HYDRAULIC TURBINES

Presented byMister Khan

Department of Instrumentation & Control Engineering

INTRODUCTION HISTORY CLASIIFICATION OF HYDRAULIC TURBINE PELTON TURBINE FRANCIS TURBINE KAPLAN AND PROPELLER TURBINE COMPARISON SOME RELATED TERMS DEFINATION EFFICIENCIES OF HYDRAULIC TURBINE DRAFT TUBE GOVERNING OF HYDRULIC TURBINE SELECTION OF TURBINE CONCLUSION

CONTENTS

Machines which convert hydraulic energy(energy possessed by water) into mechanical energy are hydraulic machines.

A hydraulic turbine converts the potential energy of water into mechanical energy which in turn is utilised to run an electric generator to get electric energy

INTRODUCTION

Water wheels have been used for thousands of years for industrial power.

The word turbine was introduced by the French engineer Claude Bourdin in the early 19th century and is derived from the Latin word for "whirling" or a "vortex".

The main difference between early water turbines and water wheels is a swirl component of the water which passes energy to a spinning rotor.

HISTORY

i. Head and quantity of water available.

ii. Name of the originator.

iii. Action of water on the moving blades.

iv. Direction of flow of water in the runner.

v. Disposition of the turbine shaft.

vi. Specific speed NS.

CLASSIFICATION OF HYDRAULIC TURBINE

• Requires high head and small quantity of flow

Impulse turbine

• Requires low head and high rate of flow.

Reaction turbine

i. Head and quantity of water available

• Lester Allen Pelton of California (USA)

Pelton turbine

• James Bichens Francis

Francis turbine

• Dr. Victor Kaplan

Kaplan turbine

ii. Name of the originator

Turbine

Reaction turbine

Francis turbine

Kaplan and Propeller turbine

Impulse Turbine Pelton turbine

iii. Action of water on the moving blades.

Tangential flow turbine

• Pelton turbine

Radial flow turbine

Axial flow turbine

• Kaplan turbineMixed flow turbine

• Francis turbine

Pelton have horizontal shaft. Francis, Kaplan have vertical shaft.

vi. Specific Speed NS

• Speed of a turbine, identical in shape, geometrical dimensions, blade angles etc., with actual turbine but with such a size that it’ll develope unit horse power when working under unit head.

• Specific Speed, NS = (N √P )/ H5/4

Where, N= Normal working Speed in rpm

P= Power output of the turbine

H= net or effective heads in meters

The specific speed for various type of runners are given below:

Type of turbineType of runner

Specific speed

PeltonSlow

NormalFast

10 to 2020 to 2828 to 35

FrancisSlow

NormalFast

60 to 120120 to 180180 to 300

Kaplan - 300 to 1000

Consists of rotor , at the peripery of which, double- hemispherical or elliptical buckets are mounted.

It is a tangential flow impulse turbine. A Pelton’s runner consists of a single wheel mounted

on a horizontal shaft.

Pelton Wheel

Pelton type

Specific Speed

Efficiency Head(in meter)

Single Nozzle

12- 30 89% 2000

2 nozzle 17-50 89% 1500

4 nozzle 24- 70 89% 500

Nozzle: It controls the amount of water striking the vanes of the runner.

Casing: It is used to prevent splashing of water and plays no part in power generation.

Runner with buckets: Runner is a circular disc on the periphery of which a number of evenly spaced buckets are fixed.

Breaking Jet: To stop the runner in short time breaking jet is used.

Main Parts of a Pelton Wheel

SPLITTER

15

Runner of a Pelton Turbine

SPLITTER

BUCKETS OR VANES

RUNNER

WORKING PRINCIPLE

Water falls towards the turbine through a pipe called penstock and flows through a nozzle.

The high speed jet of water hits the buckets (vanes) on the wheel and causes the wheel to rotate.

A spear rod which has a spear shaped end can be moved by a hand wheel.

The change in momentum of water stream produces an impulse on the blades of the wheel of Pelton Turbine.

WORKING PRINCIPLE

It is an inward-flow reaction turbine that combines radial and axial flow concepts.

Vertical shaft may also be used for small size turbines, but normally they have horizontal shaft.

FRANCIS TURBINE

Francis type

Specific Speed(in

rpm)

Efficiency Head(in meter)

Low 250-400 93% 30-60

Medium 150-250 93% 50-150

High 80-150 93% 500

CASING: The runner is completely enclosed in an air-tight spiral casing. The casing and runner are always full of water.

GUIDE MECHANISM: Water is fall down to the turbine and passed through the no’s of stationary orifices fixed all around the circumference of the runner , this is called guide vanes . The guide vanes allow the water to strike the vanes of the runner without shock at inlet

RUNNER: It is a circular wheel on which a series of curved radial guide vanes are fixed.

DRAFT TUBE: It is used for discharging water from the outlet of the runner to the tail race.

Main parts of a Francis Turbine

20

RUNNER

GUIDE WHEEL

MOVABLE VANES

STATIONARY GUIDE VANES

WORKING PRINCIPLE

In addition to electrical production, they may also be

used for pumped storage, where a reservoir is filled by the turbine (acting as a pump) during low power demand, and then reversed and used to generate power during peak demand.

APPLICATION

The Kaplan turbine is a propeller-type water turbine which has adjustable blades.

The runner of a kaplan turbine resembles with propeller of a ship. That is why, a Kaplan turbine is also called as propeller turbine.

