GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER-V (NEW) EXAMINATION - SUMMER 2019
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Subject Code: 2151903 Date: 31/05/2019Subject Name: Fluid Power Engineering
Time: 02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
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2. Make suitable assumptions wherever necessary.3. Figures to the right indicate full marks.
Q.1 (a) Explain the impulse-momentum principle. 03
(b) State the functions of following components of hydro power plant: Trash rack, surge tank, dam and power house. 04
(c) How ships are propelled ? Derive an expression for propulsive work and propulsive efficiency if the water is drawn from an orifice at right angles to the motion of ship. 07
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Q.2 (a) State major applications of hydro power plant. 03
(b) Show that the force exerted by a jet of water on an inclined fixed plate in the direction of jet is given by Fx = ρaV2sin2θ Where a = Area of the jet, V = Velocity of the jet and θ = Inclination of the plate with the jet. 04
(c) A 80 mm diameter jet having a velocity of 25 m/sec strikes a flat plate, the normal of which is inclined at 45° to the axis of the jet. Find the normal pressure on the plate 07
(i) When the plate is stationary
(ii) When the plate is moving with a velocity of 12 m/sec in the direction of jet and away from the jet.
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Also determine the power and efficiency of the jet when the plate is moving.OR
(c) A jet of water strikes at the centre of a single curved vane moving in the direction of jet with velocity u so that jet velocity relative to vane is (V — u). If the outgoing jet makes an angle θ with the entering jet prove that
(i) For maximum efficiency V = 3u and
(ii) Maximum efficiency = &frac{1}{2}(1+cosθ)
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Q.3 (a) Differentiate between Francis and Kaplan turbine. 03
(b) A Pelton wheel has a mean bucket speed of 10 m/sec with a jet of water flowing at the rate of 800 litres/sec under a head of 32 metres. The bucket deflects the jet through an angle of 165°. Calculate the power given by water to the runner and hydraulic efficiency of the turbine. Assume co-efficient of velocity as 0.98. 04
(c) What is draft tube ? State its functions. With neat diagrams explain salient features of different types of draft tube. 07
OR
Q.3 (a) Compare inward flow and outward flow reaction turbine. 03
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(b) Define the term specific speed and derive an expression for specific speed of hydraulic turbine. 04(c) What do you mean by characteristic curves for hydraulic turbines ? Discuss the main characteristic curves. 07
Q.4 (a) What do you mean by an air vessel ? Explain the function of an air vessel for reciprocating pump. 03
(b) Discuss the criteria for selection of pumps. 04
(c) Show that the pressure rise in impeller of a centrifugal pump is given by [u2Vw2 - u1Vw1] where [ is the blade angle at outlet . Neglect the friction losses. 07
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OR
Q.4 (a) Compare screw and scroll compressor. 03
(b) What is pre-whirl ? State its advantages and disadvantages. Draw velocity diagrams with and without pre-whirl. 04
(c) A single acting two stage air compressor deals with 4.2 m3/min of air under atmospheric conditions of 1 bar and 17°C with a speed of 250 rpm. The delivery pressure is 80 bar. Assume complete intercooling, find the minimum power required by the compressor and bore and stroke of the compressor. Assume a piston speed of 210 m/min, mechanical efficiency of 76 % and volumetric efficiency of 82 % per stage. Assume polytropic index of compression in both stages to be n = 1.3 and neglect clearance. 07
Q.5 (a) Explain construction and working of direct acting hydraulic lift. 03
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(b) Differentiate between fluid coupling and fluid torque converter. 04(c) Explain the phenomenon of stalling in axial flow compressor. 07
OR
Q.5 (a) With a neat sketch explain working of centrifugal compressor. 03
(b) Explain construction and working of simple hydraulic accumulator. 04
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(c) Explain function, working principle, construction and working of hydraulic jack. 07--- Content provided by FirstRanker.com ---
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