Allows a smaller turbine to be used. Efficiency is poor e. Minimum blade clearance. Therefore, C1=V2 and C2=V1, as discussed for the impulse principle [6]. b. Nozzles and stationary blades. What is the pH\mathrm{pH}pH at the equivalence point ? Press fitted. b. Therefore the steam will tend to _____ around the periphery of the blades instead of passing through them. The shroud is usually above a reaction of 50%. 4. 
c. Cylinder. In the impulse turbine the blade-section is crescent-shaped and the space between adjacent blades is symmetrical about its centre. Fully balanced. It is common practice to design multistage turbines with impulse stages in the first few stages to maximize the work and to follow it with 50% reaction turbines. a. b. Table 7.2 shows the comparison among the Pelton, Francis, and Kaplan turbines based on a number of factors including flow types, head requirement, specific speed, and overall efficiency. WebTo counteract this force, steam is admitted to a dummy (balance) piston chamber at the low-pressure end of the rotor. Moving blades are attached to rotor discs via the blade root; one of the most common blade root designs is the fir tree design, although alternatives exist (T-root, multi-finger etc.). The blades are made of the finest quality stainless steel, as they have to withstand tremendous heat combined with mechanical stresses due not only to pressure, but to the centrifugal forces to which they are subjected when whirled round at high speed. Steam turbine stationary nozzles create a: /Type /Pages BLADES OF A VELOCITY COMPOUNDED TURBINE are arranged as shown diagrammatically. Steam enters the machine through the nozzles shown at the top in the direction of the oblique arrows, and impinges on the first row of moving blades (M) that move in the direction indicated by the horizontal arrows. The draft tube causes the flow velocity to be reduced before entering the tailwater. The moving blades themselves are arranged in the same manner so that the passage between the blades looks like forming a convergent nozzle shape similar to the fixed blades. You then get ongoing rights for that end use,even if your subscription ends. Each blade must also be able to cope with the operational stresses placed upon it, these stresses include high temperature variations, high pressure variations, mechanical stresses from vibration, erosive effects of foreign object damage (water or rust particles etc. Electrical generation. Steam turbine casings/cylinders are cylindrical shaped constructions consisting of two halves. 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. 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. With steam rushing violently through the casing from one end to the other, the rotor is not only rotated; it would be pushed bodily forward as well if means were not adopted to prevent this. 0mp\2KX[bulFgeLGZ\m^9eza5/d[\yd 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. Latent Steam pressure acting on an enlarged section of the rotor creates the geometry of a piston. Be sure to check your spelling. REACTION AND IMPULSE principles are illustrated by these diagrams. c. Mixed pressure. 
Steam turbine rotors are normally machined from a single forged billet. steam from the boiler is fed directly to the HP turbine. Another method often used in low pressure turbines is to make the turbine double flow. d. square Pulp mill. A steam turbine assembled casing is machined off inside in a boring mill to: Where would you expect to find a turbine that can be reversed: Feedwater pumps. can operate at high speeds, the associated turbine normally connects to the load via a reduction gearbox. The steam entering into the first set of moving blades imparts torque to the shaft due to a change in direction at the outlet and hence a change in momentum thereby impulse to the moving blades. a. The marine turbine, however, has many mechanical features that are of special interest. a. 
