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Basic correlation between engine and fuel

By Edited Aug 14, 2016 0 2

In some countries, use of adulterated fuels has led the pollution to increase in a higher rate than normal. Some people think vehicle engine can burn any hydrocarbon and pull out the energy therein to power the vehicle. Actually it's not true. In this article I am trying to represent the correlation between internal combustion engine and hydrocarbon auto fuel. Hope, reader will be benefited.

Internal combustion engine is the heart of a vehicle where the fuel burns to give out energy. Burning can be expressed as a chemical reaction which results in production of heat energy. In the process of burning, the chemical energy stored in the fuel is expelled in the form of heat energy.

The combustion process and the fuel chemistry are a bit complicated. The fuel enters into the combustion chamber and gets compressed. Then, it is ignited by a spark or self ignited by the elevated temperature due to compression. After the combustion process is over the burnt masses are exhausted through the exhaust. Please note that, the burnt masses are lightweight and mixes with the exhaust air and goes out to the environment. Now what will happen if the combustion process is not a complete combustion? Definitely the unburnt particles will be heavier than air and hence the exhaust air cannot carry it with itself. In such a case some tiny fraction of the unburnt fuel particles will remain in the combustion chamber. Those unburnt fuel particles will try to(but cannot) mix up with the freshly introduced fuel air mixture making the mixture an inhomogeneous one. This will again lead to incomplete combustion. This cycle will continue and it starts damaging the walls of the combustion chamber gradually leading to poor engine life. To control this situation two things can be done. One, engine has to be designed in such a way that it sucks more volume of air making the mixture air rich. Two, the fuel has to such that it produces more oxygen when it burns. If we think about both the two solutions we will find that both of them points towards the same direction. For making the combustion proper we need more volume of oxygen because oxygen supports combustion. So in the first solution, supply of more volume of air is suggested so that it supplies more volume of oxygen inside the combustion chamber during the combustion. Same is the case of second solution. Here supply of oxygen to the combustion chamber along with the fuel as an inherent chemical property is suggested.

In modern vehicles, superchargers and turbo chargers are used which compresses the air outside and throw it into the combustion chamber where the air expands in heat and supplies more oxygen. Similarly, in modern auto fuels while refining and production, some chemicals are added which produces oxygen when they burn. These chemicals are known as oxygenates. One of the most popular oxygenate is MTBE. The full chemical name is Methyl Tetra Butyl Ether. But there are some environmental and health hazards associated with MTBE. This is a colorless, tasteless, and almost odorless chemical. Though it has slight pungent smell, it disappears when comes in contact with water. Specific gravity is almost equal to one. This means, MTBE is readily miscible with water. Also it is carcinogenic. Now think about a hypothetical situation where a petroleum refinery has stored huge volume of MTBE in some underground storage tanks for use in production of high grade auto fuel. Now if by any chance, MTBE leaks out of the storage tanks and misc with the ground water. Since it is miscible with water no one can even suspect it. And since it is carcinogenic, whoever consumes the ground water will attacked by cancer. In such a case it can convert cancer into an epidemic in the locality of the refinery because ground water is the mostly used water resource. Due to these fatal issues associated with MTBE some countries have banned use of MTBE. Another very popular oxygenate is ethanol. Though, its performance is not as good as MTBE as oxygenate, it don't have any harmful affect and hence there is no restriction in its use in auto fuel production. But since ethanol has a tendency of getting mixed with water, the storage and distribution system of the auto fuel produced by blending of ethanol should be completely dry. So, additional facilities have to be maintained for such fuel, and while trying to achieve this, an additional penny is spent. This tends to push the fuel price bit higher. But this additional expense is worth a spend looking at the interest of well being of the masses and also requirement of low emission fuel, which undergoes a complete combustion.

Now you may put a question, why I am not talking about designing such a car engine which cuts down the emission? Means, why it is not talked much that developed engines with modern technologies(like turbo chargers and superchargers) can also cut down the emission rather than only revising the fuel properties. It's because, even though auto manufacturers are developing new technologies to cut down fuel emissions, and manufacturing low emission vehicles, the old vehicles already plying on the roads will keep on producing more emissions. We cannot force anyone to through the outdated model of vehicle he owns(just because it creates more emission) and buy a new one. Commercial vehicles can be regulated upto certain extent and are being done in most countries. But fuel is same for everyone. Whatever fuel is produced in the industry has to be used by vehicle owners. So it is easier to limit emission level by controlling fuel properties.

However, best way to control emission is individual human effort. Let's save fuel. Let's reduce emission. Let's make the world a better place to live.

© Britul Sharma, India. February'2010.



Apr 8, 2010 10:48pm
Good informative piece! Try to get better. All the best.
May 16, 2010 3:56pm
thanks. i will try to make it better.
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