Proposed: Linear FWE Rebuild

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larry cottrill
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Proposed: Linear FWE Rebuild

Post by larry cottrill » Fri Apr 01, 2011 2:47 am

Now, here's my plan ...

After thoroughly testing the Heater FWE Type I (the linear FWE) the client reported it to be a very powerful air mover. He reported sensible warm air movement at a distance of 45 to 50 ft (13.7 to 15 m) behind the engine. His problem in using the linear engine was the strong projection of VERY hot gas out the intake, up to 15 ft (4 m) out in front of the flare. The other problem was poorly engineered mounting structures, which I corrected (at my cost, naturally) in the rebuild (Type II).

I believe this engine is very good in one particular regard: It breathes very efficiently, even though the intake is small (2.5 inches OD to match a 4 inch OD tailpipe). This is mostly because of the fairly long front cone of the chamber. I feel this is probably a far better way to design a "linear FWE" than trying to use a fairly flat front plate (which inevitably moves the explosion center somewhat rearward). That front cone acts as a smooth diffuser for incoming air, and as a very smooth nozzle for exhaust expulsion through the intake. There is some indication that sonic flow is achieved during brief parts of the engine cycle, and it is certainly very fast through most of its active duty cycle, both in and out.

The drawing shows a proposed means of making a really effective and usable engine out of it. I still have the bi-conical chamber (though it is slightly heat warped) and could easily have a new intake and tailpipe parts fabricated to complete it. Unfortunately, the Sanitary Tubing U bend would be several hundred dollars (remember, this is 4-inch stainless tubing) and it would take a few hundred more to make the mounting hardware. So, don't look for this anytime soon ;-) It would, of course, be my first "bent" engine.

What do you think, gentlemen?

L Cottrill
Attachments
Heater_FWE_Type_I_bent.png
How to bend the linear FWE and make it work.
Drawing Copyright 2011 Larry Cottrill

HPSCL
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Re: Proposed: Linear FWE Rebuild

Post by HPSCL » Fri Apr 01, 2011 4:20 am

larry cottrill wrote: Unfortunately, the Sanitary Tubing U bend would be several hundred dollars (remember, this is 4-inch stainless tubing) and it would take a few hundred more to make the mounting hardware. So, don't look for this anytime soon ;-) It would, of course, be my first "bent" engine.
Mr. Cottrill, if it interests you, there's a 16 gauge 304 Stainless Steel exhaust "U-bend" available at a company called Burns Stainless LLC, for only $136.62

To build/test a prototype, would you even consider aluminized exhaust tubing? A quick search found: Patriot Exhaust H7093 - Patriot Exhaust U-Bends for only $73.99

I've used aluminized exhaust tubing in a lot of my hobby engines. - Crudely designed and nothing more than noisemakers. However, I've run all of them with up to just shy of 100psi constant line pressure of propane gas, for sometimes over 10 minutes. The only thing that I've ever noticed (as far as the steel "flaking") is if you let the engine cool-down to quickly, i.e.- running outside in a strong breeze, or shooting compressed air out of a blowgun onto the engine's combustion chamber, immediately after shutting down.

I'd love to see you build this, as all of my builds are boring "back-enders". (If I could ever possess the ability to build a Lady-Jane Grey, I would be happy for a year!)

Jutte
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Re: Proposed: Linear FWE Rebuild

Post by Jutte » Sat Apr 02, 2011 1:13 am

re "strong projection of VERY hot gas out the intake"
In one of my Marconnet variations - the expelled intake was cold.This was the one that I
was using as a garage heater.It changed back to normal when I developed the Pulse Jet to power my bike.
I always thought that if you just wanted a heater type Pulse Jet then that type of Marconnet combustion
chamber would work.
I also watched the intake exhaust flame get sucked back before exit as well - so perhaps there could
be a set length as per a multple of the intake frequency that effectively 'sucks back' the hot intake exhaust
for a set size of a 'normal' combustion chamber.
Of course it is would be 'round-a-bouts and swings' as you would most probably lose the intake thrust-
which is what you would want for a garage heater anyway. I had planned to force the cold Marconnet intake
exhast to flow across the combustion chamber to increase more heated air - but making the Bike Pulse Jet
was more interesting.Somewhere on the internet there is a guy from India who made a Valveless
Pulse Jet with an intake that looked to be as long as the tailpipe - so there might be some
merit in the set length/intake frequency idea.
Hokay Dokay - just some radom ideas for you all to think about.

Vermin
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Re: Proposed: Linear FWE Rebuild

Post by Vermin » Thu Apr 07, 2011 4:44 pm

Hi Larry
I like the configuration :)
If you post or send me the dimms for a 1/3 scale + -, I will build it (in steel) and test for you.
Cheers
V
Vern
A desire to destroy as many man made hydrocarbon compounds as possible in one lifetime.

larry cottrill
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Re: Proposed: Linear FWE Rebuild

Post by larry cottrill » Thu Apr 14, 2011 1:02 pm

Vern -

Even at half scale it wouldn't be huge - smaller than the Lady Jane. I am now willing to reveal the IDs and lengths of the linear model. I doubt that you'll be able to get as tight a U-bend as the ones available in Sanitary Tubing, but that doesn't really matter as long as the CL length is right, of course. You might want to build a little short and use a tuning sleeve, as the length turned out to be really critical on this design. I think what I show here is the final "as built" length that really ran well. Go for it:

Intake:
Total length: 200 mm
Flare ID: 100 mm
Pipe ID: 60 mm

Front cone:
Length: 150 mm
IDs: 60 mm to 178 mm

Rear cone:
Length: 350 mm
IDs: 178 mm to 98 mm

Tailpipe:
Total length: 790 mm
ID: 98 mm

There you go. Blast away!

L Cottrill

Vermin
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Re: Proposed: Linear FWE Rebuild

Post by Vermin » Fri Apr 15, 2011 11:07 am

Hi Larry
I guess as I didn't know the dims so I was guessing at the scale. I have a couple of other projects on the go (a Stirling engine for one, advice = don't buy a cheap Chinese lathe) but will start with this ASAP.
Cheers (Thanks)
V
Vern
A desire to destroy as many man made hydrocarbon compounds as possible in one lifetime.

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