Anna University, Chennai Nov/Dec 2012 Examinations

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**Thermal Engineering - ME2301**

V Sem MECH

Unit I-V

1. Drive and expression for the air standard efficiency of Otto cycle
in terms of volume ratio

2. Drive an expression for the air standard efficiency of Diesel and
dual cycle

3. An Engine-working on Otto cycle has a volume of 0.45 m3 , pressure 1
bar and temperature 30o,C at the beginning of compression stroke. At the end of
compression stroke, the pressure is 11 bar and 210 KJ of heat is added at
constant volume. Determine (i) Pressure, temperature and volumes at salient
points in the cycle.' (ii) Efficiency

4. A six cylinder four stroke petrol engine has a
swept volume of 300 cubic cm per cylinder, a compression ratio of 10 and
operates at a speed of 35000 rpm. If the engine is required to develop an
output of 73.5 kW at this speed, calculate the cycle efficiency, the necessary
rate of heat addition, the mean effective pressure, maximum temperature of the
cycle and efficiency ratio. The pressure and temperature before is entropic compression
are 1.0 bar and 15°C respectively, take Cv = 0.72 and ? = 1.4

5.
Drive the expression for air standard
efficiency of Brayton cycle in terms of pressure ratio

6.
Explain any four types of
classification of internal Combustion engines.

7.
Explain with neat sketch the exhaust gas
analysis

8. The following data to a particular twin cylinder two stroke diesel
engine. Bore 15 cm stroke. 20 cm. speed 400 rpm. Indicated mean effective
pressure 4 bar, dead weight on the brake drum 650 N. spring balance reading 25
N Diameter of the brake drum 1 m .Fuel consumption 0.075 kg/min and calorific value
of the fuel is 44500 kj/J kg.

Determine

a. Indicated Power

b. Brake Power

c. Mechanical efficiency

d. Indicated thermal efficiency

e. Brake thermal efficiency

9.
Draw and explain the port timing diagram of
2stroke Petrol Engine

10.
A 50% reaction turbine funning at 400
rpm has the exit angle of the blades as 200 and the velocity of the steam
relative to the blades at the exit is 1.35times the mean speed of the blade.
The steam flow rate is 8.33 kg/s and at particular stage the specific volume
is1.381 m3/kg. calculate for this stage

11.
A single row impulse turbine develops
132.4 kW at a blade speed of 175 m/s using 2 kg of steam per sec. Steam leaves
the nozzle at 400 m/s. Velocity coefficient of the blade is 0.9. Steam leaves
the turbine blades axially. Assuming no shock determine the nozzle angle, blade
angles at entry and exit

12.
Drive an expression for critical pressure ratio
in terms of the index of expansion

13. Describe the construction functioning of magneto ignition system
used in modern two wheeler engines

14. A single stage reciprocating air compressor has
clearance volume 5% of stroke volume of 0.05 m3/sec. The intake conditions are
95 kN/m2, 300 K.The delivery pressure is 720 kN/m2. Determine the volumetric
efficiency referred to (i) intake conditions (ii) atmospheric conditions of 100
kN/m2 and 290 K (iii) FAD and (iv) power required to drive the compressor, if
the ratio of actual to indicated power is 1.5. Take index of compression

and expansion as 1.3

and expansion as 1.3

15. Derive an expression for maximum work required for a
two stage reciprocating air compressor with perfect inters cooling
and neglecting clearance.

16. Explain the construction and working of a sliding vane compressor
and axial flow compressor

17. A two stage singe acting air compressor compresses 2m3 airs from 1
bar and 20° C to 15 bar. The air from the low pressure compressor is cooled to
25° C in the intercooler. Calculate the minimum power required to run the
compressor if the compression follows PV1.25=C and the compressor runs at 400 rpm.

18. One kg of air at 35°C DBT and 60% RH is mixed with
2 kg of air at 20°C DBT and 13°C dew point temperature. Calculate the vapour
pressure and dew point temperature of stream one, enthalpy of both the streams
and specific humidity of the mixture

19. A sling psychrometer in alaboratory test recorded
the following readings

Dry bulb temperature = 350 C

Wet bulb temperature = 250 C

Calculate the following :

(i) specific humidity

(ii) relative humidity

(iii) vapourdensity in air

(iv) dew point temperature

(v) enthalpy of mixture per kg of dry air

Take atmospheric pressure = 1.0132 bar

Dry bulb temperature = 350 C

Wet bulb temperature = 250 C

Calculate the following :

(i) specific humidity

(ii) relative humidity

(iii) vapourdensity in air

(iv) dew point temperature

(v) enthalpy of mixture per kg of dry air

Take atmospheric pressure = 1.0132 bar

20. Explain with sketch the working principle of water-Lithium bromide
refrigeration system.

21. Explain winter, summer, and year round Alc system.