Turbines 1.ppt

‘‘Turbo MachineTurbo Machine’’ is defined as a is defined as a device device that that extracts energy from a extracts energy from a continuouslycontinuously flowing fluid by the dynamic action of flowing fluid by the dynamic action of one one or more rotating elements .or more rotating elements .

The prefix ‘The prefix ‘turboturbo’ is a ’ is a LatinLatin word word meaning meaning ‘‘spinspin’ or ‘’ or ‘whirlwhirl’ implying that turbo ’ implying that turbo

machines machines rotate in some way.rotate in some way.

TypesTypes ofof TurbinesTurbines

1.1. Steam TurbinesSteam Turbines

2.2. Gas Turbines (Combustion TurbinesGas Turbines (Combustion Turbines))

3.3. Water (Hydraulic) TurbinesWater (Hydraulic) Turbines

Srinivas School of Engineering, Mukka 3

Steam Turbines A 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 1. Electric power generation in thermal power plants.

2. Steam power plants.

3. 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.


Based on action of steam or type of Based on action of steam or type of expansion:expansion:

1.1. Impulse or velocity or Impulse or velocity or De LavalDe Laval turbine turbine

2.2. Reaction or pressure or Reaction or pressure or Parson’sParson’s turbine turbine

3.3. Combination turbineCombination turbine

Based on number of stages:Based on number of stages:1.1. Single stage turbine Single stage turbine 2. Multi-stage turbine2. Multi-stage turbine

Based on type of steam flow:Based on type of steam flow:1.1. Axial flow turbine Axial flow turbine 2. Radial flow turbine2. Radial flow turbine




. The steam is made to fall . The steam is made to fall in its pressure by in its pressure by expanding in a nozzle.expanding in a nozzle. Due Due to this to this fall in pressurefall in pressure, a , a certain amount of heat certain amount of heat energy is converted into energy is converted into kinetic energy, which sets kinetic energy, which sets the steam to flow with a the steam to flow with a greater velocitygreater velocity..

The rapidly moving particles of the steam enter the The rapidly moving particles of the steam enter the rotating part of the turbine, where it undergoes a rotating part of the turbine, where it undergoes a change change in the direction of motionin the direction of motion, which gives rise to , which gives rise to a a change of momentum and therefore a forcechange of momentum and therefore a force. . This This constitutes the driving force of the turbine.constitutes the driving force of the turbine.Srinivas School of Engineering,

Mukka 8

Impulse TurbinesImpulse Turbines (De Laval (De Laval Turbine)Turbine)

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

The jet of steam gliding over the blade The jet of steam gliding over the blade gets gets deflected very closely to surface. This deflected very closely to surface. This causes the particles of steam to suffer causes the particles of steam to suffer a a change in the direction of motion, change in the direction of motion, which gives which gives rise to a rise to a change of momentumchange of momentum and therefore a and therefore a force, force, which will be which will be centrifugalcentrifugal in nature.in nature.

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



NOZZLE

EXHAUST STEAM

TURBINE SHAFT

MOVING BLADES

HIGH PRESSURE STEAM

Schematic of Impulse Turbine

VL

PH

Q

PL

VH

R

C

B

NozzleRotor

Blades

Velocity Variation

Pressure Variation

Pressure-Velocity diagram in Impulse Turbine

A

P

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

Reaction forceReaction force:

is due to the change in momentum relative velocity of the steam while passing over the blade passage.

Centrifugal forceCentrifugal force:

is the force acting on the blade due to change in radius of steam entering and leaving the turbine.

Resultant forceResultant force:

is the resultant of Reaction force and Centrifugal force.



Fixed BladeMoving Blade

Impulse TurbineImpulse Turbine Reaction TurbineReaction TurbineThe steam expands The steam expands (pressure drops) completely (pressure drops) completely in nozzles or in the fixed in nozzles or in the fixed bladesblades

The steam expands both in The steam expands both in the fixed and moving blades the fixed and moving blades continuously as it flows over continuously as it flows over them them

The blades have The blades have symmetrical profile of symmetrical profile of uniform sectionuniform section

The blades have converging The blades have converging (aerofoil) profile(aerofoil) profile

The steam pressure while The steam pressure while passing over the blades passing over the blades remains constantremains constant

The steam pressure while The steam pressure while passing over the blades passing over the blades gradually drops gradually drops

