I'm not a fuel expert either, but I do know that octane ratings are for fuels used in piston engines. It's a measure of the tendency of a particular fuel grade to detonate ("ping"), i.e. ignite outside the desired point in the power cycle due to compression, vs. from the spark plug. That would have obvious implications in the efficient, or even safe, running of the engine.

The term octane refers to using an 8-carbon straight-chain molecule as a standard. Branched polymers are compared against octane's ability to resist auto-ignition.

Jet fuels would not need such a sensitive rating, as there is no mechanical power cycle per se to interrupt.

Any bets his new handle is now going to be “Flaps”?

Look at the lips on that thing

New name , Skid, or wheels or scratch.

I got your new handle right heah...

Same aircraft having a runway overrun at AirVenture 2011: https://www.youtube.com/watch?...FkI&feature=youtu.be

He did miss the F-16 that had a runway overrun earlier the same day.

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Originally posted by V-Tail:

quote:

Originally posted by TigerDore:

quote:

Originally posted by V-Tail:
Nope. Jet fuel.

Aviation gasoline has an octane rating. Jet fuel does not.

Thanks, V-Tail. For some reason, I remember reading a long time ago that jet fuel was around 100 octane. Thanks for clearing that up.

I have had some very rudimentary training on aviation fuels; we certainly have some forum members who know a lot more about this than I do. TatorTodd is in the business, and SigMonkey dealt with this for much of his Air Force career.

I do know that jet fuel, much closer to kerosene or diesel fuel than to gasoline, will ignite and burn, but is not as likely to explode as gasoline is.

Jet fuel and diesel fuel are rated in cetane, rather than octane, and the meaning of these ratings (cetaine and octane) are not equivalent. Tator dude, where are you when we need an education?

Crude oil goes into the fractional distillation column at the refinery, and several intermediate products and semi-finished products come out. This lighter stuff condenses and comes out on higher levels and the heavy stuff condenses and comes out on lower levels.


Kerosene comes out a little higher on the disty column than diesel. It has more light ends and lacks diesel's lubricating properties. Nearly all of the kerosene in the US is cleaned up and made into jet fuel. By cleaned up, I mean impurities like water but not sulfur (jet-A is high sulfur).

Some of the gasoline (we call it mogas) comes off the disty column higher than kerosene. I had to say some of the gasoline because it is much more complex as refineries are trying to maximize its production. We're sending heavy oils to be cracked (FCC or hydro) to be converted to gasoline, and we're sending lighter liquids and gases to the reformer to be rearranged into gasoline. Then its sent through units to treat and blend.

Avgas comes out of the gasoline processes, but has a higher octane AND has tetraethyl lead (awesome lubricant). Regulators are trying to phase out the lead, but every specification related to aviation moves exponentially slower than a snail (i.e. 50 year old standards are the norm).

You are correct that diesel is measured in cetane number and gasoline is measured in octane. Octane and Cetane are only useful numbers for compression engines. Turbines don't give a damn about fuel's compression ignition values so there is no cetane standard. This poses a problem for people who attempt to run Jet-A and even JP-8 in diesel motors as they can get low cetane fuel which will run poorly. As mentioned previously, jet fuel has sulfur in it and all modern diesels have been optimized to run on ultra low sulfur diesel so it'll cause additional engine wear on diesel motors.

Flash point is the best measure of the explosion you mentioned. Here are the flashpoints and classification:

Diesel #2: 126F (flammable)

Jet A: 100F (flammable)

Gasoline: -45F (combustible)

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Ego is the anesthesia that deadens the pain of stupidity

DISCLAIMER: These are the author's own personal views and do not represent the views of the author's employer.

Thanks for the explanation TT. Very informative.

quote:

Originally posted by kkina:
I'm not a fuel expert either, but I do know that octane ratings ...

quote:

Originally posted by tatortodd:
Crude oil goes into the fractional distillation column at the refinery, and several intermediate ...

Thanks, kkina and tatortodd.



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