Proposed Design - Straight Pipe 'Henri' Valveless Pulsejet

Moderator: Mike Everman

'Henri' Prototype Completed!

Postby larry cottrill » Thu Mar 03, 2005 12:25 am

I stayed home from my day job today so I could work on my 2004 accounting and corporate income tax, but finished Henri instead. I think it looks wonderful - most of the gold paint is still on it, except where I welded on the front plate and heated and bent flares [tailpipe end and front edge of intake slots]. It looks almost exactly like the drawing. I probably spent five hours doing it - but I have a very poor "shop" to work in [I have to saw and file in the basement, drag the vise out to the garage for welding and heating, etc., etc.]. A good metalworker with a well-equipped shop could do the whole job [including the initial cutting and squeezing] in an afternoon, easily.

There is a whopping six lineal inches of weld to the whole engine, since no engine mount lugs were added. The most tedious part was filing out the intake slots, since it was almost all done with small needle files. I probably spent more than a half hour on that alone. Another time-consuming part was flaring out the front intake edges, done by very localized flame heating and prying out with the curved handle of an old SS spoon. But, the end result at the intakes is beautiful, I think.

Variances from the drawing are slight, but as follows: The air intake slots are more square-ended instead of fully rounded at the top and bottom. I did this because I thought the front flaring would work better with them that way. I took the time to bevel the inside rear edge of the intake slots to a sort of quasi-knife-edge. The flaring of the front intake edge is slightly more pronounced than in the drawing - I just thought it "looked right" to go a bit farther. I went farther than I wanted on the tail flare, though it seems fairly uniform and nicely shaped. The copper coil is considerably closer to the intake slots than shown on the drawing. And as I mentioned earlier, I squeezed the pinched "stack" significantly tighter than shown.

Total finished weight is 13.5 ounces, with the CM-6 spark plug in place. I can't tell right now whether I'll have a chance to try it tonight or not. Construction photos next week; run photos later if all goes well.

L Cottrill
larry cottrill
 
Posts: 4140
Joined: Sun Oct 05, 2003 1:17 am
Location: Mingo, Iowa USA

Re: Proposed Design - Straight Pipe 'Henri' Valveless Pulsej

Postby Bruno Ogorelec » Thu Mar 03, 2005 11:17 am

Go for it, Larry! I am very excited by this project.
Bruno Ogorelec
 
Posts: 3542
Joined: Sat Oct 04, 2003 7:31 am
Location: Zagreb, Croatia

First Test - Some Changes Needed

Postby larry cottrill » Fri Mar 04, 2005 3:32 am

I tried it out tonight with propane and about 40 degF air temp. It took a lot of tries before I finally figured out how to get combustion, with moderate starting air coming in at about a 45 deg angle from the left rear [i.e. the side the fuel pipe is on]. What I basically got was 'blowtorch' combustion, with a few occasional muffled bangs. What I observed:

- No obvious combustion in the chamber
- Somewhat noisy combustion in the center of the intake region
- Tailpipe paint burned fairly quickly; NO evidence of heating forward of the intake area [paint not even blistered]
- No evidence of pulsation
- Very prone to flooding of the chamber with fuel; takes 20-30 sec to clear with judicious application of air
- Very touchy in terms of fuel flow
- Very sensitive to slight changes in aim of starting air [shop vac used]

Conclusions:

- The chamber is quickly pressurizing slightly, so starting air and fuel stop flowing forward; the good circulation from the inward spouting of a rear-facing intake pipe is totally absent in this design.
- Enlarging the intake ports and flares is an absolute must; their total area is much less than the sqaushed pipe cross-section. Before testing again, I will basically double the area of the ports, hopefully without completely sacrificing acoustic coupling between the front and rear engine sections or excessively weakening the top and bottom of the tube. After testing again, I'll decide whether to enlarge the flares as well.
- It may be necessary to use an air tube to make sure starting air actually circulates forward through the chamber; aiming of the tube would probably be critical, as would applied pressure. Something like my concentric air/fuel tube design could presumably be used once proper aim is established.

Comments / questions?

L Cottrill
larry cottrill
 
Posts: 4140
Joined: Sun Oct 05, 2003 1:17 am
Location: Mingo, Iowa USA

Re: Proposed Design - Straight Pipe 'Henri' Valveless Pulsej

Postby Bruno Ogorelec » Fri Mar 04, 2005 9:44 am

Larry,

I've had some fears for this type of the design precisely because of its curious layout with a single orifice. It could well be that in small sizes it will always give trouble starting because proper initial flow is difficult to establish. If you remember, Reynst had two fuel feeds -- direct into chamber for starting and at the chamber lip for continuous running.

