1. Hydrocarbon (HC) Emissions:
- Unburned Hydrocarbons (UHC): These are hydrocarbons that escape the combustion chamber without being burned. They are produced due to incomplete combustion and fuel evaporation.
- Partially Burned Hydrocarbons (PBHC): These are partially combusted hydrocarbons that include aromatic hydrocarbons, aldehydes, and ketones. They are formed due to insufficient air-fuel mixture or improper combustion conditions.
2. Carbon Monoxide (CO) Emissions:
Carbon monoxide is produced when there is insufficient oxygen during the combustion process. It occurs when the air-fuel mixture is too rich, leading to incomplete combustion.
3. Nitrogen Oxides (NOx) Emissions:
- Nitric Oxide (NO): Nitric oxide is formed when nitrogen in the air reacts with oxygen at high temperatures during the combustion process.
- Nitrogen Dioxide (NO2): Nitrogen dioxide is a secondary pollutant that is formed from the oxidation of nitric oxide in the atmosphere.
4. Particulate Matter (PM) Emissions:
Particulate matter consists of solid particles such as soot, ash, and metal particles that are emitted from the engine. They are produced during the combustion process and can be either directly emitted from the engine or formed by the condensation of unburned hydrocarbons and other gases.
5. Sulfur Oxides (SOx) Emissions:
Sulfur oxides are produced when sulfur-containing compounds, such as sulfur in the fuel, are oxidized during the combustion process. The primary pollutant in this category is sulfur dioxide (SO2).
The formation of pollutants in an internal combustion engine is influenced by several factors, including the engine design, fuel composition, air-fuel ratio, combustion temperature, and engine operating conditions. Optimizing these factors can help reduce pollutant emissions and improve the environmental impact of internal combustion engines.
