Big Lady for FWE Test Measurements

[larry cottrill]

Now under construction:
The straight-tailed FWE illustrated below.

A young friend has been negotiating with a MAJOR international player in the field of turbojet / turbofan development to allow the use of their extensive combustion lab facilities to attempt to measure pressures and temperatures within an FWE type valveless pulsejet engine. To that end, I have designed and am building a test engine combustion chamber/intake assembly (he will provide the tailpipe). Numerous test taps are provided, mainly located at the 10 percent through 60 percent stations from the front edge of the chamber cone and the 10 percent through 70 percent stations from the spouting point of the intake tube along its straight length. Test points can be rigged for either pressure (thin tube probe) or temperature (thermocouple probe) and the probes can be adjusted to practically any depth desired within the chamber or tube.

Construction is now about half completed. The chamber with its test taps is welded to the tailpipe socket and the next step is to cut the hole for the transition "cowl". The intake itself is finished, including all its test taps and the big fitting for insertion of the fuel pipe. Basic dimensions are: Max chamber ID = 150mm, chamber cone length = 300mm, tailpipe ID = 72mm, intake ID = 44.5 mm, intake straight pipe length = 245 mm (nom.), overall length = 950mm from chamber cone front edge to tail edge (tailpipe length subject to change for tuning!). The chamber dome was held down to 20mm height at center.

Once again I have to thank Jim Russell of Jim Russell Design for his shop, tools and considerable skills and his son Matt for superb welding ability (Matt did all the welding of the stainless test tap fittings onto the steel parts, and beautifully done, too).

One of the major things I'm testing on this engine is the use of an annealed form of Reynolds chrome-moly aircraft steel for the chamber and intake. Even the annealed form is a lot harder to work than the mild steel I'm used to. It welds beautifully, though! It will be interesting to see how this .040-inch (1mm) thick chamber holds up under full-bore running.

I hope to get some photos this weekend. If we really get to test this, I'll open up a new thread for that. We should get some good data; the pressure sensors can register variability to the tune of 15 khz !!!

L Cottrill

[Jutte]

Very exciting indeed. The data from that hopefully
will spawn alsorts of neat designs and theories/facts
etc.There seems to be a quiet awakening interest
in aviation re the pulse jets recently. I was talking to a
Aeronautical Engineering tutor and he was very interested.
Also had occasion to look at a well respected Aircraft enginneering
handbook/manual - what it contained in about pulse jets was pretty minamal.
I think that most of us here on the forum don't realise that we are pretty
much up there when it comes to pulse jet technology.
The Aeronautical Engineering tutor was basically stunned at what is
happening here.
OK - pats on the backs for all of us...LOL!

[Mike Everman]

Looking forward to pics, Larry!

[Dang911]

I wouldn't be so sure that pulse-jets and PDE's are left off the radar of the big jet companies. I can tell you that DARPA, Air Force, and NASA still have immense interest in these engines and have several highly active projects, they are just very well covered up as secret projects. There has been some headway we just won't see it yet for another 15 years due to its high secrecy, rest assure though, these engines are not dead, and if you find the right people on these projects you will find a great wealth of knowledge not found on the forum.

[larry cottrill]

Jutte et al -

All that I'm after is for US to get some real data that will make things more understandable, especially to validate our one-dimensional design methods (NUDiS and UFLOW). Anything we learn beyond that is gravy. I have to agree with Dang -- there are pulsejet things going on someplace that we know not of.

Last night I got the big port cut out of the cone. I'm taking off early from my day job to get back to Jim's shop this afternoon. I should be able to get the rear edge of the port pulled up flat and get the intake welded on, maybe even get the pattern made for the intake "cowl" to go on there. This noon I'll try to work out the full-scale plan for that tubular-truss mounting lug, so that can be built up sometime soon. Once the cowl is welded on, all that's left is to get the dome on the front end and get the spark plug mount welded in, and finish up with the mounting lug. And, I WILL get some photos, too.

If all goes well, sometime before the end of next week we should be ready to ship.

I'll try to get permission to post a few shots of Jim Russell's artwork on the Off Topics Forum, too.

