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Combustion in I.C Engines
February 22, 2014 Slide1
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February 22, 2014 Slide2
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February 22, 2014 Slide3
For all calculation : O2= 21% ; N2= 79% and ratio of N2/O2is 3.76Average molecular mass of air is 28.967 or 29 kg/kmol.
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February 22, 2014 Slide4
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Swirl :
The orderly motion of the air particularly almost parallel to theaxis of the engine.
Very much required for diesel engines.
Squish/Squash :
The radial inward motion of the air-fuel mixture towards
(squish) and away from the axis of the engine (squash).
Very much required for the gasoline engines.
Turbulence :
Random mixing of the burned and unburned gases
very much required for both Otto and Diesel engines.
February 22, 2014 Slide5
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February 22, 2014 Slide6
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February 22, 2014 Slide7
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Normal Combustionin SI Engines
February 22, 2014 Slide8
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February 22, 2014 Slide9
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February 22, 2014 Slide10
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February 22, 2014 Slide11
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February 22, 2014 Slide 12
Flames detected
between
Type of cycle
- 450and TDC early burn cycle
TDC and 45 Fast burning cycles
450and 900 slow burn cycles
90and BDC Late burn cycles
BDC and TDC delayed burn cycles
Flames not detected misfires and partial burncycles
Good combustion is almost entirely made up of fast burn cycles.
poor combustion consists of a high proportion of late and
delayed burn cycles.
COMBUSTION QUALITY
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EFFECT OF ENGINE VARIABLES
ON IGNITION LAG
1. Fuel
2. Mixture ratio:
February 22, 2014 Slide13
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February 22, 2014 Slide14
3. Initial temperature and pressure
4. Electrode gap :
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5. Turbulence:
February 22, 2014 Slide15
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EFFECT OF ENGINE VARIABLES ON FLAME PROPAGATION
1. Fuel-air ratio :
February 22, 2014 Slide16
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February 22, 2014 Slide17
Rate of Burning
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February 22, 2014 Slide18
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2. Compression Ratio
February 22, 2014 Slide19
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February 22, 2014 Slide20
3. Intake temperature and pressure
4. Engine load
5. Turbulence
6. Engine Speed
7. Engine size
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February 22, 2014 Slide21
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Combustion Chambers
forFour Stroke SI Engines
February 22, 2014 Slide22
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February 22, 2014 Slide23
Early Ricardo turbulent combustion chamber (1968)
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February 22, 2014 Slide24
Old type Combustion Chambers for SI engines
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February 22, 2014 Slide25
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Slide26
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February 22, 2014 Slide27
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February 22, 2014 Slide28
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February 22, 2014 I.C. Engines Slide29
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February 22, 2014 I.C. Engines Slide31
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February 22, 2014 I.C. Engines Laboratory Slide32
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Abnormal Combustionin SI Engines
February 22, 2014 I.C. Engines Slide33
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February 22, 2014 I.C. Engines Slide34
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February 22, 2014 I.C. Engines Slide35
K k Li it d P t
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Knock Limited Compression Ratio
Knock Limited Inlet Pressure
Knock Limited Indicated Mean Effective Pressure
Relative performance number, rpn :
February 22, 2014 I.C. Engines Slide 36
Knock Limited Parameters
C O G S O OC
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Density factors
Time factors
Composition factors
February 22, 2014 I.C. Engines Slide37
EFFECT OF ENGINE VARIABLES ON KNOCK
D it F t
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February 22, 2014 I.C. Engines Slide38
Compression Ratio
Mass of Inducted Charge
Inlet Temperature of the Mixture
Temperature of the Combustion Chamber Walls
Retarding the Spark Timing
Power Output of the Engine
Density Factors:
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February 22, 2014 I.C. Engines Slide39
Turbulence
Engine Speed
Flame Travel Distance
Engine Size
Combustion Chamber Shape
Location of Spark Plug
Time Factors:
C iti F t
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Fuel-Air Ratio:
February 22, 2014 I.C. Engines Slide40
Octane Value of the Fuel:
Composition Factors:
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KNOCK RATING OF SI FUELS
February 22, 2014 I.C. Engine Slide42
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Normal Combustion
