HydraulicTurbines:
•Hydraulic turbines may be defined as prime movers that transform the kinetic energy of the falling water into mechanical energy of rotation and whose primary function is to drive a electric generator.
•A cubic meter of water can give about 9800 Joules of mechanical energy for every meter it descends and a flow of a cubic meter per second in a fall of 1 meter can provide 9800 W of power.
•Hydro-power is essentially a controlled method of water descent usefully utilised to generate power.
•Hydroelectric plants utilise the energy of water falling through a head that may vary from a few meters to ~1500 or even 2000 m. To manage this yyg wide range of heads, many different kinds of turbines are employed, which differ in their working components.
•The main components of a hydroelectric system may be classified into two groups: groups: –the hydraulic system components that include the turbine, the associated conduits-like penstocks, tunnel and surge tank-and its control system, and its control system.
Necessity of Surge Tank
1.The performance of hydraulic turbines is strongly influenced by the characteristics of water conduit that feeds the turbine. These characteristics include the effect of water inertia, water compressibility and pipe wall elasticity in the penstock.
2.Hydroelectric turbines present non-minimal phase characteristics due to water inertia; this means that a change in the gate produces an initial change in hanical power, which is opposite to the one requested.
3.The water compressibility effect produces traveling waves of pressure and is usually called water hammer.
4.The water hammer is characterised by a sudden high-pressure rise caused by stopping the flow too rapidly. The wave propagation speed is around 1200 m/s.
5.In those plants where distance between the forebay or reservoir and the turbine is quite large, a surge tank is usually utilised.
6.The function of this tank is to hydraulically isolate the turbine from deviations in the head produced by the wave effects in the conduits.
7.Some surge tanks include an orifice whose function is to dampen and absorb the energy of the hydraulic oscillations.
History of Hydraulic Turbines
1.Water wheels –China and Egypt –thousands of years ago.
2.Reaction runner –J A Segnar –1950.
3.Euler turbine theory –Leonard Euler –valid till today.
4.Turbine is a designation that was introduced in 1824 in a dissertation of the French engineer Burdin.
5.Fourneyron designed a radial turbine and put to operation the first real turbine in 1827 power 2030k Windrunner diameter of 500mm in 1827 –power 20-30kW and runner diameter of 500 mm
6.Henschel and Jonval in 1840 independently developed turbine with axial water flow through it. They were the first ones to apply draft tube and in that way to utilize the water head between runner outlet and tail water level.
7.Francis in 1849 developed the radial turbine, named Francis turbine.
8.In 1870 professor Fink introduced an important improvement in Francis turbine by making the guide vanes turning on a pivot in order to regulate the flow discharge.
9.In 1890 American engineer Pelton developed impulse turbine, named Pelton turbine
Classification of Hydraulic Turbines
Hydraulic turbines are generally classified.
Impulse Turbine –Pelton, Turgo turbine
‰
Reaction Turbine –Francis,Kaplan and Propeller turbine
Based on flow direction, they are further classified as:
1.‰Tangential Flow
2.Radial Flow
‰3.Axial Flow
4.Mixed Flow
Impulse and Reaction Turbine
1.The flow energy to the impulse turbinesis completely converted to kinetic energy before transformation in the runner.
2.The impulse forces being transferred by the direction changes of the flow velocity vectors when passing the buckets create the energy converted to mechanical energy on the turbine shaft.
3.The flow enters therunner fromjets spaced aroundthe rim of the runners.The jet hits momentarily only a part of the circumference of the runner.
4.In the reaction turbines two effects cause the energy transfer from the flow to the mechanical energy on the turbine shaft: ƒFirstly, it follows from a drop in pressure from inlet to outlet ofthe runner. This is denoted as the reaction partof the energy conversion.
ƒ Secondly, the changes inthe directions of the flow velocity vectors through the runner blade channels transfer impulse forces. This is denoted as the impulse part of the energy conversion.
5.The pressure drop from inlet to outlet of the runners is obtained because the runners are completely filled with water.
