The overall efficiency of a reaction turbine is the ratio of
Power produced by the turbine to the energy actually supplied by the turbine
Actual work available at the turbine to the energy imparted to the wheel
Workdone on the wheel to the energy (or head of water) actually supplied to the turbine
None of the above
Correct Answer :
A. Power produced by the turbine to the energy actually supplied by the turbine
Related Questions
If a pump is handling water and is discharging a certain flow Q at a constant total dynamic head requiring a definite B.H.P., the same pump when handling a liquid of specific gravity 0.75 and viscosity nearly same as of water, the horse power required will be
Same
0.75 B.H.P.
B.H.P./0.75
1.5 B.H.P.
Discharge of a centrifugal pump is (where N = Speed of the pump impeller)
Directly proportional to N
Inversely proportional to N
Directly proportional to N²
Inversely proportional to N²
In axial flow fans and turbines, fluid enters and leaves as follows
Radially, axially
Axially, radially
Axially, axially
Radially, radially
A hydraulic press is a device used
To store pressure energy which may be supplied to a machine later on
To increase the intensity of pressure of water by means of energy available from a large quantity of water at a low pressure
To lift larger load by the application of a comparatively much smaller force
All of the above
In order to avoid cavitation in centrifugal pumps
The suction pressure should be high
The delivery pressure should be high
The suction pressure should be low
The delivery pressure should be low
Power required (in watts) to drive a centrifugal pump is (where Hm = Manometric head in metres, w = Specific weight in N/m3, Q = Discharge of the pump in m3/s, and ηo = Overall efficiency of the pump)
(w Hm) / (Q × ηo)
(w Hm Q) / ηo
(w Q) / (Hm × ηo)
(w Q ηo) / Hm
Francis, Kaplan and propeller turbines fall under the category of
Impulse turbines
Reaction turbines
Axial flow turbines
Mixed flow turbines
A Pelton wheel develops 1750 kW under a head of 100 metres while running at 200 r.p.m. and discharging 2500 litres of water per second. The unit speed of the wheel is
10 r.p.m.
20 r.p.m.
40 r.p.m.
80 r.p.m.
The water in a jet propelled boat is drawn through the openings facing the direction of motion of the boat. The efficiency of propulsion is given by
2V/(vr - v)
2V/(vr + v)
V/(vr - v)
V/(vr + v)
A hydraulic ram is a device used to
Store the energy of water
Increase the pressure of water
To lift water from deep wells
To lift small quantity of water to a greater height when a large quantity of water is available at a smaller height
Air vessels in reciprocating pump are used to
Smoothen flow
Reduce acceleration to minimum
Increase pump efficiency
Save pump from cavitations
According to fan laws, for the fans having constant wheel diameters, the power demand varies
Directly as fan speed
Square of fan speed
Cube of fan speed
Square root of fan speed
Which of the following turbine is preferred for 0 to 25 m head of water?
Pelton wheel
Kaplan turbine
Francis turbine
None of these
Medium specific speed of a pump implies it is
Centrifugal pump
Mixed flow pump
Axial flow pump
Any one of the above
Low specific speed of turbine implies it is
Propeller turbine
Francis turbine
Impulse turbine
Any one of the above
Saving of work done and power by fitting an air vessel to double acting reciprocating pump is of the order of
39.2 %
49.2 %
68.8 %
84.8 %
The efficiency of a hydraulic press is given by (where W = Weight lifted by ram, P = Force applied on plunger, A = Area of ram, and a = Area of plunger)
(W/p) × (A/a)
(p/W) × (a/A)
(W/p) × (a/A)
(p/W) × (A/a)
Head developed by a centrifugal pump is
Proportional to diameter of impeller
Proportional to speed of impeller
Proportional to diameter and speed of impeller
None of the above
The cavitation in reaction turbines is avoided, to a great extent by
Installing the turbine below the tail race level
Using stainless steel runner of the turbine
Providing highly polished blades to the runner
All of the above
The flow ratio in case of Francis turbine varies from
0.15 to 0.3
0.4 to 0.5
0.6 to 0.9
1 to 1.5
In a centrifugal pump casing, the flow of water leaving the
Radial
Axial
Centrifugal
Vortex
Any change in load is adjusted by adjusting following parameter on turbine
Net head
Absolute velocity
Blade velocity
Flow
In a centrifugal pump, the liquid enters the pump
At the top
At the bottom
At the canter
From sides
The force exerted by a jet of water (in a direction normal to flow) impinging on a fixed plate inclined at an angle θ with the jet is
waV/2g × sinθ
waV/g × sinθ
waV²/2g × sin2θ
waV²/g × sinθ
Multistage centrifugal pumps are used to obtain
High discharge
High head
Pumping of viscous fluids
High head and high discharge
The width of the bucket for a Pelton wheel is generally ________ the diameter of jet.
Double
Three times
Four times
Five times
According to fan laws, at constant speed and capacity, the pressure and power vary
Directly as the air or gas density
Inversely as square root of density
Inversely as density
As square of density
Discharge of a centrifugal pump is
Directly proportional to diameter of its impeller
Inversely proportional to diameter of its impeller
Directly proportional to (diameter)² of its impeller
Inversely proportional to (diameter)² of its impeller
In a Kaplan turbine runner, the numbers of blades are generally between
2 to 4
4 to 8
8 to 16
16 to 24
The specific speed of a centrifugal pump, delivering 750 litres of water per second against a head of 15 metres at 725 r.p.m., is
24.8 r.p.m.
48.2 r.p.m
82.4 r.p.m.
248 r.p.m