octane number


Also found in: Dictionary, Thesaurus, Medical, Financial, Wikipedia.
Related to octane number: cetane number, Research octane number

octane number,

figure of merit representing the resistance of gasolinegasoline
or petrol,
light, volatile mixture of hydrocarbons for use in the internal-combustion engine and as an organic solvent, obtained primarily by fractional distillation and "cracking" of petroleum, but also obtained from natural gas, by destructive distillation
..... Click the link for more information.
 to premature detonation when exposed to heat and pressure in the combustion chamber of an internal-combustion engine. Such detonation is wasteful of the energy in the fuel and potentially damaging to the engine; premature detonation is indicated by knocking or pinging noises that occur as the engine operates. If an engine running on a particular gasoline makes such noises, they can be lessened or eliminated by using a gasoline with a higher octane number. The octane number of a sample of fuel is determined by burning the gasoline in an engine under controlled conditions, e.g., of spark timing, compression, engine speed, and load, until a standard level of knock occurs. The engine is next operated on a fuel blended from a form of isooctane that is very resistant to knocking and a form of heptane that knocks very easily. When a blend is found that duplicates the knocking intensity of the sample under test, the percentage of isooctane by volume in the blended sample is taken as the octane number of the fuel. Octane numbers higher than 100 are found by measuring the amount of tetraethyl lead that must be added to pure isooctane to duplicate the knocking of a sample fuel. At present three systems of octane rating are used in the United States. Two of these, the research octane and motor octane numbers, are determined by burning the gasoline in an engine under different, but specified, conditions. Usually the motor octane number is lower than the research octane. The third octane rating, which federal regulations require on commercial gasoline pumps, is an average of research octane and motor octane. Under this system a regular grade gasoline has an octane number of about 87 and a premium grade of about 93. Most American-made cars that were built in the 1971 model year or later can use regular gasoline. To prevent knocking, premium grade gasoline must be used in many cars built before 1971 and in some new cars that have high-performance engines.

Octane Number

 

an arbitrary quantitative characterization of the antiknock qualities of motor fuels used in carburetor internal-combustion engines. The octane number is determined by comparing the fuel being tested with secondary standard fuels. The primary standards are isooctane, whose high antiknock value is arbitrarily assumed to be 100 on the octane scale, and n-heptane, whose antiknock value is assumed to be zero. The antiknock value of the fuel being tested is characterized by determining the composition of the mixture of isooctane and n-heptane that has an equivalent antiknock value. Quantitatively, the octane number indicates the percentage of isooctane (by volume) in the reference mixture.

The octane number is determined under standardized conditions using special, small one-cylinder engines according to one of three methods (the motor method, the research method, or the temperature method), which differ in the operational parameters of the engine. The motor method is used for evaluating aviation gasolines and automotive gasolines with octane numbers 65–100; the research method, for automotive gasolines; and the temperature method, in testing high-octane aviation gasolines and their high-octane components with octane numbers 90–115, and also in determining the quality grade of gasolines. The octane number characterizes the fuel under conditions of a lean mixture (excess air ratio, 0.9–1.1).

octane number

[′äk‚tān ‚nəm·bər]
(engineering)
A rating that indicates the tendency to knock when a fuel is used in a standard internal combustion engine under standard conditions; n-heptane is 0, isooctane is 100; different test methods yield other values variously known as research octane, motor octane, and road octane.

octane number

, rating
a measure of the quality of a petrol expressed as the percentage of isooctane in a mixture of isooctane and n-heptane that gives a fuel with the same antiknock qualities as the given petrol
References in periodicals archive ?
To determine whether or not ignition timing was adjusting in response to differences in octane number, the CAN signal named "learned relative octane number adjustment" was monitored throughout the tests, and cycle-to-cycle fuel consumption was examined to determine stability.
[16.] Leach, B., Pearson, R., Ali, R., and Williams, J., "C[O.sub.2] Emission Reduction Synergies of Advanced Engine Design and Fuel Octane Number," SAE Technical Paper 2014-01-2610.
Fortunately, the new alternative methods of improving the antiknock properties of petrol are now available and include the application of up-to-date technologies and chemical processing techniques in the production of petrol and the use of high octane number components (oxygenates).
Medium-sized refineries that produce 100,000 barrels per day can save almost $2 million dollars annually, Guided Wave claims, by reducing give-away by only one-tenth of an octane number. The octane number, or octane rating, is dependent on the hydrocarbon composition of the gasoline.
The tested gasoline was commercial gasoline in China with Research Octane Number (RON) of 92.
Besides, the calculation method for the motor octane number, which is established in the European standardization EN 589, different other calculation methods have been developed in the past.
The increase in average compression ratio of engines operating on unleaded regular fuel since 1973 has been primarily the result of an increased mechanical octane number, although petroleum refiners have concurrently been able to boost the average chemical octane number of unleaded fuel as well.
The regulator is also reported to have told the Petroleum Division that Pama had also complained that high manganese content in fuel emanated from a chemical to boost octane number. The Pama said there were hazardous technological and environmental repercussions of the metal content in fuel, if used beyond certain safe limits.
In November 2016, Pakistan decided to upgrade the quality of motor gasoline by introducing three grades namely Research Octane Number (RON) 92, 95 and 97 by replacing RON 87.
As a step towards cleaner environment and better engine hygiene, ECC allowed the introduction of 92 Research Octane Number (RON) premium motor gasoline (petrol) in Pakistan.
The only difference is that the Premium grade has higher octane number, also known as RON (Research Octane Number) -- usually 92 or 93+, which is achieved by adding ethanol to the oil.