Detonation rotary engine.

Vance what do you know about detonation engines? Apparently there
are two kinds of burning and detonation appears to be more efficient.
http://www.space.com/imageoftheday/image_of_day_030804.html
http://www.aardvark.co.nz/pjet/pde.shtml

"Detonation versus Deflagration
Deflagration is what happens when you burn a mixture of air and
fuel at reasonably low pressure.

The "woof" you get when igniting a dish of flammable liquid such
as gasoline is a deflagration.

Deflagration is, believe it or not, a relatively gentle process which
is simply the rapid burning the fuel.
When we cause an air/fuel mixture to deflagrate in a semi-enclosed

space

(such as a pulsejet or auto-engine) then pressure is generated and

that

pressure can be harnessed to perform some work -- eg: create thrust
or turn a crankshaft.

One of the primary attributes of deflagration is that the flame

travels at a

speed significantly lower than the speed of sound.

Detonation however is a far more powerful reaction of the air/fuel

mixture

and results in such a rapid  reaction that the pressure-wave created

travels

at super-sonic speeds.

In effect, detonation is a violent explosion and as such it produces

vastly

higher pressures than the simple burning process of deflagration.

Obviously, when we're looking to produce thrust, the more pressure we
can generate within an engine the better -- that's why researchers
are trying to build pulsejets that detonate their fuel charge rather
than just burn it in a deflagrating reaction."
End of quote.

Do you think we could use the principle in a rotary?

Paul Lamar

Did you see that article in Popular Science about pulse detonations

engines?

There was one mounted on the back of a Long-EZ in the Scaled hangar at
Rutan's birthday. Four real long tubes out the back. No one could figure

out

what it was. After I read the PopSci article I realized what it was. I

think they

also displayed it at OSH, turns out it is an Air Force project?

--
Perry Mick
Custom Composite Props
mick@bridgingworlds.com
http://www.ductedfan.com

I also saw the pulse detonation engine on the Vari EZ at Oshkosh. This is
undoubtedly
a "small business grant" from NASA. They claimed about 100 pounds of thrust
from
a system that weighs at least 800 lbs. A 2 stroke Hirth pumped the air to a
DOHC
engine whch was acting as a valve to feed the pipes. Definately an
impractical
power plant, but a study effort in converting combustion to detonation.
As stated - deflagration is the usual combustion process where flame
propagation
speeds are typically less than 100 ft/sec - Detonation (or "high order"
reactions)
have propagation rates measured in miles per second. Hydrogen is one of the
fuels
that can convert well mixed combustion to detonation if confined under
appropriate
conditions. At Rocketdyne we used a detonation wave system to assure near
simultaneous
ignition in multi chamber rocket engines (ie aerospike). Most combustion
experts
believe that the conversion  to thermal energy is no more effiucient in a
detonation than
in more conventional combustion, it is just that pressure rises are more
rapid
frequently destroying hardware - No I do not think we can get any gain in a
rotary
or any other shaft output combustion engine. The primary gain is in
hypersonic
flight - I maintain that the "supersonic combustion" in SCRAMJET has never
been
demmonstrated . At hyper sonic speed, diffusing the inlet flow to subsonic
for combustion
results in such a high temperature that fuels disasociate rather than burn -
a reaction
that absorbs heat rather than release heat - for no propulsion. However,
with a detonation
you can release energy in a supersonic flow, and at least in theory make
thrust.
I think (and at least hope) that we have flown detonation engines in a
"black" program
but the devil remains in the details. This is probably a ripe area to siphon
off some
Gov. money (as in this Vari EZ) right now.  Aren't you sorry you asked?? -
Vance

 
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