FWE experimental intake configurations!

[steve]

OK guys, here's your big oppertunity to propose new intake designs for the FWE and potentially have them tested without you having to do anything!
I had time to kill today so I quickly whipped up a FWE minus the intake. Instead of completing it in the usual style I thought we could all learn something by experimenting with it.

So start proposing those new layouts or other things you might want to see tried (rosscodyne/unicone, thermojet style, it dosn't matter to me as long as we can learn something from it)

may the best idea win!

[larry cottrill]

Steve -

Great work and great idea! There are two that I would propose:

The most interesting to most of the group, I would think, would be the Rossco intake, right down the center to the L/8 point. Use a good intake flare, just like the original FWE. If it were me doing it, I would flatten or nozzle down the inner [rear] end of the pipe to a significant degree. A nozzle for air going in; a diffuser for blast going out.

The other one I'd like to see is my original plan re-worked so that the 45-deg leg goes ALMOST to the bottom wall - this means that the hole where it penetrates the cone would move rearward considerably, so the bottom end would still be centered on the L/8 station of the engine. The cutoff angle at the bottom should be at about 5-7 degrees greater pitch than the chamber wall, and the gap at its narrowest [the front point] would be about 1 cm from the wall. The end of the tube should be flattened to just under 1/4 inch wide, inside face-to-face. This would test my hypothesis that we should be able to get the explosion fully forward, up against the dome where it belongs. This will shorten the 'parallel' leg of the pipe considerably, to maintain the L/5 length. Again, provide a good flare as before.

L Cottrill

[Bruno Ogorelec]

I agree with Larry on the straight-ahead axial intake, poking deep into the combustion chamber, as a very interesting experiment.

[But, I would be saying so, wouldn’t I, being the father of the idea? Not to hijack yet another thread, I will make this plea separately from this, in a more formal manner.]

I would use some kind of collar in the chamber bottom, to which the intake tube would be a press fit, so that it seals tightly as soon as it gets even a little hot. This will make changes in the intake length and position easy.

Some interesting points to explore:

-- Should the intake length really be a quarter of the engine length, as some of the lore suggests (with the engine length measured from the bottom of the chamber to the end of the tailpipe);

-- At what exact position of the inner intake length is the performance the best, and how the performance changes as you slide the intake further inwards or outwards;

-- Does the best point coincide with Larry’s L/8 or perhaps with Melenric’s L/12 (the latter would be interesting, given that the Thermojet intakes are turned in the opposite direction);

-- At what point does the intake start spewing hot gas, rather than just emitting pressure pulsation (what we are talking about here is really teh question of, at what point the Lockwood layout stops and a Unicone /Rossco layout starts, and with what consequences).

[steve]

sounds good. You guys decide exactly what you want me to do and I'll build it.

A thermojet style intake using two lengths of 1/2" conduit might also be interesting...

[steve]

OK here she is.... And it dosn't run. Damn!

Later I'll discuss in detail every aspect of this engine and the subsequent failed test run but right now I have homework so here's a pic to drool over in the meantime:

[larry cottrill]

Well, at least this time you got an engine mount welded on ;-)

It appears that your intake is simply welded in - non-adjustable. Is this correct?

Anyway, nice try - it almost looks too good to fail. But then, a lot of them do ... it's a tradition.

You can still experiment with the length of the intake tube, though it becomes a bit tedious. If you're at L/5, for example, you could cut off the flare and increase it to L/4. Just something to consider. A better setup would be a sliding [or threaded!] fit and a set of slightly different length tubes to force [or thread!] into it.

L Cottrill

[steve]

OK here are some details
the intake is slightly skinnier then the 3/4" conduit would have been if I had used that. It has a dramatic pinch that begins just inside of the CC walls. The intake ends at the same point inside the engine as the original intake. The flare is considderably smaller then on the original engine. Fuel is propane injected straight into the intake.

Testing:
At best I was able to get a few loud bangs out of it but nothing resembling resonance. It was extremely sensitive to mixture settings which leads me to believe that good mixing was not occuring. I believe that with the straight intake does not create much turbulence when compared to the bent and reversed layout on the first engine, and concequently mixing suffers a great deal.
I don't think it would resonate for one of three reasons- (1) the intake was too thin and the flare was insufficient for enough air to pass through it. (I doubt this because Larry's FWE runs fine with a thin intake) (2) The layout allowed most of the fuel/air mixture to pass right through the engine into the tailpipe, bypassing the CC almost completely (this would explain why most of the combustion appeared to be occuring inside the tailpipe) Because little explosion occurs in the CC, an insufficient drop in pressure results and concequently not enough air is sucked in for the next cycle. (3) The fuel/air mixing sucks


This is by no means a dead project- I can cut the current intake off and re weld the top so we can experiment with other layouts.
The one I think would be most promising is to use the original intake layout but have it positioned so that it is nearly touching the front dome of the CC. Because the majority of the explosion will be ocuring behind the intake position, perhaps we will see less gas escaping from it.

