Fourth Semester B. E. ( R ) / Fourth Semester B. E. (PTDP) Mechanical Engineering Examination

Course Code : ME 215 1 ME 611 Course Name: Hydraulic Machines

Time : 3 Hours ] [ Max. Marks : 60

Instructions to Candidates :- (1) All questions are compulsory. (2) All questions carry marks as indicated. (3) Due credit will be given to neatness and adequate dimensions. (4) Assume suitable data wherever necessary. (5) Diagrams and chemical equations should be given wherever necessary. (6) Illustrate your answers wherever necessary with the help of neat sketches.

1. (a) A Jet of water having a velocity of 3 6 d s strikes a series of radial curved vanes mounted on a wheel, which is rotating at 240rpm. The Jet makes an angle of 20° with the tangent to wheel at inlet. Jet leaves the wheel with a velocity of 6 d s at an angle of 130° to the tangent to the wheel at outlet. The outer and inner radii of the wheel are 500rnm -and 250 mrn. Determine :

(i) Vane angles at inlet and outlet.

(ii) Work done per sec. per N of water.

(iii) Efficiency of wheel.

A pelton wheel is to be designed for following specification :- /

Shaft power = 11772 KW, Head = 380 m, Speed = 750 rpm, overall

1 efficiency = 86 % Jet diameter not to exceed - th of the wheel diameter, Determine : 6

(i) The wheel diameter (ii) no. of Jet Required.

(iii) Diameter of Jet.

Take Cv = 0-985, Speed ratio = 0.45. 5

Contd.

(b) A Jet of water having a velocity of 15 d s strikes a curved vane which is moving with a vel. of 5 d s . The vane is symmetrical and so shaped that the Jet is deflected through 120" Find the angle at inlet of vane so that there is no shock. What is absolute velocity of Jet at outlet in magnitude and direction and the workdone per unit wt. of water ? Assume the vane to be smooth.

A turbine Develops 8000 KW under a Net head of 130 m at a speed of 200rpm. Assuming the coefficient of velocity for the Nozzle 0.98, hydraulic efficiency 87 %, speed ratio 0.46 and Jet diameter to wheel diameter ratio 119.

determine :

(i) Discharge required.

(ii) Diameter of wheel.

(iii) Diameter and no. of Jets required.

(iv) The specific speed.

Mechanical efficiency = 75 %. 5

(A) The following data pertains to a turbine.

Net Head = 70 m, Speed = 700 rpm, shaft power = 330 KW, Overall efficiency = 85%, Hydraulic efficiency = 9296, Flow ratio = 0.22, Breadth ratio = 0.1.

Outer diameter of runner = 2 x inner diameter of runner, velocity of flow is constant, discharge at outlet is radial. The thickness of vanes occupy 6% of circumferential area of runner.

Determine :

(i) Diameter of runner at inlet and outlet.

(ii) Width of wheel at inlet.

(iii) Guide blade angle.

(iv) Runner blade angle at inlet and outlet,

A Kaplan turbine develops 24647.6KW power at an average head of 39 m. Assuming a speed ratio of 2, flow ratio of 0.6, Diameter of boss equal to 0.35 times the diameter of runner and overall efficiency of 90%, calculate the Diameter, speed and specific speed of turbine. 7

O A B / ~ K T T / E O T - ~ ~ ~ / ~ ~ O 2 Contd.

(B) (i) Draw Hydroelectric power plant and explain the terms associated with it.

OR

(ii) Explain cavitation phenomenon in turbine.

3. (A) A centrifugal pump running at 800 rpm is working against a total head of 20.2 m. The external diameter of the impeller is 480 mm and outlet width is 60mm. If the vane angle at outlet is 40° and manometric efficiency is 70%,

determine :

(i) Flow velocity at outlet.

(ii) Abs. velocity of water leaving the vane.

(iii) Angle made by absolute velocity at outlet with direction of motion at outlet.

(iv) Rate of flow through the pump. 7

A centrifugal pump is delivering 0.216 m3/s of water against a head of 18 m. The speed of rotation of impeller is 600rpm. The diameters at outer and inner periphery of impellers are 600mm and 300rnm resp. The area of flow is constant and 0.084m2 from inlet to outlet of impeller. If the vanes of the impeller are bent at an angle of 35O to the tangent at exit, determine

(i) Manometric efficiency.

