# Hydraulic Machines-Fluid Machineries – Set 08

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## Q1. The Thomson’s turbine is _ reaction turbine.

(A) An axial flow
(B) An inward flow
(C) An outward flow
(D) A mixed flow

## Q2. According to fan laws, for the fans having constant wheel diameters, the power demand varies

(A) Directly as fan speed
(B) Square of fan speed
(C) Cube of fan speed
(D) Square root of fan speed

Answer: (C) Cube of fan speed

(A) 102 watts
(B) 75 watts
(C) 550 watts
(D) 735 watts

## Q4. The force exerted by a jet of water impinging normally on a plate which due to the impact of jet, moves in the direction of jet with a velocity v is

(A) [wa (V – v)]/2g
(B) [wa (V – v)]/g
(C) [wa (V – v)²]/2g
(D) [wa (V – v²)]/g

Answer: (D) [wa (V – v²)]/g

## Q5. Hydraulic accumulator is used for

(A) Accumulating oil
(B) Supplying large quantities of oil for very short duration
(C) Generally high pressures to operate hydraulic machines
(D) Supplying energy when main supply fails

Answer: (D) Supplying energy when main supply fails

## Q6. Puck up the wrong statement about centrifugal pump

(A) Discharge a diameter
(D) Power a speed⁴

## Q7. In axial flow fans and turbines, fluid enters and leaves as follows

(C) Axially, axially

## Q8. 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

Answer: (D) High speed with axial flow at outlet

## Q9. The maximum hydraulic efficiency of an impulse turbine is (where φ = Angle of blade tip at outlet)

(A) (1 + cos φ)/2
(B) (1 – cos φ)/2
(C) (1 + sin φ)/2
(D) (1 – sin φ)/2

Answer: (A) (1 + cos φ)/2

## Q10. Multistage centrifugal pumps are used to obtain

(A) High discharge
(C) Pumping of viscous fluids
(D) High head and high discharge

## Q11. The cavitation in reaction turbines is avoided, to a great extent by

(A) Installing the turbine below the tail race level
(B) Using stainless steel runner of the turbine
(C) Providing highly polished blades to the runner
(D) All of the above

Answer: (D) All of the above

## Q12. 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

Answer: (A) Directly proportional to H1/2

## Q13. The static head of a centrifugal pump is equal to the _ of suction head and delivery head.

(A) Product
(B) Difference
(C) Sum
(D) None of these

## Q14. Which of the following statement is correct?

(A) The centrifugal pump is suitable for large discharge and smaller heads
(B) The centrifugal pump requires less floor area and simple foundation as compared to reciprocating pump
(C) The efficiency of centrifugal pump is less as compared to reciprocating pump
(D) All of the above

Answer: (D) All of the above

## Q15. The hydraulic 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 energy imparted to the wheel
(C) Work-done on the wheel to the energy (or head of water) actually supplied to the turbine
(D) None of the above

Answer:(C) Work-done on the wheel to the energy (or head of water) actually supplied to the turbine

(A) (D/2d) + 5
(B) (D/2d) + 10
(C) (D/2d) + 15
(D) (D/2d) + 20

## Q17. The jet ratio is defined as the ratio of the

(A) Diameter of jet to the diameter of Pelton wheel
(B) Velocity of jet to the velocity of Pelton wheel
(C) Diameter of Pelton wheel to the diameter of jet
(D) Velocity of Pelton wheel to the velocity of jet

Answer:(C) Diameter of Pelton wheel to the diameter of jet

(A) 0.15 to 0.3
(B) 0.4 to 0.5
(C) 0.6 to 0.9
(D) 1 to 1.5

## Q19. Which of the following statement is correct?

(A) In an impulse turbine, the water impinges on the buckets with pressure energy.
(B) In a reaction turbine, the water glides over the moving vanes with kinetic energy.
(C) In an impulse turbine, the pressure of the flowing water remains unchanged and is equal to atmospheric pressure.
(D) In a reaction turbine, the pressure of the flowing water increases after gliding over the vanes.

Answer: (C) In an impulse turbine, the pressure of the flowing water remains unchanged and is equal to atmospheric pressure.

(A) 10° to 15°
(B) 15° to 20°
(C) 20° to 25°
(D) 25° to 30°