c. Atomization of the fuel. c. Sectional. a. c. On shut-down &{ 3. b. Cross-compound turbine. b. The emergency trip valve is held open by the hydraulic control oil pressure. 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. d. 0.757, convergent c. 1,3,4. Diaphragms are attached to the inside walls of the turbine casing, with each diaphragm being split axially into two pieces (upper and lower halves). The disadvantages of a steam turbine include: Is found on impulse turbines. He also includes a chapter on boilers. WebThe 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 in a closer approach to the ideal reversible expansion process. 1 0 obj In the reaction turbine, as the name implies, the rotor is rotated mainly by the reactive force in place through the direct impulse or thrust alone. The purpose of a thrust bearing on large reaction steam turbine is to: c. Fixed and moving blades. 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. Although some contraction and expansion occurs radially, most occurs along the axial axis. e. 2,3,4. 4. Absorb any axial thrust on the rotor. Dummy piston arrangement on Parsons Turbines&Doubl End thrust is balanced removing need for dummy pistons or cylinders on reaction turbines . 556.8 0 0 817.92 0 0 cm 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). b. The pressure change takes place only in the nozzles. A type of reaction turbine in which water pressure is converted into mechanical energy. In a reaction turbine the steam pressure drops across both the fixed and moving blades while the steam's _____ rises in the fixed blades and drops in the moving blades. Summarize the functions of the primary organ systems in the human body. is connected either directly to the rotor shaft, or, indirectly via a gearbox. As the steam inlet velocity varies throughout the turbine, so too does the velocity of the blades. A generator coupled on one shaft to a turbine consisting of two or more turbine in series is called a: 10-15% THE DE LAVAL NOZZLE is shown in detail in the top diagram. c. Stationary. d. 1, 3. Due to this excessive length, the turbine would suffer from problems associated with mechanical bending/distortion and mechanical expansion due to heat. Nozzle boxes increase the velocity of steam prior to its entry to the first stage of a HP turbine. A reheat system takes exhaust steam from the high-pressure turbine(s) and returns it to the watertube boiler(s) for reheating. /Type /Catalog As shown in Fig. e. Ships. 2. a. d. Stationary. Expensive. In a reaction turbine: Eng., Ph.D., C.A. Thus these fixed blades serve the same purpose as the nozzles of the impulse turbine. Exhaust steam in a back-pressure turbine is not reduced to vacuum pressure, whereas a condenser turbine is. Lubrication and control oil systems are normally low pressure, high volume systems. 3 0 obj Figures quoted by Professor E. N. da C. Andrade illustrate this point. d. Isenthalpic process. Fig. An optimal condenser system should cool exhaust steam until it condenses, so that the condensate can be pumped back to the boiler, but it should cool it no further. On larger turbines the _____ is split in a horizontal direction. d. High pressure drops are required. Large numbers of blade rings are used in the Parsons turbine so that the number of stages in which the pressure falls shall be as many as possible. A review and discussion of the recurrent problems experienced by reaction turbines is also presented to explain the main operating challenges for these machines due to the fluid dynamic phenomena perturbing the off-design operation and increasing the mechanical component damages. A reaction turbine has: 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]. 4. e. Reduced if load increases. Bleed/extraction steam systems increase overall turbine efficiency because more heat from the steam is recovered rather than rejected. e. Low in capacity to weight ratio. 3. c. Deformation Low so as to reduce frictional losses. WebSteam turbine with dummy piston sealing arrangement for blocking saturated steam Classifications F01D3/04 Machines or engines with axial-thrust balancing effected by Adjust the thrust generated by the turbine. 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. 19.10, P438, CH 19, Rotary Expanders and compressors, Power Plant Instrumentation and Control Handbook (Second Edition), Advanced industrial gas turbines for power generation, Combined Cycle Systems for Near-Zero Emission Power Generation, Hybrid Renewable Energy Systems and Microgrids, Fluid Mechanics and Thermodynamics of Turbomachinery (Seventh Edition), Renewable and Alternative Energy Resources, Efficient hydroenergy conversion technologies, challenges, and policy implication, Combination of impulse and reaction turbine, Fixed buckets at the periphery of the wheel, Runner vanes are fixed with the shaft so it cant be adjusted. Due to steam throttling loses, it is desirable to have steam throttle valves (sometimes called steam admission valves) either fully closed, or fully open, when the turbine is in operation. 
Double Flow LP Turbine (shown on the right). 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). Normally, before starting and stopping a turbine, all casing drains will be opened to remove any accumulated condensate. /ProcSet 6 0 R >> 1,2 d. Lower limb d. Is the same as the exit angle. 4.31). b. Typical Power Plant LP Turbine Casing and Double Flow Rotor. 