(ii) Inlet vane angle.

(iii) Loss of head at inlet to imbeller when discharge is reduced by 35%. 7

(B) What is priming ? Explain the methods of priming briefly. 3

Explain Different heads and Efficiencies of centrifugal pump with sketch. 3

OABl2KTTlEOT-6261820 3 Contd.

4. (A) The piston diameter and stroke length of a single acting reciprocating pump are 150 mm and 300 mm resp. The centre of the pump is 5 m above the water level in the sump and 33 m below the delivery water level. Both the suction and delivery pipes have the same diameter of 75 rnrn and are 65 m and 39 m long resp. If the pump is working at 30rpm, determine : (i) The pressure head on the piston at the beginning , middle and

end of both suction and delivery strokes. (ii) Power required to drive the pump. (iii) The maximum head at any instant against which the pump has

to work.

Take atmospheric pr head= 10.3 m of water and friction coefficient f=0-01 for both the pipes.

OR

A single acting reciprocating pump has plunger of 20cm diameter and stroke 40 cm. The delivery pipe is 8 cm diameter and 50 m long. If f=0.01 find the power saved by fitting a large air vessel when the speed of the pump is 60 rpm in the following cares. (i) Air vessel is direction mounted. (ii) Air vessel fitted at 2 m away from the cylinder. 7

(B) (i) What are air vessels ? Explain working and Advantages of Air vessel with sketch.

(ii) Define Slip. What is negative slip ? Also draw and explain main components of Reciprocating pump. 3

5. (A) Define unit quantities and Derive the relation for specific speed of a turbine.

A Hydraulic turbine is to develop 1015KW when running at 120rpm. Under a net head of 12m. Work out the maximum flow rate and specific speed for the turbine if the overall efficiency at the best operating point is 92%.

1 In order to predict its performance a - scale model is tested under 10

a head of 7.2 m. What would be the speed, power output and water consumption of the model if it runs under the condition similar to prototype ?

5

OAB/2KTT/EOT-6261820 4 Contd.

(El) Show by the use of Buckinghams pi theorem that the velocity through an orifice is given by

p. v = 1- f (D, --- 2-) H Q V H ' V ~ H

where H = the head causing flow.

D = Diameter of orifice

p. = Coefficient of viscosity.

8 = Mass density, o = surface tension

g = graviational acceleration.

OR

What are the different types of similarities ? Explain them. 5

6 . (A) What are the different kinds of Hydraulic accumulator used in Hydraulic system ?

OR

Discuss in brief Hydraulic Reservoir. 3

(B) Explain Gear pump with neat sketch including construction, working, Application, Advantages and limitations.

Classify Hydraulic Valves. Describe Pressure Relief valve.

.n'trBARl2KTTlEER - 626/820

Fourth Semester B. E. (R)/Fourth Semester B. E. (PTDP)Mechanical Engineering Examination

Course Code ME 21S/ME 611 Course Name: Hydraulic Machines

Time: 3 Hours] [Max. Marks : 60

Instructions to Candidates :-(1) All questions are compulsory.(2) All questions carry marks as indicated.(3) Due credit will be given to neatness and adequate dimensions.(4) Assume suitable data wherever necessary.(5) Illustrate your answers wherever necessary with the help of neat sketches.(6) Use of non programmable calculator is permitted.

1. (A) Prove that for a senes of radial curved vane the efficiency is given by

T\ =v2

15

OR

A jet of water having a velocity of 18 rnIs strikes a curved vane whichis moving with a velocity of 6rn1s. The vane is symmetrical and so shapedthat the jet is deflected through 120°.

Determine:

(i) The angle of the jet at inlet of the vane so that there isno shock.

(ii) The absolute velocity of the jet at outlet in magnitude and direction.

(iii) The work done per N of water. 5

BAR/2KTT /EER-626/820 Contd.

(B) A Pelton wheel is to be designed for the following specifications:

Shaft power

Speed

Head

Overall efficiency -

9560 KW

700rpm

300 m

85%

Jet diameter is not to exceed 1I16th of the wheel diameter. Determinethe following :

(i) The wheel diameter

(ii) Diameter of jet and

(iii) The number of jets required.

