machines which convert the energy of flowing water into mechanical energy.
example for a low head, medium head and high head turbine.
Low head turbine – Kaplan
Medium head turbine – Modern
Francis turbine High head turbine – Pelton
3. What is
impulse turbine? Give example.
In impulse turbine all the energy converted into
kinetic energy. From these the turbine will develop high kinetic energy power.
This turbine is called impulse turbine. Example: Pelton turbine
4. What is
reaction turbine? Give example.
In a reaction turbine, the runner utilizes both
potential and kinetic energies. Here portion of potential energy is converted
into kinetic energy before entering into the turbine.
Francis and Kaplan turbine.
5. What is axial
In axial flow turbine water flows parallel to the
axis of the turbine shaft. Example: Kaplan turbine
6. What is
mixed flow turbine?
In mixed flow water enters the blades radially and comes out
axially, parallel to the turbine shaft. Example: Modern Francis turbine.
7. What is
the function of spear and nozzle?
The nozzle is used to convert whole hydraulic
energy into kinetic energy. Thus the nozzle delivers high speed jet. To regulate
the water flow through the nozzle and to obtain a good jet of water spear or
nozzle is arranged.
gross head and net or effective head.
Gross Head: The gross head is the difference
between the water level at the reservoir and the level at the tailstock.
Head: The head available at the inlet of the turbine.
defined as the ratio of power developed by the runner to the power supplied by
10. Define mechanical efficiency.
It is defined as the ratio of
power available at the turbine shaft to the power developed by the turbine
11. Define volumetric efficiency.
It is defied as the volume of
water actually striking the buckets to the total water supplied by the jet.
12. Define over all efficiency.
It is defined as the ratio of power available at
the turbine shaft to the power available from the water jet.
13. Define the terms
(a) Hydraulic machines (b)
Turbines (c) Pumps. a. Hydraulic machines:
Hydraulic machines are defined as
those machines which convert either hydraulic energy into mechanical energy or
mechanical energy into hydraulic energy.
The hydraulic machines which
convert hydraulic energy into mechanical energy are called turbines.
hydraulic Machines which convert mechanical energy into hydraulic energy are
14. What do you mean by gross head?
The difference between the head
race level and tail race level when no water is flowing is known as gross head.
It is denoted by Hg.
15. What do you mean by net head?
Net head is also known as
effective head and is defined as the head available at the inlet of te turbine.
It is denoted as H
16. What is draft tube? why it is used in reaction
The pressure at exit of runner of
a reaction turbine is generally less than the atmospheric pressure. The water
at exit cannot be directly discharged to tail race. A tube or pipe of gradually
increasing area is used for discharging water from exit of turbine to tail
race. This tube of increasing area is called draft tube.
17. What is the significance of specific speed?
Specific speed plays an important
role for selecting the type of turbine. Also the performance of turbine can be
predicted by knowing the specific speed of turbine.
18.. What are unit quantities?
Unit quantities are the
quantities which are obtained when the head on the turbine is unity. They are
unit speed, unit power unit discharge.
unit quantities are important
If a turbine is working under different
heads, the behavior of turbine can be easily known from the values of unit
20. What do you understand by characteristic
curves of turbine?
Characteristic curves of a
hydraulic turbine are the curves, with the help of which the exact behavior and
performance of turbine under different working conditions can be known.
21. Define the term 'governing of turbine'.
Governing of turbine is defined
as the operation by which the speed of the turbine is kept constant under all
conditions of working. It is done by oil pressure governor.
22. What are the types of draft tubes?
following are the important types of draft tubes which are commonly used.
spreading tubes and
draft tubes with circular inlet and rectangular outlet.