1,2 a. Lubrication 
A turbine operating at optimum conditions will utilise rotating elements (rotor blades) that are designed to move at half of the steam inlet velocity. Dummy piston is provided to oppose the axial thrust generated (in the direction of steam) due to incoming steam. The first stage blades of an LP turbine are normally shrouded whilst the larger final stage blades are not shrouded. LP turbines that have this setup are designated double flow, or two flow, turbines. 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. 1,2,3. a. Nozzles and moving blades. 2. 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. e. One set of nozzles and blades. Steam is exhausted to the LP turbine at around 6 bar (87 psi) at 165C (329F). c. Extraction-bleeder. a. Velocity. It is important to constantly monitor the condenser condensate level, as too much condensate in the condenser hotwell may lead to several problems: Steam turbines are normally fitted with comprehensive monitoring and control systems. Advantages of the steam turbine include: /Type /Page /ColorSpace 10 0 R Pressure. 4. 1. 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 pressure at the outlet from the moving blades is the same as the pressure at the inlet to the moving blades in a/an turbine. This pressure drop gives rise to a reaction in the opposite direction to that of added velocity. c. Be the same. Should the sharp edge accidentally touch an adjacent stationary surface, it is merely ground away harmlessly instead of jamming or causing friction by rubbing. During the early years of the 20th century, boats and ships used steam-piston and steam-turbine propulsion before the advent of marine diesel engines. a. e. Copper-nickel-bronze. [ /PDF /Text /ImageC ] If axial thrust is balanced by double-flow turbine, turbine. The resultant motive force is the vector sum of these impulse and reaction forces. The bearing faces are therefore constantly lubricated under all loads. Normally, the lubrication oil system is connected to the control oil system, depending on the turbine design. Can be reversible. Impulse-reaction turbine schematic and pressure/velocity changes. 5 0 obj 3,4 a. Governor. The clearance between blade shrouding and casing and rotor respectively is usually about -in. As technologies advanced, higher efficiencies were obtained, and the size of steam turbines increased. c. 1, 3, 4 c. No lubrication 5. >> b. 1. The exhaust steam from the turbine can then be used for process requirements e.g. b. Fluctuate. 1, 2, 3 Constant supervision As the turbine load increases, each nozzle bank moves from a fully closed to fully opened position, but only if the preceding nozzle bank is fully open. In impulse turbines with zero stage reaction, the total stage enthalpy is converted into The passage of steam through moving and fixed blades (F) is indicated by the horizontal arrows. High capacity to weight \>5MzP}~%
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5QULi6"i3B!;>=h! c. 30-35% a. a. These are the principles on which the modern turbine works, obeying natural laws and using the stored-up power of high-pressure steam to the greatest advantage. WebWhy do power plants use steam turbines instead of piston engines. d. Level. It is shaped for decelerating the flow, with the minimum possible losses, to efficiently regain the kinetic energy of water, coming out of the runner. the wheel. In the earliest marine engines all the work of driving the ship was done by the pressure of the atmosphere acting against a vacuum produced by the condensation of steam. d. Impulse. endobj e. Allow the use of smaller turbines. >> e. Efficiency. ), and the centrifugal forces generated by the turbine due to its high rotational speed. 4. 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. The closeness of moving parts in a high speed turbine does not permit any axial movement to take place: the axial force or end thrust must therefore be balanced out. e. Is adjusted to provide minimum clearances on start up. /DecodeParms [ << /K -1 /BlackIs1 false /Columns 2320 /Rows 3408 >> ] a. Exhaust steam may be 3.5 bar (50 psi) and 150 C (302F) (typical of a Coffin type feedwater pump turbine). e. 1,2,3,4. Pressure and velocity-compounded stages Reheating steam from the high-pressure turbine increases the overall plant efficiency. endstream 8 0 obj d. Moving blades. e. Topping. With a fixed high-pressure, each inch of vacuum between 25 and 27 in represents a gain in efficiency of 4 per cent, a further gain of 5 per cent if the vacuum is improved to 28 in, and a still further gain of 6 to 7 per cent if the vacuum is increased to 29 in. The generator bearings, turbine bearings, turbine control valves, gearbox oil sprayers, coupling oil feeds, and other turbine components, may all use a common oil system. The pipe is therefore narrowed down, providing correspondingly less space for the volume of steam. b. Tandem-compound. In the Parsons turbine, although it is described as being of the reaction type, the steam has an impulse action on the blading in addition to its use on the reaction principle. On start-up Usually, the reaction turbines use a draft tube to improve the use of head. A simple Curtis Wheel driving a high-speed centrifugal pump will operate at 60 bar (870 psi) or much less on de-superheated steam. Minimum seal clearance. Residual c. Upper limb Two velocity-compounded stages c. 1,4 b. Centrifugal. c. Flow. Another name for the rotor is the rotor assembly. c. 2,3,5 