Internal Combustion Engine: Emissions and Emission Control

Cars, trucks, buses, and off-road vehicles are all considered mobile sources of air pollution.

Carbon monoxide, nitrogen oxides, and hydrocarbons are released when fuel burns in an internal combustion engine. They may also be released when vehicle tailpipes emit air and fuel residuals. Gasoline vapors also escape into the atmosphere during refueling and when fuel vaporizes from engines and fuel systems caused by vehicle operation or hot weather.

The pollutants in engine emissions from vehicles and lawn equipment cause damage to lung tissue and can lead to and aggravate respiratory diseases, such as asthma. Motor vehicle pollution also contributes to the formation of acid rain. The pollution also emits greenhouse gases that cause climate change.

Diesel engines are durable and efficient. However, because they consume diesel fuel, a complicated mix of petroleum components, they produce some pollutants. A small amount of the fuel exits the engine unburned. These airborne hydrocarbons can form larger particles in the atmosphere when they contact airborne dust and other particles.

Unlike gasoline engines, which may not get enough air into the cylinder for combustion, diesel engines operate with excess air. Hence, emissions of carbon monoxide are very low, though still measurable. Carbon monoxide is a colorless, odorless gas that combines with blood and limits its ability to transport oxygen. Since the engines consume fuel and air and create heat in the combustion process, nitrogen from the air can be transformed into nitrogen oxides, reddish-brown gases that irritate the lungs and eyes.

Pollutants emitted directly from vehicles are not the only cause for concern. On warm, sunny days, hydrocarbons react with oxides of nitrogen to create a secondary pollutant, ozone. In many urban areas, motor vehicles are the single most significant contributor to ground-level ozone which is a common component of smog.

Course Outline

Air Pollution due to IC Engine

Euro Norms / European Emission Standards of IC Engine Emissions

Classification of Engine Emissions (Exhaust and Non-Exhaust Emissions)

Causes of Hydrocarbon Emission

• Incomplete Combustion
• Crevice Volumes and Flow in Crevices
• Leakage past the Exhaust Valves
• Valve Overlap
• Deposits on Walls
• Oil on Combustion Chamber Walls

Type of Engine Emissions

1. Hydrocarbon  Emissions from SI and CI Engine
2. Carbon Monoxide (CO) Emissions
3. Oxides of Nitrogen (NOx) Emissions
4. Photochemical Smog
5. Particulates Emission
6. Aldehydes and Lead Emission
7. Oxides of Sulfur (SOx) Emissions

How to Control IC Engine Emissions by following ways.

Modification in Engine Design & Operating Parameters

1. Combustion Chamber Configuration
2. Lower Compression Ratio
3. Modified Induction System
4. Ignition Timing
5. Reduced Valve Overlap

Emissions Control by Exhaust Gas Oxidation

1. Thermal Converters
2. Catalytic Converters
3. Exhaust Manifold Reactor
4. Exhaust Gas Recirculation
5. Particulate Traps
6. Crankcase Blowby

Emission Control by Modification of Fuels