Code No: 44012

R07

Set No. 2

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II B.Tech II Semester Supplimentary Examinations,February 2010 FLUID MECHANICS AND HYDRAULIC MACHINERY Mechanical Engineering Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) Discuss the relative merits and demerits of hydropower as compared to other power sources.

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(b) Describe how water power potential is estimated before any power plant is contemplated. [8+8] 2. (a) Define the specific speed of a turbine? Derive an expression for the specific speed. What is the significance of the specific speed?

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(b) A turbine is to operate under a head of 30 m at 300 r.p.m. The discharge is 10 m3/s. If the efficiency is 90%, determine: i. Specific speed of the machine, ii. power generated, and iii. types of the turbine.

[8+8]

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3. (a) Explain how the fluid flows are classified? Explain the sketches where necessary. (b) Find the equation of stream line passing through (2,2) for the fluid flow v = −y 2 i − 6xj. [8+8] 4. (a) How will you obtain an expression for the minimum speed for starting a centrifugal pump?

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(b) Find the rise in pressure in the impeller of a centrifugal pump through which water is flowing at the rate of 15 lit/s. The internal and external diameters of the impeller are 20 cm and 40 cm respectively. The widths of impeller at inlet and outlet are 1.6 cm and 0.8 cm. The pump is running at 1200 r.p.m. The water enters the impeller radially at inlet and impeller vane angle at outlet is 300 . Neglect losses through the impeller. [16]

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5. (a) A nozzle of size 10 cm diameter issues a jet of water with a velocity of 50m/sec. The jet strikes a moving flat plate perpendicularly at the centre. The plate is moving with a velocity of 15m/sec in the direction of the jet. Calculate: i. The force exerted on the plate ii. The work done iii. Efficiency of the jet.

(b) Derive the equation for the impact of jet striking a moving inclined plate in the direction of the jet. [8+8] 6. (a) What is the basis of selection of a turbine at a particular place? 1

Code No: 44012

R07

Set No. 2

(b) An inward flow reaction turbine has an external diameter of 1 m and its breadth at inlet is 20 cm. If the velocity of flow at inlet is 1.5 m/s, find the mass of water passing through the turbine per second. Assume 15% of the area of flow is blocked by blade thickness. If the speed of the runner is 200 r.p.m. and guide blades make an angle of 150 to the wheel tangent, draw the inlet velocity triangle and find:

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The runner vane angle at inlet, Velocity of wheel at inlet, The absolute velocity of water leaving the guide vanes, and The relative velocity of water entering the runner blade.

[16]

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i. ii. iii. iv.

7. (a) Explain the working of a U tube differential manometer with a neat sketch.

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(b) A clean tube of internal diameter 3mm is immersed in a liquid with a surface tension of 0.48N/m. The angle of contact of the liquid with the glass can be assumed to be 1300 . The density of the liquid is 13600 Kg/m3 . What would be the level of the liquid in the tube relative to the free surface of the liquid outside the tube? [6+10] 8. (a) What is the principle on which a pitot tube works? Draw a neat sketch and derive the required equation.

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(b) A vertical venturimeter 40cm × 20cm is provided in a vertical pipe to measure the flow of oil of relative density 0.80. The difference in elevations of the throat section and the entrance section is 1m. The direction of flow of oil is vertically upwards. The oil mercury differential gauge shows deflection of mercury of 40 cm. Determine the discharge of oil in the pipe line. [8+8]

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2

R07

Code No: 44012

Set No. 4

1. (a) Derive the equation of continuity for one dimensional flow.

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II B.Tech II Semester Supplimentary Examinations,February 2010 FLUID MECHANICS AND HYDRAULIC MACHINERY Mechanical Engineering Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ?????

i. ii. iii. iv.

u u u u

= = = =

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(b) Which of the following can be a set of velocity components in a two dimensional flow? x + y; v = x2 + y 2 x + y; v = x − y xy; v = x/y x2 + y 2 ; v = x 2 − y 2 .

[8+8]

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2. (a) Explain firm power and secondary power in detail

(b) What are the different methods of classifying the hydroelectric power plants. Explain. [8+8]

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3. (a) What is cavitation? How can it be avoided in reaction turbine? (b) What is governing and how it is accomplished for different types of water turbines? [8+8] 4. (a) Draw a neat sketch of pipes in series and write the equation for solving the problems of pipes in series. What is equivalent pipe line?

