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The difference between octane rating and cetane number or rating?
Wiki User
∙ 13y ago
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.
- 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.
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∙ 13y ago
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What is cetane number for petrol?
There is no cetane number for petrol. Cetane is a measurement of Diesel fuel and Octane is a measure of Petrol. Each is a measure of the combustion ability. Cetane is a measure of the amount of time from injection of the fuel into the combustion chamber and the actual ignition of the fuel. Diesel's ignite the fuel through compression and not spark as in a petrol engine.
What octane is diesel?
Diesel has an octane number of about 15-25. The reason for this seemingly terrible number compared to the ones we're used to from gasoline is the fact that diesel is combusted in a totally different type of engine. Diesel has low volatility, low knock resistance, yet high energy per volume. Because of its low knock resistance, diesel should not be used in a gasoline engine as it will destroy it very quickly and efficiently. Generally speaking, diesel fuel ignition quality is not measured in octanes, as these are a unit for gasoline. A similar reference value, but for diesel, is the cetane rating. The higher the cetane number, the easier the fuel ignites when injected into an engine. The cetane number is determined by an engine test using two reference fuel blends of known cetane numbers. The reference fuels are prepared by blending normal cetane (n-hexadecane), having a value of 100, with heptamethyl nonane, having a value of 15. The higher the cetane rating, the higher the fuel's propensity to knock! Choosing a very high cetane number will not make the car run better, but using a fuel with too low cetane number may prevent the engine from starting or running.
What is the difference between octane and dodecane?
I goggle these things to find out not answer!
What is the octane rating of shell diesel fuel?
It should be listed on the pump. Generally speaking, diesel fuel ignition quality is not measured in octanes, as these are a unit for gasoline. Diesel fuel is measured in cetane not octane.Regular diesel--48Premium diesel--55Biodiesel (B100)--55Biodiesel blend (B20)--50Synthetic diesel--55A label should be affixed to the pump that states both the fuel type and cetane number. It's important to find a station that dispenses fuel of the cetane number recommended by the vehicle manufacturer.
What the relation between aniline and octane number?
nkn
What will happen when petrol is used in diesel engine?
The car won't go faster, in fact it will not run at all! Diesel is classified using the Cetane scale (15 to 100, not 0 to 100) where Cetane has been given the number 100. A diesel fuel is supposed to self ignite easily and this is measured in a standardised test using a variable compression engine. A Diesel engine uses the heat from the high compression pressure to ignite the air-fuel mixture (no spark plugs!). Cetane number = measurement from the point of injection until ignition (iqnition quality). General cetane values vary from 40-55. Gasoline is classified using the octane scale (0 to 100) where octane has been given the number 100. This sort of fuel should have a high value on the octane scale if it is to be used in a spark ignition engine. General octane values vary from 90-99. Please note that there are different test procedures when determining the Octane number, RON and MON + others. Please note that that Octane had the best know anti-knock properties when the first certification took place and that for instance ethanol, methanol etc have better anti-knock properties. If the fuel used in a spark ignition engine has too low octane number it might just have a tendency to knock (uncontrolled combustion, ignition pre-flame front) which produces a high frequency noise (can lead to engine failure). If the fuel used in a compression ignition engine (ie Diesel engine) is a high value octane fuel it is very resistant against auto-ignition and will most likely not ignite. If the gasoline ignites at all it is not likely that it will do so at the right time. The diesel fuel works as a lubricant for the fuel-injector(s)/pump so if gasoline is used this can lead to injector/fuel pump failure (over time). As a rule of thumb: Octane number = 120 - 2 * Cetane number and vice versa. To sum up: Gasoline: Low boiling point, high self-ignition temperature, bad lubrication properties Diesel: The opposite
What is the measure of the antiknock properties in a fuel?
octane number
Why n-heptane has zero octane number?
see link about octane number
How are SI engine fuels rated?
The octane rating is a measure of the autoignition resistance of gasoline and other fuels used in spark-ignition internal combustion engines. It is a measure of anti-detonation of a gasoline or fuel. Octane number is the number which gives the percentage, by volume, of iso-octane in a mixture of iso-octane and normal heptane, that would have the same anti-knocking capacity as the fuel which is under consideration. For example, gasoline with the same knocking characteristics as a mixture of 90% iso-octane and 10% heptane would have an octane rating of 90. Definition of octane rating The octane rating of a spark ignition engine fuel is the knock resistance (anti-knock rating) compared to a mixture of iso-octane (2,2,4-trimethylpentane, an isomer of octane) and n-heptane. By definition, iso-octane is assigned an octane rating of 100 and heptane is assigned an octane rating of zero. An 87-octane gasoline, for example, possesses the same anti-knock rating of a mixture of 87% (by volume) iso-octane and 13% (by volume) n- heptane. This does not mean, however, that the gasoline actually contains these hydrocarbons in these proportions. It simply means that it has the same autoignition resistance as the described mixture. A high tendency to autoignite, or low octane rating, is undesirable in a spark ignition engine but desirable in a diesel engine. The standard for the combustion quality of diesel fuel is the cetane number. A diesel fuel with a high cetane number has a high tendency to autoignite, as is preferred. It should be noted that octane rating does not relate to the energy content of the fuel (see heating value), nor the speed at which the flame initiated by the spark plug propagates across the cylinder. It is only a measure of the fuel's resistance to autoignition. It is for this reason that one highly branched form, or isomer, of octane (2,2,4- trimethylpentane) has (by definition) an octane rating of 100, whereas n-octane (see octane), which has a linear arrangement of the 8 carbon atoms, has an octane rating of -10, even though the two fuels have exactly the same chemical formula and virtually identical heating values and flame speeds.
What is the difference between unleaded and unleaded plus at Casey's?
Octane rating. regular is 87 plus is 89 or 91
Is octane use?
Octane has not special application excepting the so-called octane number.
What is the difference between 91 octane and 95 octane?
91 octane petrol will ignite at a lower temperature and burn faster, which can cause knocking in an auto engine. Lead compounds were added at one time to raise the octane rating, but recently engines have been redesigned to work on low (<98) octane petrol (or gas in the US colonies)
