Basics of Internal Combustion Engine (MG university Syllabus) for students

1. I C Engines E C Engines
ReciprocatingRotaryReciprocatingRotary
Stirling engineGasoline
Engine
Wankel
Engine
Open
Cycle
Gas
Turbine
Diesel
Engine
Steam Engine Steam
Turbine
Engine
Closed cycle Gas
Turbine
Heat Engines
1

2. Most widely used heat engines
 INTERNAL
COMBUSTION
engine
 GAS TURBINE
 STEAM TURBINE
2

3. ADVANTAGES OF I C ENGINE
OVER THE OTHER ENGINES
Considerable mechanical
simplicity and improved power
plant efficiency
High working fluid temperatures
can be employed resulting in
higher thermal efficiency
weight to power ratio is less than
that of the steam turbine
Small power output with
reasonable thermal efficiency
and cost
3

4. Disadvantages
Vibration
Not possible to use
variety of fuels in
these engines
Fuels are expensive
4

5. Applications
Automobiles
 Motor cycles
 Power boats
 Ships
 Slow speed aircrafts
 Locomotives
 Power units of relatively small
output
5

6. EXTERNAL COMBUSTION ENGINES –
Combustion takes place outside
the engine
INTERNAL COMBUSTION ENGINES –
Combustion takes place inside the
engine
6

7. Spark Ignition (SI) Compression Ignition (SI)
Reciprocating Engine
7

8. Engine Components
8

9. 9

10. 10

11. 11

12. 12

13. Nomenclature
 Cylinder Bore (d) – inner diameter of the working
cylinder (mm)
 Piston Area (A) – cross section area of bore (cm2)
 Stroke (L) – distance through which a working piston
moves between two successive reversals of its
direction of motion (mm)
 Stroke to Bore Ratio (L/d)
d<L - under-square Engine
d = L - Square Engine
d>L - Over Square Engine
 Dead center – Position of working piston at the
moment when the direction of the piston is reversed
at the ether end of the stroke
13

14. Nomenclature Continued
 Top Dead Center – Dead Center when piston is
farthest from crank shaft
 Bottom Dead Center - Dead Center when piston is
nearest from crank shaft
 Displacement or Swept Volume (VS)– Volume swept
by the piston when travelling from one dead center to
the other (cc)
 Cubic Capacity or Engine Capacity – Displacement
volume ×No. of cylinders
 Clearance Volume (VC) – Volume of combustion
chamber above piston when it is at top dead center
 Compression ratio (r) -
𝑉 𝑇
𝑉 𝐶
=
𝑉 𝐶+𝑉 𝑆
𝑉 𝐶
14

15. Working Principle of Engines
 https://www.youtube.com/watch?v=4W_NRHxek
aY
 http://www.animatedengines.com/otto.html
 http://www.animatedengines.com/diesel.html
15

16. Working Principle of Four-
Stroke SI Engine
16

17. Ideal p-V Diagram of a Four
Stroke SI Engine
 A- Intake
 B – Adiabatic compression
 C – Const. volume heat add
And Expansion
 D – Exhaust
17

18. Working Principle of Four-
Stroke CI Engine
18

19. Ideal p-V Diagram of a Four
Stroke CI Engine
19

20. Comparison of SI and CI
Engine
Description SI Engine CI Engine
Working
Cycle
Otto Cycle or Constant
Volume heat addition
cycle
Diesel Cycle or Constant
Pressure heat addition
Fuel Used Gasoline(Volatile), Self
Ignition high
Diesel oil (non-volatile), Self
Ignition is low
Introduction
of Fuel
Mixture of fuel,
Carburetor and Ignition
System
Fuel is injected at high
pressure, Fuel Pump and
Injector
Load Control Control quantity of Air-
Fuel mixture
Control quantity of fuel, Air
quantity not controlled
20

21. Comparison of SI and CI
Engine Continued
Description SI Engine CI Engine
Ignition Ignition System with
Spark Plug, Primary
voltage given by
Magneto or a battery
Self Ignition due to high
temperature of air as a
result of high compression
Compression
ratio
6 to 10, Upper limit is
fixed by antiknock
quality of the fuel
16 to 20, Upper limit is
limited by weight
increase of Engine
Speed High speed (Light weight
and homogeneous
combustion)
Low speed (Heavy
weight and
heterogeneous
combustion)
Thermal
Efficiency
Lower (Lower CR) Higher (Higher CR)
Weight Lighter (Low Peak
Pressure)
Heavier (Higher Peak
Pressure)
21

22. Two Stroke Engine
 http://www.animatedengines.com/twostroke.html
 https://www.youtube.com/watch?v=xV9jnWVeSB
4
 https://www.youtube.com/watch?v=LuCUmQ9Fx
MU
22

