Sardar Vallabhbhai National Institute of Technology 2012 B.Tech Basic of Mechanical Systems - Question Paper
This paper is common to all discipline at SVNIT 1st year students
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(iii)Stroke of an I.C. engine equals:
(a) half the crank radius. (b) the crank radius.
(c) twice the crank radius. (d) four times the crank radius.
(iv)The compression ratio of an I.C. Engine is the ratio of:
(a) swept volume to clearance volume.
(b) total cylinder volume to clearance volume.
(c) total cylinder volume to swept volume.
(d) pressure after compression to that before compression
(v)The Rolls Royce Merlin engine working on an air standard Otto cycle has the following particulars: Piston diameter (bore) = 13.7 cm, stroke length = 13.0 cm, clearance volume=280 cc. The compression ratio will be:
(a) 5.2 (b) 6.7 (c) 7.85 (d) 8.1
(B) Draw a neat labelled sketch of a simple carburettor showing names of all the parts. [02]
(C) Draw a neat line diagram of an Ice plant. Clearly show names of all the parts, cooling [03] water circuit, brine circuit and refrigerant circuit on the diagram.
(D) Answer any two of the following: [08]
(i) A 6 cylinder 4 stroke I.C. engine is developing 89.5 kW indicated power at 800 r.p.m.
The stroke to bore ratio is 1.25. Assuming mechanical efficiency of 80 % and brake mean effective pressure of 5 bar; determine the bore and stroke of the engine.
(ii)In a diesel engine during the compression process, pressure is observed to be 138 kPa at l/8th of stroke and 1.38 MPa at 7/8th of stroke. The cut-off occurs at 1715th of stroke. Calculate air standard efficiency and compression ratio, assuming indicated thermal efficiency to be half of idea! efficiency, mechanical efficiency as 80 % and calorific value of fuel =41800 kJ/kg. Assume any data if required.
(iii) Derive an expression for air standard efficiency of Dual cycle.
Q-3 (A) Derive the equation relating the chimney height with boiler draught as per standard [04] notations. Clearly state assumptions made.
(B) Justify the following: [06]
(i) The chimney is not required in the case of locomotive boiler.
(ii) Forced draught is called as positive pressure draught.
(iii) Replacement of fusible plug should be done at regular time intervals.
(C) A boiler plant operated on coal uses 380 kg of coal per hour. The boiler evaporates 2850 [06] kg of water at 45C into a superheated steam at a pressure of 12 bar and 270C. If the calorific value of coal is 32760 kJ/kg, determine:
(i) Factor of equivalent evaporation.
(ii) Equivalent evaporation from and at 100C.
(iii) Theoretical thermal efficiency of the boiler.
v
(The values from steam table are: hf=798.4 kJ/kg; hfg= 1984.3 kJ/kg; TS=190C. Take the standard values of specific heat capacity)
The End of the Question Paper
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