Spark Ignition Engine

A spark ignition engine, also known as a gasoline engine or petrol engine, is a type of internal combustion engine that uses a spark plug to ignite a mixture of air and fuel within a combustion chamber. This ignition process generates the power necessary to propel vehicles, machinery, and other mechanical devices.

In a spark ignition engine, the air-fuel mixture is typically composed of gasoline or a gasoline-ethanol blend, although alternative fuels such as compressed natural gas (CNG) or liquefied petroleum gas (LPG) can also be used. The air-fuel mixture is drawn into the combustion chamber through an intake valve during the engine's intake stroke. Once inside the combustion chamber, the mixture is compressed by the upward movement of the piston during the compression stroke.

At the top of the compression stroke, the spark plug emits a high-voltage electrical spark, which ignites the compressed air-fuel mixture. This ignition causes a rapid expansion of gases within the combustion chamber, driving the piston downward during the power stroke. The resulting mechanical energy is transferred to the crankshaft, which converts it into rotational motion to drive the vehicle or machinery.

Spark ignition engines are widely used in automobiles, motorcycles, lawnmowers, chainsaws, and many other applications due to their relatively simple design, high power-to-weight ratio, and ease of fuel availability. However, they typically have lower thermal efficiency compared to diesel engines and are more susceptible to knocking, especially under high loads and low speeds.