Reg. No. :
P 1330
B.E./B.Tech. DEGREE EXAMINATION. NO\IEMBEWDECEMBER 2007.
Fourth Semester
Mechanical Engineering
ME 237
- THERMAL ENGINEERING
Time : Three hours Maximum : 100 marks
(Use of Steam table/charts and refrigeration table/charts is permitted)
Answer ALL questions.
PART A
- (10 x2 = 20 marks)
1. What are the factors to be considered for selection of steam boilers?
2. What is the function of superheater?
3. Define two stage impulse turbine.
4. What is meant by height of blades as applied to a reaction turbine?
5. What is meant by injection lag?
6. What are the requirements of a good carburetor?
7. Define scavenging ratio.
8. Define brake mean effective pressure.
9. Define specific humidity.
10. What is meant bv adiabatic saturation?
PARTB-(5x16=80marks)
11. (a) (i) Explain the construction and working of a Lancashire boiler with
the help of neat sketch. (10)
(ii) Compare water tube boiler with fire tube boiler. (6)
www.VidyarthiPlus.in
www.VidyarthiPlus.in(b) (i) Differentiate
valve.
between lever safety valve and dead weight safety
(8)
(ii) Explain the working of an economiser rn a
sketch.
boiler plant with a neat
(8)
L2.
(a) The steam enters an impulse wheel having a nozzle angle of 20" at a
velocity of 450 m,/sec. The exit angle of the moving blade is 20o and the
relative velocity of the steam may be assumed to remain constant over
the moving blades. If the blade speed is 180 m./sec, determine
(i) Blade
angle at inlet
(ii) Work done per kg of steam
(iii) Power of the wheel,
when the turbine is supplied with 1.8 kg of steam per second.
(16)
Or
(b) The blade angles of both fixed and moving blades of reaction steam
turbine are 35o at the receiving tips and 20o at the discharglng tips' At a
certain point in the turbine, the drum diameter is 1.37 m and blade
height ts I27 mm. The pressure of steam supply to a ring of fixed blades
at this point is 1.25 bar and the drlmess fraction is 0.925. Find the work
d.one in next row of moving blades for 1 kg of steam at 600 rpm, the
steam passing through the blades without shock. Assuming an efficiency
of 8S7o for the pair of rings of fixed and moving blades, find the heat drop
in the pair and state the properties of steam at the entrance to the next
row offixed blades.
18.
(a) (i) Explain the magneto ignition system with a neat sketch-
(8)
(16)
influence on
(8)
with reference to the
(r2)
good fuel for a petrol
(4)
(ii) Explain the significance of flame speed and its
combustion in S.I.engine.
(b)
Or
(i) Compare the petrol and diesel engines
following:
(1) Porver to weight ratio
(D Accelerationresponse
(3) Economy in road transPort
(4) Maintenauce and rePair.
(ii) Enumerate the desirable properties of a
engine.
P 1330
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www.VidyarthiPlus.in14. (a) Explain briefly
(i) Indicator card method
(ii) Extrapolationmethod
(iii) Retardationmethod
(iv) Morse test.
Or
(b) A four stroke petrol engine has a piston displacement of 2210 cm3. The
compression ration is 6.4. The fuel consumption is 0.13 kg/min' The
caiorific value of fuel is 45000 KJfi<g. The brake power developed while
running aL 2500 rev/min is 50.25 KW. Determine the brake mean
effective pressure and the reiative efficiency based on brake thermal
(16)
(16)
efficiency.
15. (a) A cinema hall of seating capacity 1500 persons has been provided with an
air conditioned plant with the following data .
Outdoor conditions = 40"C DBT and 20'C WBT
Required conditions = 20"C DBT and 607o RH
Amount of air supplied = 0.3 m3/min/person.
If the required condition is achieved first by adiabatic humidifying and
then cooling, find the capacity of the cooling coil and capacity of the
humidifier.
(16)
Or
(b) (i) Explain the winter air conditioning system with the help of a neat
sketch.
(10)
(ii) Explain the following terms :
(1) Degree of saturation
(2) Dew point temperature
(3) Humidity ratio.
(6)
P 1330
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