Because of large initial Because of large initial pressure drop, the steam pressure drop, the steam and turbine speeds are very and turbine speeds are very high high

Because of gradual pressure Because of gradual pressure drop, the steam and turbine drop, the steam and turbine speeds are lowspeeds are low

The nozzles are fitted to the The nozzles are fitted to the diaphragm (the partition disc diaphragm (the partition disc between the stages of the between the stages of the turbine)turbine)

The fixed blades attached to The fixed blades attached to the casing serve as nozzlesthe casing serve as nozzles


Difference between Impulse & Reaction TurbinesDifference between Impulse & Reaction Turbines

Impulse TurbineImpulse Turbine Reaction TurbineReaction Turbine

Power is obtained only Power is obtained only due to the impulsive force due to the impulsive force of the incoming steamof the incoming steam

Power is obtained due to Power is obtained due to impulsive force of impulsive force of incoming steam as well as incoming steam as well as reaction of exit steamreaction of exit steam

Suitable for small capacity Suitable for small capacity of power generation & of power generation & occupies less space per occupies less space per unit powerunit power

Suitable for medium & Suitable for medium & high capacity power high capacity power generation and occupies generation and occupies more space per unit powermore space per unit power

Efficiency is lesserEfficiency is lesser Efficiency is higherEfficiency is higher

Compounding is Compounding is necessary to reduce necessary to reduce speedspeed

Compounding is not Compounding is not necessary necessary


Compounding of Impulse TurbinesCompounding of Impulse TurbinesAs the complete expansion of steam takes in one stage As the complete expansion of steam takes in one stage (i.e., the entire pressure drop from high pressure to low (i.e., the entire pressure drop from high pressure to low pressure takes place in only one set of nozzles),pressure takes place in only one set of nozzles), the turbine the turbine rotor rotates at very high speed of about 30,000 rpmrotor rotates at very high speed of about 30,000 rpm (K.E. is fully absorbed).(K.E. is fully absorbed).

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


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

Methods of Methods of CompoundingCompounding:: Velocity compounding Velocity compounding (Curtis Impulse Turbine)(Curtis Impulse Turbine)

Pressure compoundingPressure compounding

Pressure-velocity compoundingPressure-velocity compounding


Velocity compoundingVelocity compounding

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

Guide (Guide (fixedfixed) blades are fixed to ) blades are fixed to casing casing and are stationary.and are stationary.



Velocity Compounding Velocity Compounding (Curtis Impulse Turbine)(Curtis Impulse Turbine)

N – NozzleN – NozzleM – Moving BladeM – Moving BladeF – Fixed BladeF – Fixed Blade

Pressure compoundingPressure compounding

• Consists of Consists of two stage of nozzlestwo stage of nozzles followed by followed by two rows of moving blades.two rows of moving blades.


Pressure CompoundingPressure Compounding


Pressure-Velocity CompoundingPressure-Velocity Compounding(Combined Impulse Turbine)(Combined Impulse Turbine)

Total pressure drop is divided into two stages & the total Total pressure drop is divided into two stages & the total velocity obtained in each stage is also compoundedvelocity obtained in each stage is also compounded

A – Axial clearance, N – Nozzle, M – Moving Blade, F – Fixed BladePi and Pe – Pressure at inlet & exit, Vi and Ve - Velocity at inlet & exit



A A Gas turbineGas turbine uses the hot gases of uses the hot gases of combustion directly to produce the combustion directly to produce the mechanical power.mechanical power.

Fuels usedFuels used - - Kerosene, coal, coal gas, Kerosene, coal, coal gas, bunker oil, gasoline, producer gas, etc.,bunker oil, gasoline, producer gas, etc.,

Classification:Classification:1.1. Open cycle gas turbineOpen cycle gas turbine

2.2. Closed cycle gas turbineClosed cycle gas turbine


ApplicationsApplicationsGas turbines are used in:Gas turbines are used in:

Electric power generation plantsElectric power generation plantsSteel, oil and chemical industriesSteel, oil and chemical industriesAircrafts, Ship propulsionAircrafts, Ship propulsionTurbo jet and turbo-propeller engines like Turbo jet and turbo-propeller engines like rockets, missiles, space ships etc.,rockets, missiles, space ships etc.,


Open cycle gas turbine:Open cycle gas turbine:The entire flow of the working substance The entire flow of the working substance comes from atmosphere and is returned comes from atmosphere and is returned to the atmosphere back in each cycle. to the atmosphere back in each cycle.

