Gujarat Technological University 2010-2nd Sem B.E Mechanical Engineering , Subject code: 110006, Subject Name: Elements of - Question Paper
GUJARAT TECHNOLOGICAL UNIVERSITY
B.E. Sem-II exam June 2010
Subject code: 110006
Subject Name: Elements of Mechanical Engineering
Date: 21 /06 / 2010
Total Marks: 70
GUJARAT TECHNOLOGICAL UNIVERSITY
B.E. Sem-II Examination June 2010
Seat No. Enrolment No.
Subject code: 110006 Subject Name: Elements of Mechanical Engineering Date: 21 /06 / 2010 Time: 02.30 pm - 05.00 pm
Total Marks: 70
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
4. Use of steam table is permissible.
Q.1 (a) Define the following terms: 03
(i) Prime mover
(ii) Specific heat
(iii) Internal energy
(b) What is isothermal process? Derive an expression for the work done during 05 the isothermal process.
0.15m3 at a pressure of 1.0 bar to a volume of 0.05 m,3 when the compression
is (i) isothermal and (ii)adiabatic, Take y=1.4 Also, comment on your answer.
Q.2 (a) Define the following terms:
02
(i) Dryness fraction of steam
(ii) Degree of superheat
(b) Explain with a sketch the working of a four stroke Petrol engine.
05
07
(c) The following results refer to a test on C.I. engine
Indicated power------------------------ 37 KW
Frictional power-------------------------06 KW
Brake specific fuel consumption--------0.28 Kg/Kwh
Calorific value of fuel--------------------44300 KJ/Kg
Calculate:
(i) Mechanical efficiency
(ii) Brake thermal efficiency
(iii) Indicated thermal efficiency
OR
(c) Determine the enthalpy and internal energy of 1 Kg of steam at a pressure 10 07 bar(abs.), (i)when the dryness fraction of the steam is 0.85 (ii) when the steam is dry and saturated (iii) when the steam is superheated to300C. Neglect the volume of water and take the specific heat of superheated steam as 2.1 KJ/KgK.
Q.3 (a) For the same compression ratio the air standard efficiency of Otto cycle is 02 greater than that of Diesel cycle. Justify the statement.
(b) Draw P-V diagram for an ideal Diesel cycle and Derive an expression for its 05 air standard efficiency in terms of temperatures only.
(c) An engine operating on the ideal Diesel cycle has a maximum pressure of 44 07 bar and a maximum temperature of 1600C.The pressure and temperature of
air at the beginning of the compression stroke are 1 bar and 27 C respectively.
Find the air standard efficiency of the cycle. For air take y=1.4
(b) A boiler has equivalent evaporation of 10 Kg per Kg of coal at design 04 condition. The coal is supplied at the rate of 400 Kg per hour to the boiler.
The calorific value of the coal is 34 MJ/Kg. Calculate the thermal efficiency
of the boiler.
(c) Explain with neat sketch the construction and working of Babcock and 07 Wilcox boiler.
Q.4 (a) Give comparison between a flywheel and a governor 03
(b) State the advantages of multistage compressor and explain with P-V 05 diagram the working of two stage compressor.
(c) Classify the rotary pumps and describe with neat sketch working of a rotary 06 gear pump.
OR
Q.4 (a) Define air conditioning and classify the air conditioning systems 03
(c) A single cylinder , single acting air compressor has a cylinder diameter of 06 150mm and stroke of 300mm. it draws air into its cylinder at a pressure of 1
bar and temperature 27 C.This air is then compressed adiabatically to a pressure of 8 bar if the compressor runs at a speed of 120rpm Find,
(i) Mass of the air compressed per cycle
(ii) Work required per cycle
(iii) Power required to drive the compressor
Neglect the clearance volume and take R= 0.287 KJ/KgK Q.5 (a) Differentiate between individual drive and group drive. 03
(c) What is the function of a brake? Explain with neat sketch the working of an 06 internal expanding shoe brake.
OR
Q.5 (a) Give the statements of zeroth law, first law and second law of 03 thermodynamics.
(c) Describe in brief the various non-ferrous metals along with their applications. 06
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