L Cottrill

[larry cottrill]

All right, finally -- a few photos of what we've got so far.

All comments welcome.

L Cottrill

[Mike Everman]

Neeto. Looking good so far!

[metiz]

I'm not criticising, I'm as happy as anyone that this is going to happen but I must ask: why a FWE family design and not, say, a chinese?

[larry cottrill]

I'm not criticising, I'm as happy as anyone that this is going to happen but I must ask: why a FWE family design and not, say, a chinese?

Mostly, there were reasons it had to be something that could be put together fairly quickly and cheaply. (Well, it would have been "cheaply" if I'd used the mild steel to which I'm accustomed -- easier, too, since I'd have had the strength to bend the cone unassisted.) From my standpoint, it makes it easy to locate the test points so that the data should be easy to interpret. We also saw some advantage in using a design that has never been seriously measured before. For better or worse, I quite arbitrarily decided that the most interesting areas were the intake and the chamber front end.

Obviously, it would have been interesting to do any number of designs. One hasn't got time to do them all when you're working on an amateur basis; you just have to go with what you think you can accomplish with the resources at hand. I recognize that many would be more satisfied if a more "advanced" design had been provided. One important consideration was that with this simple design, I didn't have to provide the tailpipe, making shipping easier and allowing the recipient to be in charge of final tuning by whatever means he's comfortable with.

L Cottrill

[larry cottrill]

More construction photos. The intake "cowl" or "fairing", formed and welded. The small hole in the cowl is for Yet Another 1/8-inch Swagelok Fitting.

L Cottrill

[Johansson]

Nice work there Larry!

[Mike Everman]

Yeah!

[larry cottrill]

Thank you, gentlemen! Please understand that without help from Jim and Matt, I would have found this project utterly impossible.

I only had about four hours total to work on it yesterday, mostly in Jim's shop. Fully HALF that time was spent removing distortion from the cone (due to welding on the intake cowl) and from the tailpipe socket after having Matt weld on the bottom rails for the vise mount lug. We did simplify the mount rails, making them simple steel bars welded on parallel to one another with a 0.5-inch separation between. Note that the only thing these rails need to do is provide LOTS of weld to the chamber cone -- and there IS plenty of weld! We should have no fear of the engine ripping off the mounting lug at some unlucky moment! See full-size drawing attached.

I decided to go ahead and have Matt TIG weld the dome onto the chamber cone, because the final "rounding" step was to make a lot of little tack welds all around the rim while Jim used the dome as leverage to move the cone wall in or out slightly at various locations. (This is hard to describe and hard to visualize what I mean, if you haven't done it.) Very meticulous, but the result was beautiful once I cleaned up the joint by hand filing. Unfortunately, no new photos yet. Matt also welded on the last two Swagelok fittings -- a 1/8-inch on the little hole in the cowl and a 1/16-incher on the right side right on the cowl-to-intake weld line (on a spot I had planed smooth with my Dremel grinder). Beautiful again.

So, the only things left for me to finish up are:
- Weld in the spark plug mount
- Build the mounting lug
- Weld the lug into the bottom rails, WITHOUT re-introducing distortion to the tailpipe socket.
- Bend one of my Simpl-Jector fuel tubes to fit
- Re-gap and add on the dinky CM-6 spark plug
- Take the final photos of the whole works
- Package and ship!

More photos later.

L Cottrill

[larry cottrill]

Just about finished up. Got the mounting lug built last night, but I got tired, back aching, etc., no longer able to hold the filler rod steady, and lost the will to try to get it welded onto the belly of the engine. So I'll have Matt Russell do it for me today so I can ship it out. I got a couple of shots earlier in the day, showing the dome welded on and the mount rails. The final two Swagelok fittings also show here, as described earlier. No picture yet of the mount lug because it was too late and I was too tired. I'll try to get some pictures with my RB-67 (real film!) today before I package her up for UPS.

L Cottrill

[PyroJoe]

Looking good!
There is a certain appeal of the 15 degree FWE, sweet to the eye. Take it easy with the back, holding filler rod steady can be a task even on the good days. (looks like the porch is coming along also)
Joe