CH 6.docx

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CH 2.docx

CH 3.docx

CH 4.docx

CH 5.docx

CH – 6 MISCELLANEOUS MACHINES

THEORY

(1) With neat sketch explain construction and working of hydraulic torque Convertor [643]

(2) Write short notes on: Hydraulic intensifier and Air lift pump [628,645]

(3) Write a short note on fluid coupling.[640]

(4) Explain working of Differential hydraulic accumulator with neat sketch.(2) [623]

(5) Write a short note on hydraulic ram.(3) [638]

(6) With neat sketch explain construction and working of hydraulic crane. [630]

(7) Write a short note on hydraulic press. [619]

CH – 1 FLOW THROUGH PIPES

THEORY

(1) With usual notations derive an expression for head loss due to sudden

enlargement in pipe. [11]

(2) Explain the term ‘Minor losses’. Obtain an equation to calculate head loss due to

sudden expansion and from that equation derive equation of exit loss.[11 , 23]

(3) Prove that head loss due to friction is equal to one third of total head inlet for

maximum power transmission through nozzle. [83 , 84]

(4) Explain the following terms : (1) Major losses (2) Minor losses and (3) Equivalent

pipe. [2 , 11 , 62]

(5) Derive Darcy-Weisbach formula for calculating loss of head due to friction in a

pipe. (2) [2]

(6) Explain the phenomenon of water hammer. Obtain an expression for the rise of

pressure when the flowing water in a pipe is brought to rest by closing the valve

gradually.[91]

EXAMPLE

(1) A 2500 m long pipeline is used for transmission of power 120 KW. The power is to

be transmitted through the pipe in which water having pressure of 4000 K N/ m2

at inlet is flowing. If the pressure drop over the length of pipe is 800 K N/m2 and

f=0.006 calculate

(I)Diameter of pipe and

(II)Efficiency of transmission [86]

(2) Water is flowing through a horizontal pipe of 30 cm diameter and 50 m length.

One end of pipe is connected to a tank and the other end is open to atmosphere.

If the height of water in the tank is 6 m above the centre of pipe, determine

flowrate through the pipe. Take 4f = 0.02 in equation hf = (4flV2)/ (2gD).

(3) The diameter of a horizontal pipe which is 300mm is suddenly enlarged to

600mm. The rate of flow of water through this pipe is 0.4 m3/sec. If the intensity

of pressure in smaller pipe is 125 KN/m2,

Determine :

(I)loss of head due to sudden enlargement,

(II)intensity of pressure in large pipe,

(III)power loss due to enlargement. [15]

(4) A pipe line 300 mm dia. and 3200 m long is used to pump up 50 kg/s of an oil

whose density is 950 kg/m3 and whose kinematic viscosity is 2.1 stokes. The

centre of the pipe line at the upper end is 40 m above than that at the lower end.

The discharge at the upper and is atmospheric. Find the pressure at the lower

end and draw the hydraulic gradient and total energy line. [38]

CH – 2 IMPACT OF JET

THEORY

(1) Show that the efficiency of propulsion when the inlet orifice face the direction of

motion of ship is given by= η=2u/V+2u, where V is the absolute velocity of issuing

jet and u is velocity of ship. [152]

(2) A tank, which is free to move, is provided with an orifice on side, through which

jet of water is coming out. Obtain an equation for work done per sec on tank and

efficiency of propulsion. [147]

(OR)

Find an expression for the propelling force and the work done per sec. on a tank

which is provided with an orifice through which jet of water is coming out and

the tank is free to move. [147]

(3) Show that in case of jet striking the flat plates mounted on wheel, the efficiency

will be maximum when the tangential velocity of wheel is half of the jet. [141]

(OR)

Show that the efficiency of a free jet striking normally on a series of flat plates

mounted on the periphery of a wheel can never exceed 50 %. [141]

(4) Show that when a jet of water impinges on a series of curved vanes, maximum

efficiency is obtained when the vane is semi-circular and the velocity of jet is

double the velocity of vane.

