Jet fuel, also known as aviation turbine fuel (ATF). It is a type of fuel used to power jet engines in aircraft. The octane rating of jet fuel, however, is not measured in the same way as the octane rating of gasoline. In fact, jet fuel does not have an octane rating at all.
Octane rating is a measure of a fuel’s ability to resist “knocking” or “pinging” during combustion. Knocking occurs when the fuel-air mixture in an engine’s cylinders detonates prematurely. It causing a shock wave that can damage the engine. Gasoline is rated according to its octane rating. Which is determined by comparing its knocking characteristics to those of a reference fuel made up of isooctane and heptane.
Jet fuel is a type of kerosene. Which is a hydrocarbon-based fuel that has a different combustion process than gasoline. Kerosene has a lower octane rating than gasoline, If it were to be used in a gasoline engine. It would likely cause knocking and other engine damage. However, because jet engines operate differently from gasoline engines, the octane rating of jet fuel is not relevant to their performance.
Instead of octane rating, jet fuel is rated by its thermal stability, its flash point, and its freeze point. Thermal stability refers to the fuel’s ability to resist breakdown under high temperatures and pressures, which can lead to the formation of deposits in the engine. Flash point refers to the temperature at which the fuel gives off enough vapor to ignite in the presence of a spark or flame. While freeze point refers to the temperature at which the fuel begins to solidify.
The most commonly used jet fuels are Jet A and Jet A-1. These are kerosene-based fuels that meet the specifications of the ASTM International. Jet A is used primarily in the United States, while Jet A-1 is used internationally. Both fuels have similar properties and are interchangeable. The main difference being that Jet A has a higher freeze point (-40°C) than Jet A-1 (-47°C).
Jet A and Jet A-1 have a thermal stability rating of at least 15 minutes at 260°C. Which means that they can withstand high temperatures and pressures without breaking down. Their flash points are also high. Jet A having a minimum flash point of 38°C and Jet A-1 having a minimum flash point of 43°C. This means that the fuel is less likely to ignite accidentally. The more important for safety during fueling and in-flight operations.
In terms of their chemical composition, Jet A and Jet A-1 are very similar. Both fuels are primarily composed of hydrocarbons, with a mixture of straight and branched chain molecules, as well as cyclic compounds. The specific composition of the fuel can vary depending on the source and the refining process used to produce it.
Overall, while jet fuel does not have an octane rating, it is still a complex and carefully engineered fuel that is critical to the safe and efficient operation of aircraft. The fuel’s thermal stability, flash point, and freeze point are all important considerations in its development and use, as they impact its performance and safety characteristics. As aviation technology continues to evolve, it is likely that jet fuel will continue to be refined and improved to meet the changing needs of the industry.