EME Unit 2 Turbines Ppt by Kalyan Chakravarthy

www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS* Turbo Machine is defined as a device that extracts energy from a continuously flowing fluid by the dynamic action of one or more rotating elements .

The prefix turbo is a Latin word meaning spin or whirl implying that turbo machines rotate in some way.


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*Types of Turbines

Steam TurbinesGas Turbines (Combustion Turbines)Water (Hydraulic) Turbines


Steam TurbinesA steam turbine is mainly used as an ideal prime mover in which heat energy is transformed into mechanical energy in the form of rotary motion.

A steam turbine is used in Electric power generation in thermal power plants. Steam power plants.To propel the ships, submarines.

In steam turbines, the heat energy of the steam is first converted into kinetic (velocity) energy which in turn is transformed into mechanical energy of rotation and then drives the generator for the power generation.



www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*Based on action of steam or type of expansion:Impulse or velocity or De Laval turbineReaction or pressure or Parsons turbine Combination turbineBased on number of stages:Single stage turbine 2. Multi-stage turbineBased on type of steam flow:Axial flow turbine 2. Radial flow turbine


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*. The steam is made to fall in its pressure by expanding in a nozzle. Due to this fall in pressure, a certain amount of heat energy is converted into kinetic energy, which sets the steam to flow with a greater velocity. The rapidly moving particles of the steam enter the rotating part of the turbine, where it undergoes a change in the direction of motion, which gives rise to a change of momentum and therefore a force. This constitutes the driving force of the turbine.


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*Impulse Turbines (De Laval Turbine)

In this type of turbine, steam is initially expanded in a nozzle from high pressure to low pressure. High velocity jet of steam coming out of the nozzle is made to glide over a curved vane, called Blade.


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS* The jet of steam gliding over the blade gets deflected very closely to surface. This causes the particles of steam to suffer a change in the direction of motion, which gives rise to a change of momentum and therefore a force, which will be centrifugal in nature.

Resultant of all these centrifugal forces acting on the entire curved surface of the blade causes it to move.


Principle of working -In this type of turbine, the high pressure steam does not initially expand in the nozzle as in the case of impulse turbine, but instead directly passes onto the moving blades.




Blade shapes of reaction turbines are designed in such a way that the steam flowing between the blades will be subjected to the nozzle effect. Hence, the pressure of the steam drops continuously as it flows over the blades causing, simultaneous increase in the velocity of the steam.


Reaction force: is due to the change in momentum relative velocity of the steam while passing over the blade passage.Centrifugal force: is the force acting on the blade due to change in radius of steam entering and leaving the turbine. Resultant force: is the resultant of Reaction force and Centrifugal force.www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*Difference between Impulse & Reaction Turbines

Impulse TurbineReaction TurbineThe steam expands (pressure drops) completely in nozzles or in the fixed bladesThe steam expands both in the fixed and moving blades continuously as it flows over them The blades have symmetrical profile of uniform sectionThe blades have converging (aerofoil) profileThe steam pressure while passing over the blades remains constantThe steam pressure while passing over the blades gradually drops Because of large initial pressure drop, the steam and turbine speeds are very high Because of gradual pressure drop, the steam and turbine speeds are lowThe nozzles are fitted to the diaphragm (the partition disc between the stages of the turbine)The fixed blades attached to the casing serve as nozzles



Impulse TurbineReaction TurbinePower is obtained only due to the impulsive force of the incoming steamPower is obtained due to impulsive force of incoming steam as well as reaction of exit steamSuitable for small capacity of power generation & occupies less space per unit powerSuitable for medium & high capacity power generation and occupies more space per unit powerEfficiency is lesserEfficiency is higherCompounding is necessary to reduce speedCompounding is not necessary


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*Compounding of Impulse TurbinesAs the complete expansion of steam takes in one stage (i.e., the entire pressure drop from high pressure to low pressure takes place in only one set of nozzles), the turbine rotor rotates at very high speed of about 30,000 rpm (K.E. is fully absorbed).

High speed poses number of technical difficulties like destruction of machine by the large centrifugal forces developed, increase in vibrations, quick overheating of blades, impossibility of direct coupling to other machines, etc.To overcome the above difficulties, the expansion of steam is performed in several stages.



Utilization of the high pressure energy of the steam by expanding it in successive stages is called Compounding.

