# Rajasthan Technical University 2009-1st Sem B.E B.Techester (back) Mechanical Engineering - Question Paper

Rajasthan tech. Univercity

B.

**E.**1st Year Back

July 2009

Mechanical Engineering

(Common for all branches)

Roll No. :_<C- 6 1_ Total Printed Pages : {~4 |

|1:B706 }

jJQ B. E. I >Year Back Examination, July 2009

W Mechanical Engineering (Common to all branches of Engg.)

Time : 3 Hours] [Total Marks : 80

(Min. Passing Marks : 24

Attempt live Questions in all. Schematic diagrams must be shown wherever necessary. Any data you feel missing may suitably be assumed and stated clearly.

Use of following supporting material is permitted during examination.

(Mentioned in lorm No. 205)

______m_ 2._till______

1 (a) State thermodynamic definition of work. Also differentiate between heat, and work.

1

(Ij) Differentiate between Characteristic gas constant and Universal gas constant.

4

(c.) A gas contained in a cylinder is compressed from 1 MPa and 0.05 m^{s} to 2 MPa. Compression is governed by PV^{1}-^{4} constant and internal energy of gas is given by; u = 7.5 pv - 425, kJ

where p is pressure in kPa and v is volume in

Determine heat, work and change in internal energy assuming compression process to be quasi s'-nlic.

Also find out work interaction, if the 180 kJ of heat is transferred to system between same states. Also explain, why is it different from above.

' 8

OR

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[Contd...

1 (a) Derive the steady flow energy equation.

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(li) An air compressor requires shaft work of 200 k.I/kg of air and the compression of air causes increase in enthalpy of air by 1OTJ W/kg of air. Cooling water required for cooling the compressor picks up heat of 90 kJ/kg of air. Determine the heat transferred from compressor to atmosphere.

(c) (i) State the Kelvin-Planck and Clausius statements of second law of thermodynamics show how they are equivalent.

(i) / Show that no heat engine operating in cycles between two reservoir at constant temperature can have greater efficiency than a revessible engine operating between same two temperatures.

6

2/Aa) Explain the following terms : (In context to l.C. engine)

(i) Indicated thermal efficiency

(ii) Brake thermal efficiency

(iii) Mechanical efficiency.

6

(b) An engine working on the otto cycle has a clearance of 17% of stroke volume and initial pressure of 0.95 bar and temperature 30C. If !ne pressure at the end of constant volume heating is 28 bar. Find :

(i) An air standard efficiency

(ii) The maximum temperature in the cycle

(iii) Ideal mean effective pressure.

(3+3+4)

OR

2 (a) Compare rotary and reciprocating compressor.

4

(b) A gas turbine unit has a pressure ratio of 6:1 and maximum cycle temperature is 627C. The isentropic efficiency of compressor and turbine are 0.8 and 0.82 respectively. Calculate the power output in kW of turbine when the air enters the compressor at . 7C at the rate of 16 kg/sec.

Take Cp = 1.005 and y=1.4.

Also find thermal efficiency and work ratio. Assuming that Cp for the combustion process is 1.11 .

12

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[Contd...

3 (a) Describe Rankine cycle and compare the Rankine cycle with Carnot cycle.

6

(b) Describe the function of any two of the boiler accessories

(i) Super heater

(ii) Economizer

(iii) Air heater.

4

(c) Explain construction and working of any high pressure boiler.

6

OR

3 (a) Explain the unit of refrigeration.

4

(b) Draw a schematic diagram of vapour compression refrigeration system. Explain the working of various components.

6

(c) What is Bypass factor of a coil ? How it effects the performance of airconditioning system.

4 (a) Draw the line diagram of radial drilling machine and label its dUtereut parts.

6

(b) Explain important operations which can be performed on lathe machine.

(c) Give two methods to specify the lathe machine.

4 (a) What is hot working process ? Explain its disadvantages over cold working process.

(b) Explain the following : (Use neat sketches)

(i) Forging

(ii) Bending

(iii) Drawing.

What ate the various constituents of moulding sand and explain the properties it imparts to the moulding sand.

7

What is the principle of arc welding explain with the help of neat sketch. Also explain what is difference between welding and brazing or soldering.

(a) Explain advantages or disadvantages of v-belt drive on flat belt drive.

4

(b) Derive the expression for the length of cross belt drive.

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(c) Two pulleys, one 450 mm dia. and other 200 mm dia. are / on parallel shaft 2 m apart and are connected by cross

belt. Find the length of belt required. What power can be trasmitted by the belt when larger pulley rotates at 200 rpm and maximum permissible tension in the belt is 1000 N ? Given the coefficient of friction between the belt and pulley is 0.25.

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Attachment: |

Earning: Approval pending. |