(5) Prove that for a curved radial vane the efficiency is given by

η= �(�����±�����)

�� [144]

EXAMPLE:

(1) A jet of water moving with velocity 22m/s impinges on a curved vane at the one

end tangentially. The jet leaves the vane at an angle of 120° to the direction of

motion of the vane. The velocity of vane is 10m/s and angle of nozzle is

20°.Determine

i. Vane angle at inlet and outlet,

ii. Work done per second per init mass of water.

(2) A water jet of 80 mm diameter impinges on a curved vane at its centre and is

deflected through an angle of 1400. The water flowrate is 80 lit/s and vane moves

with velocity of 5 m/s in direction of jet. Neglecting friction,

find (i) component of force in direction of motion and

(ii) the power developed by vane and its efficiency.

(3) A jet delivers water at the rate of 60 liters per second with velocity 30 m/s. The

jet strikes tangentially on the vane moving in the direction of the jet with the

velocity of 15 m/s. The vane is so shaped that if stationary it would deflect the jet

through an angle 50°.

Calculate: (1) angle made by absolute velocity at outlet and

(2) work done per sec.

(4) A jet of water of 30 mm diameter, strikes on the hinged rectangular plate weight

100 N at the center of the plate. The velocity of the jet is 8 m/s.

Calculate: (1) angle through which the plate will swing, and

(2) force must be applied at the lower edge of the plate in order to

Keep the plate vertical. [111]

(5) A jet of water having a velocity 25 m/s strikes on a series of vanes moving with a

velocity 10 m/s.The jet makes an angle of 300 with the direction of motion of

vanes when entering and leaves at an angle of 1500 with the direction of

motion.Sketch the velocity triangles and calculate,

(i)Vane angles at inlet and outlet

(ii) Work done when the vane discharging 325 litres/s

Take loss due to friction over the vane as 10 % of relative velocity.

(6) A jet of water moving with a velocity of 27m/s impinges tangentially to a single

curved blade which is moving in the direction of jet with a speed of 12m/s. Jet is

deflected through 45°. If the friction reduces the relative velocity by 20%

calculate the angle through which the jet will leave the blade, work done /kg of

water and efficiency.

(7) A jet of water impinges on a symmetrically curved vane at its center. The velocity

of the jet is 60 m/s and the diameter 120 mm. the jet is deflected through an

angle of 120° Calculate the force on the vane if the vane is fixed. Also determine

the force if the vane moves with a velocity of 25 m/s in the direction of the jet.

What will be the power and efficiency? [131]

CH – 3 HYDAULIC TURBINES

THEORY

(1) Sketch and describe a modern method of regulation to maintain constant speed

for Pelton turbine. Explain performance characteristic curves of pelton turbine.

[267 , 257 ]

(2) Explain function of draft tube. State types of draft tube and explain importance of

cone angle (θ) in draft tube.(3) [236]

(3) (i) Differentiate clearly between Impulse turbine and Reaction turbine. [171]

(ii) Explain function of components of Pelton turbine.[174]

(4) Give detailed classification of Francis turbine and explain function of wicket gate.

Compare Francis turbine with Kaplan turbine also.[217 , 218 , 231]

(5) Explain the following terms with reference to water turbines. Give expression of

each efficiencies. (1) Hydraulic efficiency (2) Mechanical efficiency and (3) Overall

efficiency [172]

(6) Why governing of water turbine is required? Explain governing of any one

hydraulic turbine with neat sketch. [266]

(7) Sketch a hydro-power plant and explain its different elements.(2) [163]

(8) Explain the governing of francis turbine with neat sketch.(2) [269]

(9) What are the ill effects of cavitation in turbine ? Give causes and remedies to

avoid cavitation in a hydraulic turbine.[262]

(10) Explain how hydraulic turbines are classified. [168]

(11) Define specific speed of a turbine and derive an expression for the same. [244]

EXAMPLE

(1) A conical draft turbine tube having inlet and outlet diameter 1.2m and 1.8m

discharges water at outlet with a velocity of 3m/s. The total length of draft tube

is 7.2 m and 1.44 m of the length of draft tube immersed in water. If the

atmospheric pressure head is 10.3 m of water and loss of head due to friction in

draft tube is equal to 0.2 x velocity head at outlet of tube determine

i. Pressure head at inlet and

ii. Efficiency of draft tube.