in CI Engines
February 22, 2014 I.C. Engines Slide43
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February 22, 2014 I.C. Engines Slide44
Schematic representation of a fuel jet
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February 22, 2014 I.C. Engines Slide45
Schematic representation of a fuel jet
Disintegration of a fuel jet
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February 22, 2014 I.C. Engines Slide46
Disintegration of a fuel jet
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February 22, 2014 I.C. Engines Slide47
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February 22, 2014 I.C. Engines Slide48
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Stages of combustion in CI engines
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Stages of combustion in CI engines
February 22, 2014 I.C. Engines Slide50
P-t diagram showing delay period
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P-t diagram showing delay period
February 22, 2014 I.C. Engines Slide51
Steps of combustion process in CI engine
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Steps of combustion process in CI engine
February 22, 2014 I.C. Engines Slide52
Combustion Rate (CI)
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Combustion Rate (CI)
February 22, 2014 I.C. Engines Slide53
Effect of varying the amount of fuel
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February 22, 2014 I.C. Engines Slide54
injected on P-diagram
FACTORS AFFECTING THE DELAY PERIOD
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Compression ratio
Engine speed
Power output
Atomization of fuel and duration of injection
Injection timing
Quality of the fuel Intake temperature
Intake pressure
February 22, 2014 I.C. Engines Slide55
FACTORS AFFECTING THE DELAY PERIOD
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Effect of compression ratio on maximum air temperature and
minimum autoignition temperature
February 22, 2014 I.C. Engines Slide56
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Effect of speed on ignition delay in a diesel engine
February 22, 2014 I.C. Engines Slide57
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Effect of injection timing on indicator diagram
February 22, 2014 I.C. Engines Slide58
Effect of engine variables on ignition delay
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February 22, 2014 I.C. Engines Slide59
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Abnormal Combustion
in CI Engines
February 22, 2014 I.C. Engines Slide60
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February 22, 2014 I.C. Engines Slide62
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February 22, 2014 I.C. Engines Slide63
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February 22, 2014 I.C. Engines Slide65
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Combustion Chambers for
Four Stroke CI Engines
February 22, 2014 I.C. Engines Slide66
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CI Engine Combustion chambers
Open chamber or DI engine
Divided chamber or IDI engine
February 22, 2014 I.C. Engine Slide67
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February 22, 2014 I.C. Engines Slide68
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February 22, 2014 I.C. Engines Slide69
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Phases of Combustion in Toroidal
open combustion chamber
February 22, 2014 I.C. Engines Slide70
M Combustion chamber
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M-Combustion chamber
February 22, 2014 I.C. Engines Slide71
IDI Combustion chambers
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IDI Combustion chambers
Swirl generation: Induction induced swirl
Compression induced swirl
Combustion induced swirl
February 22, 2014 I.C. Engines Slide72
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February 22, 2014 I.C. Engines Slide73
Combustion in Ricardo swirl Chamber - Comet
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February 22, 2014 I.C. Engines Slide74
Swirl chambers
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February 22, 2014 I.C. Engines Slide75
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Pre-combustion chambers
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February 22, 2014 I.C. Engines Slide77
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February 22, 2014 I.C. Engines Slide78
Mercedes Benz
Pre-combustion System
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February 22, 2014 I.C. Engines Slide79
Advantages of DI engines
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Advantages of DI engines
Fuels of poorer ignition quality can be used.
Single-hole injection nozzles and moderateinjection pressures can be used and cantolerate greater degrees of nozzle fouling.
Higher fuel-air ratios can be used withoutsmoke.
February 22, 2014 I.C. Engines Slide80
Disadvantages of IDI Engines
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Disadvantages of IDI Engines
More expensive cylinder construction.
More difficult cold starting because of
greater heat loss through the throat.
Poorer fuel economy due to greater heat
losses and pressure losses through the
throat, which result in lower thermal
efficiency and higher pumping loss.
February 22, 2014 I.C. Engines Slide81
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Knock Rating of CI Engine Fuel
Cetane number
Variable compression ratio engine
February 22, 2014 I.C. Engines Slide82
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THE END