KAPLAN AND PROPELLER TURBINE

Type Specific speed(in

rpm)

Efficiency Head (in meters)

Propeller& Kaplan

340-1000 93% 10-60

Bulb 1000-2000 91% 3- 9

24

Kaplan Turbine Runner

HUBB OR BOSS

VANESSHAFT

WORKING PRINCIPLE

The turbine wheel, which is completely under water, is turned by the pressure of water against its blades.

Guide vanes regulate the amount of water reaching the wheel.

WORKING PRINCIPLE

The Kaplan turbine is the most widely used of the propeller-type turbines, but several other variations exist:

Propeller turbines have non-adjustable propeller vanes.

Bulb or Tubular turbines are designed into the water delivery tube. A large bulb is centered in the water pipe which holds the generator, wicket gate and runner. Tubular turbines are a fully axial design, whereas Kaplan turbines have a radial wicket gate.

Pit turbines are bulb turbines with a gear box. This allows for a smaller generator and bulb.

VARIATION

Straflo turbines are axial turbines with the generator outside of the water channel, connected to the periphery of the runner.

S- turbines eliminate the need for a bulb housing by placing the generator outside of the water channel. This is accomplished with a jog in the water channel and a shaft connecting the runner and generator.

VLH turbine an open flow, very low head "kaplan" turbine slanted at an angle to the water flow. It has a large diameter, is low speed using a permanent magnet alternator with electronic power regulation and is very fish friendly (<5% mortality). VLH Turbine

Tyson turbines are a fixed propeller turbine designed to be immersed in a fast flowing river, either permanently anchored in the river bed, or attached to a boat or barge.

Inexpensive micro turbines on the Kaplan turbine model are manufactured for individual power production with as little as two feet of head.

Kaplan turbines are individually designed for each site to operate at the highest possible efficiency, typically over 90%.

APPLICATION

S.No. Scheme/Project Location (State)

Source of water

1. Bhakra- Nangal project Gangwal & Kota(Punjab) Nangal hydel

2. Hirakud dam project Hirakud (orissa) Mahanadi river

3. Nizam Sagar projectNizam sagar

(Andhra Pradesh)

Nanjira river

4. Radhanagri hydroelectric scheme

Kolhapur (Maharashtra) Bhagvati river

5. Tungbhadra hydroelectric scheme

Tungbhadra (karnataka)

Tungbhadra river

KAPLAN TURBINE INSTALLATION IN INDIA

Francis turbine versus Pelton turbine:(i) Mechanical efficiency of Pelton decreases faster

with wear than Francis.(ii) Size of powerhouse required is small and

economical if Francis is used than Pelton.(iii) Cavitation is an ever present danger in Francis.(iv) The water hammer effect is more trouble in

Francis.(v) In Francis , variation in the operating head can be

easily controlled.

COMPARISON

Kaplan versus Francis turbine:

(i) Kaplan is more compact.(ii) Part load efficiency is high.(iii) Low frictional losses in Kaplan.

COMPARISON

Cavitation: Cavitation is the formation of empty cavities in a liquid by high forces and the immediate implosion of them.

Cavitation occurs when a liquid is subjected to rapid changes of pressure causing the formation of cavities in the lower pressure regions of the liquid.

Prof. Dietrich Thoma of Munich (Germany) suggested a factor ,called cavitation factor.

SOME RELATED TERM’S DEFINATION

Methods to avoid cavitation:

(i) Runner/turbine may be kept under water.(ii) Cavitation free runner may be designed.(iii) By selecting materials that can resist better the

cavitation effect.(iv) By polishing the surfaces.(v) By selecting a runner of proper specific speed for

given load.

Runway Speed: The runaway speed of a water turbine is its speed at

full flow, and no shaft load. The practical values of run away speeds for various

turbines with respect to their rated speed N are as follows:

Pelton Wheel …1.8 to 1.9NFrancis turbine (mixed flow) …2.0 to 2.2NKaplan turbine (axial flow) …2.5 to 3.0N

(i) Hydraulic efficiency, is ratio of power developed by the runner of a turbine to the power supplied by the water at the inlet.

(ii) Mechanical efficiency, ratio of power available at the shaft to power developed at the runner.

(iii) Volumetric efficiency, ratio of volume of the water actually striking the runner to the volume of water supplied to the turbine.

(iv) Overall efficiency, ratio of power available at the shaft of the turbine to the power supplied by the water at the inlet of the turbine.

Efficiencies of a turbine

The draft tube is a pipe of gradually increasing area which connects the outlet of the runner with the tailrace.

It creates a negative head at the outlet of the runner thereby increasing the net head on the turbine.

It converts a large proportion of rejected kinetic energy into useful pressure or potential head.

DRAFT TUBE

Two types of draft tube:(i) Canonical type: used on low powered units for all

specific speeds, frequently, on large head units.

(ii) Elbow type: used to turn the water from the vertical to horizontal direction with minimum depth of excavation and with high efficiency.

Means speed regulation

Governing of Impulse turbine: (i) Spear regulation. (ii) Deflector regulation. (iii) combined

Governing of Reaction turbine

GOVERNING

Specific Speed. Rotational Speed. Efficiency. Part load operation. Cavitation. Disposition of turbine Shaft. Head.

SELECTION OF TURBINE

On overall discussion , we can conclude that generation of electricity by hydraulic turbine is best way of restricting pollution and no fuel required, although we must be particular about the site.

We can also conclude Kaplan and propeller is best among all.

CONCLUSION

THANKYO

U