The difference between octane rating and cetane number or rating?
Answer:
Octane number is the measure of the resistance of gasoline against detonation or preignition of the fuel in the engine. it is measured relative to the mixture of iso octane (2,2,4 trimethylpentane) and n-heptane. A fuel with 100 octane has the same preignition properties as 100% 2,2,4 trimethylpentane.
Higher octane fuel has a greater resistance to autoignition under higher combustion pressure and heat. While octane is not a measure of power, higher octane allows more power to be extracted from the fuel by using higher compression and
Cetane number is the measure of combustion quality of diesel oil or it is the measure of the ignition delay. the higher the cetane number of diesel the shorter the ignition delay, and the greater the fuel quality, and vice versa. A short delay affords more time for diesel fuel to burn completely.
Both Cetane Number (CN) and Octane Number, known also as Research Octane Number (RON), are expressions of the autoignition resistance of a fuel. The differences are significant for each fuel type. In diesel fuel, the fuel needs to ignite quickly to provide more time to complete burning. Cetane expresses the speed to autoignite in a diesel engine. Diesels need early ignition since they do not have spark plugs and distributors. A high cetane fuel acts like a timing advance, igniting the fuel during the compression stroke, thereby allowing a more complete burn as the piston gets to the top dead center.
Gasoline engines use ignition systems to trigger the combustion process in fuel. The higher Octane Number means the opposite that a high Cetane Number means, but offers the same for performance. In a gasoline engine with higher compression, the ignition system starts combustion before the piston finishes compressing the fuel. A high octane fuel supports even flame propagation under high heat and compression. This means that the fuel burns at a steady rate and speed even under high pressure. Lower octane fuels will predetonate under high heat and pressure conditions. This means that the fuel will have multiple unstable flames. Without a single front, this causes pressure wakes in the combustion chamber, and robs the engine of power. The fuel is consumed in small explosions, like popcorn in a pan, rather than one single explosion pushing the piston. This preigniting popcorn is known as knocking and pinging because of the sound, and is indicative of this loss of power due to combustion instability.
Higher octane fuel has a greater resistance to autoignition under higher combustion pressure and heat. While octane is not a measure of power, higher octane allows more power to be extracted from the fuel by using higher compression and
Cetane number is the measure of combustion quality of diesel oil or it is the measure of the ignition delay. the higher the cetane number of diesel the shorter the ignition delay, and the greater the fuel quality, and vice versa. A short delay affords more time for diesel fuel to burn completely.
Both Cetane Number (CN) and Octane Number, known also as Research Octane Number (RON), are expressions of the autoignition resistance of a fuel. The differences are significant for each fuel type. In diesel fuel, the fuel needs to ignite quickly to provide more time to complete burning. Cetane expresses the speed to autoignite in a diesel engine. Diesels need early ignition since they do not have spark plugs and distributors. A high cetane fuel acts like a timing advance, igniting the fuel during the compression stroke, thereby allowing a more complete burn as the piston gets to the top dead center.
Gasoline engines use ignition systems to trigger the combustion process in fuel. The higher Octane Number means the opposite that a high Cetane Number means, but offers the same for performance. In a gasoline engine with higher compression, the ignition system starts combustion before the piston finishes compressing the fuel. A high octane fuel supports even flame propagation under high heat and compression. This means that the fuel burns at a steady rate and speed even under high pressure. Lower octane fuels will predetonate under high heat and pressure conditions. This means that the fuel will have multiple unstable flames. Without a single front, this causes pressure wakes in the combustion chamber, and robs the engine of power. The fuel is consumed in small explosions, like popcorn in a pan, rather than one single explosion pushing the piston. This preigniting popcorn is known as knocking and pinging because of the sound, and is indicative of this loss of power due to combustion instability.
- High cetane in diesel allows the fuel to start burning early in the compression stroke of a diesel for more performance. Higher cetane means more performance in diesel, since no diesel has no external ignition timing control.
- High octane in gasoline allows the fuel to resist preignition under high pressure and heat, and allows a steady propagation of a single explosion to push the piston once the fuel is combusted by the ignition system.
- Cetane and diesel are opposite in what they measure, but the result is the same. High cetane has a low resistance to preignition, while high octane has a high resistance to preignition; both high cetane and high octane provide the ability to extract more power from fuel.