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(b) When a sudden contraction from 50cm diameter to 25cm diameter is introduced in a horizontal pipeline, the pressure changes from 105 KPa to 69 KPa. Assuming a coefficient of contraction of 0.65, calculate the flow rate. [8+8]

5. (a) How will you determine the possibility of the cavitation to occur in the installation of a turbine or a pump?

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(b) A single-acting reciprocating pump running at 30 r.p.m., delivers 0.012 m3 /s of water. The diameter of the piston is 25 cm and stroke length 50 cm. Determine: i. The theoretical discharge of the pump ii. Co-efficient of discharge, and iii. Slip and percentage slip of the pump.

6. (a) Deifne and discuss the following fluid properties: i. Specific gravity ii. Viscosity 3

[8+8]

Code No: 44012

R07

Set No. 4

iii. Surface tension iv. Vapour Pressure (b) The velocity distribution in a viscous flow over a plate is given by u = 4y − y 2 f or y ≤ 2m

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Where u = velocity in m/sec at a point which is at a distance of distant y from the plate. If the coefficient of dynamic viscosity is 1.5Pa.s determine the shear stress at y=0 and at y=2.0m. [8+8]

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7. (a) A 100 mm diameter jet with a velocity of 50m/sec strikes a flat plate, the normal of which is inclined at 35 degrees to the axis of he jet. Find the normal force exerted on the plate when the plate is stationary and when the plate is moving with a velocity of 10 m/sec

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i. in the direction of jet and, ii. away from the jet.

(b) Explain how the efficiency of jet is defined and found when it strikes a moving flat plate normally. [8+8]

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8. (a) Obtain an expression for the work done per second by water on the runner of a Pelton wheel. Hence derive an expression for maximum efficiency of the Pelton wheel giving the relationship between the jet speed and bucket speed. (b) Two Jets strike at buckets of a Pelton wheel, which is having shaft power as 14,715 kW. The diameter of each jet is given as 15 cm. If the net head on the turbine is 500 m, find the overall efficiency of the turbine. Take Cv = 1.0 [16]

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4

Code No: 44012

R07

Set No. 1

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II B.Tech II Semester Supplimentary Examinations,February 2010 FLUID MECHANICS AND HYDRAULIC MACHINERY Mechanical Engineering Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ?????

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1. (a) A jet of water 70 mm diameter and having a velocity of 30m/sec, impinges at the centre of a hemispherical vane. The linear velocity of vane is 10m/sec in the direction of the jet. Find the force exerted on the vane and efficiency of the jet.

(b) Explain how the jet gets distributed at two tips when a jet of water strikes an inclined stationary plate at the centre. What will be the work done? [8+8]

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2. (a) Obtain an expression for unit speed, unit discharge and unit power for a turbine.

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(b) A Pelton wheel is revolving at a speed of 200 r.p.m. and develops 5886 kW S.P when working under a head of 200 m with an overall efficiency of 80%. Determine unit speed, unit discharge and unit power. The speed ratio for the turbine is given as 0.48. Find the speed, discharge and power when this turbine is working under a head of 150 m. [8+8] 3. (a) Describe storage and pondage in detail (b) Draw a line diagram of general arrangement of a pumped storage power plant and explain. [8+8] 4. (a) Draw a neat sketch of a sudden expansion in a horizontal pipe line showing the stream lines and derive the equation for loss of energy.

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(b) Three pipes are connected in parallel between two reservoirs A and B. The details of the pipes are given below. If the difference in the water levels of the two reservoirs is 12m, calculate the flow in each pipe line. [8+8] Pipe Diameter(cm) Length(m) f 1 10 1000 0.022 2 15 800 0.018 3 12 950 0.020

5. (a) The 18mm space between two square flat parallel plates is filled with oil. Each side of the plate is 900mm. The upper plate which moves at 4.2m/sec requires a force of 160N to maintain the speed. Determine the dynamic viscosity of the fluid. (b) List the important fluid properties and derive the equation for Newton‘s law of viscosity from fundamentals. [8+8] 6. (a) Explain, what total energy line drawn for a pipe line flow interprets. Draw a neat sketch and discuss. 5

Code No: 44012

R07

Set No. 1

(b) The following details are available for flow of a fluid with specific gravity 0.85 calculate the total head neglecting the losses. Diameter of the pipe : 78mm Pressure : 200 KN/m2 Velocity of flow : 3.5m/sec Datum head : 6m. [8+8]

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7. (a) With the help of a neat diagram explain the construction and working of a Pelton wheel turbine.