•Hydraulic turbines may be defined as prime movers that transform the kinetic energy of the falling water into mechanical energy of rotation and whose primary function is to drive a electric generator.
•A cubic meter of water can give about 9800 Joules of mechanical energy for every meter it descends and a flow of a cubic meter per second in a fall of 1 meter can provide 9800 W of power.
•Hydro-power is essentially a controlled method of water descent usefully utilised to generate power.
•Hydroelectric plants utilise the energy of water falling through a head that may vary from a few meters to ~1500 or even 2000 m. To manage this yyg wide range of heads, many different kinds of turbines are employed, which differ in their working components.
•The main components of a hydroelectric system may be classified into two groups: groups: –the hydraulic system components that include the turbine, the associated conduits-like penstocks, tunnel and surge tank-and its control system, and its control system.
Necessity of Surge Tank
1.The performance of hydraulic turbines is strongly influenced by the characteristics of water conduit that feeds the turbine. These characteristics include the effect of water inertia, water compressibility and pipe wall elasticity in the penstock.
2.Hydroelectric turbines present non-minimal phase characteristics due to water inertia; this means that a change in the gate produces an initial change in hanical power, which is opposite to the one requested.
3.The water compressibility effect produces traveling waves of pressure and is usually called water hammer.
4.The water hammer is characterised by a sudden high-pressure rise caused by stopping the flow too rapidly. The wave propagation speed is around 1200 m/s.
5.In those plants where distance between the forebay or reservoir and the turbine is quite large, a surge tank is usually utilised.
6.The function of this tank is to hydraulically isolate the turbine from deviations in the head produced by the wave effects in the conduits.
7.Some surge tanks include an orifice whose function is to dampen and absorb the energy of the hydraulic oscillations.
History of Hydraulic Turbines
1.Water wheels –China and Egypt –thousands of years ago.
2.Reaction runner –J A Segnar –1950.
3.Euler turbine theory –Leonard Euler –valid till today.
4.Turbine is a designation that was introduced in 1824 in a dissertation of the French engineer Burdin.
5.Fourneyron designed a radial turbine and put to operation the first real turbine in 1827 power 2030k Windrunner diameter of 500mm in 1827 –power 20-30kW and runner diameter of 500 mm
6.Henschel and Jonval in 1840 independently developed turbine with axial water flow through it. They were the first ones to apply draft tube and in that way to utilize the water head between runner outlet and tail water level.
7.Francis in 1849 developed the radial turbine, named Francis turbine.
8.In 1870 professor Fink introduced an important improvement in Francis turbine by making the guide vanes turning on a pivot in order to regulate the flow discharge.
9.In 1890 American engineer Pelton developed impulse turbine, named Pelton turbine
Classification of Hydraulic Turbines
Hydraulic turbines are generally classified.
Impulse Turbine –Pelton, Turgo turbine
‰
Reaction Turbine –Francis,Kaplan and Propeller turbine
Based on flow direction, they are further classified as:
1.‰Tangential Flow
2.Radial Flow
‰3.Axial Flow
4.Mixed Flow
Impulse and Reaction Turbine
1.The flow energy to the impulse turbinesis completely converted to kinetic energy before transformation in the runner.
2.The impulse forces being transferred by the direction changes of the flow velocity vectors when passing the buckets create the energy converted to mechanical energy on the turbine shaft.
3.The flow enters therunner fromjets spaced aroundthe rim of the runners.The jet hits momentarily only a part of the circumference of the runner.
4.In the reaction turbines two effects cause the energy transfer from the flow to the mechanical energy on the turbine shaft: ƒFirstly, it follows from a drop in pressure from inlet to outlet ofthe runner. This is denoted as the reaction partof the energy conversion.
ƒ Secondly, the changes inthe directions of the flow velocity vectors through the runner blade channels transfer impulse forces. This is denoted as the impulse part of the energy conversion.
5.The pressure drop from inlet to outlet of the runners is obtained because the runners are completely filled with water.
Hydraulic Turbines - Working, types and Specifications
Reviewed by Unknown
on
June 15, 2018
Rating:
Reviewed by Unknown
on
June 15, 2018
Rating:
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