That is just one idea, though. As before, keep posting things you might want to see tried!

[larry cottrill]

Steve -

Before you take a torch to it, ram a 'large grape' size wad of copper or stainless steel kitchen scrubber down to the far end of the intake and try again. You should end up with enough so that only tiny points of light shine through. This is what I've had some success with on tiny engines - what I have called a 'draggy diffuser'. It should greatly help turbulent mixing, and radically slow down the air right where you need it. This will, of course, greatly increase back pressure in the intake! [It also may blow out on the first decent bang you get, if you don't push it far enough to 'hang' on the inside edge.]

Obviously, the nozzled intake is just not the right approach in this case - the mixture is getting blown right past the optimum combustion point at a velocity too high to maintain ignition there. Please don't ask why I didn't see this coming ;-) The nozzle is right for a Chinese or Short lady configuration; it's just wrong here, where you want the air to grind to a halt just aft of the pipe and ignite right there!

L Cottrill

[Mike Everman]

I'd consider another fueling point, like radially inward toward the inner end of the intake, and another feed to get starting air into the CC...

[larry cottrill]

The last picture looks like something out of the beginnig of a Bond movie, except with a silhouette of a sparkplug rather than Bond.

Interesting experiment. It's a sort of Uniconeâ„¢ at that point.

Steve, it looks like your spark is well located, but you should widen that gap on the plug, to get greater spark length rather than intensity.

L Cottrill

[steve]

I've never had problems with my sparkplug gap, probably because I almost always use propane instead of liquid fuel. I could mess with it, but I have no reason to, so I usually don't.

Obviously, the nozzled intake is just not the right approach in this case - the mixture is getting blown right past the optimum combustion point at a velocity too high to maintain ignition there. Please don't ask why I didn't see this coming ;-)

I am convinced that this layout will not work for the reason you stated above and it would probably be more productive to start trying new ones rather then trying to get this one to work (I want to see it running! now! only glowing steel can fill that empty void inside me! not literally of course [/end random thought pattern])

Sorry to shoot down your ideas, but if you had been there when I tested it, you would understand just how badly the test failed and how unlikely it is that this particular layout can be made to run with any amount of tinkering.

[larry cottrill]

Steve -

Well, it's your labor, time and money, so you have to proceed as you see fit. Let me tell you, I've seen some miserable return on investment in those terms over the last few years!

HOWEVER -

Remember that in pulsejets, especially valveless, little tweaks in the geometry go a LONG way. I'm convinced that what this lady needs to succeed is an Everman-style Kazooenstein intake; i.e. a venturi right behind the flare, followed by a long diffuser. Do that and I'll bet she'd run for you!

But, it's your choice - shoot, if I wanted to see it badly enough, I'd try my next one that way myself. It wouldn't be any harder than what I've already done, given that I still have another set of cones from you to play around with. But, of course, I have other ideas for that ;-)

L Cottrill

[steve]

Remember that in pulsejets, especially valveless, little tweaks in the geometry go a LONG way. I'm convinced that what this lady needs to succeed is an Everman-style Kazooenstein intake; i.e. a venturi right behind the flare, followed by a long diffuser. Do that and I'll bet she'd run for you!

OK, that is simple enough for me to do. I'll give it a shot!
how much do you think I should pinch it?

[larry cottrill]

Remember that in pulsejets, especially valveless, little tweaks in the geometry go a LONG way. I'm convinced that what this lady needs to succeed is an Everman-style Kazooenstein intake; i.e. a venturi right behind the flare, followed by a long diffuser. Do that and I'll bet she'd run for you!

OK, that is simple enough for me to do. I'll give it a shot!
how much do you think I should pinch it?

I presume you're still using 3/4-inch EMT. Make the venturi pinch down to where you can't quite get a 1/4-inch drill shank into it and stop there. It will seem like a heck of a reduction, but there's still a LOT of area left there! Don't get it so close to the front that you can't easily bring your flare back into decent shape with a little hand work [that doesn't mean it still has to be circular - check out Mike's Kazooenstein photos]. I think that will do it.

If it runs, I'll bet you won't see any flame out the front. The blast will start to nozzle out through it, right behind the blast wave, but as soon as the main blast gas gets fully turned around by reflection from the front dome and heads to the rear, what's in the pipe should stall and turn around - it is a very small low-density mass. If there's no flame but you can feel the blast wave come out, you'll have exactly what Ross reported from his big one.

Good luck!

L Cottrill

[Bruno Ogorelec]

Sorry to shoot down your ideas, but if you had been there when I tested it, you would understand just how badly the test failed and how unlikely it is that this particular layout can be made to run with any amount of tinkering.

It is not quite the same, but Rossco got a similar layout working even on pretty weird fuels, like diesel. I mean, look at the expression on his face. Does that man look like somene whose engine has failed? OK, so his engine was a lot bigger and big engines work more easily, but still...

Maybe you are just a €#@%-hair away from a loud roar.