Take Cv = 0.985, speed ratio = 0.45OR

Design a pelton wheel for a head of 80 m and speed of 300 RPM.The pelton wheel develops 110 kW. Take co-efficient of velocity = 0.98,speed ratio = 0.48 and overall efficiency = 80%. 5

2. (A) In an inward flow hydraulic reaction turbine, the supply head is 12 mand the maximum discharge is 0.28m3/s. The external diameter is twicethe internal diameter and the velocity of flow is constant and equal to0.15 v' 2gH . The runner vanes are radial at inlet and the runner rotatesat 300 revolutions per minute Determine :

(i) The guide vane angles,

(ii) The vane angle at exit for radial discharge,

(iii) Widths of runner at inlet and exit

The vanes occupy 10 percent of the circumference and the hydraulic efficiencyis 80 percent. Draw the velocity triangles. 6

OR

BAR12KTT/EER-626/820 2 Contd.

An inward flow reaction turbine has external and internal diameters as1m and 0.6 m respectively. The hydraulic efficiency of the turbine is 90%When the head on the turbine is 36 m. The velocity of flow at outletis 2.5m/sec and discharge at outlet is radial. The vane angle at outletis 15° and width of wheel is 10 ern at inlet and outlet. Determine :

(i) The guide blade angle

(ii) Speed of the turbine

(iii) Vane angle of the runner at inlet

(iv) Volume flow rate of turbine

(v) Power developed. 6

2. (B) A conical draft tube having diameter at the top as 2 m and pressurehead as 7 m of water (vacuum), discharges water at the outlet with avelocity of 1.2 m/sec at the rate of 25 m3/sec. If atmospheric pressurehead is 10.3 m of water and losses between the inlet and outlet of thedraft tubes are negligible, find the length of draft tube immersed in water.Total length of tube is 5m.

OR

Kaplan turbine develops 24647.6 KW power at an avg. Head of 39 m.assuming a speed ratio of 2, Flow ratio of 0.6, Diameter of boss equalto 0.35 times the diameter of runner and an overall efficiency of 90%Calculate the diameter, Speed and Specific speed of turbine. 4

3. (A) A Centrifugal pump running at 800 rpm is working against a total headof 20.2 m The external diameter of the impeller is 480 rom and outletwidth 60 rom. If the vane angle at outlet is 40° and manometric efficiencyis 70% determine .....

(i) Flow velocity at outlet

(ii) Absolute velocity of water leaving the vane

(iii) Angle made by absolute velocity at outlet with the direction ofmotion at outlet

(iv) Rate of flow through the pipe

BAR12KTT/EER-626/820 3 Contd.

OR

A centrifugal pump impeller has outlet diameter of 360 mm and width is60 mm. The vanes are curved backwards at 35° to the tangent at outerperiphery and thickness of vanes occupy 20% of peripheral area and thevelocity of flow is constant from inlet to outlet. The impeller rotates at800 rpm. If the rate of flow of the pump is 0.13 m3/s

Determine:

(i) The pressure nse In the impeller.

(ii) The % of total work con verted to K. E. 7

OR

(B) Derive the expression for the minimum speed for starting a centrifugal pump.

What is pnrrung of a centrifugal pump ? Explain clearly why pnrrung ISessential before starting a centrifugal pump. 3

(1) Piston Diameter = 150mm.

(2) Stroke = 350mm.

(3) Suction head = 3 m.

(4) Delivery Head = 20 m

(5) RPM = 35

(6) Dia. Of suction and delivery pipe = 100mm.

(7) Length of suction pipe = 5 m.

(8) Length of delivery pIpe = 30 m

(9) Friction factor = 0.0l.

(10) Atm.pressure Head = 10.3 m.

4. (A) Following data is referred to a single acting-reciprocating pump.

Find the pressure head at the start, middle and end of suction and deliverystrokes. 7

BARl2KTT/EER-626/820 4 Contd.

OR

The diameter and stroke of a single acting reciprocating pump are 300mm and SOOmm respectively. The pump takes water from 3.2 m belowthe pump axis through a pipe 9 m long and 200 mm diameter. If theseparation occurs at 2.4 m of the water absolute, determine

(i) The speed at which the separation may take place at the beginningof the suction stroke.