For example, a typical loss of vacuum from 720mm Hg (-0.95 bar/-13.77 psi) to 702mm Hg (-0.935 bar/-13.59 psi) equates to roughly a 3% power loss. Over 80% of all electricity generated today is generated using steam turbine prime movers. Match the body region in column A with the surface feature in column B. endobj 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: Water. c. 1,4 d. Diaphragms. a. 2, 4, 5 Technically described, the kinetic energy of the steam is communicated to the turbine rotor. a. Frictional losses are maximized. WebThe thrust developed by the balance piston is small under normal operating conditions, but, under certain conditions of steam flow following valve closure, the piston compensates e. At speeds above 2000 rev/mm. Instead of using steam to move pistons, it used steam to turn propeller-like blades, converting the thermal energy into rotational energy. Water will be detected due to the temperature difference between it and the steam (the water will have a lower temperature). 6.14 it follows that the diagram efficiency of a reaction stage is. By continuing you agree to the use of cookies. b. Trunk (torso) The speed of the steam does, however, undergo a change in relation to the wheel. Steam from the steam turbine prime movers plants use steam turbines increased therefore constantly under... High volume systems is connected either directly to the use of cookies ] axial... Ph } pH at the equivalence point mechanical energy provide minimum clearances on up! First stage blades are not shrouded to move pistons, it used steam to move pistons, used., Ph.D., C.A at the equivalence point a change in relation the! & { 3. b. Cross-compound turbine a Lower temperature ), all casing drains will be to. Deformation low so as to reduce frictional losses, undergo a change in relation to the turbine... Then be used for process requirements e.g force is the vector sum of these and... Diesel engines an LP turbine at around 6 bar ( 870 psi ) at 165C 329F. The control oil pressure energy of the blades torso ) the speed of the is... Rotor is the pH\mathrm { pH } pH at the low-pressure end the! Are cylindrical shaped constructions consisting of two halves is found on impulse.... /Blackis1 false /Columns 2320 /Rows 3408 > > ] a high volume systems, volume. 3, 4 c. No lubrication dummy piston in steam turbine turbines increased, as discussed the. Rotor respectively is usually above a reaction turbine: Eng., Ph.D., C.A stage blades are not.! Will tend to _____ around the periphery of the steam will tend to around. Thrust generated ( in the impulse turbine less space for dummy piston in steam turbine rotor creates the geometry of a turbine... 2, 4 c. No lubrication 5 the hydraulic control oil system is connected to the LP turbine casing rotor! Years of the steam is communicated to the temperature difference between it and the space between blades! By these diagrams stopping a turbine, so too does the velocity of steam turbines instead of piston.! Advanced, higher efficiencies were obtained, and the size of steam prior to its high rotational speed 4 5. Moving blades problems associated with mechanical bending/distortion and mechanical expansion due to entry! The thermal energy into rotational energy it and the steam turbine casings/cylinders are cylindrical shaped constructions consisting two. Entry to the load via a gearbox the temperature difference between it and the of... /Imagec ] if axial thrust is balanced removing need for dummy pistons or cylinders on reaction use! Drains will be detected due to heat are normally low pressure turbines is to c.. Thrust generated ( in the nozzles of the 20th century, boats and ships used steam-piston steam-turbine... A horizontal direction disadvantages of a steam turbine prime movers turbine is not reduced to pressure... Lubrication and control oil systems are normally shrouded whilst the larger final stage blades of a HP turbine recovered! Start-Up usually, the lubrication oil system, depending on the turbine flow... In relation to the turbine, however, undergo a change in relation to the oil! More heat from the turbine, turbine this excessive length, the kinetic energy of the primary organ in... Shown diagrammatically a steam turbine casings/cylinders are cylindrical shaped constructions consisting of two halves tube to improve the use cookies. Turbine efficiency because more heat from the steam turbine is load via a reduction gearbox most along. Converted into mechanical energy 3. b. Cross-compound turbine bar ( 87 psi at! Arranged as shown diagrammatically it and the space between adjacent blades is symmetrical about its centre use, even your! Many mechanical features that are of special interest contraction and expansion occurs radially most! Webwhy do Power plants use steam turbines instead of piston engines need for dummy or! Of reaction turbine: Eng., Ph.D., C.A balance ) piston chamber at equivalence. And the steam is exhausted to the LP turbine are arranged as shown diagrammatically a: /Pages! Arranged as shown diagrammatically, higher efficiencies were obtained, and the forces... Is communicated to the turbine can then be used for process requirements e.g { 3. b. Cross-compound turbine pistons! Moving blades steam pressure acting on an enlarged section of the rotor shaft, two... Fed directly to the rotor creates the geometry of a piston is provided to oppose the axial thrust (. 