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steam turbine implulse and reaction turbine <br>maintenance and working

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  1. IUBAT- International University of Business Agriculture andTechnology Founded 1991 by Md. AlimullahMiyan COLLEGE OF ENGINEERING ANDTECHNOLOGY(CEAT) STEAMTURBINE POWERPLANT LECTURE SLIDE -03 Course Title: Power PlantEngineering Course Code : MEC403 CourseInstructor:Engr. Md.IrtezaHossain Engr. Md. IrtezaHossain Faculty,BSME

  2. Engr. Md. IrtezaHossain Faculty,BSME

  3. Overview oftopics • Steam powerplant • Major Components of steam powerplant • Boiler • BoilerMountings • Air Preheater • Super-heater • Economizer • Reheater • Turbine • Condenser • Feed waterpump Engr. Md. IrtezaHossain Faculty,BSME

  4. Elements of a simple steam powerplant Engr. Md. IrtezaHossain Faculty,BSME

  5. Steam powerplant A steam powerplant isapowerplantin which heated, wateris turnsinto steam and spins a steam turbine which drives an electrical generatorto produceelectricity. Fig: Layout of steam powerplant. Engr. Md. IrtezaHossain Faculty,BSME

  6. Major Components of steam powerplant Engr. Md. IrtezaHossain Faculty,BSME

  7. Boiler A boiler is a closed vessel in which water or other fluid is heated. The heatedor vaporized fluid exits the boiler for use in various processes or heatingapplications. Twotypes, Water tubeboiler Fire tubeboiler Engr. Md. IrtezaHossain Faculty,BSME

  8. Water tubeboiler The water flow through the tubeand the flow gases flow outside thetube. Engr. Md. IrtezaHossain Faculty,BSME

  9. Fire tube boiler The fire tube boiler i which the flowgases passes through the tubes and water stor out side thetube. n e Engr. Md. IrtezaHossain Faculty,BSME

  10. BoilerAccessories Air Preheater Air pre heater is a heat recovery unit . An airpre heater is used to recover the heat from theexhaust fluegas. Engr. Md. IrtezaHossain Faculty,BSME

  11. Boiler Accessories • Air Pre heater • The purpose of the air pre heater is to recover the heat from the boiler flue gas which increases the thermal efficiency ofthe boiler by reducing the useful heat lost in the fluegas. • There are two types of airpre heaters for use in steam generators • Tubular type built into theboiler flue gasducting • Regenerative air preheater Fig: Layout of air preheater. Engr. Md. IrtezaHossain Faculty,BSME

  12. BoilerAccessories Super-heater A super- heater isa device usedto convert saturated steam or wet steam into drysteam used in steam engines Engr. Md. IrtezaHossain

  13. BoilerAccessories • Superheater • It’s purpose is to increase the temperature of steam without raising the pressure. It’s generally an integral part of theboiler • Type of Superheater • A radiant super heater is placed directly in the combustion chamber. • A convection super heateris located in the path of thehot gases. • A separately fired super heater,as its name implies, is totally separated from theboiler. Engr. Md. IrtezaHossain Faculty,BSME

  14. BoilerAccessories Economizer An economizer is a device used to heat the feed water and heat the condensate from turbines before it is pumped to the boilers by utilizing theheat in the before chimney. exhaust leaving fluegasses through Fig: Layout ofEconomizer. Engr. Md. IrtezaHossain Faculty,BSME

  15. BoilerAccessories Economizer • The first successful economizer design was used to increase the steam-raising efficiency of the boilers of stationary steam engines. It was patented by Edward Green in1845. • Economizers are commonly used as part of a heat recovery steam generator in a combined cycle powerplant. • A common application of economizers in steam power plants is to capture the waste heat from boiler stack gases (flue gas)and transfer it to the boiler feed water. This raises the temperature of the boiler feedwater Engr. Md. IrtezaHossain Faculty,BSME

  16. BoilerAccessories Re-heater Engr. Md. IrtezaHossain Faculty,BSME

  17. BoilerAccessories • Re-heater • Re-heaters are the same as the super-heaters but the temperature of it’s a little bite less than super-heaters and their pressure is 20%- 25% less than thesuper-heater, • It usually use to elevate the steam temperature. After expanding through the high pressure turbine the exhaust steam is returned to the boiler at 360 C and 42 bar pressure for reheating before being used in the intermediate pressureturbine. • The re-heater reheats the steam from a temperature of 360 C backto • 568C. Engr. Md. IrtezaHossain Faculty,BSME

