JNTU II B.Tech I Semester Supplimentary Examinations, November 2008
Fluid mechanics and hydraulic machinery
(Electrical & Electronic Engineering)
1. (a) Obtain an expression for capillary rise of a liquid.
(b) The velocity distribution over a plate is given by V = 1/3 y -y2 in which v is the velocity in m/sec at adistance y metres obve the plate. Determine the stress at y = 0 and y = 0.1 m. Take ? = 0.835N ? s/m2
2. A pipeline is 15 cm in diameter and is at an elevation of 100 m at section A. At section B, it is at an elevation of 107.0 m and has a diameter of 30 cm. When a discharge of 50 lit/sec of water is passed through this pipe, the pressure at section A is observed to be 30 KPa. The energy loss in the pipe is 2 m. Calculate the pressure at B when the flow is (i) from A to B, (ii) from B to A.
3. (a) Explain how the following flow problems are analyzed.
i. Series pipe connection
ii. Parallel pipe connection
iii. Equivalent pipe connection.
(b) Water flows through a 10cm diameter, 30m long pipe at a rate of 1400 rpm. What percent of head would be gained by replacing the central one third length of pipe by another pipe of 20cm diameter. Assume that the changes in section are abreept and f = 0.008 for all pipes. Neglect entrance and exit losses but consider major loss and losses due to sudden contraction and sudden expansion.
4. (a) Derive an expression for the force exerted by a jet striking the curved plate at one end tangentially when the plate is symetrical.
(b) A jet of water 120 mm in diameter and moving with a velocity of 25m/sec strikes normally on a flat plate. Determine the power developed and the efficiency of the system when
i. the plate is stationary
ii. the plate is moving with a velocity of 8m/sec in the direction of the jet.
iii. the plate is moving with a velocity of 8m/sec towards the jet.
5. (a) What is the name of hydroelectric power station that uses the flow of stream as it is available ? How do you compare this with reservoir or storage type of power station ? Explain with neat sketches if necessary.
(b) The hydro power plant has a turbine with the following details. Find the power developed and what is the specific speed of the turbine. Hydraulic efficiency = 90%. Net head =65m1 discharge=15m3/s, speed=100 rpm
6. (a) What is the classification of turbines ? How do you differentiate among low
head, medium head and high head turbines ?
(b) A Pelton wheel is working under a head of 45m and the discharge is 0.8m3/sec.
The mean bucket speed is 14m/sec. Find the power produced if the jet is deflected by the blades through an angle of 1650. The coefficient of velocity is 0.985
7. (a) What is specific speed of a turbine ? Derive its expression and compare it with unit speed. What are its applications ?
(b) An Impulse turbine has to maintain the same efficiency under different working conditions. By what percentage shall the discharge increase if the head changes from 50m to 75m.
8. (a) What is manometric efficiency of a centrifugal pump? Define with the help of a sketch. Differentiate it from volumetric efficiency and mechanical efficiency.
(b) A single acting reciprocating pump has a plunger of diameter 0.3m and stroke of length 0.4m. If the speed of the pump is 60 rpm and coefficient of discharge is 0.97, determine the percentage slip and actual discharge of the pump.