337514(37)
B.E (Fifth Semester) Examination,
Nov.-Dec., 2008
(Mechanical Branch)
FLUID MACHINERY -I
Time allowed : THREE Hours
Maximum Marks : 80
Minimum Pass Marks : 28
Note :- Part (a) from each question is compulsary. Attempt any two parts from the remaining.
1. (a) Define the terms : laminar boundary layer, turbulent boundary layer. 2
(b) Oil with a free stream velocity of 2 m/s flows over a thin plate 2 m wide and 2 m long. Calculate the boundary layer thickness and the shear stress at the trailing end point and determine the total surface resistance of the plate. Take specific gravity as 0.86 and kinematic viscocity as 10-5 m2/s. 7
(c) What is the expression for the drag on a sphere, when the Reynolds number of the flow is upto 0.2 ? Hence prove that the co-efficient of drag for sphere for this range of Reynolds number is given by :
Cv = 24/R
Where Re = Reynolds number.
(d) A flate plate 1.5 m x 1.5m moves at 50 km/hour in stationary air of specific weight 1.15 kg/m3. If the co-efficient of drag and lift are 0.15 and 0.75 respectively, determine:
The lift force
The drag force
The resultant force
The power required to keep the plate in motion
2. (a) Define the terms :
Impact of jets
Jet propulsion
(b) Show that the efficiency of a free jet stricking normally on a series of flat plates mounted on the periphery of a wheel can never exceed 50%. 7
(c) A Pelton wheel is to be designed for the following specifications: 7
Power (brake or shaft ) ..................... 9560 kW
Head ..................................................350 metres
Speed ................................................. 750 rpm
overall efficiency .................................... 85%
Jet daimeter not to exceed 1/6th of the wheel daiometer
Determine the following :
The wheel daimeter
Daimeter of the jet, and
The Number of the jets required
Take Cv = 0.985, speed ratio = 0.45
(d) Describe governing of impulse turbine. 7
3. (a) What is degree of reaction as applied to reaction turbine? 2
(b) Draw a schematic diagram of a Francis turbine and explain briefly its construction and woking. 7
(c) an inward flow reaction turbine has an exit diameter of 1 meter and its breadth at inlet is 25 cm. If the velocity of flow at inlet is 2 meter/sec, find the weight of water passing through the turbine per second. Assume 10% of the area of flow blocked by blade thickness.
If the speed of the runner is 210 rpm and the guide blades make an angle of 10o to the wheel tangent, draw the inlet velocity triangle and the runner vane angle at inlet, the velocity of wheel at inlet and absolute velocite of water leaving the guide vanes and the relative velocity of water entering the runner blade. 7
(d) What do you understand by the characteristics curves of a turbine ? Describe the important types of charteristics curves. 7
4. (a) Define the terms : suction head, delivery head, static head and manometric head. 2
(b) Define specifc speed of a centrifugal pump. Obtain an expression for the same . 7
(c) A centrifugal pump is to discharge 0.118 m3/s at a speed of 1450 rpm against a head of 25m. The impeller daimeter is 250 mm, its width at outlet is 50 mm and manometric efficiency is 75%. Determine the vane angle at tje outer periphery of the impeller. 7
(d) A three stage centrifugal pump has impellers 40 cm is diameter and 2 cm wide at outlet. the vanes are curved back at the outlet at 45o and reduce the circumferential area by 10%. The manometric efficiency is 90% and the overall efficiency is 80%. Determine the head generated by the pump when running at 100 rpm delivering 50 litres per second. What should be the shaft horse power ? 7
5. (a) Classify the reciprocating pumps. 2
(b) Describe the principle and working of a reciprocating pump. 7
(c) A single acting reciprocating pump has a piston daimeter of 150 mm and stroke 350 mm. The centre of the pump is 3.5 m above the water surface is the pump is 3.5 m above the water surface is the pump and 22m below the delivery water level. Both the suction and delivery pipes have the same daimeter of 100 mm and are 3m and 30m long respectively. If the pump is working at 30 rpm, determine : 7
(i) The pressure heads on the piston at the begining, middle and end of both suction and delivery strokes.
(ii) the power required to drive the pump .
Take the atmosheric pressure as 10.3 m of water .
(d) Explain with neat sketch the working of air lift pump.Mention its advantages. 7