(ii) The speed of the pump if an air vessel is fitted on the suctionside 2.4m above the sump water level. Take Patm = 10.3 mand Coeff.of friction = 0.01 7

(B) Explain the working of a reciprocating pump with help of neat sketch3

OR

Define slip, percentage slip and negative slip and separation with referenceto reciprocating pumps. 3

S. (A) In order to predict the performance of a large centrifugal pump, a scalemodel of 1/6th size was made with the following speciation: powerP = 2SKW, Head Hmano = 7 m, Speed = 1000 rpm. If the prototypepump has to work against a head of 22m, calculate its working speed,the power required to drive it and the ratio of flow rates handle bythe two pumps. S

OR

Find an expression for drag force R on a smooth sphere of diameterD moving with uniform velocity V In a fluid of density p and dynamicviscosity /-to S

(B) Define unit quantities. Derive the expression for specific speed of a turbine.S

OR

Explain the method of dimensional analysis using Buckingham's 7t Theorem.S

BAR12KTT IEER-626/820 5 Contd,

6. (A) Discuss the types, construction, working and application of the Gear pumpwith neat sketch.

OR

What are different types of Accumulators used In hydraulic circuits ?5

(B) What do you mean by hydraulic actuator ? Explain anyone with neatsketch.

OR

What are different types of control valves used in hydraulic circuits? Discussanyone specific valve with a neat sketch. 5

BAR12KTT/EER-626/820 6 55

EAG/2KETIES - 293/388

Fourth Semester B. E. (R)1Fourth Semester B. E. (PTDP) MechanicalEngineering Examination

Course Code ME 215/ME 611 Course Name Hydraulic Machines

Time : 3 Hours ] [ Max. Marks : 60

Instructions to Candidates :-(l) All questions are Compulsory.(2) All questions carry marks as indicated.(3) Assume suitable data wherever necessary ..(4) Diagrams and chemical equations should be given wherever necessary.(5) Illustrate your answers wherever necessary with the help of neat sketches.(6) Use of non programmable calculator is permitted.

1. (a) A jet of water having velocity' of 35 mls impinges on the vane movingwith a velocity of 20 mls. The angle made by absolute velocity is 30°at inlet and 60° at outlet. Draw velocity triangles and find' (i) vane angleat inlet and outlet. (ii) Work done per N of water. (iii)The efficiency.

5

OR

A jet of water 60 mm diameter strikes a curved plate at center with avelocity of 24 mls. The curved plate is moving with a velocity of 10 ms/s.Find the force exerted on the plate in the direction of jet, power andefficiency of the jet if the jet is deflected through an angle 160°.

5

(b) A Pelton wheel required to develop 9 MW running at 500 rpm and operatingunder a head of 300 m. Take jet ratio= IO and overall efficiency 85%.Calculate following (1) Quantity of water required (2) Diameter of wheel(3) Number of jets (4) Number and major dimensions of bucket. Assumespeed ratio=0.45. 5

OR

(b) A single jet pelton wheel. is required to develop 10000 kW under a headof 760 m. If ngcn= 95%, nh = 87%, Kv = 0.97, Ku = 046, outlet angle

EA G/2KET /ES-293/388 Contd.

of bucketse l S" Vr2Nrl = 0.85 Find :

(i) Flow (ii) Jet diameter (iii) The best synchronous speed at 50 Hz if(Did) ratio is not to be less than 10. 5

2. (a) The following data IS given for Francis turbine

Net head = 60 m; speed N = 700 rpm; S.P. = 295 kW;Overall efficiency = 84%;

Hydraulic efficiency = 93% ; Flow ratio = 0.20; BID ratio at inlet = 0.1;

Outer diameter of runner = 2* inner diameter of runner.

Velocity of flow m constant at inlet and outlet and discharge is radialat outlet.

Detemine

(i)

(ii)

(iii)

Guide blade angle.*Runner vane angle at inlet and outlet.

,Diameter of runner inlet and outlet.

(iv) Width of wheel at inlet. 7

OR

2. (a) The following data refers to a Kaplan turbine

Power available at the shaft 11772 kW, Head 20 m,

11h =' 0.88, :·110 = 0.84, Outer diameter of the runner = 3.5 m. Diameterof the hub = 1.75 m. The guide blade angle at the extreme edge of therunner is 35°. Assuming that the turbine discharges without the whirl atthe exit detemine

(i) runner vane angles (inlet and outlet) at the hub and the outerperiphery.

