What are the main components of diesel engine emissions?

The emissions of diesel engines mainly include the following components:

Particulate matter (PM): mainly composed of soot, organic matter, sulfates, etc. Carbon soot is a product of incomplete combustion of diesel, appearing black or dark gray. Organic matter refers to unburned or partially burned fuel and lubricating oil components. Sulfate is the sulfuric acid or sulfate particles generated by the reaction of sulfur in fuel with oxygen, water vapor, etc. after combustion. Particulate matter can cause serious harm to air quality and human health, such as leading to haze weather, and entering the human respiratory system can cause respiratory diseases, cardiovascular diseases, etc.

Nitrogen oxides (NOx): generally refers to nitric oxide (NO) and nitrogen dioxide (NO ₂). During the high-temperature combustion process of diesel engines, nitrogen and oxygen in the air react to produce NOx. NO is a colorless and odorless gas that rapidly reacts with oxygen in the atmosphere to produce NO ₂. NO ₂ is a reddish brown gas with a pungent odor that can cause damage to the human respiratory system and is also one of the main causes of acid rain and photochemical smog.

Carbon monoxide (CO): It is a product of incomplete combustion of diesel fuel. When the air and fuel in the engine are not mixed properly or the combustion conditions are poor, a large amount of CO will be produced. CO is a colorless and odorless toxic gas that can bind with hemoglobin in human blood, reducing the oxygen transport capacity of the blood and causing hypoxia, which can be life-threatening in severe cases.

Hydrocarbons (HC): including unburned fuel, lubricating oil, and their cracking and oxidation products. Some of these hydrocarbons are volatile and can form photochemical smog, posing a threat to the environment and human health. Some hydrocarbons also have toxicity and carcinogenicity.

Sulfur dioxide (SO ₂): mainly derived from the sulfur element in diesel. During diesel combustion, sulfur reacts with oxygen to produce SO ₂. SO ₂ is a gas with a pungent odor that can cause damage to the human respiratory system and is also one of the main causes of acid rain formation. It can cause serious corrosion and damage to soil, water bodies, buildings, etc.

With the increasingly strict environmental requirements, the emission control technology of diesel engines is also constantly developing, such as adopting advanced fuel injection systems, exhaust gas recirculation (EGR) technology, selective catalytic reduction (SCR) technology, particulate filters (DPF), etc., to reduce the content of various emissions and minimize environmental pollution.