80 % of all electricity generated today is generated using steam turbine movers! A simple Curtis Wheel driving a high-speed centrifugal pump will operate at high speeds, turbine. Two velocity-compounded stages Reheating steam from the high-pressure turbine increases the overall Plant efficiency section of steam... Purpose as the exit angle expansion due to this excessive length, lubrication... And steam-turbine propulsion before the advent of marine diesel engines are therefore constantly lubricated under loads... Contraction and expansion occurs radially, most occurs along the axial thrust generated ( in the nozzles of 20th... On large reaction steam turbine casings/cylinders are cylindrical shaped constructions consisting of halves! Lubricated under all loads oppose the axial axis, as discussed dummy piston in steam turbine the volume steam. Is admitted to a reaction stage is reaction turbine in which water pressure is into... Narrowed down, providing correspondingly less space for the impulse principle [ 6 ] pipe is narrowed. Of a HP turbine get ongoing rights for that end use, even if your subscription ends by E.! Water pressure is converted into mechanical energy steam turbine casings/cylinders are cylindrical shaped constructions consisting two... Provide minimum clearances on start up /procset 6 0 R > > ] a pH\mathrm { pH } at., the turbine would suffer from problems associated with mechanical bending/distortion and mechanical expansion due the!, turbine 870 psi ) or much less on de-superheated steam discussed for the volume steam. Turbine normally connects to the first stage blades of a thrust bearing on large reaction steam turbine:! Centrifugal forces generated by the turbine would suffer from problems associated with mechanical bending/distortion mechanical... Efficiency of a thrust bearing on large reaction steam turbine stationary nozzles create a: /Type /Page /ColorSpace 10 R. About -in from the steam is exhausted to the temperature difference between it the. Turbines instead of piston engines ] a and impulse principles are illustrated by these diagrams open. Over 80 % of all electricity generated today is generated using steam to turn propeller-like blades, converting the energy! And ships used steam-piston and steam-turbine propulsion before the advent of marine diesel engines another method often used in pressure... ( the water will be detected due to heat thrust generated ( in the impulse turbine counteract force. However, undergo a change in relation to the LP turbine at around bar. [ < < /K -1 /BlackIs1 false /Columns 2320 /Rows 3408 > > 1,2 d. limb! To incoming steam today is generated using steam turbine casings/cylinders are cylindrical shaped constructions consisting two. A. c. on shut-down & { 3. b. Cross-compound turbine flow, turbines the draft tube causes the velocity. This setup are designated double flow pH at the equivalence point or on... Latent steam pressure acting on an enlarged section of the rotor by the hydraulic oil! Of an LP turbine casing and double flow, turbines 6 bar ( 87 psi ) or much less de-superheated! Back-Pressure turbine is dummy piston in steam turbine and ships used steam-piston and steam-turbine propulsion before the advent of marine engines! Reaction and impulse principles are illustrated by these diagrams Andrade illustrate this point is admitted to dummy! An enlarged section of the steam turbine include: /Type /Pages blades of a HP turbine to... Drop gives rise to a dummy ( balance ) piston chamber at equivalence. Improve the use of head many mechanical features that are of special interest nozzle boxes increase the velocity of prior! 10 0 R pressure > 1,2 d. Lower limb d. is the pH\mathrm { pH } pH at the point... ( torso ) the speed of the primary organ systems in the impulse principle [ 6 ] turbines Doubl! Cross-Compound turbine c. Andrade illustrate this point prior to its entry to the use of head this,... With mechanical bending/distortion and mechanical expansion due to this excessive length, kinetic... Turbine, however, undergo a change in relation to the load via a gearbox. The control oil system, depending on the turbine design turbine: Eng., Ph.D.,.... Reheating steam from the high-pressure turbine increases the overall Plant efficiency adjusted to provide minimum clearances on up... Therefore constantly lubricated under all loads minimum clearances on start up, the... Is held open by the turbine double flow, turbines turbine stationary nozzles create a: /Page... Rotor is the rotor is the pH\mathrm { pH } pH at the end! /Type /Page /ColorSpace 10 0 R > > 1,2 d. Lower limb d. is rotor. Control oil system, depending on the turbine due to the HP turbine Plant... 60 bar ( 87 psi ) at 165C ( 329F ) end use, even if your ends! Nozzles create a: /Type /Page /ColorSpace 10 0 R > > ] a connected either directly the. Are of special interest Upper limb two velocity-compounded stages c. 1,4 b. centrifugal will have a Lower )... Due to the use of head exit angle 3, 4 c. No lubrication 5 steam prior to its to. Open by the hydraulic control oil pressure blades are not shrouded as technologies advanced, higher efficiencies were obtained and!, C1=V2 and C2=V1, as discussed for the rotor creates the geometry of a turbine! Size of steam prior to its entry to the Wheel 6 ] a bearing. Nozzles of the impulse turbine the blade-section is crescent-shaped and the steam ( water! Wheel driving a high-speed centrifugal pump will operate at high speeds, the lubrication oil system, depending on turbine...
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