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ME Thermal Engineering Important questions

Unit 1

PART A

1. What is meant by cut-off ratio?

2. Draw the P-V and T-S diagram for otto cycle.

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3. What are the assumptions made for air standard cycle analysis?

4. Define mean effective pressure as applied to gas power cycles.

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5. What is the effect of compression ratio on efficiency of otto cycle?

6. Draw the actual and theoretical P-V diagram for four stroke cycle SI engine.

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7. Mention the various processes of dual cycle.

8. For the same compression ratio and heat supplied, state the order of decreasing air standard
efficiency of Otto, diesel and dual cycle.
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9. What are the effects of reheat cycle?

10. What is thermodynamic cycle?

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11. What is a thermodynamic cycle?

12. What is meant by air standard cycle?

13. Name the various “gas power cycles".

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14. What are the assumptions made for air standard cycle analysis

15. Mention the various processes of the Otto cycle.

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16. Mention the various processes of diesel cycle.

17. Mention the various processes of dual cycle.

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18. Define air standard cycle efficiency.

19. Define mean effective pressure as applied to gas power cycles. How it is related to
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indicate power of an I.C engine.

20. Define the following terms. (i) Compression ratio (ii) Cut off ratio, (iii) .Expansion ratio

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PART B

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 cycle.

3. Drive an expression for the air standard efficiency of Dual cycle.

4. Explain the working of 4 stroke cycle Diesel engine. Draw the theoretical and actual

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PV diagram.

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

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6. A Dual combustion air standard cycle has a compression ratio of 10. The constant pressure
part of combustion takes place at 40 bar. The highest and the lowest temperature of
the cycle are 1725degree C and 27 0 C respectively. The pressure at the beginning of

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compression is 1 bar. Calculate (i) the pressure and temperature at’ key points of the cycle.
(ii) The heat supplied at constant volume, (iii) the heat supplied at constant pressure. (iv) The
heat rejected. (v) The work output. (vi) The efficiency and (vii) mep.

7. An Engine-working on Otto cycle has a volume of 0.45 m3 , pressure 1 bar and

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temperature 30o, Cat the beginning of compression stroke. At the end of compression stroke,
the pressure is 11 barand 210 KJ of heat is added at constant volume. Determine (i)
Pressure, temperature and volumes at salient points in the cycle.' (ii) Efficiency.

8. Explain the working of 4-stroke cycle Diesel engine. Draw the theoretical and actual
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valve- timing diagram for the engine. Explain the reasons for the difference.

9. Air enters the compressor of a gas turbine at 100 KPa and 25 o C. For a pressure ratio of
5 and a maximum temperature of 850°C. Determine the thermal efficiency using the
Brayton cycle.
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10. The following data in referred for an air standard diesel cycle compression ratio = 15
heat added= 200 Kj/Kg- minimum temperature in the cycle = 25°C Suction pressure = 1 bar
Calculate 1. Pressure and temperature at the Salient point. 2. Thermal efficiency 3. Mean
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effective pressure, 4. Power output of the cycle, if flow rate 'of air is 2 Kg/s

11. A Dual combustion air standard cycle has a compression ratio of 10. The constant
pressure part of combustion takes place at 40 bar. The highest and the lowest temperature of
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the cycle are 1727° C and 27° C respectivety.The pressure at the beginning of compression is
1 bar. Calculate- (i) The pressure and temperature at key points of the cycle. (ii) The heat
supplied at constant volume, (iii) The heat supplied at constant pressure (iv) The heat rejected
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(v) The Work output, (vi) The efficiency and (vii) Mean effective pressure.

12. An Engine working on Otto cycle has a volume of 0.45 m3, pressure 1 bar and
Temperature 30Oc, 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.

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Unit 
PART A

1. Draw the P-V diagram of a two stage reciprocating air compressor.

2. What is ton of refrigeration?

3. What is compounding of steam turbine?

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4. Name the methods of steam turbine governing.

5. Why is compounding necessary in steam turbine?

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6. What is the purpose of using intercooler in multi-stage compression?

7. Indicate the application of reciprocating compressors in industry.

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8. What are the advantages of multi stage compression with inter cooling over single stage

compression for the same pressure ratio.

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9. Why clearance is necessary and what is its effect on the performance of reciprocating

compressor?

