GOVERNMENT ENGINEERING COLLEGE, PATAN
Mechanical engineering Department
FLUID MECHANICS AND HYRAULIC MACHINES
Important Questions
1.
Prove
that the force exerted by a jet of water on a fixed semi-circular plate in the
direction of jet when the jet strikes at the centre of semi-circular plate is
two times the force exerted by the jet on a fixed vertical plate.
2.
Derive
an expression and condition to obtained maximum efficiency for the curved vane
if the jet strikes at centre of the vane.
3.
A
jet of water having velocity of 30 m/s enters on a series of moving vanes
having velocity of 15 m/s. The jet makes an angle of 25o to the
direction of motion of the vane at inlet and leaves with a velocity 8 m/s and
at an angle of 15o. Draw the velocity diagram.
Determine,
(1) Vane
angle at inlet and outlet
(2) Work
done per unit weight of water
(3) Hydraulic
efficiency
4.
A
jet of water diameter 35 mm, having a velocity of 30 m/s, strikes a curved vane
moving with a velocity of 15 m/s in the direction of jet. The jet leaves at an
angle of 60o to the direction of motion of the vane at outlet.
Determine,
(1)
The
force exerted by the jet on the vane in the direction of motion
(2)
Work
done per second by the jet
5.
Explain
Construction and working of Pelton wheel.
6.
Explain
the governing mechanism of Pelton wheel.
7.
A
Pelton wheel generates 8 MW under net head of 130 m at a speed of 200 rpm.
Assume Cv = 0.98, Hydraulic
efficiency = 0.8, speed ratio = 0.46, mechanical efficiency = 0.75 and the
wheel diameter is 9 times the jet diameter.
Determine:
(1)
Discharge
(2)
Diameter
of the wheel
(3)
Diameter
and number of jet
(4)
Specific
speed
8.
A
Pelton wheel has a mean bucket speed of 10 m/s with a jet of water flowing at a
rate of 0.7 m3/s under a head of 30 m. If bucket deflects the jet
through an angle of 160o. Calculate the power given by water to the
runner and hydraulic of the turbine if Cv = 0.98.
9.
Compare
the Impulse and reaction turbines.
10. With the sketch describe the
function of various components of Francis turbine.
11. Differentiate Francis and Kaplan
turbines.
12. Explain the working of propeller
and Kaplan turbine.
13. A Kaplan turbine has hydraulic efficiency 0.9
and mechanical efficiency 0.95 with a runner diameter 6 m and a boss diameter
of 1.8 m. If the discharge of turbine is 180 m3/s, calculate the
head on the turbine and the power of the turbine. Neglect losses in turbine and
assume that there is no whirl at outlet and discharge is free.
14. For the Francis turbine:
Shaft
power = 130 kW Net
head = 9 m
Speed
=120 rpm Overall
efficiency = 0.75
Hydraulic
efficiency =0.9 Flow
velocity at inlet = 1.15 H1/2
Maximum
speed at inlet = 3.45 H1/2
Assume
radial discharge at exit, find
(1)
Guide
vane angle at inlet
(2)
Moving
vane angle at inlet
(3)
Diameter
of runner at inlet
15. Explain the main components of
centrifugal pump.
16. Derive an
expression for specific speed of centrifugal
pump.
17. A centrifugal pump delivers 1.27
m3 of water per minute at 1200 rpm. The impeller diameter is 350 mm
and breadth at outlet is 12.7 mm. The pressure difference between inlet and
outlet of pump casing is 272 kN/ m2. Calculate the impeller exit
blade angle if manometric efficiency is 0.63
