What is a Combustion Chamber?

A combustion chamber is an enclosed space within an internal combustion engine in which a mixture of fuel and air is burned. When fuel is burned, a gas is released that increases the mixture temperature and volume. When you heat the gas, the atoms in the gas bounce off each other, giving it more energy and vitality. The violent impact caused them to continue racing and expand the entire cloud of gas.

Some engines prevent the gas from expanding while warming up by limiting the gas to a certain amount. The pressure rises because the gas cannot expand. Other engines are designed to use the increased pressure to expel exhaust gases at high speeds. Engine designs differ in order to increase the volume, pressure, or speed of the gas mixture to do work.

The combustion chambers are most widely used in the petrol engines, diesel engine, Wankel engines and many other engines. 

Types of Combustion Chambers

1) Hemispherical combustion Chamber 

The hemispherical combustion chamber has a domed cylinder head so that when the piston is at the highest point in the cylinder the space between the piston top and the cylinder head is hemispherical.

The intake and exhaust valves are on the opposite side of the dome and the spark plugs are on top of the cylinder head. This arrangement minimizes heat loss and creates an efficient air flow. In addition, the valve position allows for larger intake and exhaust valves than usual, increasing the maximum engine output at high speeds.

Despite the added power, the hemispherical combustion chamber has two main disadvantages. First, it burns fuel at an abnormally high temperature and releases a large amount of nitrogen oxide gas. Therefore, manufacturers of engines with hemispherical combustion chambers must also take additional measures to clean exhaust gases. Second, hemispherical cylinder heads are heavy and expensive to manufacture, adding to the weight and cost of the vehicle.

2. Pentroof

The sloping roof combustion chamber resembles a hemispherical combustion chamber, but the sloping roof design includes four smaller valves (two inlets and two outlets) instead of the two large valves in the hemispherical version. The inlet and outlet valves are located opposite each other in the cylinder head and are V-shaped.

The spark plug sits in the middle of the top of the cylinder head, i.e. exactly in the middle of the four valves. This enables faster combustion and lower temperatures, thereby reducing emissions. The concave combustion chamber is also smaller than the hemispherical combustion chamber, has a smaller surface area, and further reduces heat loss, resulting in higher fuel consumption.

3. Wedge

Wedge-shaped combustion chambers have been used by automobile manufacturers for decades and continue to enjoy great popularity. The upper interior of the cylinder head is an inclined basin, and the inlet and outlet valves are at a fixed angle, so that the gap between the piston and cylinder head is wedge-shaped in the upper middle position. I can see.

This construction pushes the air / fuel mixture down with great force during the compression stroke, which leads to the accumulation of kinetic energy and increases the power released when the air / fuel mixture is ignited.

The efficiency and performance of the wedge-shaped combustion chamber is not as good as that of the hemispherical or concave design. However, this is a reliable and proven solution that is still used by many automobile manufacturers.

4. Bathtub/Heart

The old pan-shaped combustors of the 1950s have been replaced with more efficient oval or heart-shaped combustors, but the basic principle is the same. The top inside the cylinder head is shaped like an inverted bathtub, the inlet valve and exhaust valve are placed side by side in the center of the top, and the spark plug is placed on one side.

The incline of the combustion chamber wall is gentler than the wedge-shaped combustion chamber, so less explosive energy is emitted when ignited, but this design makes the pan / EKG combustion chamber more effective than the wedge-shaped combustion chamber. However, the arrangement of the inlet and outlet valves next to one another causes a large amount of heat loss.

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