23. Indicator Diagram of a two
Stroke Engine
23

24. Comparison of Four Stroke
and Two Stroke Engine
Four Stroke Engine Two Stoke Engine
Four Stokes, two revolution of
crankshaft, One power stoke
in two revolution of CS
Two strokes, one revolution of crank
shaft, one power stoke in each
revolution of crank shaft
Heavier Flywheel Lighter Flywheel
Weight of engine per hp is
high
Weight of engine per hp is
comparatively low
There are inlet and exhaust
valves in the engine
There are inlet and exhaust ports
instead of valves
Thermal efficiency is high Thermal efficiency is comparatively
low
24

25. Comparison of Four Stroke
and Two Stroke Engine conti’d
Four Stoke Engine Two Stoke Engine
Lesser cooling and lubrication,
Lower rate of wear and tear
Greater cooling and lubrication,
Higher rate of wear and tear
Initial cost of engine is more Initial cost is less
Volumetric Efficiency is higher Volumetric Efficiency is lower
Used where efficiency is
important (Buses, trucks, tractors,
aero planes etc.)
Used where Low cost.
Compactness and light weight
are important (mopeds, scooters,
motorcycle, hand sprayers etc.)
25

26. Actual Indicator Diagram of a 2-stoke(a)
and 4-stroke (b) SI engine
26

27. Theoretical Valve timing
Diagram
27

28. Valve timing Diagram of Diesel Engine
 https://www.youtube.com/watch?v=DBD
GOvsxpq8
28

29. Valve timing Diagram of Petrol Engine
29

30. Valve timing Diagram of Two
Stroke Engine
30

31. CLASSFICATION OF IC ENGNES
1. Cycle of Operation
(i) Two Stroke engines
(ii) Four Stroke engines
2. According to cycle of Combustion
(i) Otto cycle engine (Combustion at
constant volume)
(ii) Diesel Engine (Combustion at constant
Pressure)
(iii) Dual-combustion or Semi- Diesel cycle
engine(Combustion partly at constant
volume and partly at constant
pressure)
31

32. CLASSFICATION OF IC ENGNES
3. According to arrangement of cylinder
32

33. CLASSFICATION OF IC ENGNES
4. According to their uses
i. Stationary Engine
ii. Portable Engine
iii. Marine Engine
iv. Automobile Engine
v. Aero Engine
33

34. CLASSFICATION OF IC ENGNES
5. According to the speed of engine
i. Low Speed
ii. Medium Speed
iii. High Speed
6. According to the method of Ignition
i. Spark-Ignition
ii. Compression-Ignition
7. According Method of cooling the Cylinder
i. Air-cooled
ii. Water-cooled
34

35. CLASSFICATION OF IC ENGNES
8. According to method of governing
i. Hit and Miss governed
ii. Quality governed
iii. Quantity governed
9. According to valve arrangement
i. Over Head Valve
ii. L-head type
iii. T-head type
iv. F-head type
35

36. Valve arrangements
36

37. CLASSFICATION OF IC ENGNES
10.According to number of Cylinders
i. Single Cylinder
ii. Multi Cylinder
11.According Air intake process
I. Naturally aspirated
II. Supercharged
III. Turbo charged
37

38. CLASSFICATION OF IC ENGNES
12. According to fuel employed
i. Oil Engine (Fuel Oil)
ii. Petrol Engine
iii. Gas engine (coal gas, producer gas, biogas, landfill gas)
iv. Kerosene Engine
v. LPG engine
vi. Alcohol-ethyl, methyl engine
vii. Duel fuel engine
viii. Gasohol
38

39. CLASSFICATION OF IC ENGNES
13.Method of Fuel Input
i. Carbureted
ii. Multi point port fuel injection
iii. Throttle body fuel injection
39

40. First Law Analysis of Engine Cycle
40

41. Reciprocating Engine as an
Open System
41

42. Performance Parameters
Mechanical efficiency
ηm =
𝑏𝑝 (𝑘𝐽/𝑠)
𝑖𝑝(𝑘𝐽/𝑠)
fp = 𝑖𝑝 − 𝑏𝑝
Indicated Thermal efficiency
ηith =
𝑖𝑝 (𝑘𝐽/𝑠)
𝑒𝑛𝑒𝑟𝑔𝑦 𝑖𝑛 𝑓𝑢𝑒𝑙 𝑝𝑒𝑟 𝑠𝑒𝑐𝑜𝑛𝑑(𝑘𝐽/𝑠)
Break Thermal efficiency
ηbth=
𝑏𝑝 (𝑘𝐽/𝑠)
𝑒𝑛𝑒𝑟𝑔𝑦 𝑖𝑛 𝑓𝑢𝑒𝑙 𝑝𝑒𝑟 𝑠𝑒𝑐𝑜𝑛𝑑(𝑘𝐽/𝑠)
42

43. Performance Parameters
 Volumetric Efficiency
ηv =
𝑚 𝑐𝑕𝑎𝑟𝑔𝑒
𝑚 𝑡𝑕𝑒𝑜𝑟𝑖𝑡𝑖𝑐𝑎𝑙
It is affected by
I. Density of fresh charge at intake
II. Pressure and temperature of outgoing
burnt gas
III. Design and exhaust of manifolds
IV. Timing of opening and closing of intake
and exhaust valve
43

