum, or -lb in pressure, at the condenser end of the turbine, but of 200 lb per square inch at the high-pressure end. WebThe leakage flow across this dummy piston reduces the turbine cylinder efficiency. a. Condensing-bleeder. 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. WebSteam turbine with dummy piston sealing arrangement for blocking saturated steam Classifications F01D3/04 Machines or engines with axial-thrust balancing effected by b. In the impulse turbine the blade-section is crescent-shaped and the space between adjacent blades is symmetrical about its centre. c. 1, 3, 4. a. Little steam leaks past the knife-edges of the labyrinth, whose action is assisted by the shaft in carrying the steam round with it. Match the body region in column A with the surface feature in column B. b. Shipping Wonders of the World 2012-23 | Contents | Site Map | Contact Us | Cookie Policy, The 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 and by Giovanni Branca in 1629. d. 0.757, convergent e. Provide an area to install a labyrinth deal. A back-pressure turbine with exhaust steam going to an old boiler header that is supplying steam to an old lower pressure turbine is called a: c. 1,2,3 4. Can be reversible. Pobitra Halder, M.M.K. e. 0.577, convergent or convergent-divergent. A split casing design allows personnel to access the turbine internals relatively easily, which reduces the time needed for maintenance interventions. 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. The fixed and the moving blades are arranged in this manner, but they face in opposite directions to effect reversal of the flow of steam. 3. Medium to large turbine designs utilise plain white metal bearings and tilting pad bearings (Michell Bearings). a. Velocity, pressure. Steam turbine rotors are normally machined from a single forged billet. b. The heat is conserved by lagging the casing with a covering of insulating material. b. d. 1,3 Operation at the design rotational speed. The second major purpose is to regain the static suction head, where the runner is located all above the level of the tail water, of the draft tube. Whenever steam is bled, it is referred to as bleed steam, or extraction steam. The first stage blades of an LP turbine are normally shrouded whilst the larger final stage blades are not shrouded. 20-25% Turbines with higher HP speeds and lower LP speeds are referred to as Tandem Articulated or Cross Compounded turbines; these types of turbine shafts are not directly coupled together. c. 3rd Feedwater pumps. c. 1,4

Topping. b. Cross-compound turbine. e. Mixed pressure. 8 0 obj Dipak K. Sarkar, in Thermal Power Plant, 2015. The curved passage ways between the blades are approximately parallel and the steam rushes through without any change in pressure. ), and the centrifugal forces generated by the turbine due to its high rotational speed. Steam pressure acting on an enlarged section of the rotor creates the geometry of a piston. b. Disc rotors: c. 1,3,4. 2. Pressure drops in the stationary blades In the chapter Steam Turbine Engines was traced the story of the turbine over a period of nearly two thousand years. Examples of bleed steam applications include condensate and boiler feed water heating (the steam is passed through a shell and tube heat exchanger). Building heating. LP turbines that have this setup are designated double flow, or two flow, turbines. For example, it is not unusual for a lubrication oil system to have High High, High, Low, Low Low, oil pressure setpoints; each setpoint will also have an associated alarm and/or trip response. A rotors actual construction material depends upon the operational stresses it will encounter. c. Maintained constant regardless of turbine load. The shaft itself forms the bearing journal surface upon which the plain bearings are mated. The pads are arranged in a casing, radially for a thrust bearing, axially for a shaft bearing, and their construction enables them to tilt under the action of a revolving collar or shaft. c. Too expensive to maintain. The lower diagram shows the application of the nozzle at the side of a row of impulse blades. Make grooves for diaphragms. The blades increase in size from the high- to the low-pressure end of the machine, but the blades in each group are of the same size. 0.757, convergent c. Polytropic process. << 2.40. The blading of such turbines is arranged at either end to face the central steam supply. a. Axial. /MediaBox [0 0 556.8 817.92] b. The type of turbine that is more widely used than any other, especially for marine work, is the reaction turbine developed by the late Sir Charles Parsons. b. In these circumstances the surface condenser is of even greater importance to the turbine than to the reciprocating engine. Similar knife-edges are provided in the Parsons turbine to prevent leakage of steam out through the shaft bearings at the high-pressure end, or incursion of air at the low-pressure end. Condenser Water Box from a Large Power Station Condenser. WebTo counteract this force, steam is admitted to a dummy (balance) piston chamber at the low-pressure end of the rotor. a. e. 3, 4. The ends of the nozzles are bevelled off to permit of close approach to the blading. THOUSANDS OF BLADES are fitted to the rotor and to the casing of a steam turbine. a. Shaft. By adopting this system, the difference in pressure on either side of any ring of blades is comparatively small, and an extremely high rate of rotation is not necessary to use the steam economically. d. Cross-compound.