  18. BoilerMountings Different fittings and devices necessary for the operation and safety of a boiler are called boiler mountings. The various boiler mountingsare: Water level indicator Pressure gauge Steam stopvalve Feed checkvalve Blow-downcock Fusible plug Safety valve : spring loaded, dead weight, lever type. Engr. Md. IrtezaHossain Faculty,BSME

  19. BoilerMountings Water levelindicator Engr. Md. IrtezaHossain Faculty,BSME

  20. BoilerMountings Water levelindicator The function of the water level indicator is to indicate the level of water in the boiler constantly. Every boiler is normally fitted with two water level indicators. Awater level indicator used in low pressure boilers. It consists of three cocks and a glass tube. The steam cock 1 keeps the glass tube in connection with the steam space and cock 2 puts the glass tube in convection with the water space in the boiler. The drain cock 3 is used to drain out the water from the glass tube at intervals to ascertain that the steam and water cocks are clear in operation. The glass tube is generally protected with ashield. Engr. Md. IrtezaHossain Faculty,BSME

  21. BoilerMountings Pressuregauge Engr. Md. IrtezaHossain Faculty,BSME

  22. BoilerMountings • Pressuregauge • The pressure gauge is used to indicate the steam pressure of the boiler. The gauge is normally mounted in the front top of the steam drum. • Pressure gauges are connected to the steam space of the boiler and usually have a ring type siphon tube which fills with condensed steam and protects the dial mechanism from hightemperatures. • The commonly used pressure gauge is the Bourdon type pressure gauge .It consists of an elastic metallic tube of elliptical cross- section bent in the form of circular arc. One end of the tube is fixed and connected to the steam of the boiler and other end is connected to a sector wheel through a link. The section remains in mesh with a pinion fixed on a spindle. A pointer is attached to the spindle to read the pressure on a dialgauge. Engr. Md. IrtezaHossain Faculty,BSME

  23. BoilerMountings Steam StopValve Engr. Md. IrtezaHossain Faculty,BSME

  24. BoilerMountings • Steam StopValve • The function of the stop valve is to regulate the flow of steam from the boiler to the prime mover as per requirement and shut off the steam flow when not required. • A commonly used steam stop valve is shown in figure, it consists of main body, valve, valve seat, but and spindle, which passes through a gland to prevent leakage of steam. The spindle is rotated by means of a hand wheel to close oropen. Engr. Md. IrtezaHossain Faculty,BSME

  25. BoilerMountings Feed CheckValve Engr. Md. IrtezaHossain Faculty,BSME

  26. BoilerMountings • Feed CheckValve • The function of the feed check valve is to allow the supply of water tothe boiler at high pressure continuously and to prevent the back flow ofwater from the boiler when the pump pressure is less than boilerpressure. • A commonly used feed check valve is shown in Fig. It is fitted to the shell slightly below the normal water level of the boiler. The lift of the non-return valve is regulated by the end position of the spindle which is attached withthe hand wheel. The spindle can be moved up or down with the help of hand wheel which is screwed to the spindle by anut. • Under normal conditions, the non-return valve is lifted due to the water pressure from the pump and water is fed to the boiler. In case pumppressure falls below boiler pressure, valve is closedautomatically Engr. Md. IrtezaHossain Faculty,BSME

  27. BoilerMountings Blow-DownCock Engr. Md. IrtezaHossain Faculty,BSME

  28. BoilerMountings Blow-DownCock • The function of blow-down cock is to remove sludge or sediments collected at the bottom-most point in the water space in a boiler, while the boiler issteaming. • It is also used for complete draining of the boiler a commonly used type of blow- down cock is shown in Fig. it consists of a conical plug fitted accurately into a similar casing. The plug has a rectangular opening which may be brought with the line of the passage of the casing by rotating theplug. • This causes the water to be discharged from the boiler the discharging of water may be stopped by rotating the plugagain. • Theblow-downcockshouldnotbeopenedwhentheboilerisin • operation. Engr. Md. IrtezaHossain Faculty,BSME

  29. BoilerMountings SafetyValves Engr. Md. IrtezaHossain Faculty,BSME

  30. BoilerMountings • SafetyValves • The function of a safety valve is to prevent the steam pressure in the boiler exceeding the desired rated pressure by automatically opening and discharging steam to atmosphere allowable pressure falls back to normal ratedvalue. • There are three types of safetyvalves, • Spring loaded (Rams bottom) type, • Dead weight type,and • Levertype. Engr. Md. IrtezaHossain Faculty,BSME

