JNTU II B.Tech I Semester Supplimentary Examinations, November 2008
FLUID MECHANICS AND HYDRAULIC MACHINERY
(Electrical & Electronic Engineering)
1. (a) State Newton’s equation of viscosity and give examples of its application.
(b) An oil of viscosity 5 poise is used for lubrication between a shaft and sleeve. The diameter of shaft is 0.5 m and it rotates at 200 rpm. Calculate the horse power lost in the oil for a sleeve length of 100 mm. The thickness of the oil film is 1.0 mm.
2. (a) Explain what is meant by stream tube. What is the use of concept of streamtube?
(b) At a point in the pipe line where diameter is 20 cm, the velocity of water is
4 m/s and the pressure is 343 kN/m2. At a point 15 cm downstream, the diameter reduces to 10cm. Calculate the pressure at this point, if the pipe is vertical with flow downward. Neglect the losses.
3. (a) Define Major Energy Loss and Minor Energy Loss.
(b) Briefly explain Hydraulic Gradiant Line and Total Energy Line.
(c) The rate of flow of water through a horizontal pope is 0.3m3/sec. The diameter of the pipe is suddenly enlarged fron 25cm to 50cm. The pressure intensity in the smaller pipe is 1.4Kgf/cm2. Determine loss of head due to sudden enlargement, pressure intensity in the large pipe and power lost due to enlargement.
4. (a) Derive the expressions for force and work done per second by the jet when it
strikes a flat vertical plate moving in the direction of the jet and away from the jet.
(b) A jet of water of 75mm diameter strikes a curved vane at its center with a velocity of 20m/sec. The curved vane is moving with a velocity of 8m/sec in the direction of jet. Find the force exerted on the plate in the direction of the jet power and efficiency of the jet. Assume the plate to be smooth.
5. (a) List and write elaborately about the elements of Hydroelectric station with neat sketches .
(b) The head and discharge of a hydro electric plant are 28m and 330m3/sec respectively. The installed turbine works with an efficiency of 86%. Find the power developed.
6. (a) How are the turbines classified under different heads ? Give sketches wherever
(b) A Pelton wheel turbine works with the following details. Determine the water power available at the nozzle and hydraulic efficiency
Net head = 700 m
Speed of runner = 950 rpm
Diameter of runner = 1.2 m
Discharge through the nozzle = 0.15 m3/ sec
Side clearance angle = 150
Coefficient of velocity Cv = 0.9
Blade friction coefficient K = 1
7. (a) What is meant by cavitation ? What is Thoma,s cavitation factor and what is its significance for turbines ? Elaborate what you understand by water hammer phenomenon in turbines.
(b) A turbine works under a head of 25m at 200 rpm and the discharge is 9m3 /sec. If the overall efficiency is 90%, determine Power generated, Specific speed of the turbine and Type of turbines.
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.