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(b) A conical draft tube having inlet and outlet diameters 0.8 m and 1.2 m discharges water at outlet with a velocity of 3 m/s. The total length of the draft tube is 8 m head is 10.3 m of water and loss of head due to friction in the draft tube is equal to 0.25 times the velocity head at outlet of the tube, find: i. Pressure head at inlet, and ii. Efficiency of the draft tube.

[16]

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8. (a) Obtain an expression for the work done by impeller of a centrifugal pump on water per second per unit weight of water.

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(b) A centrifugal pump having outer diameter equal to two times the inner diameter and running at 1200 r.p.m. works against a total head of 75 cm. The velocity of flow through the impeller is constant and equal to 3 m/s. The vanes are set back at an angle of 300 at outlet. If the outer diameter of the impeller is 60 cm and width at outlet is 5 cm, determine: i. vane angle at inlet ii. work done per second by impeller’ iii. manometric efficiency.

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[8+8]

Code No: 44012

R07

Set No. 3

in

II B.Tech II Semester Supplimentary Examinations,February 2010 FLUID MECHANICS AND HYDRAULIC MACHINERY Mechanical Engineering Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) Describe different types of pumped storage plants what are the relative merits of them.

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(b) Explain what is mass curve and how it is constructed. Draw a neat sketch. [8+8] 2. (a) How does the pressure vary with depth in a static fluid. Derive the required equation. (b) Calculate the guage pressure and the absolute pressure with in

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i. A droplet of water 0.4cm in diameter ii. A jet of water 0.4cm in diameter.

[8+8]

3. (a) Discuss the assumptions made in the derivation of Bernoulli’s equation from fundamentals.

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(b) Discuss at least one application of each of the following: i. Continuity equation ii. Momentum equation iii. Bernoulli’s equation.

[8+8]

4. (a) What is priming? Why is it necessary? Explain how it is done.

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(b) Find the number of pumps required to take water from a deep well under a total head of 156 m. Also, the pumps are identical and are running at 1000 r.p.m. The specific speed of each pump is given as 20 while the rated capacity of each pump is 150 lit/s. [8+8]

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5. (a) Define the terms ‘unit power’, ‘unit speed’ and ‘unit discharge’ with reference to a hydraulic turbine. Also derive expressions for these terms. (b) Sketch and describe a modern method of regulation to maintain a constant speed for either i. Pelton wheel or ii. Francis turbine.

[8+8]

6. (a) Explain when the following will converge, diverge and remain parallel: i. Hydraulic gradient line ii. Total energy line.

7

Code No: 44012

R07

Set No. 3

in

(b) Two pipes A and B with following details are connected in parallel between two points: Pipe Diameter(cm) Length(m) f A 12 1000 0.032 B 18 800 0.028 Calculate the size of an equivalent pipe of length 700 m and having a friction factor of 0.015. [8+8]

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7. (a) A jet of fluid (specific gravity 0.74) 100 mm diameter and having a velocity of 25 m/sec impinges at the centre of a hemispherical vane. The linear velocity of the vane is 10m/sec in the direction of the jet. Find the force exerted on the vane.

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(b) Prove that the force exerted by a jet of water on a moving curved vane when the jet strikes at the centre is F = ρa(V-v)2 (1+Cosθ) where ρ = Mass density of water A = Area of cross section of the jet V = Velocity of the jet v = Velocity of the vane in the direction of the jet θ = Angle of the curved plate at the outlet. [8+8]

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8. (a) A Pelton wheel, 2.45 m in diameter, operates under the following conditions: Net head = 370 m; co-efficient of velocity = 0.98: speed ratio = 0.47; relative velocity of water at outlet = 0.90 times that at inlet; deflection of jet = 1600 ; diameter of the jet = 0.88m. Determine the following: i. The input power to the shaft, and ii. The r.p.m. of the wheel. (b) An inward flow reaction turbine of inlet diameter 1.2 m operates under a head of 150 m and requires a discharge of 6 m3 /s at a rotational speed of 400 r.p.m. The guide vane angle is 200 and the water leaves the runner blade axially. If the runner is 0.1 m wide at the inlet, calculate:

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i. The torque and power supplied to the shaft, and ii. The efficiency of the turbine.

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[8+8]