Mike's Build Log

[milisavljevic]

Hello Mike --

The fueling plenums that you have added, AKA the "Collins Collars", are a most marvelous innovation.

Just don't tell Viv that I said as much... hehehe... little buddy!

Cheers!
M.

[hinote]

Here's the triple. I think I want to bump up the intake dia, considering how well the upscale went at a little higher confinement ratio.

Mike Just a couple of thoughts (which you may have already considered):

1. The rendering seems to depict the intake and exhaust ends adjacent to each other; this would raise concerns about acoustic interference between them. This has been discussed before--E. Beck and others. Maybe you're not actually going to build it quite like the rendering?

2. The triple tube exhaust end may not be preferable to a single exhaust with the same x-section area; the decreased surface to volume ratio and attendant reduction in boundary layer effects might be advantageous.

Bill

[Mike Everman]

Yep, building it just like that. The conjunction of the exits seems to work so well on Pocket Jet that I've abandoned any concerns over interference. It may be actually constructive, considering the 31 N/L mark it hits, or it's just irrelevant, or my u-bend has them too far away from each other for a detrimental effect.
I know the triple exhaust seems a lot of work and weight, but a single exhaust would have to be longer and would change everything. The concept here is only tripling the areas in the CC, with an elliptical section so that the average radius is similar to it's "single parent", so if combustion time is truly dependent on flamespeed radially inward, it is the same as the single. The triple exhaust then has the same head loss, skin friction or pick a name (I hesitate to say impedence). The supposition here is that if I am to keep the same lengths as the single parent, the goal and point of the experiment is to have the exact same surface area to cross-sectional area on the exit tubes. On a single exhaust, the obvious next step would be to actually make it some star shaped cross-section that has the same surface area to c-s area as three pipes.

It would truly be something to have over 10 lb thrust out of this 1.5L! SFC not a being a goal, of course. Then on to augmenters!

As much as I want to continue with the scale-ups, this one has been the plan for a while to be my 1.5L entry. On to forming dies, which need to be NC'd by one of my trusty machinists.

[Kool]

Looks like this, two inlets, two exhausts and one combustion chamber. It's from the Russian company Enics.



http://www.e-vid.ru/index-m-192-p-63-article-16553.htm

viewtopic.php?f=3&t=4738 (this topic is about enics)

[milisavljevic]

Very nice Enics drone. It was mis-identified in the article (not type E95), but very nice indeed.
Combined with a thermojet combustor-intake system, twin tailpipes reduce the overall length.

Good find!

Cheers,
M.

[Mike Everman]

Thanks, Poech, that's cool.

I've gotten a bit done on liquid fueling for the recent motor. Just a collar and needle valve to go across the intake tube. I can't wait to try this motor on kero, but must wait until next weekend.

(under it, you can see the tooling fixture for holding the triple exhaust motor parts for welding.)

[milisavljevic]

Good morning, Mike!

I've gotten a bit done on liquid fueling for the recent motor.

This gets better and better, almost every day... A bit like watching something grow. Too cool.

Cheers,
M.

[Mike Everman]

OK, all set to run out to the shop and try Pocket Jet on some kerosene! Here's a vid of the fuel feed test. At least it works well with a 100 psi directed jet of air, ha ha. I wonder how it's going to do? Back in a couple of hours!

[Mike Everman]

Well, aaaaalmost. It was drawing fuel up a good foot and a half but not running on it or rather it would be over-fueled when the kero got there. When I closed it enough to (what I thought would) be a good fueling, it wouldn't draw up. I set it up for only a few inches draw and messed with the injector rotation and needle location and then filed the end of the injector at a more rakish angle, and did it all again. I got it to be running on about 90% kero for one run, just a trickle of propane still going in. It quit when I turned that off. I tried a little starting from kero only, pushing the start air deep in next to the injector. Kero clouds and unpredictable wind made me quit.

All in all, it sucked. The screw got hard to turn. The wind was constantly shifting, so I burned hair off of both arms, and I was generally nervous. Flame-outs on kero make a nasty cloud and my throat hurts. Waaaaah!

Most settings just made lots of bubbles in the kero tank, and one very finicky spot actually drew pretty well. i think I need a one-way valve of some sort 'cause the fuel tube was getting frothy... and a pressure tap off the cc would be good too...and a better fuel tank that can take some pressure, or just go full pressurized injection.

I thought this would be an easy approach, but not, though it did have its moments. Maybe just a bit higher fidelity parts and a decent tank with pressure tap. The tiniest bit of positive pressure would do it.

[PyroJoe]

Mike,
It is good to hear she is close to running on liquid. Do you think you may try methanol at some point?
Dang burnt hair takes some time to wear off. My sideburns haven't looked right for weeks. Wind is brutal this time of year.

Joe

[Mike Everman]

Yeah, James just suggested I put a quicker burning additive. I'll try that, but make a quick detour to a better needle (with a fricking handle on it this time!).

[Mark]

I wonder how well a direct tap into the side of the combustion chamber would work with a little flap valve? There is that Russian book that has an illustration of something along those lines. You can arrange for the tap to create pressure or draw a vacuum depending on which way the reed is positioned. Maybe a fuel line with the ability to draw in a slight bit of air, like the intake venturi on a Dynajet, only 95% smaller would work, have the valved fuel line offset/channeled a bit so as not to be exposed to the heat of the chamber so much. The tiny fuel/air port would not really affect the workings of the valveless I should think. I once put a "Sibley" reed valve in the front of my Logan and left the side port as is and it reved up just as peppy as without the reed, sort of a hybrid. But what I am describing would be something with a much smaller signature, just a fuel line that works by tapping the vacuum phase of the engine.
Another time I used an expensive, tiny store-bought reed, not much larger than a few BBs, that sleeved inside some silicone fuel tubing to tap the pressure off the front end of my little Logan. I had one of those brass fittings screwed into the head of the Logan and nippled off to the silicone line which fed into an air tight fuel tank. The tank recieved pressure from the silicone line and drove the fuel into the side port of the Logan. But what happened was a non-linear effect. The pressure kept increasing and the engine would flood and after it stopped the fuel kept spraying for a bit, sort of a fluidic capacitor effect. ha
Lastly, we can recall a few examples of a valveless drawing liquid fuel without the aid of pressure; however I think, as with my Logan experiments, that it is tricky to do so without some of the fuel getting spewed out of the intake, wasted because it is not delivered properly to the pulsejet. And instead of pressurizing an entire tank, I would like to think there is some way to grab a portion of the fuel line and pressurize/partition only that segment of the system so as not to reinvent the propane tank. Wouldn't it be neat to make a little fuel pump that ran on the heat of the engine?
http://blog.modernmechanix.com/2006/04/ ... pulse-jet/
http://www.elderrubber.com/duckbill-valves.htm

[Mike Everman]

Yeah, thought about whether you'd need a reed valve. I don't think you do, because the average pressure is positive in the CC, and must be somewhat lower in the intake. that method was for valvers, where the intake is ambient pressure.
When I dream of test rigs, I think about the reed valves going both ways so you can gage the lowest and highest values in the cc. I wonder what we can do with a partial vacuum, other that brake assist on our vehicle, ha.

[Viv]

Hi Mike

The Collins collar was originally conceived to run on ether or both liquid fuel or propane gas, but that was with a much larger plenum volume than you have in your current design (vapor space/heat conduction evaporator area) , but it could still be fun to give it a try, maybe when your hair grows back a bit

On the Bruno's BCVP the inlet was an exhaust half the time so there was a lot more heat to play with for vapor production.

Viv

[Mike Everman]

Here's a little vid of the first attempt.