Diluting jet fuel with water to increase mass flow.

I looked on the web curious about thrust augmentation concepts for jet
engines and found a 1952? NACA report that detailed an experiment where
water was injected into the combustion chamber to increase mass flow and so
thrust.

However, the water and fuel were injected separately and the researchers
limited themselves to only adding 20% (I think) water because they thought
it would start interfering with combustion stability or something.

Has anyone heard of any research into pre-mixing the water and fuel together
to avoid this problem? Or any other similar research like running jets on
water-alcohol fuels, or water-oil emulsions to achieve the same effect.

Toby.

toby wrote:

Has anyone heard of any research into pre-mixing the water and fuel together
to avoid this problem?

They don't mix. Quite literally like water and oil, unless you're using
alcohol-type fuels (methanol, frex).


--
Scott Lowther, Engineer
Remove the obvious (capitalized) anti-spam
gibberish from the reply-to e-mail address

"toby" wrote in message
...
I looked on the web curious about thrust augmentation concepts for jet
engines and found a 1952? NACA report that detailed an experiment where
water was injected into the combustion chamber to increase mass flow and
so
thrust.

However, the water and fuel were injected separately and the researchers
limited themselves to only adding 20% (I think) water because they thought
it would start interfering with combustion stability or something.

Has anyone heard of any research into pre-mixing the water and fuel
together
to avoid this problem? Or any other similar research like running jets on
water-alcohol fuels, or water-oil emulsions to achieve the same effect.

Hi, Toby. Water is the most common contaminant found in jet fuel and can
cause icing in aircraft fuel systems and corrosion of fuel system
commponents - so it's best not pre-mixed with the fuel at all or for any
length of time.

There are a few things that *are* commonly added to jet fuel: eg. F-34
AVTUR (air force grade)contains small amounts of FSII (Fuel System Icing
Inhibitor), ASA (Anti-static Additive) and some kind of lubricity improver
to help things along and common-or-garden JET-A1 is the same stuff minus the
FSII.

To answer your question, water injection (either straight de-ionised water
or a DI water/alcohol mix (50/50, IIRC) ) is still used occasionally on some
freight/commercial aircraft to increase thrust on take-off. It is stored in
a separate tank on the aircraft and is injected directly into the combustion
chamber as required.

With the ever-increasing efficiency of modern turbo-fan engines, the need
for this sort of thust enhancement is waning dramatically, so it would not
surprise me to hear there has been no further research on this subject.

I hope this helps.

Cameron:-)

Injecting water in to the jet engines it's a common practice.

This is a part of the book: "The jet engine" by Rolls Royce...In the 17th
chapter it's written:

"The maximum power output of a gas turbine engine depends to a large extent
upon the
density or weight of the airflow passing through the engine.
There is, therefore, a reduction in thrust or shaft horsepower as the
atmospheric pressure decreases with altitude,
and/or the ambient air temperature increases. Under these conditions, the
power output can be restored or,
in some instances, boosted for take-off by cooling the airflow with water or
water/methanol mixture (coolant).
........ the injection of the coolant into the combustion chamber is usually
more suitable for axial flow compressor engines....

I think that pre mixing water with fuel it's hard to achieve 'cause these
two substances are difficult to mix
and the result could be an emulsion and not a perfect mixing.




"toby" ha scritto nel messaggio
...
I looked on the web curious about thrust augmentation concepts for jet
engines and found a 1952? NACA report that detailed an experiment where
water was injected into the combustion chamber to increase mass flow and
so
thrust.

However, the water and fuel were injected separately and the researchers
limited themselves to only adding 20% (I think) water because they thought
it would start interfering with combustion stability or something.

Has anyone heard of any research into pre-mixing the water and fuel
together
to avoid this problem? Or any other similar research like running jets on
water-alcohol fuels, or water-oil emulsions to achieve the same effect.

Toby.

"toby" wrote in message
...
I looked on the web curious about thrust augmentation concepts for jet
engines and found a 1952? NACA report that detailed an experiment where
water was injected into the combustion chamber to increase mass flow and
so
thrust.

However, the water and fuel were injected separately and the researchers
limited themselves to only adding 20% (I think) water because they thought
it would start interfering with combustion stability or something.

Has anyone heard of any research into pre-mixing the water and fuel
together
to avoid this problem? Or any other similar research like running jets on
water-alcohol fuels, or water-oil emulsions to achieve the same effect.

Toby.

Not a jet, but the V-2 burned an alcohol-water fuel mixture (IIRC,
one-third water) to improve its thrust.

In article et,
Carey Sublette wrote:
Not a jet, but the V-2 burned an alcohol-water fuel mixture (IIRC,
one-third water) to improve its thrust.

Not quite right. The alcohol-water mix, yes, but the motive wasn't higher
thrust. The presence of some water was partly to improve the fuel's
coolant properties, and partly to reduce flame temperature. Later
LOX/alcohol rockets, with better chamber cooling, eliminated the water.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

"Scott Lowther" wrote in
message ...
toby wrote:

Has anyone heard of any research into pre-mixing the water and fuel
together
to avoid this problem?

They don't mix. Quite literally like water and oil, unless you're using
alcohol-type fuels (methanol, frex).

Actually they *do* mix - at least in enough quantity to do enormous harm if
you don't do anything about it.

The ASA helps small amounts of water to mix in nicely, but any larger
amounts will settle out as soon as the fuel flow stops. The fuel is
filtered more times than you would probably care to believe between the
refinery and the engine - mainly to get rid of entrained water. If there is
too much water in the fuel ("off spec") it turns up on supermarket shelves,
with a blue dye added, for twice the price!

I don't know what it is about kero, but it does seem to "attract" water.

Cameron:-)

"Cameron Dorrough" wrote in
message ...

To answer your question, water injection (either straight de-ionised water
or a DI water/alcohol mix (50/50, IIRC) ) is still used occasionally on
some
freight/commercial aircraft to increase thrust on take-off. It is stored
in
a separate tank on the aircraft and is injected directly into the
combustion
chamber as required.

If finally remembered what they call it!... a Google search on "Power Boost
Fluids" turns up

http://www.csgnetwork.com/jetfuel.html

and I think this will help answer your questions.

Cameron:-)

Cameron Dorrough wrote:




To answer your question, water injection (either straight de-ionised water
or a DI water/alcohol mix (50/50, IIRC) ) is still used occasionally on some
freight/commercial aircraft to increase thrust on take-off. It is stored in
a separate tank on the aircraft and is injected directly into the combustion
chamber as required.

Any idea whether this combustion chamber injection is fuel rich or is a
lean mixture.

I imagine the max thrust you could get from this would be when you have
just enough water to stop coking and you run very fuel rich to ensure
the combustion temperature remains tolerable. this should give the
greatest mass flow if your not interested in fuel efficiency.

Or is that wrong?


With the ever-increasing efficiency of modern turbo-fan engines, the need
for this sort of thust enhancement is waning dramatically, so it would not
surprise me to hear there has been no further research on this subject.


It seems to me to be of importance to space applications though.

I hope this helps.
Yes, thanks.

Toby

Cameron:-)

"Scott Lowther" wrote in
message ...
toby wrote:

Has anyone heard of any research into pre-mixing the water and fuel
together
to avoid this problem?

They don't mix. Quite literally like water and oil, unless you're using
alcohol-type fuels (methanol, frex).


--
Scott Lowther, Engineer

An emulsifier could be added which would make a mix, however it probably
wouldn't ignite.
Mike.



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