Emission Gases from Compression Ignition(CI) engine

Automobiles are an integral part of society. Human depended too much on it. As the population of India is increasing the number of automobiles also increases on the road. The more the vehicle on the road more would be the bad environment due to the dangerous gases like NO_x, CO₂, CO, HC, smoke, and PM.

Road Traffic 

The complete combustion of diesel in the combustion chamber emits only CO₂ and H₂O. But due to the some of the reasons (air-fuel ratio, fuel turbulence, combustion temperature, ignition timing, etc.) ideal combustion did not take place and emits dangerous gases like , CO₂, CO, HC, smoke, and PM (particulate matter). These gases are listed below.

Harmful Emission from Automobiles

1. Oxides of Nitrogen (NOx)

Oxides of nitrogen mostly created from the nitrogen in the air. The highest quantity of the NO_x is produced by the diesel engine. CI engine emits all three types of the oxides of nitrogen-N₂O (nitrous oxides), NO (Nitric oxides), and NO₂ (Nitrogen Oxides). All three gases are not suitable for a clean environment because they initiate the ozone depletion, acid rain, eye’s problem other harmful things.  High temperature and high pressure produce high nitrogen oxides by the diesel engine. Burning of plant material also leads to the higher oxides of the nitrogen from the engine. SCR (Selective Catalytic Reduction) and SNCR (Selective Non-Catalytic Reduction) method are used to remove the NO_x from the exhaust gases. The quantity of NO_x reduction can be done by the EGR (Exhaust gas recirculation) or by decreasing the combustion temperature.  One of the methods to reduce the NO_x from the diesel engine is fuel additives.

2. Carbon dioxides (CO₂)

CO₂ gas is responsible for the greenhouse effect and global warming. It does not directly affect the human being. Quantity of CO₂ is the deciding factor of the health of the earth. Fuel economy is one of the methods for reducing carbon dioxide. Efficiency comes into the frame with the fuel economy. By enhancing the efficiency of the engine we can reduce the quantity of the CO₂.

3. Carbon mono oxides (CO)

It is a colorless and toxic gas. Carbon mono oxides generated because of the incomplete combustion in the engine. High equivalence ratio with the richness of the air-fuel mixture, the carbon mono oxides are increases. CI engine emits less CO compare to the SI engine because of the lean air-fuel ratio. At the starting of the CI engine, high CO generated due to the rich mixture required for starting the engine. The amounts of CO in the human body stop the supply of oxygen to the lung. A catalytic converter is a good method for reducing carbon mono oxides from the exhaust gases. Another method of minimizing the CO is fuel additives.

4.  Hydrocarbon (HC)

Not burnt fuel particle and incomplete combustion cause to emit high hydrocarbon from the diesel engine. The low temperature was found near to the cylinder wall that causes a high-temperature zone at the center of the cylinder. Hydrocarbon emission is also caused by the leakage past the exhaust valve. Hydrocarbon is a big family of alkalis, alkaline, and aromatic. Usually, the hydrocarbons are generated at the low load condition on the engine. Quantities of the HC from the engine depending upon the type of fuel, engine design. Besides that irregular operating condition causes the high HC. Hydrocarbon is toxic and promotes dangerous diseases like cancer and irritation. The catalytic converter, fuel additive, and electronic fuel injection system have the capability to reduce the HC from exhaust gases.

5.  Smoke (soot) and Particulate Matter

Smoke is the solid and liquid particles of the exhaust gases. Excessively black smoke indicates the solid or carbon particle (soot) of the exhaust gases. White smoke emitted because of the presence of vaporized water and not burnt fuel particles. Blue smoke is generated due to the higher concentration of not burnt fuel particles.

Particulate Matter (PM) is the second-highest gas emission from the CI Engine. PM can be defined as “any matter other than water from the diesel engine exhaust”.