HYDRAULIC TURBINES : I
IKRAM SINGH HARIKA
B TECH 6MAE-1Y
A2305408048 HYDRAULIC TURBINES What are Hydraulic Machines? : What are Hydraulic Machines? Machines which convert hydraulic energy(energy possessed by water) into mechanical energy(which is further converted into electrical energy)-Turbines.
Machines which convert mechanical energy into hydraulic energy-Pumps. 2 Hydraulic Turbines : Hydraulic Turbines Hydraulic Turbines convert hydraulic energy of water into mechanical energy which is further converted into electrical energy. This energy obtained is know as hydro-electric power which is one of the cheapest forms of energy generation.
Hydraulic turbines consist of Pelton Wheel, Francis and Kaplan Turbine. 3 Layout of a Hydro-Electric Power Plant : Layout of a Hydro-Electric Power Plant 4 Pelton Wheel : Pelton Wheel In a Pelton Wheel or Pelton Turbine water strikes the vanes along the tangent of the runner and the energy available at the inlet of the turbine is only kinetic energy, therefore it is a tangential flow impulse turbine.
This turbine is used for high heads and named after L.A Pelton, an American engineer. 5 Main Parts of a Pelton Wheel : Main Parts of a Pelton Wheel 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. 6 Runner of a Pelton Turbine : Runner of a Pelton Turbine SPLITTER BUCKETS OR VANES RUNNER 7 Working Principle : Working Principle The high speed water coming out of the nozzle strikes the splitter which divides the jet into two equal streams. These stream flow along the inner curve of the bucket and leave it in the direction opposite to that of incoming jet. The high pressure water can be obtained from any water body situated at some height or streams of water flowing down the hills.
The change in momentum (direction as well as speed) of water stream produces an impulse on the blades of the wheel of Pelton Turbine. This impulse generates the torque and rotation in the shaft of Pelton Turbine. 8 Francis Turbine : Francis Turbine Francis Turbine is the first hydraulic turbine with radial inflow. It was designed by an American scientist James Francis. If the water flows radially through the runner , from outwards to inwards then it is known as an inward radial flow turbine.
Francis turbine is a reaction turbine as the energy available at the inlet of the turbine is a combination of kinetic and pressure energy. 9 Main parts of a Francis Turbine : Main parts of a Francis Turbine CASING: The runner is completely enclosed in an air-tight spiral casing. The casing and runner are always full of water.
GUIDE MECHANISM: It consists of a stationary circular wheel on which stationary guide vanes are fixed. 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. 10 Slide 11: RUNNER GUIDE WHEEL MOVABLE VANES STATIONARY GUIDE
VANES 11 Kaplan Turbine : Kaplan Turbine Kaplan turbine is an axial flow reaction turbine.The water flows through the runner of the turbine in an axial direction and the energy at the inlet of the turbine is the sum of kinetic and pressure energy .
In an axial flow reaction turbine the shaft is vertical. The lower end of the shaft is larger and is known as ‘hub’ or ‘boss’. It is on this hub that the vanes are attached. If the vanes are adjustable then it is known as kaplan Turbine and if the vanes are non adjustable then it is known as Propeller Turbine. 12 Slide 13: Kaplan turbine is best suited where large quantity of low head water is available.
The main parts of a kaplan Turbine are:
Guide vane Mechanism
Hub with Vanes
Draft Tube 13 Kaplan Turbine Runner : Kaplan Turbine Runner HUBB OR
BOSS VANES SHAFT 14 Working Principle : Working Principle The water enters the turbine through the guide vanes which are aligned such as to give the flow a suitable degree of swirl. The flow from guide vanes pass through the curved passage which forces the radial flow to axial direction.
The axial flow of water with a component of swirl applies force on the blades of the rotor and looses its momentum, both linear and angular, producing torque and rotation (their product is power) in the shaft. The scheme for production of hydroelectricity by Kaplan Turbine is same as that for Francis Turbine. 15 Schematic View : Schematic View GUIDE VANES MOVABLE
VANES SHAFT HUBB OR BOSS 16 Draft Tube : Draft Tube The draft tube is a pipe of gradually increasing area which connects the outlet of the runner with the tailrace. One end of the draft tube is connected to the outlet of the runner while the other end is submerged below the level of water in the tail race.
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 energy 17 Elbow-Type Draft Tube : Elbow-Type Draft Tube 18 Governing of Turbines : Governing of Turbines It is the operation by which the speed of the turbine is kept constant under all conditions of working load. This is done automatically by a governor which regulates the rate flow through the turbines according to the changing load conditions on the turbine.
Governing of a turbine is absolutely necessary if the turbine is coupled to an electric generator which is required to run at constant speed under all fluctuating load conditions. 19 Slide 20: Thank You 20