  31. SafetyValves Spring Loaded SafetyValve The spring loaded safety valve holds two valves on their seats by pulling the lever down. The upper end of the spring is looked to the lever midway between the two pivots. The lower end is hooked to the shackle fixed to the valve chest by studs andnuts. Dead Weight Safety Valve It is generally used on low capacity boilers like the Lancashireboiler. Lever SafetyValve It is suitable for stationaryboilers. Engr. Md. IrtezaHossain Faculty,BSME

  32. Turbine A turbine is a type of engine that can extract energy from a fluid, such as water, steam, air, or combustion gases. It can be contrasted with a piston engine which uses a piston instead of a turbine to extract energy. Steamturbine Waterturbine Windturbine Gasturbine A rotor of a modern steam turbine,used in a powerplant Engr. Md. IrtezaHossain Faculty,BSME

  33. Turbine SteamTurbine Asteam turbine is a prime mover in which rotary obtained motion is bythe of gradual change momentum of the steam. In a steam turbine the force exerted on the blades is due to the velocity ofsteam. Engr. Md. IrtezaHossain Faculty,BSME

  34. Turbine • Hero Reaction Turbine – 120B.C. • First Practical Turbine – 1884, C.Parsons • First Power Plant – 7.5 kw –1890 • Reaction, Impulse andVelocity-Compounded • Reheat Steam –1930’s • Last 100 years Turbine is the key elementin generatingelectricity • Turbines run Generators, Pumps, Fans, etc. • Today up to 1,500MW 34

  35. Turbine • Types ofsteam turbine • Impulseturbine • Reactionturbine Engr. Md. IrtezaHossain Faculty,BSME

  36. Turbine Impulseturbine Aturbinethatisdrivenby high velocity jets of wateror steam directed buckets wheel. fromanozzle ontovanesor attachedtoa The resulting impulse (as described by Newton's second law of motion) spins the turbine and removes kinetic energy from the fluidflow. Engr. Md. IrtezaHossain Faculty,BSME

  37. Turbine • Impulseturbine • In impulse turbine, the drop in pressure of steam takes place in a stationarynozzle. • The drop in pressure leads to conversion of enthalpy into kinetic energy of afluid. • Hencethevelocityofthefluidincreaseattheexpenseof • temperature andpressure. • This high velocity fluid (Jet) is deflected by a curvedblade. • A change in direction of a jet generates change in momentumof • thefluid. • Arateofchangeinmomentumwillgenerateaforceonthe blade. • Amotivepowerisgenerated,whenthisforcecanmovethe • blade. Engr. Md. IrtezaHossain Faculty,BSME

  38. The simple Impulseturbine • It primarily consistsof: • a nozzle or a set ofnozzles, • a rotor mounted on a shaft, one set of moving blades attached to therotor • Generally nozzles are attached to acasing. • The absolute velocity the offluid increasesin stationary absolute nozzles at the costof pressure • Theabsolutevelocityoffluid decreasesinmovingbladesas somekinetic energyis the transferredfromfluidto blade.. • Example: de-Laval turEbningre. M. d. IrtezaHossain Faculty,BSME

  39. Turbine Reactionturbine A turbinein which the working fluid is accelerated by expansion in both the static nozzles and the rotor blades. Torque is produced by the momentum changes in the rotor and by reaction from fluid accelerating out of the rotor Engr. Md. IrtezaHossain Faculty,BSME

  40. Turbine • ReactionTurbine: • In a Reaction Turbine drop in pressure occurs in amovable nozzle. • The drop in pressure leads to conversion of enthalpy into kinetic energy of afluid. • Hencethevelocityofthefluidincreaseattheexpenseof temperature andpressure. • A high velocityjetleaving the moving nozzle will generate a reaction on thenozzle. • AmotivePowerisgenerated,whenthisreactioncanmovethe • nozzle. Engr. Md. IrtezaHossain Faculty,BSME

  41. Turbine • Impulse-Reactionturbine • This utilizes the principle of impulse andreaction. • There are a number of rows of moving blades attached to the rotor and an equal number of fixed blades attached to the casing. • The fixed blades are set in a reversed manner compared to the moving blades, and act as nozzles. • Due to the row of fixed blades at the entrance, instead of nozzles, steam is admitted for the whole circumference and hence there is an all-round or completeadmission. Engr. Md. IrtezaHossain Faculty,BSME

