Subject: Re: Small model jet turbine engines

From: [email-masked] (Bruce Durocher II)
Date: 2 Jul 1996 04:41:20 GMT

Boris Beizer ([email-masked]) wrote:

: >    saying pulsejets have excellent performance, it was *pressure* jets I was
: >    refering to.
: >    Pressure jets, as designed by Eugene M. Gluhareff, run *only* on propane,
: >    have no moving parts, and have both the best thrust to weight ratio and 
: >    the best specific fuel consumption of *any* jet engine short of a full-
: >    sized turbofanjet.

: What's a "pressure jet."  Educate us.  Never heard of that kind of engine. 
: It's not a pulse jet, as you said.  And obviously not a ramjet.  If it has
: no moving parts, what does the compression?  Or does this run at atmospheric
: pressures?  I assume that when you say "runs only on propane" you mean as a 
: fuel and presumably the oxygen comes from air.  So where's the compressor?
: Without a compressor of some kind (moving parts or no) it will have to violate
: some laws of physics to get decent thrust--or as Scotty say's "I can nae break
: the Laws of Physics, Cap'n."

	The Gluhareff "pressure jet" engines (I have the blueprints for 
the type used in the flying platform built in the Seattle area in the 
80's, but my blueprints for the ones Gluhareff used in his series of 
backpack helicopters were destroyed when I lent them to a friend who died 
suddenly) are vaguely reminiscent of pulse-jet engines.  
	What Gluhareff did was to run a fuel line from a propane tank
through the combustion chamber so that the liquid propane would be changed
to vapor and be propelled by thermal expansion through a series of
precisely designed funnels to get the proper air/fuel ratio for the
combustion chamber.  You can find several articles on the engine in
Mechanics Illustrated and Science & Mechanics magazine in the late 60's
and early 70's--I remember one where he mounted one on his son's go-kart. 
Don't know that the kid ever had the balls to open it up to the suspected
150mph, but a gent mounted two on a higher-tech go-kart and used to race
dragsters with it. 
	They've been used in helicopters and such-like, and at least one 
maniac mounted a pair on a BD-5.  Don't know that he ever flew it, 
unfortunately.  I talked to Gluhareff over the phone some years ago for 
ten minutes or so before I bought the helicopter plans, as I wanted to 
know about the stability of those old designs.  I remember he said "I let 
both my sons fly them in the tests, and they're not dead yet!"

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From: [email-masked] (Paolo Zini)
Date: 2 Jul 1996 15:19:39 GMT

In article <[email-masked]>, [email-masked] (david allen) says:
>>80's, .... reminiscent of pulse-jet engines.  
>>       What  did was to run a fuel line from a propane tank
I have made some experiment on Gluhareff PULSE jets, i have also seen a "large" model,
more or less the size of a 10 years hold boy.
If You know the sound of that jet, You know for shure that it is a pulse jet and
your ears are gone.

>thermal expansion is omni-directional, how is the flow maintained ONLY in the 
>forward direction?

You do not need any moving part to have te effect of the traditional reed valve of
traditional pulse jets, between other phenomena you can count on aerodinamic asimmetry
of some shapes; i try some ascii art...

     __________________

             /
            <             ----> low loss direction
             \            <---- high loss direction

     ___________________

this is one example of a "fluidic diode" (I hope that the translation is correct..)
Gluhareff PULSE jets are "L" shaped, the intake is 90 degree respect to the exaust and
the corner of the L is, I tink, the "valve".
The Gluhareff PULSE jet use also the pressure energy of liquid propane (about 10 bar ),
propane pass thru one spiral tube in the combustion chamber and it is vapourized, it 
arrives to one iniector placed at the top of the intake at High pressure, high temperature;
the iniector converts this energy on speed and the propane exit from the iniector at
supersonic speed, this accellerates the air and contributes to create the asimmetry 
required to have a working pulse jet.  

>venturi are common methods of inducting air flow and mixing gases, however, 
>they will not prevent the combustion pressure wave from back propagating.  how 

Correct, but "back"
1) is summed up to the high speed air flow induced by propane iniector, then means more or
    less one "slower forward".
2) is one high loss direction

>is thrust achieved if pressure is flowing in opposite directions?
>

All this is the best I can do to explain the Gluhareff PULSE jets operations.
I am not one aerodinamicist, and I cannot bet that all this is accurately correct.
One couple of things i can confirm for shure:
1) Gluhareff PULSE jets are PULSE jets (the original catalog has the frequency specs)
2) that jet WORKS.
3) that jet generates one impressive, terrific amount of noise, when the engine ( a small 
    model, about 5 pounds of thrust if I am right) is on the ground wibrates.
4) It drinks impressive amount of propane.

