1. Intake Stroke:
* Air is drawn into the cylinder through the intake valve.
* This air is mixed with a precise amount of fuel (petrol) injected by the fuel injectors.
2. Compression Stroke:
* The piston moves upward, compressing the air-fuel mixture.
* This compression increases the temperature and pressure of the mixture.
3. Combustion:
* A spark plug ignites the compressed air-fuel mixture.
* The rapid burning of the fuel creates a controlled explosion, pushing the piston downward.
* This force is the power that turns the crankshaft, which ultimately drives the wheels.
4. Exhaust Stroke:
* The piston moves upward again, pushing the burned exhaust gases out of the cylinder through the exhaust valve.
The Chemistry of Combustion:
* Fuel: Petrol is a complex mixture of hydrocarbons (molecules made of hydrogen and carbon).
* Oxygen: The air drawn into the engine provides the oxygen necessary for the combustion reaction.
* Burning: The spark plug provides the energy needed to start the chemical reaction, which is essentially the rapid combining of hydrocarbons with oxygen.
* Products: The combustion process creates:
* Carbon Dioxide (CO2): A major greenhouse gas.
* Water (H2O): A by-product of the reaction.
* Other Gases: Small amounts of nitrogen oxides (NOx), unburned hydrocarbons, and other pollutants.
Key Concepts:
* Engine Timing: The precise timing of the intake, compression, combustion, and exhaust strokes is crucial for efficient engine operation.
* Air-Fuel Ratio: The correct balance of air and fuel is essential for optimal combustion and power.
* Emissions Control: Modern cars have exhaust systems and catalytic converters to reduce harmful emissions.
Important Notes:
* This is a simplified explanation. Real engine processes are much more complex.
* The quality of the fuel and engine design play a significant role in the efficiency and emissions of the combustion process.
Let me know if you have any other questions about car engines or combustion!
