TOPIC- TURBINES Name of students -En. N- 1. MAHESURIA OMPRAKASH ISHVARLAL | Website for Students | VTU NOTES | QUESTION PAPERS 1

2 ‘Turbo Machine’ is defined as a device that extracts energy from a continuously ‘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. 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.

| Website for Students | VTU NOTES | QUESTION PAPERS 3 Types of Turbines 1.Steam Turbines 2.Gas Turbines (Combustion Turbines) 3.Water (Hydraulic) Turbines

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. | Website for Students | VTU NOTES | QUESTION PAPERS4

5 Based on action of steam or type of expansion: 1.Impulse or velocity or De Laval turbine 2.Reaction or pressure or Parson’s turbine 3.Combination turbine Based on number of stages: 1.Single stage turbine 2. Multi-stage turbine Based on type of steam flow: 1.Axial flow turbine 2. Radial flow turbine

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8 . 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.

| Website for Students | VTU NOTES | QUESTION PAPERS 9

10 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’. 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’.

| Website for Students | VTU NOTES | QUESTION PAPERS 11 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. 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. Resultant of all these centrifugal forces acting on the entire curved surface of the blade causes it to move.

| Website for Students | VTU NOTES | QUESTION PAPERS12 NOZZLE EXHAUST STEAM TURBINE SHAFT MOVING BLADES HIGH PRESSURE STEAM Schematic of Impulse Turbine VLVL PHPH Q PLPL VHVH R C B Nozzle Rotor 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. | Website for Students | VTU NOTES | QUESTION PAPERS13

| Website for Students | VTU NOTES | QUESTION PAPERS 14 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 Reaction force: is due to the change in momentum relative velocity of the steam while passing over the blade passage. Centrifugal force Centrifugal force: is the force acting on the blade due to change in radius of steam entering and leaving the turbine. Resultant force Resultant force: is the resultant of Reaction force and Centrifugal force. | Website for Students | VTU NOTES | QUESTION PAPERS15

| Website for Students | VTU NOTES | QUESTION PAPERS16 Fixed Blade Moving Blade

| Website for Students | VTU NOTES | QUESTION PAPERS 17 Impulse Turbine Reaction Turbine The steam expands (pressure drops) completely in nozzles or in the fixed blades The steam expands both in the fixed and moving blades continuously as it flows over them The blades have symmetrical profile of uniform section The blades have converging (aerofoil) profile The steam pressure while passing over the blades remains constant The 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 low The 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 Difference between Impulse & Reaction Turbines

| Website for Students | VTU NOTES | QUESTION PAPERS 18 Impulse Turbine Reaction Turbine Power is obtained only due to the impulsive force of the incoming steam Power is obtained due to impulsive force of incoming steam as well as reaction of exit steam Suitable for small capacity of power generation & occupies less space per unit power Suitable for medium & high capacity power generation and occupies more space per unit power Efficiency is lesser Efficiency is higher Compounding is necessary to reduce speed Compounding is not necessary

| Website for Students | VTU NOTES | QUESTION PAPERS 19 Open cycle Closed cycle Lesser thermal efficiency Higher Loss of working fluid No loss of working fluid Bigger in size Smaller Big compressor is needed Smaller one is sufficient Possibility of corrosion of blades and rotor Free from corrosion Economical Not economical Exhaust gases from turbine exit to atmosphere Fed back into the cycle Difference between open & closed cycle turbine

| Website for Students | VTU NOTES | QUESTION PAPERS20

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| Website for Students | VTU NOTES | QUESTION PAPERS22 It is a prime mover, which converts hydro power (energy of water) into mechanical energy and further into hydro- electric power.

| Website for Students | VTU NOTES | QUESTION PAPERS23 Classification of Water Turbines Based on action of water: 1.Impulse turbine – pelton wheel. 2.Reaction turbine – francis and kaplan. Based on name of originator: 1.Pelton turbine or Pelton wheel 2.Francis turbine 3.Kaplan turbine Based on head of water: 1.Low head turbine 2.Medium head turbine 3.High head turbine

| Website for Students | VTU NOTES | QUESTION PAPERS24 Pelton Turbine (Pelton Wheel or Free Jet Turbine) High head, tangential flow, horizontal shaft, impulse turbine

| Website for Students | VTU NOTES | QUESTION PAPERS25 PELTON TURBINE

| Website for Students | VTU NOTES | QUESTION PAPERS26 Pelton Turbine Runner

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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. guide blades 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. | Website for Students | VTU NOTES | QUESTION PAPERS28

| Website for Students | VTU NOTES | QUESTION PAPERS29 Francis Turbine Mixed flow, medium head reaction turbine. spiral casingguide bladesmoving blades (vanes)runner 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. draft tube. 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.

| Website for Students | VTU NOTES | QUESTION PAPERS30 FRANCIS TURBINE

| Website for Students | VTU NOTES | QUESTION PAPERS31 FRANCIS TURBINE & GENERATOR

| Website for Students | VTU NOTES | QUESTION PAPERS32 Kaplan Turbine Axial flow, low head. Similar to Francis turbine except the runner and draft tube. runnerBoss Hub Propeller turbine 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.

| Website for Students | VTU NOTES | QUESTION PAPERS33 KAPLAN TURBINE (SCROLL CASING) (GUIDE VANE) (RUNNER VANE)

| Website for Students | VTU NOTES | QUESTION PAPERS34

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| Website for Students | VTU NOTES | QUESTION PAPERS36 Propeller Turbine Runner

| Website for Students | VTU NOTES | QUESTION PAPERS 37