(ii) Speed of the runner. 7

(b) . A conical draft tube is discharging water at the outlet with a velocity of2.5 mls Its inlet and the outlet diameters are 1 m and 1.5 m respectively.The total length of the draft tube is 6 m and 1.2 m of the length ofthe draft tube is immersed in water. If the atmospheric head is 10.3 m

EA G/2KET /ES-293/388 2 Contd.

of the water and the loss of head due to the friction in the draft tubeIS 0.2 times velocity head at the outlet of the draft tube find

(i) Pressure head at the inletEfficiency of the draft tube. 3

OR

(b) A Kaplan Turbine, operating under a net head of 20 m, develops 36787.5KW with an overall efficiency of 86%. The speed ratio is 2.0 and flowratio is 0.60. The hub diameter of the wheel is 0.35 times the outsidediameter of the wheel. Find the diameter and speed of the turbine. 3

3. (a)

(b)

4. (a)

A three stage centrifugal pump has impellers 40 cm in diameters and 2em wide at out let. The vanes are curved back at 45° and they reducethe circumferential area by 10% at the outlet. The manometric efficiencyis 90% and the overall efficiency is 80%. Determine the head generatedby the pump when running at 1000 RPM, delivering 50 liters per second.What should be the shaft power ? 7

OR

A centrifugal pump impeller has outlet diameter of 360 mrn and width is60 mrn. The vanes are curved backwards at 35° to. the tangent at outerperiphery and thickness of vanes occupy 20% of peripheral area andthe velocity of flow is constant from inlet to inlet to outlet. The impellerrotates at 800 rpm. If the rate of flow of the pump is 0.13 m3js determine:(i) The pressure rise in the impeller.(ii) The % of total work converted to K.E. 7

What is NPSH ? State it's significance. 3

OR

Derive the expression for muumum starting speed of a centrifugal pump.3

Following data is referred to a single acting-reciprocating pump.Piston Diameter = 150 mrn (2) Stroke=350 mrn.(3) Suction .head = 3 m (4) Delivery Head = 20 m.(5) RPM = 35 (6) Dia. of suction and delivery - pipe =100 mm.

EAG/2KET /ES-293/388 3 Contd.

4. (a)

(b)

\5. (a)

(7) Length of suction(9) Friction factor =Find the pressure headstrokes.

pipe = 5 m (8) Length of delivery pipe =30 m0.01 (10) Atm. pressure Head = 10.3 mat the start, middle and end of suction and delivery

7OR

The diameter and stroke of single acting reciprocating pump are 75 mmand 150 mm respectively. It takes the supply of water 3 m below thepump through a pipe of 5 m long and 40 mm. diameter. If the separationoccurs at 75 kN/m2 below the Atmospheric pressure. Find the speed atwhich pump should operate without. separation. 7

Explain the function of Air vessel in a reciprocating pump. 3

OR

Find an expression for the work done per second In case of a singleacting reciprocating pump. 3

Derive the expression for specific speed of a turbine and find out theexpression for specific speed of a Pelton wheel in terms of a constantand jet ratio. 5

OR

The diameter of a centrifugal pump which is discharging 0.03 m3/s of wateragainst a total head of 20 m is 0.40 m. The pump is running at 1500RPM. Find the head, discharge and rauo of powers of a geometrically similarpump of diameter 0.25 m when it is running at 3000 RPM. 5

(b) Explain the method of dimensional analysis using Buckingham's 1t Theorem.5

6.

OR

Derive on the basis of dimensional analysis suitable parameters to presentthe power developed by a turbine. Assume power developed by the turbineis a function of density p ., Acceleration due to gravity g, Head H. diameter D,RPM N. 5

(a) What are the essential Elements of a hydraulic system.sketch.

Explain with neat5

EA G/2KET /ES-293/388 4 Contd.

OR

Discuss the con-truction and working of the following with neat sketch(anyone)

(i) Gear pump (ii) Vane Pump (iii) Screw Pump. 5

(b) Distinguish between Linear and rotary actuators and discuss anyone ofthem with· the help of neat sketch. 5

OR

What are different types of Accumulators used in hydraulic circuits? Discussanyone specific valve with a neat sketch. 5

EAG/2KET/ES-293/388 5 255