Hydraulic Machines
30
CHAPTER 5
TURBINES
5.1
Introduction
Hydraulic turbines are the machines which use the energy of water and convert it to
mechanical energy. The mechanical energy developed by a turbine is used in running an electric generator which is directly coupled to the shaft of the turbine. The electric generator thus develops electric power, which is known as hydro-electric power.
5.2
Elements of Hydraulic Power Plants
Fig.5.1
General Layout of a Hydraulic Power Plant
31
Fig.5.1 shows a general layout of hydraulic power plant, in which an artificial storage reservoir formed by constructing a dam has been shown.
5.3
General Classification of Turbines
Turbines are hydraulic machines that convert energy into rotating mechanical energy
which in turn generators to produce electrical energy. Originally developed from the water wheels, hydraulic turbines are the prime mortars of importance in modern water power development. According to their hydraulic action, turbines are broadly divided into two classes. (1) Impulse Turbine: Impulse turbines are more efficient for high heads. At the inlet to the turbine runner, pressure head can be completely converted into kinetic head in the form of a jet of water issuing from one or more nozzles. The free jet will be at atmospheric pressure before as well as after striking the vanes. The turbines are regulated by nozzles which may be a simple straight flow type or a deflector type. The impulse turbines are commonly represented by Pelton Wheels. Turgo turbine is also an impulse turbine but with different buckets, when compared with pelton. Turgo and cross flow turbines are relatively new developments in this class.
The main advantages of these turbines are:
•
They can be easily adopted to power variation with almost constant efficiency.
•
The penstock overpressure and the runner overspeed control are easier.
•
The turbine enables an easier maintenance.
•
Due to
CHAPTER 5
TURBINES
5.1
Introduction
Hydraulic turbines are the machines which use the energy of water and convert it to
mechanical energy. The mechanical energy developed by a turbine is used in running an electric generator which is directly coupled to the shaft of the turbine. The electric generator thus develops electric power, which is known as hydro-electric power.
5.2
Elements of Hydraulic Power Plants
Fig.5.1
General Layout of a Hydraulic Power Plant
31
Fig.5.1 shows a general layout of hydraulic power plant, in which an artificial storage reservoir formed by constructing a dam has been shown.
5.3
General Classification of Turbines
Turbines are hydraulic machines that convert energy into rotating mechanical energy
which in turn generators to produce electrical energy. Originally developed from the water wheels, hydraulic turbines are the prime mortars of importance in modern water power development. According to their hydraulic action, turbines are broadly divided into two classes. (1) Impulse Turbine: Impulse turbines are more efficient for high heads. At the inlet to the turbine runner, pressure head can be completely converted into kinetic head in the form of a jet of water issuing from one or more nozzles. The free jet will be at atmospheric pressure before as well as after striking the vanes. The turbines are regulated by nozzles which may be a simple straight flow type or a deflector type. The impulse turbines are commonly represented by Pelton Wheels. Turgo turbine is also an impulse turbine but with different buckets, when compared with pelton. Turgo and cross flow turbines are relatively new developments in this class.
The main advantages of these turbines are:
•
They can be easily adopted to power variation with almost constant efficiency.
•
The penstock overpressure and the runner overspeed control are easier.
•
The turbine enables an easier maintenance.
•
Due to
References: 1.Hydraulics and Fluid Mechanics P.N.Modi and S.M.Seth 2. Hydraulics, Fluid Mechanics and Hydraulic Machines R.S.Khurmi 3. Fluid Mechanics Victor L.Streeter