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Path: utzoo!watmath!clyde!cbosgd!ihnp4!mhuxd!wolit
From: wolit@mhuxd.UUCP (Jan Wolitzky)
Newsgroups: net.aviation
Subject: Pulsejets
Message-ID: <3024@mhuxd.UUCP>
Date: Fri, 4-Oct-85 10:32:02 EDT
Article-I.D.: mhuxd.3024
Posted: Fri Oct  4 10:32:02 1985
Date-Received: Sat, 5-Oct-85 06:45:37 EDT
Organization: AT&T Bell Laboratories, Murray Hill
Lines: 22

Could one of the technically knowledgeable people on this net
enlighten the rest of us about pulsejets?  I seem to recall that the
V-1 "buzz bomb" used one, and that they work by having a set of
venetian-blind type shutters at the front open and close at a high
rate (hence the "buzz"), with the fuel charge being ignited when the
shutters are closed (high-speed exhaust goes out the back, providing
thrust) and the new fuel-air mix introduced when they're open.
I always thought, though, that you needed a rocket-assisted take-off
in order to get the airflow going, which contradicts what's been said
here about starting them on the ground at zero speed (in models).
Is there any compression of the charge in pulse-jets?  If so, how is
that done?  Without compression, they'd seem to be pretty inefficient:
just a gasoline fire with the hot stuff coming out one side only.
How durable are they?  It would seem that the shutters take a beating,
slamming back and forth like they do.  On the other hand, pulsejets
ought to be pretty cheap to manufacture -- or am I forgetting some
component with tight tolerances?  How much did the model airplane
engine cost, and how did its cost/thrust ratio compare with the
ubiquitous glow-head 2-stroke piston engines everyone uses?
-- 
Jan Wolitzky, AT&T Bell Labs, Murray Hill, NJ; 201 582-2998; mhuxd!wolit
(Affiliation given for identification purposes only)


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