> >> The main problem besides efficiency is ignition. You need to put at
> >> least 10mJ of ignition energy into a spark to ignite the mixture
> >> firmly every time. With high speed motors (like pulse reactors like
> >> the V1), you end up needing several Watts of power to  run the
> >> ignition.
> >
> >A pulse jet only requires an external source of ignition to get
> >started. Once it's going it is self-sustaining. It also needs a means
> >of generating airflow (eg. a foot pump) to get started.
>
> I do not aggree. There has to be an ignition source inside. Usually it
> is a part that is designed to run red hot and has enough inertia to
> stay that way between detonations (even two apart). In small ones it
> is simply a glow plug. Since there is no compression worth mentioning
> in the tube (2-5at is not really compression) a heat source is
> required. This lowers the detonation point so it happens just before
> the maximum back pressure (providing fixed ignition advance).

Your experience obviously differs from mine. I've never seen one
with a glow plug and can't imagine that it would all that easy to
start (if at all). A glow plug is a pretty poor ignition source in a low
compression environment (ie. starting).
My understanding of them is that there is still plenty of combustion
products in the chamber when the reversion pulse arrives and
opens the petal valve for the next cycle and that provides the
ignition source. The ones that I have played with either had a spark
plug or a couple of wires shoved up the tailpipe but, once started,
they needed no more external ignition source.

Steve.

======================================================
Steve Baldwin                Electronic Product Design
TLA Microsystems Ltd         Microcontroller Specialists
PO Box 15-680, New Lynn      http://www.tla.co.nz
Auckland, New Zealand        ph  +64 9 820-2221
email: steveb@tla.co.nz      fax +64 9 820-1929
======================================================

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.