hydraulics and hydraulic machinery 2009 jntuk question paper

7/22/2019 Hydraulics and Hydraulic Machinery 2009 JNTUK QUESTION PAPER

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Code No: 3220103 Set No. 1

II B.Tech II Semester Regular Examinations, April/May 2009HYDRAULICS AND HYDRAULIC MACHINERY

(Civil Engineering)Time: 3 hours Max Marks: 80

Answer any FIVE QuestionsAll Questions carry equal marks

1. (a) What is critical flow? Derive the condition for maximum discharge for a givenvalue of specific energy.

(b) The specific energy for a 6 m wide rectangular channel is to be 5 kg-m/kg.

If the rate of flow of water through the channel is 24 m3

/s. Determine thealternate depths of flow. [8+8]

2. Water flows at a steady and uniform depth of 2 m in an open channel of rectangularcross - section having base width equal to 5 m and laid at a slope of 1 in 100. Itis desired to obtain critical flow in the channel by providing a hump in the bed.Calculate hump height and sketch the flow profile. Consider the value of Manningsrugosity coefficient n = 0.02 for the channel surface. [16]

3. Prove that the resistance F of a sphere of diameter d moving at a constant speed through a fluid of density and dynamic viscosity may be expressed as F =2

vd

. [16]

4. (a) Define the term: impact of jets. Obtain an expression for the force exerted bya jet of water on a fixed vertical plate in the direction of the jet.

(b) Find the force exerted by a jet of water of diameter 100mm on a stationaryflat plate, when the jet strikes the plate normally with a velocity of 30m/sec.

[8+8]

5. A Francis turbine having an overall efficiency of 75% is required to give 200kwunder a head of 9m when running at 120 rpm. The velocity of periphery of the

wheel and the velocity of flow at inlet are 3.47Hand 1.15

H respectively. If

the hydraulic losses in the turbine are 20% of the available energy, find

(a) Guide blade angle at inlet

(b) Wheel vane angles at the inlet and out let and

(c) diameter of the wheel at inlet and outlet. [16]

6. (a) A model turbine 1m in diameter acting under a head of 2m runs at 150 rpm.Estimate the scale ratio if the prototype develops 20 KW under a head of 225m with a specific speed of 100.

(b) What are the physical indicators for the presence of cavitation in turbines?[10+6]

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7. (a) What is meant by priming of a centrifugal pump? What are the differentpriming arrangements employed for small and big pumping units?

(b) A centrifugal pump works against a head of 30 m and discharges 0.25 m3/swhile running at 1000 rpm. The velocity of flow at the outlet is 3 m/s and thevane angle at outlet is 300. Determine the diameter and width of impeller atoutlet if the hydraulic efficiency is 80 per cent. [8+8]

8. The load on a hydel plant varies from a minimum of 10,000kW to a maximum of35,000kW. Two turbo-generators of capacities 22,000kW each have been installed.Calculate

(a) Total installed capacity of the plant

(b) Plant factor

(c) Maximum demand

(d) Load factor. [16]

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1. (a) Derive the condition for the best side slope of the most economical trapezoidalchannel.

(b) Design a concrete lined channel to carry a discharge of 500 cumecs at a slope of

1 in 4000. The side slopes of the channel may be taken as 1:1. The Manningsroughness coefficient for the lining is 0.014. Assume permissible velocity inthe section as 2.5 m/s [8+8]

2. (a) Explain the criterion for critical state of flow. Derive the expression?.

(b) In a flow through a rectangular channel for a certain discharge the Froudenumbers corresponding to the alternate depths are F1 and F2. Show that

F1

F2

2/3=

(2+F22 )(2+F2

1). [8+8]

3. Assuming that the viscous force F exerted by a fluid on a sphere of diameter D

depends on the viscosity , mass density of the fluid , and the velocity of thesphere , obtain and expression for the viscous force. [16]

4. A jet of water having a velocity of 40m/sec strikes a curved vane, which is movingwith a velocity of 20m/sec. The jet makes an angle of 300 with the direction ofmotion of the vane at inlet and leaves at an angle of 900 to the direction of motionof the vane at outlet. Draw the velocity triangles at inlet and outlet and determinethe vane angles at inlet and outlet so that the water enters and leaves the vanewithout shock. [16]

5. (a) Draw a neat diagram of a reaction turbine and explain its working. State the

equations for power produced and efficiency.

(b) Explain any two types of draft tubes with neat diagrams. [8+8]

6. (a) A hydraulic turbine develops 120 KW under a head of 10 m at a speed of90 rpm and gives an efficiency of 92%. Find the water consumption and thespecific speed. If a model of scale 1: 30 is constructed to operate under a headof 8m what must be its speed, power and water consumption to run under theconditions similar to prototype.

(b) What are the constant head characteristic curves of a turbine? What is theuse to develop them? [10+6]

7. (a) Define a centrifugal pump. Explain the working of a single stage centrifugalpump.

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(b) The water is to be pumped out of a deep well under a total head of 90m. Anumber of identical pumps of design speed 1000 rpm and specific speed 900rpm with a rated capacity of 150 lps are available. How many pumps will berequired and how should they be connected ? [8+8]

8. Explain in detail about high head diversion power plants along with its components?[16]

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1. (a) What do you mean by most economical section of a channel. What are theconditions for the rectangular channel of the best section?