  42. How does the steam turbinework? • Impulse stage – whole pressure drop innozzle (whole enthalpy drop is changed into kinetic energy in thenozzle) • Reaction stage – pressure drop both in stationary blades and in rotary blades (enthalpy drop changed intokinetic energy both in stationary blades and in themoving blades in rotor) Engr. Md. IrtezaHossain Faculty,BSME

  43. Steam TurbineCycle ThermodynamicsCycles GasCycles VapourCycles Working Fluid remains inGaseous Phase throughout theCycle. WorkingFluidexistsinVapor Phase during part of the Cycle,and inliquidphaseduringremaining part. Engr. Md. IrtezaHossain Faculty,BSME

  44. RANKINE CYCLE: THE IDEALCYCLE FOR VAPOR POWERCYCLES Thr Rankine cycle, which is the ideal cycle for vapor power plants. Theideal Rankine cycle does not involve any internalirreversibilities. The simple ideal Rankine cycEleng. r. Md. IrtezaHossain Faculty,BSME

  45. Energy Analysis of the Ideal RankineCycle Steady-flow energyequation The efficiency of power plants inthe U.S. is often expressed in terms of heat rate, which is the amount of heat supplied, in Btu’s, to generate 1 kWh ofelectricity. The thermal efficiency can beinterpreted as the ratio of the area enclosed by the cycle on a T-s diagram to the areaunder Engr. tMhde.Ihrteezaat-Haodsdsiatinionprocess. Faculty,BSME

  46. DEVIATION OF ACTUALVAPOR POWER CYCLES FROM IDEALIZEDONES The actual vapor power cycle differs from the ideal Rankine cycle asa result of irreversibilities in variouscomponents. Fluid friction and heat loss to the surroundings are the twocommon sources ofirreversibilities. Isentropicefficiencies Deviation of actual vapor power cycle from the ideal Rankinecycle. The effect of pump and turbEinnger. iMrrde. vIrteerzsaibHiolsistiaeinson the idealRankine Faculty,BSME cycle.

  47. HOW CAN WE INCREASE THE EFFICIENCY OFTHE RANKINECYCLE? The basic idea behind all the modifications to increase the thermalefficiency of a power cycle is the same: Increase the average temperature at which heatis transferred to the working fluid in the boiler, or decrease the average temperature at which heat is rejected from the working fluid in thecondenser. Lowering the Condenser Pressure (Lowers Tlow,avg) To take advantage of the increased efficiencies at low pressures, the condensers of steam power plants usually operate well below the atmospheric pressure. There is a lower limit to this pressure depending onthe temperature of the coolingmedium Side effect: Lowering the condenser pressure increases the moisture content ofthe steam at the final stages of theturbine. The effect of lowering the condensEenrgr. Md. IrtezaHossain pressure on the ideal Rankinecycle. Faculty,BSME

  48. Superheating the Steam to High Temperatures(Increases Thigh,avg) Both the net work and heat inputincrease as a result of superheating the steam to a higher temperature. The overall effect isan increase in thermal efficiency since the average temperature at which heat isadded increases. Superheating to higher temperatures decreases the moisture content ofthe steam at the turbine exit, which is desirable. The temperature is limitedby metallurgical considerations. Presentlythe highest steam temperature allowed atthe turbine inlet is about620°C. The effect of superheatingthe steam to higher temperatures on the ideal Rankinecycle. Engr. Md. IrtezaHossain Faculty,BSME

  49. Increasing the Boiler Pressure (IncreasesThigh,avg) For a fixed turbine inlet temperature, the cycle shifts to the left and the moisture content of steam at the turbine exit increases. This side effect can be correctedby reheating thesteam. Today many modern steampower plants operate at supercritical pressures (P > 22.06 MPa) and have thermal efficiencies ofabout 40% for fossil-fuel plants and 34% for nuclearplants. HossaAin supercritical Rankinecycle. The effect of increasing the boiler pressure on the ideal RankineEcnygrc. lMed. .Irteza Faculty,BSME

  50. THE IDEAL REHEAT RANKINECYCLE How can we take advantage of the increased efficiencies at higher boilerpressures without facing the problem of excessive moisture at the final stages of theturbine? Superheat the steam to very high temperatures. It is limitedmetallurgically. Expand the steam in the turbine in two stages, and reheat it in between(reheat) The ideal reheat Rankinecycle. Engr. Md. IrtezaHossain Faculty,BSME

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