95HE-4
Sr. No. 6
EXAMINATION OF MARINE ENGINEER OFFICER
Function: Marine Engineering at Operational Level
HEAT ENGINES
India (2004)
M.E.O. Class IV
(Time allowed - 3hours)
Afternoon Paper
Total Marks 100
NB : (1) All Questions are Compulsory
(2) All Questions carry equal marks
(3) Neatness in handwriting and clarity in expression carries weightage
(4) Illustration of an Answer with clear sketches / diagrams carries weightage.
1.
The mass analysis of a fuel is 87% carbon, 11 % hydrogen and 2% oxygen. Calculate the volume
of air in cubic metres at 1.0 bar and 250C required for perfect combustion per kg of fuel.
Take the values: R for air = 0.287 kJ/kg K. Mass analysis of air = 23% oxygen, 77% nitrogen.
Atomic weights, hydrogen 1, carbon 12, oxygen 16.
2.
One side of a steel plate is exposed to a stream of hot gases and the other side to an air stream.
The plate is 13 mm thick and the surface temperatures of the plate are at 230°C and 150°C. If the
coefficient of thermal conductivity of the steel is 44 W/m K, calculate the heat transferred per
square metre of plate area per minute.
3.
Calculate (i) the mass of 1.13 litre of nitrogen at 5.86 bar and 61°C, and (ii) the volume of this
mass of nitrogen at 1.38 bar and 15°C. R for nitrogen = 297 J/kg K.
4.
The effective radius of the pads in a single collar thrust block is 230 mm and the total load on the
thrust block is 240 kN when the shaft is running at 93 rev/min. Taking the coefficient of friction
between the thrust collar and pads as 0.025, find (I) the power lost due to friction (ii) the heat
generated per hour, (iii) the mass flow of oil in kilogrammes per hour through the block assuming
all the heat is carried away by the oil, allowing an oil temperature raise of 20° C and taking the
specific heat of the oil as 2kJ/kg K.
5.
A solid cast iron sphere is 150 mm diameter. If 2110 kJ of heat energy is transferred to it, find the
increase in diameter, taking the following values for cast iron.
(a) Density = 7.21 g/cm3.
(b) Specific heat = 0.54 kJ/kg K
Coefficient of linear expansion = 1.12 x 10-5/°C
6.
The area of an indicator diagram taken off a four-cylinder, single-acting, four-stroke, internal
combustion engine when running at 5.5 rev/s is 390 mm2, the length is 70 mm, and the scale of the
indicator spring is 1 mm = 0.8 bar, The diameter of the cylinders is 150 mm and the stroke is
200 mm. Calculate the indicated power of the engine assuming all cylinders develop equal power.
7.
The diameter of an air compressor cylinder is 140 mm, the stroke of the piston is 180 mm, and the
clearance volume is 77 cm3. The pressure and temperature of the air in the cylinder at the end of
the suction stroke and beginning of compression is 0.97 bar and 13°C. The delivery pressure is
constant at 4.2 bar. Taking the law of compression as pV1.3 = constant, calculate (i) for what length
of the stroke air is delivered (ii) the volume of air delivered per stroke, in litres (iii) the
temperature of the compressed air.
8.
3 kg of wet steam at 14 bar and dryness fraction 0.95 are blown into 100 kg of water at 22°C.
Find the resultant temperature of the water.
9.
Describe the working of a throttling calorimeter and its use.
Steam at a pressure of 14 bar from the main steam pipe is passed through a throttling calorimeter.
The pressure in the calorimeter is 1.2 bar and the temperature 119°C. Taking the specific heat of
the low pressure steam as 2.0 kJ/kgK calculate the dryness fraction of the main steam.
10.
During a test on a single-cylinder steam engine, the mean effective pressure was 4.05 bar when
running at 3 rev/s. The brake load was 1.9 kN acting at an effective radius of 1.2 m. If the cylinder
diameter is 0.275 m and the stroke 0.4 m, calculate (a) the indicated power, (b) the brake power,
(c) the mechanical efficiency.
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