(He also had two chamber volumes -- big for starting and small for continuous running -- but I guess we should not follow the original too blindly; shall we? :o)

Basically, this design will have to be able to start without the usual starting flow with shop air. Alas, it was mostly big engines that have shown penchant for such easy starting so far.

I have three ideas for a way out.

The first is the simplest -- it's the favorite game of our veteran jam-jar experimenter, Mark 'Thixis'. Just spray some starting liquid into the chamber to start proceedings with a bang. Hope that it will pick up the propane feed after a few jam-jar style cycles that such a starting method provides.

Another idea is much more complex and of questionable practicality. But, for what it's worth, here it is.

A measure of initial through-flow might be introduced by having a barrier separating the two intake orifices. If a short flat splitter plate is positioned at the tube centerline so that it masks the direct path between one intake slot and the other, and you only blow into one slot, a measure of through-flow will be enabled. How to mount such a splitter plate inside the tube is a question I will leave to your imagination. Mine has stalled.

Finally, your own idea (described elsewhere in the forum) of having a combined air and gas stinger might work here. Such a probe inserted into the engine fairly deeply -- almost to the chamber bottom -- might create good starting conditions. When the thing catches up, you withdraw the fueling probe. Relatively simple in the shop, less so in the field.

Frankly, if the Thixis Method fails to produce results, I am worried.
Bruno Ogorelec
 
Posts: 3542
Joined: Sat Oct 04, 2003 7:31 am
Location: Zagreb, Croatia

Re: Proposed Design - Straight Pipe 'Henri' Valveless Pulsej

Postby larry cottrill » Fri Mar 04, 2005 1:35 pm

Bruno -

Interestingly, I too thought of the 'splitter plate' idea, but find it artistically distasteful. More seriously, it seems to me to be one of those superficially simple things that would be hard for a beginning metalworker to accomplish. I could do it without too much trouble by drilling a 1/16-inch hole through the top and bottom and cutting them into slots with the round needle file. Or, if I had my old Dremel tool working, I could slot the top and bottom with careful use of those thin abrasive wheels [what we used to call 'cutoff wheels', since we used them to cut through music wire for model airplane landing gear, etc.].

If your slots were small and finely crafted enough, you could actually have a removable splitter plate just for starting and slide it out, like the daggerboard on some little sailing craft. Rather than being unfortunate 'leaks', the slots are right where they should be to help with breathing. I'm assuming that the plate would only need to cover the immediate area behind the ports, of course. Even if a permanent plate is used, I guess we wouldn't have to worry about rapid disassembly since it would presumably be cooled by the air coming in.

Using an air pipe means shifting from low-pressure high-volume sources [e.g. shop vac] to regulated pressurized air. But, I used to be quite confortable with that when the Dynajet was my only engine. In the field, a small reservoir of pressurized air is much easier to manage than an electric powered blower, anyway. If the outer end of your pipe were threaded like a tire valve, it would match the Dynajet 'flowjector' air entrance exactly.

The 'business end' of our air pipe could be a short 'duckbill' flat at the end of the pipe, to get good velocity out of very low flow volume. With high velocity discharge, you shouldn't have to get it clear into the front of the chamber to make it work. In fact, I wonder if it couldn't be a 'bent duckbill' that conveniently hooks over the front flare of the intake slot so it would be very easy to place and remove.

I'm sure that the key here is proper air circulation during the starting phase, just as you've said. In fact, I think in general the basic problem with starting almost any pulsejet is getting the right volume of air at the right place. I think fuel has to be somewhere close to right, of course, but getting the air delivery just right is the critical issue. A "Chinese" style intake makes it fairly easy, because it establishes a good circulatory path right from the get-go.

Mark's methanol pre-charge method would never have occurred to me if you [or someone] hadn't mentioned it. I'll have to try it, just to see what I can get to happen.

Thanks!

L Cottrill
larry cottrill
 
Posts: 4140
Joined: Sun Oct 05, 2003 1:17 am
Location: Mingo, Iowa USA

Re: Proposed Design - Straight Pipe 'Henri' Valveless Pulsej

Postby Bruno Ogorelec » Fri Mar 04, 2005 2:04 pm

Larry, this was a wonderful treatise on the ways to transform my hot air into cool practical solutions.... Gives me hope that one day, my feverish concepts may actually fly.

What amazes me, however, is the way your ideas parallel mine at times. I've heard other people in the forum say so about you, too.

Given a few more years, you'll have the entire ground covered and there will be no pulsejet idea left that has not already been conceived, analyzed, improved upon and beautifully drawn in MS Paint -- in other words, Cottrillized.