44. Performance Parameters
 Relative Efficiency or Efficiency Ratio – Thermal
efficiency of an actual cycle to that of ideal
cycle
ηrel =
𝐴𝑐𝑡𝑢𝑎𝑙 𝑡𝑕𝑒𝑟𝑚𝑎𝑙 𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦
𝐴𝑖𝑟−𝑆𝑡𝑎𝑛𝑑𝑎𝑟𝑑 𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦
 Mean Effective Pressure – Average pressure inside
the cylinder of an internal combustion engine
based on the calculated or measured output
i. Indicated mean effective pressure (imep)
pim =
60000×𝑖𝑝
𝐿𝐴𝑛𝐾
ii. Break mean effective pressure (bmep)
pbm =
60000×𝑏𝑝
𝐿𝐴𝑛𝐾
44

45. Performance Parameters
Mean Piston Speed
sp = 2LN
Specific Power Output – Power output
per unit piston area
Ps = bp/A
= constant ×Pbm ×sp
Specific Fuel Consumption
sfc =
𝐹𝑢𝑒𝑙 𝑐𝑜𝑛𝑠𝑢𝑚𝑝𝑡𝑖𝑜𝑛 𝑝𝑒𝑟 𝑢𝑛𝑖𝑡 𝑡𝑖𝑚𝑒
𝑃𝑜𝑤𝑒𝑟
45

46. Performance Parameters
Inlet – Valve Mach Index
Z =
𝑔𝑎𝑠 𝑒𝑙𝑜𝑐𝑖𝑡𝑦 𝑡𝑕𝑟𝑜𝑢𝑔𝑕 𝑡𝑕𝑒 𝑖𝑛𝑙𝑒𝑡 𝑣𝑎𝑙𝑣𝑒 (𝑢)
𝐼𝑛𝑙𝑒𝑡 𝑠𝑜𝑛𝑖𝑐 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 (α)
u =
𝐴 𝑝
𝑆 𝑝
𝐶𝑖
𝐴𝑖
Ap - Piston area
Sp - Mean piston speed
Ci - inlet valve average flow co-efficient
Ai - intake valve opening area
46

47. Inlet-Valve Mach Index
47

48. Performance Parameters
 Fuel – Air Ratio(F/A) or Air Fuel Ratio (A/F)
i. Stoichiometric fuel-air ratio or chemically
correct – a mixture that contains just enough air
for complete combustion of all the fuel in the
mixture is called a chemically correct or
stoichiometric fuel-air ratio
ii. Equivalence Ratio
Ф =
𝐴𝑐𝑡𝑢𝑎𝑙 𝑓𝑢𝑒𝑙−𝑎𝑖𝑟 𝑟𝑎𝑡𝑖𝑜
𝑆𝑡𝑜𝑖𝑐𝑕𝑖𝑜𝑚𝑒𝑡𝑟𝑖𝑐 𝑓𝑢𝑒𝑙−𝑎𝑖𝑟 𝑟𝑎𝑡𝑖𝑜
Ф = 1 chemically correct
Ф > 1 Rich mixture
Ф< 1 Lean mixture
48

49. Performance Parameters
 Calorific Value or Heating Value or Heat of
Combustion – Thermal Energy released per unit
quantity of the fuel when the fuel is burned
completely and the product of combustion are
cooled back to the initial temperature of the
combustible mixture
i. Higher Calorific Value – when the products are
cooled to 25 0C, practically all the water vapor
resulting from combustion process is condensed.
The heating value so obtained is called higher
calorific value or gross calorific value
ii. Lower Calorific Value or net Calorific Value – Heat
released when water vapor in the products of
combustion is not condensed and remains the
vapor form
49

50. Reversible Process Delvers the most and
Consumes the least Work
50

51. Friction renders a Process
Irreversible
51

52. Totally and Internally reversible
Process
52

53. Irreversible Compression and
Expansion
53

54. Execution of Carnot Cycle in a
Closed System
54

55. P-V Diagram of a Carnot
Cycle
55

56. Questions
 Mean Effective Pressure
 Pumping Losses
 C-tane number
 Ignition lag
 Difference between diesel cycle and Otto cycle
 Variation of specific heats
 Battery ignition system and magneto ignition system
 Effect of dissociation during combustion
 Stratified charge engine
 Expression for Thermal efficiency of Diesel Engine
 Prove eff of otto is more than diesel cycle for same compression ratio
 Qualities of fuel
 Ignition timing
 Variable compression engine
 Chemical equilibrium
 Effect of cut off
 Effect of volatility
 HUCR
 Diff between four and two
 Diff between SI and CI
 Brake, Mechanical, Indicated, Volumetric Efficiency
 Compression Ratio, Cut off Ratio, Expansion Ratio
56