The design of a combustion chamber for a spark Ignition Engine involves the shape of the combustion chamber, location of the spark plug and the location of the inlet valve and exhaust valve. Due to this design, the combustion chamber has a great influence on engine performance. In this article, we are going to discuss the Different types of combustion chambers for SI Engines.
The main objectives and importance of the combustion chamber is to provide the following objectives.
- Smooth Engine operation
- High power output and thermal efficiency
Smooth engine operation can be achieved by reducing the possibility of knocking in the engine. This can be done by the locate the spark plug at the correct position, proper Cooling of the spark plug and the exhaust valves area.
High power output and thermal efficiency can be achieved by creating a high degree of turbulence and sucking more amount of charge to attain high volumetric efficiency, improved antiknock characteristics, compact design. all these can be achieved by a suitable combustion chamber for the engine. There are different types of combustion chambers for SI engines. Let’s discuss them in detail.
Different types of combustion chambers for SI Engines
- T-Head type
- L-Head type
- I-Head type
- F-Head type
Check out the T-Head type of the combustion chamber for the spark ignition engines. As you can see there will be two valves on each side and a spark plug from the top side. This type of combustion chambers was used in the early stages of the engine’s development. In this type of combustion chamber, the knocking tendency is more because of the distance across the combustion chamber is long. There is need of two cam shafts for the two valves. which is another disadvantage.
As you can see one of the disadvantages in the T-head type is having two valves on either side which needs two camshafts to operate them. Bringing these inlet and exhaust valves to the same side will solve this problem. In this L-Head type combustion chamber, you can see both inlet and the exhaust valve will be on the same side operated by the same camshaft.
Check out the above L-Head type(Left side) combustion chamber. L-Head type combustion chamber the charge need to take a right angle turn to enter into the combustion chamber. This cause the loss of velocity and low turbulence results in the slow combustion process. To avoid this we have Ricardo’s turbulent head design for the L-Head combustion chamber(Right side picture). The head design will be helpful to create the turbulence for the charge to keep the velocity for improving the combustion process.
Also, the spark plug is placed at the centre of the combustion chamber, the flame travel length is reduced. The knocking is also reduced with this head design.
This I-Head type combustion chamber is also called as the overhead valve combustion chamber. As you can see the inlet and the exhaust valves are located on the top of the cylinder head.
The main advantage of this combustion chamber is that it can achieve high compression ratios, and also less tendency to the knock. High volumetric efficiency. We can avoid the thermal failures by keeping the hot exhaust valve in the head instead of the cylinder.
F-Head type combustion chamber is an inspired design from the L-head type and the I-Head type combustion chambers. As you can see the F-Head type combustion chamber in the above diagram, One exhaust valve is in the cylinder head, the inlet valve in the side, and the spark plug is in the cylinder head. Again this has the same disadvantage as the T-Head type combustion chamber as the two valves need to be operated by two different camshafts.
These are the different types of combustion chambers for the SI engines
We have discussed the different types of combustion chambers for the SI engines. In the next article, we have discussed the different types of combustion chambers for the CI engines. If you have any further thoughts on this topic, let us know in the comment section below.