Methods of Compounding: Velocity compounding (Curtis Impulse Turbine) Pressure compounding Pressure-velocity compounding


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS* Velocity compounding

Comprise of nozzles and two or more rows of moving blades arranged in series. In between two rows of moving blades, one set of guide (fixed) blades are suitably arranged. Guide (fixed) blades are fixed to casing and are stationary.


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*Velocity Compounding (Curtis Impulse Turbine)


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS* Consists of two stage of nozzles followed by two rows of moving blades.


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS* Pressure Compounding


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*Pressure-Velocity Compounding(Combined Impulse Turbine)Total pressure drop is divided into two stages & the total velocity obtained in each stage is also compounded


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*A Gas turbine uses the hot gases of combustion directly to produce the mechanical power.

Fuels used - Kerosene, coal, coal gas, bunker oil, gasoline, producer gas, etc.,Classification:Open cycle gas turbineClosed cycle gas turbine


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*ApplicationsGas turbines are used in:Electric power generation plantsSteel, oil and chemical industriesAircrafts, Ship propulsionTurbo jet and turbo-propeller engines like rockets, missiles, space ships etc.,


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*Open cycle gas turbine:The entire flow of the working substance comes from atmosphere and is returned to the atmosphere back in each cycle. Closed cycle gas turbine:The flow of the working substance of specified mass is confined within the cyclic path. ( Air or Helium is the working substance)


COMPRESSOR:draws in air and compress it before it is fed into combustion chamberCOMBUSTOR:fuel is added to the compressed air and burnt to produce high velocity exhaust gas TURBINE:extracts energy from exhaust gaswww.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*Difference between open & closed cycle turbine

Open cycleClosed cycleLesser thermal efficiencyHigherLoss of working fluidNo loss of working fluidBigger in sizeSmallerBig compressor is neededSmaller one is sufficientPossibility of corrosion of blades and rotorFree from corrosionEconomicalNot economicalExhaust gases from turbine exit to atmosphereFed back into the cycle


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*It is a prime mover, which converts hydro power (energy of water) into mechanical energy and further into hydro-electric power.


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*Classification of Water TurbinesBased on action of water:Impulse turbine pelton wheel.Reaction turbine francis and kaplan. Based on name of originator:Pelton turbine or Pelton wheelFrancis turbineKaplan turbineBased on head of water:Low head turbineMedium head turbineHigh head turbine


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*Pelton Turbine (Pelton Wheel or Free Jet Turbine)

High head, tangential flow, horizontal shaft, impulse turbine


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*PELTON TURBINE


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*Pelton Turbine Runner


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS* Only a part of the pressure energy of the water is converted into K.E. and the rest remains as pressure head.


First, the water passes to the guide vanes which guide or deflect the water to enter the blades, called moving blades, mounted on the turbine wheel, without shock. The water from the guide blades are deflected on to the moving blades, where its part of the pressure energy is converted into K.E., which will be absorbed by the turbine wheel. The water leaving the moving blades will be at a low pressure.www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*



The difference in pressure between the entrance and the exit of the moving blades is called Reaction pressure, which acts on moving blades of the turbine wheel and sets up the turbine wheel into rotation in the opposite direction.

Examples: Francis turbine, Kaplan turbine, Propeller turbine, Thompson turbine, Bulb turbine.


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*Francis TurbineMixed flow, medium head reaction turbine.

Consists of a spiral casing enclosing a number of stationary guide blades fixed all round the circumference of an inner ring of moving blades (vanes) forming the runner, which is keyed to the turbine shaft.

Radial entry of water along the periphery of the runner and discharge at the center of the runner at low pressure through the diverging conical tube called draft tube.


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*FRANCIS TURBINE


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*Francis Inlet Scroll, Grand Coulee Dam


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*Francis Runner, Grand Coulee Dam


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*FRANCIS TURBINE & GENERATOR


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*Kaplan TurbineAxial flow, low head.Similar to Francis turbine except the runner and draft tube.

The runner (Boss or Hub) resembles with the propeller of the ship, hence some times it is called as Propeller turbine.Water flows parallel to the axis of the shaft.


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*KAPLAN TURBINE


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*Vertical Kaplan Turbine (Courtesy: VERBUND-Austrian Hydro Power)


www.bookspar.com | Website for Students | VTU NOTES | QUESTION PAPERS*Propeller Turbine Runner


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EME Unit 2 Turbines Ppt by Kalyan Chakravarthy