(2) A Kaplan Turbine produces 25MW operating under a head of 40 m. The blade tip

diameter is 2.5 times the hub diameter and the overall efficiency is 0.9. If the

speed and flow ratio are 2.0 and 0.6 resply, calculate the diameter and speed of

the turbine. [SAME AS 241]

(3) A Pelton wheel is required to develop 8000 kW while working under head of 380

m at a speed of 500 rpm. If overall efficiency is 88%, find (i) flowrate through the

turbine, (ii) runner diameter, (iii) no. of nozzles and (iv) no. of buckets in runner.

Assume jet ratio of 10, coefficient of velocity as 0.97 and speed ratio of 0.46.

(4) A Francis turbine develops 160 kW at 150 rpm under head of 10 m. The

peripheral velocity at inlet and flow velocity at inlet of runner are 0.3(2gH) 0.5

and 0.9(2gH) 0.5 respectively. The overall efficiency of turbine is 78% and

hydraulic efficiency is 82%. Assuming radial discharge at outlet, find (i) guide

blade angle and runner vane angle at inlet and (ii) diameter and width of runner

Sat inlet.

(5) The following data is related to Pelton wheel turbine

Heat at the base of the nozzle=80 m

Diameter of the jet = 100 mm

Discharge of the nozzle=0.30m3/s

Power at the shaft=206 kw and

Power absorbed in mechanical resistance= 4.5 kw

Determine: (1) power lost in nozzle and (2) power lost due to hydraulic resistance

in the runner. (2) [272]

(6) Francis turbine designed to develop 160 kw working under a head 10 m and

running at 200 rpm. The hydraulic losses in turbine are 15% of available energy.

The overall efficiency of turbine is 80%. Assume flow ratio=0.94 and speed

ratio=0.25. Calculate: (1) guide blade angle and runner vane angle at inlet and (2)

diameter and width at inlet. [221]

(7) The following data relate to a pelton wheel.

Tangential velocity of bucket=25 m/s

Head of water=65 m

Deflection of jet on bucket=1650

Discharge through the nozzle=110 litres/s

Co-efficient of nozzle=0.95

Determine the power developed by the runner and the efficiency.[SAME AS 180]

(8) A Pelton turbine is to be designed for following specifications: shaft

power=11770KW, Head=380m, speed=750rpm, overall efficiency=86%, jet

diameter not to exceed one sixth of wheel diameter, Determine the wheel

diameter, number of jets required, diameter of jet. assume Cv=0.985,

v=0.45(2gH)0.5

(9) A turbine is to operate under a head of 25 m at 200rpm. The discharge is

9m3/sec. If the efficiency is 90% determine, specific speed of machine, power

generated, type of turbine and performance under head of 20 m. [SAME AS 253]

CH – 4 PUMPS

THEORY

(1) Compare Reciprocating pump with Centrifugal pump.[380]

(2) Draw theoretical indicator diagram of reciprocating pump and explain function of

air vessel. [355 , 369]

(3) Enlist the various types of impeller used in centrifugal pump and explain any one from it with a neat sketch [286].

(4) Give classification of Reciprocating pump. Draw neat sketch of single acting reciprocating pump [348]

(5) Write a short note on Submersible pump.(2) [377]

(6) Discuss the various characteristic curves of a centrifugal pump.[342]

(7) Explain following terms: Net positive suction head, Priming, Cavitation in pump(2)

[339 , 340 ,344]

(8) How will you obtain an expression for the minimum speed for starting of a centrifugal pump? [328]

(9) With neat sketch explain construction and working of Mud pump and deep well pump [376 , 379]

EXAMPLE

(1) A double acting reciprocating pump is fitted with an air vessel on suction side close to pump. The suction lift of pump is 4.5m. The length and diameter of suction pipe are 7.5m and 80mm resply. The stroke of piston and its diameter both are 200 mm each. Coefficient of friction is 0.01. The atmospheric pressure head is 10.3m and separation pressure head 2.5m of water absolute. Determine i. The speed at which separation commences

ii. Maximum permissible speed without air vessel.

