Pulse detonation?

In article YgU0b.9585$cj1.2354@fed1read06, Fox2 wrote:
He He, spaceships with sparkplugs.

Not that rare. There are high-tech sparkplugs in many rocket engines.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

In article YgU0b.9585$cj1.2354@fed1read06, (Fox2) wrote:

Hmm, sounds like a problem for automotive engineers.

A fuel injector to mix the oxidizer and fuel with a sparkplug for
the ignition. Low injection pressure + a proven technology.

Except that the fuel-air mix in automotive engines doesn't detonate. If
it did, combustion would complete almost instantly, and the working
fluid would lose heat into the walls of the cylinder before it fully
expanded, reducing efficiency.

Disclaimer: I am not an automotive engineer.

--
Christopher James Huff
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG:
http://tag.povray.org/

(Arthur Hansen) wrote in message . com...
(Iain McClatchie) wrote in message . com...

The article is enthusiastic but not informative. Here's a basic
question: why would a pulse detonation engine be any more efficient
than a fanjet?

The basic premise is that "exploding" fuel is more energetic and
efficient than just burning it, isn't it?


No. The energetic content of a fuel is essentially the same for detonation
vs. burning. There is *slightly* greater energy release in the detonation
case due to suppressed chemical dissociation at the high pressures in
detonations vs. flames for the same initial conditions, but this is
negligible for propulsion applications.

Experiments we have done at McGill University have shown that the impulse
imparted on a tube containing hydrogen-oxygen mixtures is independent of
whether it is detonated or simply burned in a high-speed, turbulent flame.
The net impulse appears to be simply a function of the chemical energy
content of the mixture and independent of how that energy is released.

See our publication:

Kiyanda, C.B., Tanguay, V., Higgins, A.J., and Lee, J.H.S.,
"Effect of Transient Gas Dynamic Processes on the Impulse
of Pulse Detonation Engines," Journal of Propulsion and Power,
Vol. 18, No. 5, September 2002, pp. 1124-1126.

...available in most engineering libraries.
--
Andrew J. Higgins Mechanical Engineering Dept.
Assistant Professor McGill University
Shock Wave Physics Group Montreal, Quebec CANADA
http://www.mcgill.ca/mecheng/staff/academic/higgins/