Hydraulic Machines MCQs : This section focuses on the "Hydraulic Machines". These Multiple Choice Questions (MCQs) should be practiced to improve the Hydraulic Machines skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.
A centrifugal pump will start delivering liquid only when the pressure rise in the impeller is equal to the
A. kinetic head
B. velocity head
C. manometric head
D. static head
A Francis turbine is used when the available head of water is
A. 0 to 25 m
B. 25 m to 250 m
C. above 250 m
D. none of these
A hydraulic coupling belongs to the category of
A. power absorbing machines
B. power developing machines
C. energy transfer machines
D. energy generating machines
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 power of the wheel is
A. 0.25 kW
B. 0.75 kW
C. 1.75 kW
D. 3.75 kW
Delivery head of water of a centrifugal pump is inversely proportional to diameter of its impeller.
Discharge (Q) of a centrifugal pump is given by (where D = Diameter of impeller at inlet, b = Width of impeller at inlet, and Vf = Velocity of flow at inlet)
A. Q = π.D.Vf
B. Q = π.b.Vf
C. Q = π.D.b.Vf
D. Q = D.b.Vf
Discharge of a centrifugal pump is
A. directly proportional to diameter of its impeller
B. inversely proportional to diameter of its impeller
C. directly proportional to (diameter)2 of its impeller
D. inversely proportional to (diameter)2 of its impeller
Discharge of a centrifugal pump is (where N = Speed of the pump impeller)
A. directly proportional to N
B. inversely proportional to N
C. directly proportional to N2
D. inversely proportional to N2
For centrifugal pump impeller, the maximum value of the vane exit angle is
A. 10° to 15°
B. 15° to 20°
C. 20° to 25°
D. 25° to 30°
Geometric similarity is said to exist between the model and the prototype, if both of them
A. have identical velocities
B. are equal in size and shape
C. are identical in shape, but differ only in size
D. have identical forces
If Hg is the gross or total head and hf is the head lost due to friction, then net or effective head (H) is given by
A. H = Hg/hf
B. H = Hg x hf
C. H = Hg + hf
D. H = Hg - hf
In a Kaplan turbine runner, the number of blades are generally between
A. 2 to 4
B. 4 to 8
C. 8 to l6
D. 16 to 24
In a reaction turbine, the draft tube is used
A. to run the turbine full
B. to prevent air to enter the turbine
C. to increase the head of water by an amount equal to the height of the runner outlet above the tail race
D. to transport water to downstream
In a reaction turbine, the pressure head of water, while flowing over the vanes, is converted into kinetic head before leaving the wheel.
In a reciprocating pump, air vessels are fitted to the suction pipe and delivery pipe close to the cylinder of the pump.
In an impulse turbine, the jet of water impinges on the bucket with a low velocity and after flowing over the vanes, leaves with a high velocity.
In the casing of a centrifugal pump, the kinetic energy of the water is converted into pressure energy before the water leaves the casing.
Manometric head, in case of a centrifugal pump, is equal to
A. Suction lift + Loss of head in suction pipe due to friction + Delivery lift + Loss of head in delivery pipe due to friction + Velocity head in the delivery pipe
B. Workdone per kN of water - Losses within the impeller
C. Energy per kN at outlet of impeller - Energy per kN at inlet of impeller
D. all of the above
Multi-stage centrifugal pumps are used to
A. give high discharge
B. produce high heads
C. pump viscous fluids
D. all of these
Power required to drive a centrifugal pump is directly proportional to __________ of its impeller.
B. square of diameter
C. cube of diameter
D. fourth power of diameter
Slip of a reciprocating pump is defined as the
A. ratio of actual discharge to the theoretical discharge
B. sum of actual discharge and the theoretical discharge
C. difference of theoretical discharge and the actual discharge
D. product of theoretical discharge and the actual discharge
The breast water wheels are those in which the wheel runs partly by the weight of water and partly by the impulse of water.
The capacity of a hydraulic accumulator is generally specified as the maximum amount of energy stored.
The discharge of a centrifugal pump working under constant head __________ with the speed.
The discharge of a double acting reciprocating pump is (where L = Length of stroke, A = Cross-sectional area of piston, and N = Speed of crank in r.p.m.)
B. 2 L.A.N
The efficiency of a centrifugal pump will be maximum when the blades are bent backward.
The efficiency of a Pelton wheel working under constant head __________ with the increase in power.
A. remains same
The maximum efficiency of jet propulsion of a ship with inlet orifices at right angles to the direction of motion of ship, is
The maximum number of jets, generally, employed in an impulse turbine without jet interference are
The mechanical efficiency of an impulse turbine is
A. ratio of the actual power produced by the turbine to the energy actually supplied by the turbine
B. ratio of the actual work available at the turbine to the energy imparted to the wheel
C. ratio of the Work done on the wheel to the energy of the jet
D. none of the above
The overall efficiency of a reaction turbine is the ratio of
A. power produced by the turbine to the energy actually supplied by the turbine
B. actual work available at the turbine to the energy imparted to the wheel
C. workdone on the wheel to the energy (or head of water) actually supplied to the turbine
D. none of the above
The overshot water wheels are those in which the wheel runs entirely by the __________ of water.
The power produced by the reaction turbine is __________ to the head of water.
A. directly proportional
B. inversely proportional
The principle of jet propulsion is used in driving the ships and aeroplanes.
The ratio of actual work available at the turbine to the energy imparted to the wheel is known as __________ efficiency.
The ratio of quantity of liquid discharged per second from the pump to the quantity of liquid passing per second through the impeller is known as
A. manometric efficiency
B. mechanical efficiency
C. overall efficiency
D. volumetric efficiency
The specific speed from 160 to 500 r.p.m. of a centrifugal pump indicates that the pump is
A. slow speed with radial flow at outlet
B. medium speed with radial flow at outlet
C. high speed with radial flow at outlet
D. high speed with axial flow at outlet
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
A. 24.8 r.p.m.
B. 48.2 r.p.m
C. 82.4 r.p.m.
D. 248 r.p.m
The speed of a turbine runner is
A. directly proportional to H1/2
B. inversely proportional to H1/2
C. directly proportional to H3/2
D. inversely proportional to H3/2
The speed of an imaginary turbine, identical with the given turbine, which will develop a unit power under a unit head, is known as
A. normal speed
B. unit speed
C. specific speed
D. none of these
The speed ratio of a Francis turbine is defined as the ratio of the theoretical jet velocity to the peripheral speed at inlet.
The static head of a centrifugal pump is equal to the __________ of suction head and delivery head.
Theoretical power required (in watts) to drive a reciprocating pump is (where w = Specific weight of liquid to be pumped in N/m3, Q = Discharge of the pump in m3/s, Hs = Suction head in metres, and Hd = Delivery head in metres)
C. wQ(Hs - Hd)
D. wQ(Hs + Hd)
When the speed of the pump increases, its net positive suction head (NPSH) requirement decreases.
Which of the following pump is preferred for flood control and irrigation applications?
A. Centrifugal pump
B. Axial flow pump
C. Mixed flow pump
D. Reciprocating pump
Which of the following turbine is preferred for 0 to 25 m head of water?
A. Pelton wheel
B. Kaplan turbine
C. Francis turbine
D. none of these
Work done by a turbine __________ upon the weight of water flowing per second.
B. does not depend