List four types of combustion chambers used in S.I. engine. Explain any one in detail with neat sketch.

List four types of combustion chambers used in S.I. engine. Explain any one in detail with neat sketch.
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1 Answer

Answer :

Combustion chambers used in S.I. engine:-

1) T - Head

2) I - Head.

3) F - Head.

4) L – Head

5) Divided combustion chamber.


1. T Head Type Combustion chambers. 
This was first introduced by Ford Motor Corporation in 1908. This design has following disadvantages. 1. Requires two cam shafts (for actuating the in-let valve and exhaust valve separately) by two cams mounted on the two cam shafts. 2. Very prone to detonation. There was violent detonation even at a compression ratio of 4. This is because the average octane number in 1908 was about 40 -50.
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2. I head combustion chamber 
This type of combustion chamber has both the inlet valve and the exhaust valve located in the cylinder head. An overhead engine is superior to side valve engine at high compression ratios. The overhead valve engine is superior to side valve or L-head engine at high compression ratios, for the following reasons: 1. Higher volumetric efficiency from larger valves or valve lifts. 2. Less distance for the flame to travel and therefore greater freedom from knock. 3. Lower surface-volume ratio and, therefore, less heat loss and less air pollution.
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3. F - Head 
In F-head combustion chamber one valve is in head and other in the block. This design is a compromise between L-head and I head combustion chambers.
Advantages are :
High volumetric efficiency.
Maximum compression ratio for fuel of given octane rating.
High thermal efficiency.
It can operate on leaner air-fuel ratios without misfiring.
Drawback This design is the complex mechanism for operation of valves and expensive special shaped piston.
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4. L Head Type Combustion chambers
It is a modification of the T-head type of combustion chamber. It provides the two valves on the same side of the cylinder, and the valves are operated by a single camshaft.
Advantages:
1. Valve mechanism is simple and easy to lubricate.
2. Detachable head easy to remove for cleaning and decarburizing without disturbing either the valve gear or main pipe work.
3. Valves of larger sizes can be provided.
Disadvantages:
1. Lack of turbulence as the air had to take two right angle turns to enter the cylinder and in doing so much initial velocity is lost.
2. Extremely prone to detonation due to large flame length and slow combustion due to lack of turbulence.
3. More surface-to-volume ratio and therefore more heat loss.
4. Valve size restricted.
6. Thermal failure in cylinder block also. 
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