(2) The impeller of centrifugal pump is 1m in diameter and rotates at 1500 rpm. The blades are curved backward and make an angle of 30° to the tangent at the periphery. Calculate the power required if the velocity of flow at outlet is 20m/s. Determine the head to which water can be lifted when a diffuser casing reduces the outlet velocity to 60%.

(3) A centrifugal pump running at 900 rpm is working against head of 18 m. The outlet diameter of impeller is 380 mm and outlet width is 40 mm. If outlet blade angle is 280 and manometric efficiency is 78 %, find discharge of the pump.

(4) Find the power required to drive a centrifugal pump which delivers 0.04 m3/sec

of water to a height of 20m through a 15 cm diameter pipe and 100 m long. The overall efficiency of the pump is 70% and co efficient of friction f=0.015 used in Darcy’s equation. [311]

(5) A centrifugal pump has impeller of 25 cm diameter at inlet and 50 cm diameter at outlet and runs at 1600 rpm.The vanes are set back at an angle of 300 to the outer rim if velocity of flow through impeller is constant at 3 m/s and entry to the impeller is radial.Calculate the vane angle at inlet and workdone on the wheel per kg of water.

(6) A centrifugal pump raises the head of water through 4m and delivers 1.5m3/sec.

The speed of the impeller is 180rpm. The impeller diameter at the outlet is 1.3m and area at the periphery is 0.3m2. The ratio of the outlet at the inlet diameter is 2m and vane angle at the outlet is 30° .Determine the hydraulic efficiency, power required and minimum starting speed.

(7) A triple cylinder reciprocating pump raises the water level by 100m and discharge is 100l/s. The diameter of piston is 250mm and stroke is 600mm.The velocity of water in the delivery pipe is 1.4m/s. The friction losses amount to 2m in the suction pipe and 18m in delivery pipe. Taking efficiency of pump as 90% and slip 2%, calculate speed and power input of the pump.

(8) Find the power required to drive a centrifugal pump which delivers 0.04m3/s of water to a height of 20 m through a 15 cm diameter pipe and 100 m long. The overall efficiency of the pump is 70 % and co-efficient of friction f = 0.015 in the formulae hf = 4flv2 / 2gd

CH – 5 COMPRESSORS

THEORY

(1) Define the lift and drag co-efficient and derive their expressions. [570]

(2) With neat sketch explain construction and working of Scroll compressor. [485]

(3) A two stage air compressor has perfect intercooling in intercooler. Show this process on P – V diagram.[435]

(4) Explain effect of pre- whirl in centrifugal compressor. [517]

(5) State types of impeller used in centrifugal compressor and show their

characteristics curves. [501 ,

(6) For a centrifugal compressor, draw impeller having radial blades with its outlet velocity triangle and state function of volute casing.

(7) Draw stage velocity diagram of an axial flow compressor.

(8) Derive an expression for the optimum value of the intercooler pressure in a

two stage reciprocating air compressor for perfect inter cooling condition.

(9) With a suitable sketch explain the working principle of an axial flow compressor. Draw the stage velocity triangles.

(10) Show that for a two stage reciprocating air compressor with complete intercooling the total work of compression becomes minimum when the pressure ratio in each stage is equal.

(11) Describe principle construction and working of centrifugal compressor.

(12) Explain with neat sketch Root blower.

(13) Describe the working of a screw compressor and list its applications.

(14) With the help of velocity triangles and head-capacity curves,discuss salient features of radial, backward and forward curved vanes in a centrifugal compressor.

(15) Justify the need for multistaging in a reciprocating air compressor. List any two advantages of multistage compression.

(16) Explain the phenomenon of surging and stalling in an axial flow compressor.

(17) What is pre-whirl? Sketch the velocity diagrams with and without pre whirl for a centrifugal compressor.

(18) Explain the phenomenon of surging and stalling in an axial flow air compressor.

