The ignition delay of the fuel can then be calculated as the time difference. Fuels ar0cn43, ar0cn55 and ar0cn62 have cetane number of 43, 55 and 62, respectively, with aromatic content of 0 wt%. Thus a fuel with an octane number of 80 has an antiknock rating equal to that of a test mixture containing 80 per cent of isooctane. Difference between octane number and cetane number. Prediction of cetane number of biodiesel fuel from fame composition 23 fuel cetane number reference caprylic acid methyl ester 18. Hexadecane also called cetane is an alkane hydrocarbon with the chemical formula c 16 h 34. They can be differentiated based on few considerations. It determines how fast the fuel will enter combustion stage. Octane and cetane number are standard measure of performance of a fuel. Average absolute difference between dcn by iqt and values measured by other methods. After that point, the effect of the additive becomes less. The higher the octane number the better is the higher cetane number means that the the resistance of gasoline to combustion diesel will ignite readily and, therefore, prematurely, known as knocking. What is difference between octane number and cetane number.
The octane number was derived from the fuelsubstitution methodology. The addition of 2ethylhexyl nitrate was designed to raise fuel cetane number to three stages, 50, 52 and 55 compared to the used conventional diesel fuel whose cn was 48. A rating on a scale used to indicate how quickly a fuel will ignite in a diesel engine, a figure of merit for diesel fuel as the octane number is a figure of merit for gasoline burned in spark ignition engines. European literature says 49 cetane number for the alh engine. If the cetane measured of the two fuels is the cetane index and not the number, then a 5050 mix of 60 index and 40 index will give you a 50 cetane index. While gasolines octane number signifies its ability to resist autoignition also referred to as preignition, knocking, pinging, or detonation, diesels cetane number is a measure of the fuels delay of ignition time the amount of time between the injection of fuel into the combustion chamber and the actual start of combustion of the fuel.
It denotes the percentage by volume of cetane chemical name hexadecane in a combustible mixture containing cetane and 1methylnapthalene whose ignition characteristics match those of. An octane rating, or octane number, is a standard measure of the performance of an engine or aviation fuel. Watch this video to learn about octane and cetane number. The higher the octane number, the more compression the fuel can withstand before detonating igniting.
In the octane number scale, high values represent fuels that resist spontaneous ignition and. Octane number, cetane number octane number indicates the tendency of fuels to knock. Hydrocarbons, a compound comprised of carbon and hydrogen, typically make up the bulk of various petroleums. Cetane number or cn is a measurement of the combustion quality of diesel fuel during compression ignition.
The octane rating is the 87, 91, 93 or numbers close to these that you see at the gas pump when youre filling up your car. Cetane is one such hydrocarbon that appears in a colorless fluid form. The octane rating of gasoline is measured in a test engine and is defined by. The cetane number of the test fuels was known by using mixtures of the cetane number secondary reference fuels srfs t26 and u19, which are fullblend certification fuels used in the place of 2,2,4,4,6,8,8heptamethylnonane and nhexadecane for engine cetane number testing. Effects of fuel cetane number and aromatics on combustion. The average cetane number is calculated by using equation 6. The cn is an important factor in determining the quality of diesel fuel, but not the only one. Cetane number cetane rating is an indicator of the combustion speed of diesel fuel and compression needed for ignition. Cetane is the shortdelay reference fuel and is mixed. Octane number is the ability of resistance of a fuel to knocking in comparison to isooctane, which has octane number 100 and has high antiknock quality. Octane number and cetane number are very important in determining the best fuel that can be used for engines of automobiles. Octane numbers are associated with petrol and cetane number with diesel. One of the strokes is the compression stroke, where the engine compresses a cylinderfull of air and gas into a much smaller volume before igniting it with a spark plug.
The cetane specification per astm d975 is the cetane number. Difference between octane number and cetane number pdf do you know that higher the octane number, better the fuel is for a spark ignition engines. A cetane number is a measure of the ignitiondelay period in a diesel engine provided by the fuelthe higher the cetane number the shorter the delay period. It plays a similar role for diesel as octane rating does for gasoline. In the newer vehicles, the same result is achieved by the engine design that increases turbulence in the combustion chamber, andor by adding aromatic hydrocarbons such as xylenes and oxygenates oxygencontaining compounds such as alcohols to the gas the unleaded gas. Cetane number is actually a measure of a fuels ignition delay. The higher the octane number, the more compression required for fuel ignition.
By increasing the cetane number of the fuel, the knock intensity is decreased by the. Distinguish between octane number and cetane number. Better antiknock quality allows us to compress the airfuel mixture to a larger extent befo. For soybean oilderived biodiesel, the values range from 48 to as high as 67. In broad terms, fuels with a higher octane rating are used in highcompression engines that generally have higher performance.
Pdf a methodology for estimating the octane index oi, the research. The octane number of a fuel is measured in a test engine, and is defined by comparison with the mixture of isooctane and normal heptane which would have the same antiknocking capacity as the fuel under test. The total ignition delay time is defined as the time difference between the. Pdf cetane number is the accepted indicator for quantifying the autoignition characteristics of diesel fuels in compression ignition engines. Cetane number testing of biodiesel jon van gerpen abstract reported values of the cetane number for biodiesel vary widely. North america literature says 45 cetane number, minimum. The octane number of a sample of fuel is determined by burning the gasoline in an engine under controlled. The difference between ron and mon is known as fuel sensitivity s.