No, no, I'm telling you; that poster of The Pope of Pulsejets, with an Elektra sitting casually in the crook of his arm, is going to be worth millions one day.
Bruno Ogorelec
 
Posts: 3542
Joined: Sat Oct 04, 2003 7:31 am
Location: Zagreb, Croatia

Henri Engine - First Construction Photos

Postby larry cottrill » Fri Mar 04, 2005 5:03 pm

Well, here's a few pix from the very beginning of construction.

L Cottrill
Attachments
Henri_tube_marking_crop1_small.jpg
Here's how I get a straight cut in tubing - wrap a piece of paper around it so the straight edge overlaps perfectly, then mark it. Photo Copyright 2005 Larry Cottrill
Henri_tube_marking_crop1_small.jpg (157.35 KiB) Viewed 5387 times
Henri_tube_pinched_crop1_small.jpg
Engine tube fully pinched, fresh from the vise. Region was carefully marked before pinching. Photo Copyright 2005 Larry Cottrill
Henri_tube_pinched_crop1_small.jpg (169.25 KiB) Viewed 5387 times
Henri_intake_marked_crop1_small.jpg
Marking of the intake slot center and limits, with ultra-thin permanent marker. Hole will be drilled at center point. Marks for the pinched region are visible, also. Photo Copyright 2005 Larry Cottrill
Henri_intake_marked_crop1_small.jpg (155.72 KiB) Viewed 5388 times
Henri_intake_filing_crop1_small.jpg
After drilling a 7/32-inch hole, the Heller needle files were used for making the intake slots - time-consuming, but not difficult with such thin-walled tubing. Photo Copyright 2005 Larry Cottrill
Henri_intake_filing_crop1_small.jpg (164.19 KiB) Viewed 5387 times
Henri_plug_mount_finished_crop1.jpg
Finished spark plug mount - M10x1.0 bicycle hub nut welded to a 1/2-inch washer [about 1.4 inch OD]. Bolt and nuts were used to protect the threading while welding. Photo Copyright 2005 Larry Cottrill
Henri_plug_mount_finished_crop1.jpg (154.23 KiB) Viewed 5388 times
larry cottrill
 
Posts: 4140
Joined: Sun Oct 05, 2003 1:17 am
Location: Mingo, Iowa USA

More Testing, More Promising

Postby larry cottrill » Mon Mar 07, 2005 1:43 pm

Since I was gearing up for compressed air starting of the Elektra II with its new air/fuel pipe setup, I made a starting air jet for Henri. It consists of about an inch of 1/4-inch brake line with the end smashed flat and bent at 45 deg so it 'hooks into' the same air intake where the fuel pipe is located. It sits there just below where the fuel pipe enters [the orientation of the fuel pipe is unchanged]. Various air pressures to the tube were tried. The tube is mounted via a hokey 'harmonica holder' made out of a piece of 1/16-inch SS welding rod, an ideal material for such purposes.

Use of the air tube resulted in a lot of pops and bangs and burning the paint off the chamber, finally! There also were some 'machine gun' pulsating runs under the influence of starting air, up to [I'm guessing here] 20 or 25 cycles per second! Only a fairly high starting air pressure [20-35 PSIG] would make it pulse like that. The pulse rate was dependent on the rate of fuel feed, and if you try to push it too far it suddenly switches to Bunsen burner mode. There is a fair amount of leakage out through the intake ports during bangs, significantly less in 'machine gun' mode, and lots in burner mode.

The air tube is obviously a huge improvement, since it seems to succeed in getting the air [and fuel] forward in the chamber where it's needed for explosion development. I think the high pressure requirement is probably due to the fact that the flat 'duckbill' of the tube is squeezed almost tight - I'll make another one that has a more open profile in the nozzle zone so it will deliver more flow, and try again.

I think the low-rate 'machine gun' pulsation is, once again, evidence that the device isn't currently capable of picking up enough air for good cycling. I haven't done anything yet to enlarge the air intake ports, and probably won't until I think I have the air tube pretty well optimized.

Comments?

L Cottrill
larry cottrill
 
Posts: 4140
Joined: Sun Oct 05, 2003 1:17 am
Location: Mingo, Iowa USA

Re: Proposed Design - Straight Pipe 'Henri' Valveless Pulsej

Postby Bruno Ogorelec » Mon Mar 07, 2005 7:37 pm

Good progress, Larry.

I have to go back to Reynst and his volumes. Obviously, a bigger volume makes for easier starting. Unfortunately, changing the volume is not an option.

Can you think of a way to build a prototype with a variable volume?

Have you tried the Thixis Method of kick-starting the thing?

I'm thinking hard. I really, really, want this to work.
Bruno Ogorelec
 
Posts: 3542
Joined: Sat Oct 04, 2003 7:31 am
Location: Zagreb, Croatia

Re: Proposed Design - Straight Pipe 'Henri' Valveless Pulsej

Postby mk » Mon Mar 07, 2005 8:41 pm

Cool that you got the engine pulsating, at least with additional air.

