Question: Elements of Mechanical Engg. : Jun 2013 - First Year Engineering (Semester 1) | Gujarat Technological University (GTU)
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## Elements of Mechanical Engg. - Jun 2013

### First Year Engineering (Semester 1)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS
(1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks.
1 (a) Explain working of four stroke Diesel Engine with P-V diagram.(5 marks) 1 (b) A four cylinder four stroke petrol engine has 100mm bore and stroke is 1.3 times bore. It consumes 4 kg of fuel per hour having calorific value of 40500 kJ/kg. If engine speed is 850 rpm. Find its Indicated thermal efficiency. The mean effective pressure is 0.75 N/mm2 (5 marks) 1 (c) Define Pressure and explain Absolute Pressure, Guage Pressure and Atmospheric pressure(4 marks) 2 (a) Explain construction and working of Locomotive boiler with neat sketch.(7 marks) 2 (b) State the function of the following (1) Fusible plug. (2) Economiser (3) Safety valve (3 marks) 2 (c) Define : (i) Sensible heat (ii) Latent heat (iii)Dryness fraction (iv)Enthalpy of evaporation. (4 marks) 3 (a) Derive Expression PV/T=constant with the help of Boyle?s law and Charle?s law(5 marks) 3 (b) A steel cylinder contains O2 at pressure of 25 bar and temperature of 27°C, After using some quantity of the gas 0the pressure was found to be 5 bar and temperature of 20°C. 700 liters of O2 was originally put in the cylinder at NTP Density of O2 at NTP is 1.43 gm/liter. Find the mass of O2 used. (6 marks) 3 (c) Define Calorific value and explain Higher and Lower Calorific values. (3 marks) 4 (a) Explain Separating Calorimeter with neat sketch.(5 marks) 4 (b) Find internal energy of 1 kg of steam at a pressure of 15 bar when
(i) The steam is superheated with temperature of 400°C.
(ii) The steam is wet with dryness fraction =0.9Take Cps=2.1 kJ/kg K
(5 marks)
4 (c) What are different methods of IC engine governing? Explain governing method used in the Petrol engine. (4 marks) 5 (a) Derive expression for the efficiency of the Carnot cycle(5 marks) 5 (b) In an ideal Diesel cycle the temperature at the beginning and at the end of compression are 57°C and 603°C. The temperature at the beginning and at the end of expansion are 1950°C and 870°C.Find the ideal efficiency of the cycle. If the pressure is 1 bar find the maximum pressure in the cycle. (5 marks) 5 (c) Explain Oldham?s coupling with neat sketch. (4 marks) 6 (a) Explain working of main parts of centrifugal pump with neat sketc(5 marks) 6 (b) Explain difference between Recipr ocating and Rotodynamic compressor.(5 marks) 6 (c) Draw and explain Internal expanding brake.(4 marks) 7 (a) Explain Vapour absorption Refrigeration system with the neat sketch. (6 marks) 7 (b) Define (i) Hardness (ii) Creep (iii) Resilience (iv) Toughness(4 marks) 7 (c) What are Bearings and how they are classified?(4 marks)