(b) Determine the dimensions of the most economical trapezoidal earth-lined chan-

nel (Manning-s n = 0.02) to carry 14 m3

/s at a slope of 4 in 10,000. [8+8]

2. Water flows at a steady and uniform depth of 2 m in an open channel of rectangularcross - section having base width equal to 5 m and laid at a slope of 1 in 100. Itis desired to obtain critical flow in the channel by providing a hump in the bed.Calculate hump height and sketch the flow profile. Consider the value of Manningsrugosity coefficient n = 0.02 for the channel surface. [16]

3. The resisting torque T against the motion of a shaft in a lubricated bearing dependson the viscosity , the rotational speed N the diameter D and the bearing pressure

intensity p. Show that T = ND3 p

N. [16]

4. A jet of water having a velocity of 60m/sec is deflected by a vane moving at 25m/secin a direction at 300 to the direction of jet. The water leaves the vane normally tothe motion of the vane. Draw the inlet and outlet velocity triangles and find outthe vane angles for no shock at entry and exit. Take the relative velocity at theexit as 0.8 times the relative velocity at the entrance. [16]

5. A Pelton wheel working under a head of 500m has an overall efficiency of 85% andruns at 400 rpm, and developes 7000 kw of power. Taking the bucket speed as 0.47times the jet speed and assuming Cv = 0.97, find

(a) The wheel diameter and

(b) The jet diameter. [16]

6. (a) Where is servo meter used in governing mechanism of turbines? Explain itsuse?

(b) A Kaplan turbine is to develop 2400 KW when running at 240 rpm under anet head of 49m. In order to predict its performance a model of scale 1:5 istested under a net head of 25m. At what speed should the model run andwhat power would it develop. Determine the discharge in the model and infull scale turbine if the overall efficiency of the model is 85%. [8+8]

7. (a) What is meant by priming of a centrifugal pump? What are the differentpriming arrangements employed for small and big pumping units?

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(b) A centrifugal pump works against a head of 30 m and discharges 0.25 m3/swhile running at 1000 rpm. The velocity of flow at the outlet is 3 m/s and thevane angle at outlet is 300. Determine the diameter and width of impeller atoutlet if the hydraulic efficiency is 80 per cent. [8+8]

8. When a run-of-river plant operates as a peak load station with a weekly load factorof 20%, all its capacity is firm capacity. What will be the minimum flow in theriver so that the station may serve as the base load station?. It is given that Ratedinstalled capacity of generator = 10,000kWOperating head = 15mPlant efficiency = 80%Estimate the daily load factor of the plant, if the stream flow is 15cumec. [16]

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1. (a) Derive the condition for depth of flow of a most economical circular channelsection subject to the condition for maximum velocity.

(b) Water flows in a channel of the shape of isosceles triangle of bed width aand

sides making an. angle of 450

with the bed. Determine the relation betweendepth of flow d., and the bed width a for maximum velocity and for maximumdischarge condition. Use Mannings formula and note that d is less than 0.5a. [8+8]

2. (a) Define specific force in open channel applying momentum principle, obtain anexpression for specific force.

(b) A trapezoidal channel of bed width 6m and side slopes 1:1, carries a uniformflow of 25m3/s.

i. Plot a specific energy curve and find the value of critical depth and min-

imum specific energy.ii. Calculate the alternate depths and their corresponding Froudes number

for a specific energy of 2.5m

iii. Determine the depth alternate to 1.5m

iv. Determine the type of flow for y=0.5m and y=2.5m. [8+8]

3. The resistance R, to the motion of a completely submerged body is given by R =

v22

v

.where and g are the density and the kinematic viscosity of the fluid

while l is the length of the body and v is the velocity of flow. If the resistance tothe motion of a one-eight scale air ship model when tested in water at 12 metresper second is 22 kg, what will be the resistance to the motion in air of the airshipat the corresponding speed? Kinematic viscosity of air is 13 times that of waterand density of water is 810 times that of air. [16]

4. A jet of water moving at 12m/sec impinges on vane shaped to deflect the jet through1200 when stationary. If the vane is moving at 5m/sec, find the angle of the jet sothat there is no shock at inlet. What is the absolute velocity of the jet at exit inmagnitude and direction and the work done per second? Assume that the vane issmooth. [16]

5. Obtain an expression to the work done per second by water on the runner of aPelton wheel. Hence derive an expression for maximum efficiency of the Peltonwheel giving the relationship between the jet speed and the bucket speed. [16]

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6. (a) A hydraulic turbine develops 120 KW under a head of 10 m at a speed of90 rpm and gives an efficiency of 92%. Find the water consumption and thespecific speed. If a model of scale 1: 30 is constructed to operate under a headof 8m what must be its speed, power and water consumption to run under theconditions similar to prototype.

(b) What are the constant head characteristic curves of a turbine? What is theuse to develop them? [10+6]

7. (a) How will you obtain an expression for the minimum speed for starting a cen-trifugal pump.

(b) A centrifugal pump with 1.2m diameter runs at 200 rpm and pumps 880 litresper second, the average lift being 6m. The angle which the vanes make atexit with the tangent to the impeller is 260 and the radial velocity of flow is2.5 m/s. Determine the manometric efficiency and the least speed to startpumping against a head of 6m, the inner diameter of the impeller being 0.6m. [8+8]

8. The load on a hydel plant varies from a minimum of 10,000kW to a maximum of35,000kW. Two turbo-generators of capacities 22,000kW each have been installed.Calculate

(a) Total installed capacity of the plant

(b) Plant factor(c) Maximum demand

(d) Load factor. [16]

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hydraulics and hydraulic machinery 2009 jntuk question paper

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