(19) Derive an expression for indicated work of reciprocating air compressor considering its clearance.

(20) Explain the following i. Influence of inlet and outlet blade angles on performance of centrifugal compressor

ii. Testing of pump as per B.I.S

(21) With usual notations derive an expression for indicated work of

reciprocating air compressor by considering clearance.

EXAMPLE

(1) In an axial flow compressor, overall stagnation pressure achieved is 4 and overall stagnation isentropic efficiency 85%. The inlet stagnation pressure and temperature are 1 bar and 300 K resply. The mean blade velocity is 180m/s. degree of reaction 50% at mean radius with relative air angles of 12° and 32° at rotor inlet and outlet resply. The work done factor is 0.9 calculate

i. Stagnation polytropic efficiency ii. Inlet temperature and pressure

iii. Number of stages iv. Blade height in first stage , if ratio of hub to tip diameter is 0.42 , mass flow rate is 19.5 Kg/s.

(2) Calculate the power required to run the vane compressor and its efficiency, when it handles 6m3 of air per minute from 1 bar to 2.2 bar. The pressure rise due to compression in compressor is limited to 1.6 bar. Assume mechanical efficiency of compressor 80%.

(3) A single stage, single acting reciprocating air compressor compresses 7x 10-3 m3 of air /s from pressure of 1.013 bar to 14 bar. The index of polytropic compression process is 1.3 and mechanical efficiency is 82%. Neglecting effect of clearance, determine power required to drive the compressor and show the process on P-V diagram.

(4) A centrifugal air compressor has a pressure ratio of 4:1 with an isentropic

efficiency 88% when running at 14000 rpm and including air at 25° C. Curved vanes at inlet give the air a pre-whirl of 18° to axial direction at all radii and the mean diameter of eye is 245 mm. The absolute air velocity at inlet is 120 m/s. Impeller tip diameter is 580 mm. Calculate slip factor.

(5) Air at 1 bar and 200 C is compressed to a pressure of 55 bar in a two stage reciprocating air compressor.Intercooler cools the air to a temperature of 400C at 10 bar.The diameter of low pressure cylinder is 175 mm and both the cylinders have 225 mm stroke.If the compression follows the law pV1.2=C,find the indicated power of compressor if it runs at 150 rpm.

(6) A centrifugal compressor (ηc=0.85) runs at 14000 rpm inducting air at 200 C ,the work done by the impeller is 160 kJ/kgK.Guide vanes at inlet gives the air a prewhirl at 250 .Mean eye diameter is 225 mm,the absolute air velocity at inlet is 130 m/s.At the exit ,the blades are radial and the slip factor is 0.75. Calculate (i) the pressure ratio and (ii) impeller tip diameter

(7) In a three stage compressor, air is compressed from 98KPa to 20 KPa

.Calculate for 1m3 of air per second, (1) Work under ideal condition for n=1.3

(2) Isothermal work. (3) Saving in work due to multi-staging. (4) Isothermal efficiency.

(8) Prove that the work done / kg of air in single stage reciprocating air compressor without clearance is given by n R T1 W = ---------- { ( P2 / P1) (n-1)/n - 1 } (n – 1) Where notations have their usual meaning.

(9) An axial flow air compressor stage has a mean diameter of 60 cm. and runs at 15000 rpm if the actual temp. rise and pressure ratio developed are 30 °C and 1.35 respectively. Determine : (I) Power required to drive the compressor while delivering 57 kg/s of air, if the mechanical efficiency is 86 percent and inlet temp. rise is 35 °C.

(II) The stage loading coefficient. (III) The degree of reaction if the temp. at the rotor exit is 55 °C

(10) A centrifugal compressor running at 1440rpm, handles air at 101KPa and 20 °C and compress it to a pressure of 6 bar isentropically. The inner and outer diameters of the impeller are 14cm and 25cm, resply, The width of the blade at the inlet is 2.5cm. The blade angles are 16° and 40° at entry and exit. Calculate massflow rate of the air degree of reaction , power input and width of the blades at outlet