Re: jet fuel question

From:         greg@bronze.ucs.indiana.edu (Gregory R. TRAVIS)
Organization: Indiana University
Date:         06 Jul 94 00:52:20 
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In <airliners.1994.1406@ohare.Chicago.COM> stedder@tulsix.utulsa.edu (Stephen Tedder) writes:

>Another interesting fact is that at a typical oil refinery, from 100 barrels
>of crude oil, 45 barrels of gasoline are produced. The quantity of jet
>fuel produced from the same 100 barrels is about 8 barrels. So about
>5.5 times as much gasoline is produced as jet fuel, roughly consistent
>with the energy consumption figures above.

>In fact, we're so desperate to increase the gasoline output that we build
>catalytic crackers to crack the heavy gas oil fraction into gasoline,
>catalytic reformers to make reformed gasoline out of naphtha, and 
>even polymerize some of the gaseous fraction for gasoline! In Europe,
>only about 20% of crude oil is made into gasoline.

One thing to keep in mind, when slinging around numbers such as these,
is that a jet engine will burn just about anything, including
automobile gasoline*.  A turbine engine is nowhere near as sensitive
as a reciprocating gasoline engine to octane quality.

Jets mostly burn "jet" fuel because it's cheaper and just as
suitable power-wise as a more higly refined distillate (like
gasoline)**.  Reciprocating gasoline engines burn gasoline because
other fuels cause them to self-destruct pretty quickly.

greg

*Long-term use of gasoline in turbine engines can cause deterioration of
turbine blades and burn cans if the fuel controls and combustion chambers
are not "set up" for gasoline use.  In other words, it's almost always
OK to fuel your unmodified 727 with gasoline occasionally, but if you're going
to make a habit of it it's best to have the engine's internals modified
a bit.

**Other advantages to jet fuel include a lower volatility (less chance
of accidental explosion and lower losses due to evaporation).