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Newsgroups: sci.environment,,talk.environment,,,,
From: (Bruce Hamilton)
Subject: Aviation Fuels - was Re: electric vehicles
Date: Tue, 8 Oct 1996 07:17:43 LOCAL

In article <...> Dodge Boy <> writes:
>Matt Kennel wrote:
>>     However, I see *NO* feasible replacement for aircraft fuel, and no
>>     even remote chance of developing any.
>> We can make electric cars, nuclear ships, but aircraft need oil.

Hydrogen has been used - it's light, very high energy/mass
ratio. The reality is that fossil aviation fuels will probably be
replaced with another hydrocarbon fraction ( perhaps even
a single HC ) similar in properties to the Avgas and Jet A1
fractions, probably derived from renewable carbon processes.
The technology is there, but the economics probably won't be
justified until crude reaches about $50/bbl. There were some
synthetic avialtion fuels produced in the 1960s, but economics
killed them early, and catalysis has developed further since
then. I agree that aviation fuels will be the hardest to replace,
if only because of the long design life of aircraft - requiring
backwards compatibity ( because it will probably not be economic
to have multiple fueling systems worldwide ), and because of
the need for large quantities of the Jet A1 fuel to be available
worldwide.  It's not such a problem for Avgas, as the quantities
are much smaller, and many engines can now run on Mogas
( Automotive Gasoline ) as well. The increasing use of Jet A1
has meant that it is now the dominant kerosine fraction, and
some countries have abandoned their lighting kerosine grades
altogether, supplyinhg Jet A1 as the sole kerosine. Note that
Jet B ( the widecut military grade ) includes some of the gasoline
fraction, thus isn't a "true" kerosine - and isn't approved for
most commercial passenger aircraft.

> We'll I can see to possibilities to explore.  Alcohol for the piston
>engine planes, and for the jets vegtable oil.  It has already been
>proven that it is a viable substitute for diesel.  Jet fuel is a variant
>of diesel, and with additives it may work.  That also gives the
>possiblity of the piston engines being converted to diesel, the Germans
>had many diesel airplanes during WWII.

Firstly, alcohols aren't viable substitutes because they
are low calorific value by mass because they contain
oxygen - it would be preferable to convert them to
hydrocarbons just to maintain the range and capacity
of planes. Secondly, they produce lots of carbonyl
emissions, especially formaldehyde ( MeOH ) and
acetaldehyde ( EtOH ). There are techniques for
making gasoline from alcohols eg the Mobil ZSM-5
zeolite process used in New Zealand

Vegetable oil is a useless fuel for aviation - it
goes solid at -10C, when aircraft fuels have to
remain fluid at -45C. Even if it was transesterified
to make esters it would still have problems with
viscosity at such low temperatures. Also the pure
oil tends to form gums rapidly and readily emulsifies
with water - problems of great significance when the
fuel goes from 40C tropical temperatures to -45C
in flight. The esters have good energy contents, but
would need significant levels of additives to match
the existing stability, viscosity index and water
separation properties of existing fuels.

Jet fuel is not a variant of diesel, it is a form
of kerosine. Diesel is much higher molecular
weight, and many international grades will
solidify at temperatures around - 20C. Diesel
also contains many trace elements that will
produce corrosive compounds in aircraft
turbine engines.

I suggest you read the Aviation Fuels sections
in Modern Petroleum Technology or the Kirk
Othmer Encyclopedia of Chemical Technology
to become just a little less ignorant.

I admire your arrogance at being so keen to
display your ignorance around Usenet. I'm
wondering if you even know anything about
Dodge cars as well.

               Bruce Hamilton

Newsgroups: sci.environment,,talk.environment,,,,
From: (Bruce Hamilton)
Subject: Re: Aviation Fuels - was Re: electric vehicles
Date: Thu, 10 Oct 1996 15:13:09 GMT

Jason <> wrote:

I previously wrote...

>>Firstly, alcohols aren't viable substitutes because they
>>are low calorific value by mass because they contain
>>oxygen...  Secondly, they produce lots of carbonyl
>>emissions, especially formaldehyde ( MeOH ) and
>>acetaldehyde ( EtOH ).

>     EtOH is ethanol
>     MeOH is methanol
>     H
>      \
>       C=O is formaldehyde
>      /
>     H

My apologies, I should have been more precise, I forgot the
extensive cross-posting meant some people may not have
been familiar with  alcohol combustion products.

Formaldehyde ( HCHO) results from methanol ( CH3OH )
Acetaldehyde (CH3CHO) results from ethanol (CH3CH2OH)

>     Now, many different grades of jet fuel are used.  Partly
>because they are required by design.

There are really only two types of Jet fuel used worldwide,
"narrow cut " Jet-A1 which is used for almost all civilian aircraft,
and Jet-B, the "wide-cut" ( includes some of the gasoline fraction
as well as the kerosine fraction ) fuel used by the military. Most
engines are designed to handle both, and the varying specification
names are mainly historical, however ( AFAIK ), all civilain passenger
aircraft use Jet-A1 worldwide. During the last two decades the only
divergence has been in the changes of freezing point, as the original
-50C maximum specification was really only required for a few
high altitude long-distance routes ( eg over Himalayas ), and
that a relaxation to -47C would be acceptable, with the ocassional
need  to modify flight plans to avoid cold air. That reduction was
estimated to increase the global availablity of Jet-A1 by almost
10%, thus keeping the prices down.  There is now also provision
in the Jet-A1 specification for carriers and suppliers to negotiate
the freezing point. Jet A is similar to Jet A-1 except that the maximum
freezing point is -40C, and so it is not commonly used internationally.

There are a large number of specification that are variants of
Jet-A1, with anti-icing additives, static dissipators, and ( more
recently ) differing freezing points for some regional products,
but they are all essentially Jet-A1 and are compatible with each
other. The military also have special versions of kerosine, the
widecut specification was originally designed to maximise yield
of jet from crude oil ( up to 40% ) which could be in short supply
during wars, and also to have excellent low temperature properties
( - 60C maximum freezing point ) for global operational use.

There are other military kerosines, eg for safety reasons,
aircraft carriers use a high flash point fuel, minimum FP=60C,
versus 38C for Jet-A1. There is no flash point limit for Jet-B, but
it will be much lower.

Essentially today there are only two common types, Jet-A1 and
Jet-B, each of which is covered by multiple specifications.

Jet-A1 = AVTUR = NATO F-35, and ( with slightly differing static
dissipating additive related specifications ), = AVTUR/FSII,
Nato F-34, US JP-8. Jet A is  identical to Jet A1, except for
freezing point specification.

Jet-B = AVTAG/FSII = Nato F-40 = US JP-4

The less common high flash aircraft carrier fuel is
AVCAT/FSII = Nato F-44 = US JP-5.

               Bruce Hamilton

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