What are the main harmful substances emitted by diesel engines?
3 Answers
The main harmful substances emitted by diesel engines are: nitrogen oxides and particulate matter. The working principle of a diesel engine is: 1. Intake stroke: The crankshaft rotates, the exhaust valve closes and the intake valve opens, the piston moves downward from the top dead center, the cylinder volume increases and the pressure decreases, air is drawn into the cylinder through the intake valve, and the piston moves downward to the bottom dead center; 2. Compression stroke: The crankshaft continues to rotate, forming a closed volume in the cylinder. As the piston moves upward, the pressure and temperature continuously rise; 3. Power stroke: Diesel is atomized and mixed with air through the high-pressure fuel injection pump and injector, forming a combustible mixture, which is injected into the cylinder with high-pressure and high-temperature gas, and combustion releases heat; 4. Exhaust stroke: The rotating crankshaft drives the connecting rod piston to move from the bottom dead center to the top dead center, and under the push of the piston, the exhaust gas is discharged from the exhaust valve.
Diesel engines emit a significant amount of harmful substances when running, with nitrogen oxides being a major component. These can irritate the respiratory tract and contribute to smog formation. There are also those black, sooty particles containing carbon soot and polycyclic aromatic hydrocarbons, which are harmful if inhaled. Additionally, diesel fuel contains sulfur, which turns into sulfur dioxide after combustion—that pungent smell is its doing. Although diesel engines emit less carbon monoxide, excessive accumulation can still cause dizziness and poisoning. Modern vehicles now use urea systems and particulate filters to reduce these emissions. Older vehicles emitting thick black smoke are a clear sign of excessive particulate matter, so it's best to check the exhaust treatment system before hitting the road.
From an environmental perspective, each harmful substance emitted by diesel engines poses different hazards. Nitrogen oxides degrade air quality and harm trees and plants. The ultrafine particles in particulate matter can penetrate lung alveoli, and long-term inhalation may easily trigger asthma. The polycyclic aromatic hydrocarbons emitted by diesel vehicles are highly carcinogenic, and these components are also found in barbecue smoke. Acid rain produced by burning sulfur-containing diesel is most damaging to buildings, as stone carvings and metals cannot withstand the corrosion. Fortunately, the sulfur content in diesel sold at gas stations is now controlled below ten milligrams, so using high-quality fuel is the first step toward environmental protection. Regularly cleaning the fuel system and replacing filters can help the engine burn cleaner, naturally reducing emissions.
