GTU exams question papers -BE- Sem-Vth -Fluid Power Engineering -Nov/Dec-2011

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GUJARAT TECHNOLOGICAL UNIVERSITY

BE SEM-V Examination-Nov/Dec.-2011

Subject code: 151903 

Subject Name: Fluid Power Engineering 

Instructions:

1. Attempt all questions.

2. Make suitable assumptions wherever necessary.

3. Figures to the right indicate full marks.

Q.1 (a) 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.                       

(b) 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.                       

Q.2 (a) Sketch a hydro-power plant and explain its different elements.                         

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

OR

(b) Explain the governing of francis turbine with neat sketch.                         

Q.3 (a) What are the ill effects of cavitation in turbine ? Give causes and remedies

to avoid cavitation in a hydraulic turbine.                       

(b) 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                       

OR

Q.3 (a) Discuss the various characteristic curves of a centrifugal pump.                         

(b) 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.                        

Q.4 (a) 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.                      

(b) 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.                       

OR

Q.4 (a) With the help of velocity triangles and head-capacity curves,discuss

salient features of radial, backward and forward curved vanes in a

centrifugal compressor.                       

(b) 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                       

Q.5 (a) Justify the need for multistaging in a reciprocating air compressor. List

any two advantages of multistage compression.                       

(b) Explain the phenomenon of surging and stalling in an axial flow

compressor.                       

OR

Q.5 (a) Describe the working of a screw compressor and list its applications.                         

(b) Write a short note on hydraulic ram.                         

 

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