If your fuel has a high cetane number, it will have a low octane number, and vice versa. The higher the cetane number, the better the engine will run, and also the quieter and more efficient it will be, he says. Cetane rating is done considering the ignition of cetane. Fuels with high octane numbers are used in high performance gasoline engines. Cetane is a chemical compoundalso known as hexadecan. Isooctane is given a maximum octane nhexadecane is given a maximum octane number, i. What is the difference between derived cetane number and. Furthermore, octane is highly volatile while cetane is not volatile. Generally fuels rating is given for their antiknock qualities.
Cetane and octane number data for oxygenates other than esters. Bohacz says its number represents the fuels eagerness to ignite through the pressure and heat created by the piston compressing the air in a diesel engine. Octane number and cetane number are exactly opposite to each other. Hexadecane consists of a chain of 16 carbon atoms, with three hydrogen atoms bonded to the two end carbon atoms, and two hydrogens bonded to each of the 14 other carbon atoms. The difference between octane rating and cetane number or. Therefore, all fuel suppliers offer a higher octane level of premium gasoline. Difference between petrol and diesel engine duration. It signifies the time gap between time of injection and time of ignition of a diesel. This only works for cetane index, not the cetane number of the fuel.
Some of this variation may be due to differences in the fatty acid composition of the soybean oil but other factors are also important. Griffiths b a department of chemistry, y ork university, t oronto, ontario. Prediction of cetane number of biodiesel fuel from the. Octane number definition of octane number by merriamwebster. A correlation between derived cetane number and ron is also provided. Cetane number 16 carbon atoms its for diesel engine due to composition of diesel has mostly 16 carbon atoms. The main difference between octane number and cetane number is that octane number gives an idea about the performance of a fuel whereas. A group contribution method for estimating cetane and octane. The higher the cetane number, the shorter the ignition delay and the better the ignition quality. The difference between cetane and octane successful farming. Octane number is related to petrol and cetane number gives quality of diesel. The percentage by volume of cetane in a mixture of cetane and. The guys from the psc online store break it down and explain the difference between cetane and octane in gasoline and diesel fuel systems. The amount of compression is called the compression ratio of the engine.
Like octane number rating, cetane numbers are established by comparing the. The difference between sse and msse was less than 1%. Octane number is the measure of the resistance of gasoline against detonation or preignition of the fuel in the engine. When it comes under extreme compression, the pressure causes it to ignite quite quickly. Table 1 provides some of the product specifications for each fuel. A kind of cetane number improver has been proposed and tested to be used with diesel fuel as ameans of reducing exhaust emissions.
Usually, theres a limit to how much a fuel can be boosted, usually in the range of 24 cetane numbers. The equations are developed between cetane number and ignition delay for different loads based on reference fuels are given in equations 1 to 5. The higher the octane number, the more compression the fuel can withstand before detonating. Ar24cn55 fuel is the base fuel with cetane number of 55 and aromatic content of 24 wt%. Cetane number is a measure of the ignition quality of diesel engine fuels as it indicates the comparative ease with. The key difference between octane and cetane is that octane has 8 carbon atoms whereas cetane has sixteen carbon atoms per molecule.
Cetane number cn and aromatic content ar are changed as the fuel properties. Effect of fuel cetane number on multicylinders direct. Both these are hydrocarbon compounds that are used as references for the ranking of different engine fuels according to their performance octane rating and. As with octane, higher cetane fuel will create a quieter combustion event that enjoys less diesel knock than a fuel with a low number.
Pdf effects of different cetane number enhancement strategies on. Effect of cetane number on specific fuel consumption and. The higher the octane number the more difficult the autoignition. Following are provided some basic difference between octane number and cetane number based on the general basic points of difference. Do you know why highperformance cars use high octane rating fuels. Pdf relating the octane numbers of fuels to ignition delay times. It is the fuels eagerness to ignite from the heat created in the bore from the compression of the air. The difference between cetane and octane petroleum service. Quick difference between octane and cetane number english.
Octane numbers are based on a scale on which isooctane is 100 minimal knock and heptane is 0 bad knock. Cetane number cn is an empirical parameter associated with the ignition delay time of diesel fuels, which is determined by means of standard tests based on the astm d6 standard. Correlation between cetane number and research octane number suggests cetane number for. Cetane, octane a gasoline internal combustion engine. The rating of fuels is done by defining two parameters called octane number and cetane number for gasoline and diesel oil respectively. Octane goes in your cars fuel, but cetane goes in a diesels. Differences between octane number and cetane number. Cetane ignites easily under compression and was assigned a cetane number of 100, while alphamethyl naphthalene was assigned a cetane number of 0. The fuel component ncetane hexadecane, c16h34,is given the cetane number value of 100, while heptamethylnonane hmn, c12h34,is given the value of 15. Both these are hydrocarbon compounds that are used as references for the ranking of different engine fuels according to their performance octane rating and cetane rating. A diesel engine run on a fuel with a lower cetane number than it was designed for will be harder to start, noisier, operate roughly and have higher. Higher the octane number, better the quality of petrol, and hence the vehicle gives higher efficiency. Ignition delay is the time interval between the start of fuel injection and the beginning of the oxidation reaction.