Closed cycle gas turbine:Closed cycle gas turbine:The flow of the working substance of The flow of the working substance of

specified mass is confined within the cyclic specified mass is confined within the cyclic pathpath. . ( Air or Helium is the working ( Air or Helium is the working substance)substance)


• COMPRESSOR:

draws in air and compress it before it is fed into combustion chamber

• COMBUSTOR:

fuel is added to the compressed air and burnt to produce high velocity exhaust gas

• TURBINE:

extracts energy from exhaust gasSrinivas School of Engineering,

Mukka 31

Open cycle gas turbineOpen cycle gas turbine






Open cycleOpen cycle Closed cycleClosed cycleLesser thermal efficiencyLesser thermal efficiency HigherHigher

Loss of working fluidLoss of working fluid No loss of working No loss of working fluidfluid

Bigger in sizeBigger in size SmallerSmaller

Big compressor is neededBig compressor is needed Smaller one is Smaller one is sufficientsufficient

Possibility of corrosion of blades and Possibility of corrosion of blades and rotorrotor

Free from corrosionFree from corrosion

EconomicalEconomical Not economicalNot economical

Exhaust gases from turbine exit to Exhaust gases from turbine exit to atmosphereatmosphere

Fed back into the Fed back into the cyclecycle

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Difference between open & closed cycle turbine

PharmaceuticalPharmaceuticalPharmaceuticalPharmaceutical


HospitalsHospitalsHospitalsHospitals


Pulp and PaperPulp and PaperPulp and PaperPulp and Paper




It is a It is a prime moverprime mover, which converts , which converts hydro hydro power (energy of water) power (energy of water) into mechanical into mechanical energy and further into energy and further into hydro-electric hydro-electric power.power.


Classification of Water TurbinesClassification of Water TurbinesBased on action of water:Based on action of water:

1. Impulse turbine – pelton wheel.2. Reaction turbine – francis and kaplan.

Based on name of originator:Based on name of originator:1. Pelton turbine or Pelton wheel2. Francis turbine3. Kaplan turbine

Based on head of water:Based on head of water:1.1. Low head turbineLow head turbine2.2. Medium head turbineMedium head turbine3.3. High head turbineHigh head turbine


Pelton TurbinePelton Turbine

(Pelton Wheel or Free Jet Turbine)(Pelton Wheel or Free Jet Turbine)

High head, tangential flow, horizontal High head, tangential flow, horizontal

shaft, impulse turbineshaft, impulse turbine



PELTON TURBINE


Pelton Turbine Runner


Only a part of the pressure energy Only a part of the pressure energy of of the water is converted into K.E. and the water is converted into K.E. and

the rest remains as pressure head.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 bladesguide 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.


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

Examples:Examples: Francis turbineFrancis turbine, , Kaplan turbineKaplan turbine, , Propeller turbinePropeller turbine, Thompson turbine, , Thompson turbine, Bulb Bulb turbine.turbine.


Francis TurbineFrancis TurbineMixed flow, medium head reaction turbine.Mixed flow, medium head reaction turbine.

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

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



FRANCIS TURBINE


Francis Inlet Scroll, Grand Coulee Dam


Francis Runner, Grand Coulee Dam


FRANCIS TURBINE & GENERATOR


Kaplan TurbineKaplan TurbineAxial flow, low head.Axial flow, low head.

Similar to Francis turbine except the runner Similar to Francis turbine except the runner and draft tube.and draft tube.

The The runnerrunner ( (Boss Boss oror Hub Hub) resembles with the ) resembles with the propeller of the ship, hence some times it is propeller of the ship, hence some times it is called as called as Propeller turbinePropeller turbine..

Water flows parallel to the axis of the shaft.Water flows parallel to the axis of the shaft.



KAPLAN TURBINE

(SCROLL CASING)

(GUIDE VANE)

(RUNNER VANE)




Vertical Kaplan Turbine (Courtesy: VERBUND-Austrian Hydro Power)


Propeller Turbine Runner

Turbines 1.ppt

Documents

curtis impulse

francis turbine

high pressure

pelton turbine

impulse turbine

inlet amp

srinivas school

reaction turbine