When turbine blade velocity is equal to one half the steam velocity, then exiting steam:

during a turbines heating-up and cooling-down. Increase the absolute velocity. d. Two sets of nozzles. The steam accordingly passes through the first ring of fixed blades or nozzles and, with an increase of velocity and decrease of pressure, imparts an impulse to the first ring of moving blades. 1,3,4 To permit the required expansion of the steam, without change of temperature, special nozzles are used. The blades, instead of being placed on the rotor with the horns of the crescents in a fore-and-aft position, are arranged with staggered edges. Greater power per unit size may be absorbed. d. 3,5 Radial. e. 1, 3. e. Axial. The oil is supplied to the bearings by pumps, and as it becomes heated while lubricating, it is circulated through special cooling apparatus. Alfred Dunley has a chronic lung condition and is seen annually for pulmonary function tests that are performed in the Department of_________________________________________ at Allegheny General Hospital. a. e. Reduced if load increases. A reaction turbine uses the reactionary force of the steam changing direction over the blades to rotate the rotor. b. Bowel pins. For reaction less than zero, the rotor has a diffusing action.

Carbon rings, when used for turbine shaft seal require: 3. Contents 1 History 2 Manufacturing 3 Types 3.1 Blade and stage design 3.2 Blade design challenges Velocity diagram of a reaction stage. He states that almost the same power can be obtained from steam at 200 lb expanded to -lb (29 in of vacuum) as from steam at 400 lb expanded to 1 lb (28 in of vacuum). Where would you expect to find a turbine that can be reversed: The use of smaller units reduces the centrifugal forces present on larger units and thus reduces the likelihood of cracking. This arrangement of the turbine, with every wheel using part of the steams energy, is known as velocity compounding. c. Radial. The fixed blades act as nozzles. Volume, pressure, velocity - all are interwoven to serve one of the most wonderful machines ever devised by man. A steam turbine assembled casing is machined off inside in a boring mill to: e. Cross-compound. High level - poor control concerning maintaining of the condensate close to saturation temperature. c. 105 d. Tandem compound 6.14 it follows that the diagram efficiency of a reaction stage is. As shown in Fig. Therefore the steam will tend to _____ around the periphery of the blades instead of passing through them. In the turbine there is enough room to expand the steam to a much lower pressure than is possible in a reciprocating engine cylinder. Nearest to the ideal. d. Disappears. e. Sensible. c. 2,4 To allow for this axial movement, sliding feet, panting beams, plates and/or elongated holes in the holding down bolts are used. A further advantage in the turbine is the use of large exhaust passages which are always open to the condenser. Place the letter of your choice in the space provided. Increase steam velocity 4.31). Double flow turbines are primarily used to equalise the thrust load from the opposing turbines, which minimises the size of the thrust bearings that the LP turbine requires. Table 7.2. Electrical generation. On the left is shown the reaction engine invented by Hero of Alexandria about AD 50. e. One set of nozzles. Column B Reaction blading, however, differs from that used for impulse turbines in the shape of the section as well as in its arrangement on the rotor. Impulse/reaction blades can thus be combined to form an impulse-reaction turbine. e. Weight. For this reason, a gearbox represents an additional potential failure mode. b. This is done to oppose axial forces generated by the turbine 6.13 changes to, From Eq. Then be sure to check out our Engineering Video Courses! c. 1,2,3 Due to these centrifugal forces, LP turbines are very sensitive to overspeed situations. 1. It depends for its action on the tilting action of metal pads that comprise its working surfaces. 4. Hence, the cost of a reaction turbine for the same amount of work is much higher, since it requires more stages. Expensive. 1,2,3 15% d. Absolute velocity equals zero. 0mp\2KX[bulFgeLGZ\m^9eza5/d[\yd The entrance angle of a reaction blade is: b. Welded on. The size and shape of the turbine rotor blade can then be designed to ensure its resultant velocity is half of the steam velocity for that particular row of blades. A typical power plant steam turbine will have steam entering the HP turbine at 180 bar (2610 psi), 540C (1,000F). Exhaust steam in a back-pressure turbine is not reduced to vacuum pressure, whereas a condenser turbine is. b. Due to the steams velocity increase, a corresponding pressure decrease also occurs. When building up the complete rotor the blades are placed sideways in the -grooves, and are then given a twist to secure them in position with the V-grooves interlocked. b. This increase in size may be compared with the successively larger cylinders of triple- and quadruple-expansion reciprocating engines described in the chapter Compound Triple & Quadruple Expansion Engines. The pressure change takes place only in the nozzles. END-TIGHTENED BLADES are clearly shown in this illustration. Compensate for axial expansion and contraction of the rotor. A firework, the well-known catherine-wheel, provides a good illustration of reaction. Schematic of a reaction type turbine showing the distribution of the thermodynamic and fluid mechanic properties. Those at the low-pressure or exhaust end of the machine are much larger than those at the high-pressure end, into which steam is admitted from the boilers. /Count 5 The 50% reaction turbine has been used widely and has special significance. The steam enters the blades at great speed and loaves them slowly compared with the speed o! The high-pressure blades, fixed and moving, are provided at the tips with a continuous strip of metal, or shrouding, to which they are firmly secured. a. (4.42), we may conclude that since the cross section of the flow at the end of the draft tube is bigger than that directly behind the turbine, Uw,5 has to be less than Uw,4. a. The resultant motive force is the vector sum of these impulse and reaction forces. Steam turbine casing joints are made steam tight by matching _____ exactly. a. Such a form of gland is impossible for the turbine shaft revolving at high speed, and a type known as a labyrinth gland is used, with knife edges similar to those on the shrouding, referred to above. To summarize, this turbine combines the rotational forces of the previously described turbines; that is, it derives its rotational force or torque from both the impulse of the steam striking the turbine blades and the reactive force of the steam with increased velocity and changing direction. To analyze the entire action in detail, it can be stated that in an impulse-reaction turbine, the rotor spinning is caused primarily by three forces: (i) reactive force produced on the moving blades as the steam velocity increases due to expansion while passing through the nozzle-shaped spaces between the blades, (ii) reactive force produced on the moving blades during the steam flow path changes its direction, and (iii) impulse/thrust of the gas impinging upon the blades. The hub is close to an impulse turbine. b. a. For example, steam enters nozzle bank 1 and each of the valves in nozzle bank 1 moves from the fully closed to fully open position in sequence. b. The speed of the steam does, however, undergo a change in relation to the wheel. 2.39. The diameter of the rotor at the low-pressure end of the turbine is also increased to impart a greater speed to the low-pressure blades. Transmit power from one shaft to another. Moving rotor blades are attached to rotor discs which are mounted on the rotor shaft. d. 10% Reheating steam from the high-pressure turbine increases the overall plant efficiency. Due to their large size, cost, and susceptibility to fouling, condensers almost always utilise the shell and tube heat exchanger design (not the plate heat exchanger design). 1. Therefore, for maximum utilization. 6.15 with respect to U/C1 when equating to zero will yield the maximum diagram efficiency. c. Higher steam pressure use. Considering the energy (and cost) required to generate the steam, it is not desired that some of that energy should then be rejected to atmosphere due to overcooling. Exhaust steam should not be excessively cooled because this will lead to a rejection of more heat than is necessary to change the state of the steam to condensate; this overcooling corresponds to a resultant reduction in efficiency. Nozzle boxes increase the velocity of steam prior to its entry to the first stage of a HP turbine. Centrifugal forces increase with the _____ of the speed. With this arrangement steam enters at the centre of the shaft and flows along in opposite directions.

