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Combustion Chambers
Important functions of CI combustion chamber
1. To provide proper mixing of fuel and air in a short time
2. The fuel injector should have multi hole orifices
3. It should provide high air swirl
4. required Turbulence chamber shape
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Classification of CI engine Combustion Chamber
Direct Injection (Also called as open combustion chamber):
Entire volume of the combustion chamber is located in the main
cylinder and the fuel is injected into this volume
Indirect Injection
Combustion space is divided into two parts, further divided
into
Swirl chamber, Pre-combustion chamber and Air cell chamber
Combustion Chambers
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Combustion Chamber
Direct Injection Chambers 1. Hemispherical combustion
Chamber(HCC)
2. Cylindrical combustion Chamber(CCC)
3. Shallow Depth combustion chamber(SCC):
4. Toroidal combustion Chamber(TCC)
Hemispherical combustion Chamber
Gives small squish, but depth to diameter ratio for a
cylindrical chamber can be varied to give any desired squish to
give better performance
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Cylindrical Chamber The cylindrical chamber is modified in the
form of truncated
cone with base angle of 30 degree
The swirl is produced by masking the valve for nearly 180 degree
of circumference
Squish can also be varied by varying the depth
Shallow Depth: Depth of the cavity in the piston is quite
small
Adopted in large engines running at low speeds
The cavity diameter is very large, the squish
is negligible
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Combustion Chamber
Toroidal Chamber Provides powerful squish along with air
movement
Mask needed in the inlet valve is small due to powerful
squish
Better utilisation of oxygen
Cone angle of spray for this chamber is 150 160 degree
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Combustion Chamber
Direct Injection Chambers
Types Advantages
Shallow Depth Minimum Heat loss
Hemispherical Better efficiency
Cylindrical No cold starting problems
Toroidal Fine atomization
Drawbacks
High fuel injection pressure required and hence complex design
of fuel injection pump
Necessity of accurate metering of fuel by the injection system,
particularly for small engines
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Indirect Injection Chambers
Creates considerable pressure difference between the two divided
space during combustion process.
Swirl Chamber
Pre-combustion chamber
Air cell Chamber
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Comparison of DI and IDI