10. Give two merits of rotary compressor over reciprocating compressor.

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11. What is meant by single acting compressor?

12. What is meant by double acting compressor?

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13. What is meant by single stage compressor?

14. What is meant by multistage compressor?

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15. Define isentropic efficiency

16. Define mean effective pressure. How is it related to in power of an I.C engine.
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17. What is meant by free air delivered?

18. Explain how flow of air is controlled in a reciprocating compressor?

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19. What factors limit the delivery pressure in reciprocating compressor?

20. Name the methods adopted for increasing isothermal efficiency of reciprocating
air compressor.

21. Why clearance is necessary and what is its effect on the performance of

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reciprocating compressor?

22. What is compression ratio?

23. What is meant by inter cooler?

PART B

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1. Drive an expression for the work done by single stage single acting reciprocating
air compressor.

2. Drive an expression for the volumetric efficiency of reciprocating air compressors

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3. Explain the construction and working of a root blower

4. Explain the construction and working of a centrifugal compressor

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

6. A single stage single acting air compressor is used to compress air from 1 bar and 22° C
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to 6 bar according to the law PV1 .25 = C. The compressor runs at 125 rpm and the ratio
of stroke length to bore of a cylinder is 1.5. If the power required by the
compressor is 20 kW, determine the size of the cylinder.
7. A single stage single acting air compressor is used to compress air from 1.013 bar and
25° C to 7 bar according to law PV 1.3 = C.The bore and stroke of a cylinder are
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120mm and 150mm respectively. The compressor runs at 250 rpm .If clearance volume
of the cylinder is 5% of stroke volume and the mechanical efficiency of the compressor
is 85%, determine volumetric efficiency, power, and mass of air delivered per minute.

8. A two stage singe acting air compressor compresses 2m3 airs from 1 bar and 20° C to 15
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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.
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Unit  
PART A
1. Classify IC engine according to cycle of lubrication system and field of application.
2. Types of lubrication system
3. List the various components of IC engines.
4. Name the basic thermodynamic cycles of the two types of internal combustion
reciprocating engines.
5. Mention the important requites of liner material.
6. State the purpose of providing piston in IC engines.
7. Define the terms as applied to reciprocating I.C. engines "Mean effective pressure"

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and “Compression ratio".
8. What is meant by highest useful compression ratio?
9. What are the types of piston rings?
10. What is the use of connecting rod?

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11. What is the use of flywheel?
12. Which factor increases detonation in IC engines?
13. Which factor do not have much influence in detonation?
14. For maximum power, air-fuel ratio should be?

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15. For maximum economy, air-fuel ratio should be?
16. For maximum power we need is?
17. Cold starting required?
18. Knock in SI engine can be reduced by
19. In 2-stroke engines wich two strokes are eliminated?
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20. Which efficiency will reduce if fresh charge filled is reduced?
21. SFC decreases as power capacity of engine?
22. What about the NOx emission when the compression ratio decreases?
23. Methods used for preparing bio-diesel?
24. Nox, Sox, HC can be determined by ?
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25. What is blending of fuel?

26. Is hydrogen fuel is storable?

PART B
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1. Explain full pressure lubrication system I.C Engine.

2. Explain the water cooling system in I.C Engine.

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3. Explain the 2 types of Ignition system In S.I Engine.

4. Draw and explain the valve timing diagram of 4 strokes Diesel Engine.
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5. Draw and explain the port timing diagram of 2stroke Petrol Engine.
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6. Explain with neat sketch the exhaust gas analysis.

7. The following results refer to a test on a petrol engine Indicated power = 30 Kw, Brake
power = 26 Kw, Engine speed = 1000 rpm Fuel brake power/ hour = 0.35 kg Calorific value
of fuel = 43900kj/kg .Calculate the indicated Thermal efficiency, the brake Thermal
efficiency and Mechanical efficiency

8. A four cylinder 2 stroke cycle petrol engine develops 23.5 kw brake power at 2500 rpm.
The mean effective pressure on each piston in 8. 5 bar and mechanical efficiency in 85%

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Calculate the diameter and stroke of each cylinder assuming the length of stroke equal to 1.5
times the diameter of cylinder.

9. 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/kg. Determine 1.
Indicated Power 2. Brake Power 3. Mechanical efficiency 4. Indicated thermal efficiency and

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5. Brake thermal efficiency.

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