Table of Contents

What is Car Emissions – Car Emission Pollutants

ENGINE EMISSION

Emission control is a term frequently used in day-to-day life among automobile and other manufacturing industries throughout the world. The awareness among the public about climate change and greenhouse effect due to environmental pollution, over the last century has made the government and industrial corporate throughout the world, highly conscious about the control of emissions from their products.

Presently, automobile engine emissions are one of the main elements which play a major role in environmental pollution. Day-by-day the number of vehicles increases which leads to increase the emission of pollutants from vehicles.

I.C. engines convert heat energy into mechanical energy by burning fuel in its combustion chamber called cylinder. Mostly, petrol and diesel oil are used as fuels for I.C. engines. These fuels contain hydrogen and carbon in various combinations. During combustion, oxygen combines with hydrogen and carbon to form water (H20), carbon monoxide (CO) and carbon dioxide (C02). The fuel of the nitrogen in air combines with oxygen forming nitrogen oxide (N02). Remaining fuel goes unburnt by resulting smoke and ash. Mainly incomplete combustion offuels in automobile emits polluted engine exhaust. Exhaust gas constituents consist of partly burnt petrol, carbon monoxide, nitrogen oxides and if sulphur in petrol and sulphur oxides pollute the air. The oxides of nitrogen together with hydrocarbons react in the presence of sunlight and they form petrochemical smog. As a result, smog is created, the atmosphere becomes dirty and breathing becomes difficult. Its bad effect includes crop damage, eye irritation, objectionable odour, decrease of visibility, cracking in rubber etc.

Smog is a kind of fog mixed with other substances. The smog covers the cities like a blanket for days together during winter. The heat generated in large cities tends to circulate air within a dome-like shape. Smog with smoke is the most visible evidence of air pollution.
Some of the atmospheric pollutants are not visible until mixed with moisture. Unburnt petrol, carbon monoxide, leaded compounds from leaded petrol and other gases which pollute the air may not be seen. All these pollutants are deadly harmful for men, animals and food crops.

Automobile Engine Pollutants

Pollutants are produced by the incomplete combustion of the air-fuel mixture in the combustion chamber of the automobile engines. The following pollutants are emitted from the exhaust of the automobile engine.

1) Carbon monoxide (CO):
CO is mostly produced under rich air fuel mixture due to the lack of sufficient oxygen for the combustion of the fuel. CO has more affinity than oxygen for hemoglobin in our blood. It reduces the ability of hemoglobin to carry O2 to body tissues. Hence, it will affect the nervous system and vision if the percentage of CO is more. Finally, it affects heart.

2) Carbon Dioxide (CO2):
During complete combustion, the hydrocarbons in the fuel are converted into carbon dioxide which is 13.7% of exhaust gas. The amount of carbon dioxide in the exhaust gas is directly proportional to the fuel consumption.

3) Oxides of nitrogen (NOx):
NOx is produced from secondary reactions which occur in all combustion processes where air containing nitrogen is burned. In high temperatures, nitrogen reacts with oxygen and produces nitric oxide (NO) and nitrogen dioxide (N02)’ They affect living organisms. They affect the blood purification system. It may be mixed with moisture. It may also produce dilute nitric acid in the heart and affect the heart.

4) Hydrocarbons:
Hydrocarbon (HC) emissions are also the result of inadequate amount of oxygen being present to support the complete combustion of the air fuel mixture. Hydrocarbon produces smog. It affects the vision of human being. Smog is the mixture of fog and smoke.

5) Water:
The chemical reaction which occurs between hydro carbons based on fuel and air from the atmosphere causes water to be produced as one of the products. Water constitutes 13.1% of exhaust gas from an IC engine.

6) Photo chemical smog:
Some hydrocarbons and oxides of nitrogen in exhaust react with atmospherics in the presence of sunlight and produce photo chemical smog. It damages the plant’s life. It reduces the visibility. It produces eye irritation and affects the respiratory system of human beings.

7) Smoke:
Smoke is produced because of insufficient mixing of fuel and air. It contains CO and CO2. When cold starting, blue white smoke is produced when more carbon particles are mixed with exhaust. Smog is produced by smoke. It causes irritation of eyes, coughing, headache and vomiting.

8) Lead:
Lead is poisonous. It is a toxic air pollutant. It is produced from the combustion of gasoline. It affects liver and kidneys. It causes mental effects to children.

9) Particulate:
Particulates are minute separate particles found in the air. They may be solid or liquid particles. The dust soot and fly ash are included in it. It causes respiratory diseases such as bronchitis and lung cancer and allergic diseases.

10) Sulphur oxide:
Sulphur oxide is produced if the fuel has sulphur. It may damage the plants. It causes irritation to eye and throat and it gives respiratory troubles to children. It corrodes materials.