\SCJ3E(yj"Z-eUbjzQQKHB}TedGRjMmDKj'PMJ"!&F/-dv]I=!2Bk3kgO,_ .oji[ ,~/~?vKq_LrZuD^6mB> |4CRg~NnLmuwrOLJ#OMIO 4u ~W,TktbPR7m'iClrxOa]4k`!gH$""""AU>;L"bhDE4o2an 8vLg[X +})M0 Putting the value of Eq. In a turbine the bearings are exceptionally well fitted and are supplied with oil under pressure. Due to the considerable reactionary forces on the LP turbine blades (due to their large size), larger LP turbine designs usually admit steam into the centre of the turbine; the steam then flow outwards through two opposing and identical stages. The design of steam turbines continued to evolve over the following years. The gearbox not only increases the torque applied to the loads shaft, but also ensures the load is driven at its design speed (measured in rpm). 3,4 Muhammad Asif Hanif, Umer Rashid, in Renewable and Alternative Energy Resources, 2022. Rotor discs are mounted directly onto the rotor shaft, and rotor blades are mounted to the rotor discs. By continuing you agree to the use of cookies. 2. Cavitation leads to damage of a pumps internal components and a rapid loss in pump efficiency (reduced flow rate etc.). 3 0 obj REACTION BLADING is illustrated by this diagram. A small clearance between the discs prevents: In an impulse steam turbine nozzle the following events take place: A turbine that expands the steam in two or more sets of nozzles in series, each set having velocity-compounded blades to receive the steam issuing from the nozzles is called a/an: In a back-pressure turbine the process steam pressure is: Extraction turbines are turbines where steam is extracted at one or more points at constant: a. On the right is the impulse machine designed by Giovanni Branca in 1629. It is very important that a turbines emergency lubrication DC pumps are tested periodically, failure to operate when needed will most likely lead to significant damage of a turbines components. A steam turbine has a high capacity to _____ ratio: b. c. 30-35% >> A turbine operating at optimum conditions will utilise rotating elements (rotor blades) that are designed to move at half of the steam inlet velocity. The clearances of the radial knife-edges facing the bottom of the rotor grooves are not adjustable, but the axial clearances of the edges adjacent to the sides of the -shaped rotor grooves are adjusted by the same micrometer collar that determines the clearance of the shrouding. Couplings: Efficiency is poor The utilization factor for a fixed nozzle angle will increase as the reaction approaches 100%. Reduce steam and blade velocity. Dummy piston: 34CrNiMo6: 28CrNiMoV85: X22CrNi17: X22CrNi17: X20CrMoV121: X20CrMoV121: Bearing pedestal: GGG-40: GGG-40: GGG-40: GGG-40: However, this setup is not practical as the length of the cylinder/casing would be quite long (assuming numerous turbine stages).