Hope this helps.

Ciao

Paolo

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Paolo Zini                TTTTTTTTT
CNUCE institute of CNR    | | | | |
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[email-masked]      TTTTTTTTT
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From: [email-masked] (david allen)
Date: Tue, 02 Jul 96 12:48:13 GMT

da

Copyright, Dr. D.R. Allen, D.Chem., 1996. Microsoft Network is
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From: [email-masked] (Bart Smaalders)
Date: 2 Jul 1996 15:34:52 GMT

> is thrust achieved if pressure is flowing in opposite directions?

My _guess_ is that the Gluhareff "pressure jet" engine works as follows:

The (liquid) propane is taken from the tank (under vapor pressure ~100 or more 
psi) and heated in the combustion chamber ( a nice way of cooling the walls
a bit, btw).  This causes the propane to vaporize and _greatly_ increases the 
volume and hence the speed.  This hot jet of pressurized propane vapor is then
introduced into a series of venturi not unlike those in a steam injector which
converts the momentum of the hot propane into pressure and mixes the propane
with the appropriate amount of air for combustion.

The idea seems straightforward enough, but if the venturi are anything
like those in a steam injector, there are a lot of quite tight
tolerance and lots of small precision tapers and bores.  The calcs for
a beast like this are tricky, since there's a lot of interdependent
stages (multiple venturi and a regenerative heating system for the
propane).  My guess is you have to start it with a large "weed burner"
type torch, and that combustion could be a little erratic, esp. if much
throttle control was wanted.

For those of you unfamiliar with steam injectors, they take steam from a boiler
and using no moving parts, pump water into the boiler against the steam pressure.

If these jets really do work (they've got "Tesla turbine" written all 
over them :-)), this would be a kick to put on a small go-kart
and run in the desert.

Pure guesswork, but fun -

- Bart

---
Bart Smaalders			Solaris Clustering	SunSoft
[email-masked]		(415) 786-5335		MS UMPK17-301
http://playground.sun.com/~barts			2550 Garcia Ave
							Mt View, CA 94043-1100

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From: [email-masked] (Bruce Durocher II)
Date: 4 Jul 1996 04:26:14 GMT

Bart Smaalders ([email-masked]) wrote:

: My _guess_ is that the Gluhareff "pressure jet" engine works as follows:

: The (liquid) propane is taken from the tank (under vapor pressure ~100 or more 
: psi) and heated in the combustion chamber ( a nice way of cooling the walls
: a bit, btw).  This causes the propane to vaporize and _greatly_ increases the 
: volume and hence the speed.  This hot jet of pressurized propane vapor is then
: introduced into a series of venturi not unlike those in a steam injector which
: converts the momentum of the hot propane into pressure and mixes the propane
: with the appropriate amount of air for combustion.

: The idea seems straightforward enough, but if the venturi are anything
: like those in a steam injector, there are a lot of quite tight
: tolerance and lots of small precision tapers and bores.  

	Based on the two sets of plans I have seen (the 80# thrust models 
in the flying platform I have plans for, and the 25# thrust models in the 
backpack helicopter plans I had that were destroyed by accident), the 
venturi aren't *that* fiddly.  In fact, the welding job on the version 
built by Mechanix Illustrated magazine looks downright primitive...

: The calcs for
: a beast like this are tricky, since there's a lot of interdependent
: stages (multiple venturi and a regenerative heating system for the
: propane).  My guess is you have to start it with a large "weed burner"
: type torch, and that combustion could be a little erratic, esp. if much
: throttle control was wanted.

	Both sets of plans that I have owned used glow-plug type 
ignition for the jets.  The tricky part on the backpack helicopter was 
constructing an electrical connector to carry current from the ignition 
switch on the handle to the engine on the blades...

: If these jets really do work (they've got "Tesla turbine" written all 
: over them :-)), 

	Ask Interlibrary Loan for Science & Mechanics May 1973, pages 42, 
43, 88, and 92.  I can't find the Mechanix Illustrated issue that I have 
for the page numbers, but the Reader's Guide to Periodical Literature 
should have it.

: this would be a kick to put on a small go-kart
: and run in the desert.

	The old Gluhareff product literature showed stills of the gent 
who built the twin-engined cart racing a dragster.  The Science & 
Mechanics article's author says that the version Gluhareff built for his 
kids had slow accelleration, but that Gluhareff had broken 60mph at Palm 
Springs Airport in 1972 using a 40# thrust model.