Introduction to IC Engines and engine cycles

 

TOTAL MECHANICAL ENGINEERING

Section 1	Section 2	Section 3	Section 4
Section 5	Section 6	Section 7	Section 8

Introduction to IC Engines and engine cycles

Quiz

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1. Compression ratio in diesel engine is of the order of
   1.   5 – 7
   2.   10 – 12
   3.   7 – 10
   4.   14 – 20
2. In four stroke IC engine camshaft rotates at
   1.   Same speed as crankshaft
   2.   Half the speed of the crankshaft
   3.   Twice the speed of crankshaft
   4.   none of these.
3. The air standard Otto cycle consists of
   1.   Two constant volume and two isentropic processes
   2.   Two constant pressure and two isentropic processes
   3.   Two constant pressure and two constant volume processes
   4.   None of the above.
4. The major loss in CI engine is
   1.   Direct heat loss
   2.   loss due to incomplete combustion
   3.   rubbing friction loss
   4.   pumping loss.
5. The cylinder temp. after the compression in a diesel engine is
   1.   200°C
   2.   450°C
   3.   900°C
   4.   1000°C
6. The volume generated by the working piston when travelling from one dead centre to other is called
   1.   Clearance volume
   2.   swept volume
   3.   stroke
   4.   engine capacity
7. The major loss in SI engine is due to
   1.   Exhaust blow down
   2.   pumping
   3.   incomplete combustion
   4.   variation in sp. heat and chemical eqm
8. Valve overlap occurs between
   1.   Intake and compression strokes
   2.   Power and exhaust strokes
   3.   compression and power strokes
   4.   exhaust and intake strokes
9. Modern heavy duty engines exhaust valve made of
   1.   High carbon steel
   2.   cobalt alloy
   3.   nimonic alloys
   4.   none of these
10. If N is the rpm, number of power strokes per minute in a four stroke engine is
    1.   2
    2.   N/2
    3.   N
    4.   4N
11. Compared to a 4S engine of the same capacity, a 2S engine will have
    1.   Lower power output
    2.   higher bsfc
    3.   lower emissions
    4.   both a) and c)
12. Time loss factor in actual engine cycle is due to
    1.   Progressive combustion
    2.   heat loss through cylinder walls
    3.   gas leakage
    4.   friction
13. If N is the rpm, number of power strokes per minute in a two stroke engine is
    1.   2
    2.   N/2
    3.   N
    4.   4N
14. If L is stroke and N is rpm, then mean piston speed of two stroke engine is
    1.   LN
    2.   LN/2
    3.   2LN
    4.   LN/4
15. For a given value of ϒ (gamma) efficiency of Otto cycle
    1.   Decreases with compression ratio
    2.   Increases with compression ratio
    3.   is not affected
    4.   none of these.
16. If the spark timing is at TDC, the work output is
    1.   Less
    2.   more
    3.   unaffected
    4.   none of these
17. Engines used for ships are normally
    1.   4S – SI engines of very high power
    2.   2S – CI engines of high power
    3.   4S – CI engines of high speed
    4.   2S – SI engines of high power
18. When the spark is advanced, work output is less as
    1.   The peak pressure is low
    2.   The peak temperature is low
    3.   additional work is required to compress the burning gas
    4.   frictional losses increases
19. Main advantage of a 2-S over 4-S engine is
    1.   More uniform torque on crank shaft
    2.   More power output for the cylinder of same dimensions
    3.   absence of valves
    4.   all of the above
20. Fuel – air cycle efficiency is less than air-standard cycle efficiency by an amount
    1.   Pumping loss
    2.   Loss due to sp. heat variation and chemical equilibrium
    3.   friction loss
    4.   exhaust blow down
21. Volumetric efficiency of the SI engine is comparatively
    1.   Lower than CI engine
    2.   higher than CI engine
    3.   will be same as CI engine
    4.   none of the above
22. Gudgeon pin forms the link between
    1.   Piston and big end of connecting rod
    2.   Piston and small end of connecting rod
    3.   Piston and small end of connecting rod
    4.   Piston and small end of connecting rod
23. Thermal efficiency of CI engine is higher than that of SI engine due to
    1.   Fuel used
    2.   higher compression ratio
    3.   constant pressure heat addition
    4.   constant pressure heat addition
24. An IC engine gives an output of 3 kw when the input is 10,000 J/s. the thermal efficiency of engine is
    1.   33.3%
    2.   30%
    3.   60%
    4.   66.6%
25. In a 4-S SI engine during suction
    1.   Only air is sucked
    2.   only fuel is sucked
    3.   fuel-air mixture is sucked
    4.   none of these.
26. With dissociation exhaust gas temperature
    1.   Decreases
    2.   increases
    3.   remains unchanged
    4.   increases initially and then decreases
27. Stochiometric air-fuel ratio for a petrol engine is approximately
    1.   50:1
    2.   25:1
    3.   15:1
    4.   5:1
28. Main advantage of a two-stroke over four-stroke engine is
    1.   More uniform torque on crank shaft
    2.   More power output for the cylinder of same dimensions
    3.   absence of valves
    4.   all of these