Adding a fueling line to the second inlet port might help at least a bit by equalizing the flow characteristics of "both inlets".

I cannot help myself, I'm still seeing a more or less "annular" Chinese/Thermojet engine in the "Henri" engine.
mk
mk
 
Posts: 1053
Joined: Mon Jan 19, 2004 8:38 pm
Location: FRG

Re: Proposed Design - Straight Pipe 'Henri' Valveless Pulsej

Postby larry cottrill » Tue Mar 08, 2005 2:14 am

Bruno Ogorelec wrote:I have to go back to Reynst and his volumes. Obviously, a bigger volume makes for easier starting. Unfortunately, changing the volume is not an option.

Can you think of a way to build a prototype with a variable volume?

Not in any simple way. I think that has a lot to do with his 'jam jar' style starting, anyway. There shouldn't be any reason this won't start and sustain with a fixed geometry, like any other of my supposedly "successful" engines.

Have you tried the Thixis Method of kick-starting the thing?

No, haven't gotten around to it. I've got a couple of spray cans of methanol just sitting there 6 ft away from my test bench, and I still never think of grabbing one!

I'm thinking hard. I really, really, want this to work.

As do I. I'm still sure it's basically just a matter of fuel/air volume at the front of the chamber. That's all there is to it.

mk wrote:Adding a fueling line to the second inlet port might help at least a bit by equalizing the flow characteristics of "both inlets".

I actually think strict equalization from side to side isn't critical. It's more a matter of getting the right flow of air down to the end where it's really usable.

I cannot help myself, I'm still seeing a more or less "annular" Chinese/Thermojet engine in the "Henri" engine.

Of course - it's not that different, really, especially in wave terms. Controlling the mass flows before explosion is the whole issue, and that's where the differences lie.

L Cottrill
larry cottrill
 
Posts: 4140
Joined: Sun Oct 05, 2003 1:17 am
Location: Mingo, Iowa USA

Re: Proposed Design - Straight Pipe 'Henri' Valveless Pulsej

Postby mk » Tue Mar 08, 2005 5:05 pm

Larry,
have you seen the dimension drawing of the homebuilt Thermojet type engine having two intakes?

Take a careful look at the fuel injection methode. Would surely be worth giving it a try at the Henri engine, then a bit smaller, of course. Advantage: Youd get the fuel where you want it, at the nose of the engine. I'd never ever have thought of such a "double stage bottom" since it didn't work for my Reynst combustor.
mk
mk
 
Posts: 1053
Joined: Mon Jan 19, 2004 8:38 pm
Location: FRG

Re: Proposed Design - Straight Pipe 'Henri' Valveless Pulsej

Postby Mark » Tue Mar 08, 2005 5:27 pm

I was noticing that too last night, the different point of fuel injection and wanted to try it on my larger larger plumbing pipe side ported Logan that I know to work. It would be easy for me to install/screw a 1/8th inch fuel fitting in at the tip of my jet and feed in propane that way.
Mark
Presentation is Everything
Mark
 
Posts: 10511
Joined: Sat Oct 11, 2003 10:14 pm

Re: Proposed Design - Straight Pipe 'Henri' Valveless Pulsej

Postby larry cottrill » Tue Mar 08, 2005 5:42 pm

It's neat that they got that to work - that was really an unexpected detail to see. But, to me, injecting at the air inlet is just simpler to rig. Even even with their configuration, they still need starting air, so why not use it to carry the starting fuel charge along?

I suppose I'm just prejudiced toward the air inlet location, since I've had such good success with that, especially after Steve "perfected" it. As Bruno has said, it just makes sense to me.

L Cottrill
larry cottrill
 
Posts: 4140
Joined: Sun Oct 05, 2003 1:17 am
Location: Mingo, Iowa USA

Re: Proposed Design - Straight Pipe 'Henri' Valveless Pulsej

Postby mk » Tue Mar 08, 2005 5:55 pm

Larry Cottrill wrote:[...] I suppose I'm just prejudiced toward the air inlet location, since I've had such good success with that, especially after Steve "perfected" it. As Bruno has said, it just makes sense to me.


Surely, but for such a small engine as the Henri represents it might bring some (--- also to me --) obscure advantages, atleast for sarting, perhaps.

But before doing s.th. in this direction, try Mark's starting methode.
mk
mk
 
Posts: 1053
Joined: Mon Jan 19, 2004 8:38 pm
Location: FRG

PreviousNext

Return to Valveless pulsejet forum

Who is online

Users browsing this forum: No registered users and 2 guests