EXPERIMENT NO 1 AIM:TO STUDY THE MODEL OF HYDROELECTRIC POWER PLANT AND DRAW ITS LAYOUT. APPARATUS:Model of hydroelectric power plant. THEORY AND WORKING:The purpose of hydroelectric power plant is to provide power from water flowing under pressure. It has two forms of energy, kinetic energy and potential energy. Kinetic energy depends upon the mass velocity of flow while the potential energy exists as a result of difference in water level below two points. The turbine converts potential and kinetic energy possessed by water in to mechanical energy. Thus the turbine is a prime mover which when coupled to a generator produces electricity. ELECTRIC POWER:Hydroelectric power can be developed when water continuously flowing under pressure is available. Dam is constructed to restrict the river water flow. Essential components of a hydroelectric power plant are as follows:-
(1) STORAGE RESERVOIR:The water available from an attachment area is stored in a reservoir so that it can be utilized to run the turbine for producing power according to requirement. (2) DAM WITH CONTROL WORKS:Dam is a structure ejected on a suitable site to provide for the storage of water and create head. Dam may be built to make an artificial reservoir from valley or it may be created in a river to control the flowing water. (3) WATER WAYS:Water way is a passage through which the water carried from the storage reservoir to the power house. It may consist of tunnel control, force pipe and penstock. Tunnel is water passage made by cutting the mountain to save the distance for bay in an enlarged section of a canal spread out to accommodate the required width of intake. Its function is to store temporarily water ejected by plant. (4) PENSTOCK:It is a pipe of large diameter caring water under pressure from storage to turbine. (5) POWER HOUSE:It is a building to house the turbine, penstock and other for operating the machines. RATED QUANTITIES:The rated quantities refer to the parameter for which the turbine is designed. EFFIENCY OF HYDROELECTRIC POWER PLANT:An appraisal of the performance of a hydraulic turbine is made by its overall efficiency. power available at the shaft Overall efficiency = power available at the water jet shaf tpower water power P = WQH Where H – is the net or efficiency head in meters and Q – is the total discharge in m³/s. ήo =
EXPERIMENT NO 2 AIM:TO STUDY THE CONSTRUCTIONAL DETAILS OF KAPLAN TURBINE AND DRAW ITS FLUID FLOW CHART. APPARATUS:Model of Kaplan turbine. THEORY:Kaplan turbine is a reaction turbine which is particularly suited for low heads (up to 30 m) and high flow rate installations. In a Kaplan turbine water flow is purely axial. CONSTRUCTIONAL DETAILS AND OPERATION:(1) PENSTOCK: - it is large sized conduit which conveys water from upstream of the dam to the turbine runner. It is made of steel. Tamaracks are provided at inlet of penstock to obstruct entry of any foreign matter. (2) SCROLL CASING: - it constitutes of a closed passage whose cross section area gradually decreases along the flow direction. Area is maximum at inlet
and nearly zero at outlet. The decrease in area is in proportion to decreasing volume of water to handle and that velocity of water is constant along its path. The casing is made of cast steel and plate steel and concrete depending upon the pressure head. (3) GUIDE VANES OR WICKET GATES: - a series of air foil shaped vanes called guide vanes are arranged inside the casing to form a no of flow passages between casing and runner blades. Guide vanes direct the water on to runner at an angle appropriate to design. These are fixed in position, however they can swing around their own axis and that helps to bring about a change in the flow area between two consecutive runner blades. (4) RUNNER AND RUNNER BLADES: - the runner is in the form of a boss which is nothing but extension of bottom end of shaft into bigger diameter. On the periphery of the boss are mounted equidistantly 3 to 6 vanes made of stainless steel. The runner blades are directly attached to the hub and this feature eliminates the frictional losses with proper adjustment of the blades during its running. The Kaplan turbine is capable of giving a high efficiency for a wide range of load conditions. (5) REGULATION: - Kaplan turbine has double regulation which comprises movement of guide vanes and rotation of runner blades. The mechanism employs two servomotors, one control guide vanes and the other operates the runner vanes. The governing is done by governors (servomotors). From the inside of the hollow shaft of turbine runner and the movement of piston is employed to twist the blades through suitable linkage. The double regulation ensures a balanced and most satisfactory relationship between relative position of guide and working vanes. (6) DRAFT TUBE: - after passing through the runner the water is discharged to tail race through a gradually expending tube called draft tube. The free end of draft tube is submerged deep into tailrace. Because of its gradually increasing cross section, the discharge velocity from turbine runner is not all wasted, it is partially converted into a useful pressure head and water discharges at a relatively low velocity to the tail race. SALIENT POINTS:(1) Purely axial flow turbine (2) Only vertical shaft disposition (3) Runner blades are adjustable (4) Smaller no of vanes, 3 to 8 (5) Low head turbine(30 m) (6) Specific speed ranges from 250-850 (7) Heavy duty governor is essential for speed control due to smaller sizes of the servomotors.