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M1E Preview

Posted: Sat Oct 02, 2004 12:08 am
by hinote
This is to announce my current pulsejet project.

It's called "M1E" (for "My First Engine"); it's an attempt to develop a high-density engine--that is, I'm hoping for something like l00 lbf max from an engine that is only 60 inches long.

The first iteration is shown in the bottom photo; this configuration was not successful in my attempts to get it to sustain.

The top photo shows the current version; there are a number of modifications, to reflect my ongoing education in this engine type.

The combustion chamber is 6 inches in diameter, and so is the final portion of the tailpipe.

This engine was designed with the aid of Uflow, and a lot of analysis of similar engines. It's based on the successful Ecrevisse type, and shows very powerful cyclic action in the sim. I'm hoping it will live up to my expectations, but right now I'm trying to get it to resonate--by adjusting the length of the intake (starting with a too-long dimension); I've got a split aluminum sleeve clamped to the 2 parts of the intake, and I can remove the front part and cut down the length--and then try again. About 5 minutes downtime per effort.

Current fueling is with 2 propane jets--gasified delivery at unregulated pressure (typically at 100 psig or more). After my hoped-for self-sustained operation, I will attempt to convert to liquid fueling early-on.

I have decided to reveal this effort earlier than planned. I hope this effort will be successful, and I would like to share the effort to get it to be a good-running pulsejet.

Keep your fingers crossed for me.

Bill H.
Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."

Re: M1E Preview

Posted: Sat Oct 02, 2004 12:23 am
by Mike Everman
Bill,
OH MY!

I'm speechless! And humbled. I'd like to call for a moment of silence in honor of big bertha...

Re: M1E Preview

Posted: Sat Oct 02, 2004 12:30 am
by larry cottrill
Yes, guys, that is an impressive sucker.

Bill, are the flat 'flanges' just stiffeners to strengthen the [relatively] thin cones & tubes, or do they serve some other purpose? Intuitively, if they are just strengthening webs or stiffeners, they seem conservatively large.

But, overall, looks wonderful to me!

L Cottrill

Re: M1E Preview

Posted: Sat Oct 02, 2004 12:46 am
by hinote
Larry Cottrill wrote:
Bill, are the flat 'flanges' just stiffeners to strengthen the [relatively] thin cones & tubes, or do they serve some other purpose? Intuitively, if they are just strengthening webs or stiffeners, they seem conservatively large.

L Cottrill
Larry, you're right. They're 'way too large--but, they're also formed from (available) 20-gauge stock (.037-inch). It was just easier to cut these as pictured.

They really help to hold the circularity of the megaphones as they are welded up. They're also a sort of "template" to indicate how close I'm getting to a nice round cross-section, as I attempt to form them as well as I can.

Bill H.
Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."

Re: M1E Preview

Posted: Sat Oct 02, 2004 1:10 am
by Viv
Very nice Bill, good luck.

It looks good from here i like the proportions

Viv

Re: M1E Preview

Posted: Sat Oct 02, 2004 1:16 am
by paul skinner
Holy crap.

That thing is huge. Post a video if and when you can of it running. I bet it's a monster.

Re: M1E Preview

Posted: Sat Oct 02, 2004 1:33 am
by hinote
Viv wrote:Very nice Bill, good luck.

It looks good from here i like the proportions

Viv
Thank you all for your positive comments.

A couple of additional remarks:

1. The current effort reflects my newly-found skill in TIG welding. It's the only way to weld-up these things, IMHO. I'm still on a "steep learning curve" (that means I'm still learning a lot!), but I'm far enough along to be able to weld-up a nice strong assembly.

2. The proportions are changed quite a lot from the original. The flat front face of the combustion chamber has been exchanged for a transition cone; the combustion chamber is lengthened, and the "E-Cone" (my term) has been shortened, to conform with my current analysis of this engine type.

Luckily, Uflow is especially adaptable to this particular pulsejet type. I have done several hundred iterations to arrive at the current configuration; I hope I can prove this method as a way to design a high-performance engine.

Bill H.
Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."

Re: M1E Preview

Posted: Sat Oct 02, 2004 2:51 am
by hinote
hinote wrote: right now I'm trying to get it to resonate--by adjusting the length of the intake (starting with a too-long dimension); I've got a split aluminum sleeve clamped to the 2 parts of the intake, and I can remove the front part and cut down the length--and then try again.
Please see the attached.

Here's the first attempt at shortening the intake length. The decrease is 7/16-inch (arbitrary). The cutter is a cheap piece from Harbor Freight ($15 US).

The result--still no resonance; if anything, it seems to be less active.

I'll keep trying, and let you-all know.

Bill H.
Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."

Re: M1E Preview

Posted: Sat Oct 02, 2004 3:28 am
by Mike Everman
Bill, I think you should be lengthening the intake. I suggest this because it seems like the intake is an aggressively high percentage of the CC dia, and looks to have started at less than 5 intake diameters long(?)

Re: M1E Preview

Posted: Sat Oct 02, 2004 4:46 am
by resosys
Bill,

I agree 100% with Mike, although I have no scientific reason other than my own experiments with scaling my strong running lockwoods down.

Luckily, it looks like you can easily try just about any length intake you want with those nice clamps.

Very nice work. I wish you the best of luck!

Chris

Re: M1E Preview

Posted: Sat Oct 02, 2004 2:33 pm
by Bruno Ogorelec
I am still speechless. This thing, when it works, will lift cargo aircraft by the looks of it.

We should not be surprised by it, though. When I remember how impressive that Kentfield four-piper looked, the shape of this one is only natural.

I'm keeping my fingers crossed for this one.

Re: M1E Preview

Posted: Sat Oct 02, 2004 3:01 pm
by Mark
I think it looks kind of big for a prototype. In the past I assembled some really large and far-fetched shapes that I could barely carry. I used my 2.5 gallon snorkel tank and then a two inch plumbing pipe necked up to a 4 foot length of 3 inch plumbing pipe. It was all I could do to screw the pipe fittings together held in a large vise with a large pipe wrench and lug the whole thing out into the yard for an ignition test. After about 5 or 6 tries of various variations and bell flares and neckings, I decided I would rather assemble and test smaller designs.
It's a nice looking design that Bill has, but I sense a lot of trial and error lurking about. Pulsejets can be monumentally hard to coax the genie out of hiding.
Mark

Re: M1E Preview

Posted: Sat Oct 02, 2004 3:25 pm
by hinote
Mark wrote:I think it looks kind of big for a prototype.

I sense a lot of trial and error lurking about. Pulsejets can be monumentally hard to coax the genie out of hiding.
Mark
Hey Mark:

I guess it's all in your viewpoint. I look at most of the pulsejet activity here, and it seems too SMALL to me!

BTW I have had really good success with 2 prior "large" engine projects: The Kentfield 4-tube, and M.'s QD. These both ran right out of the box, first time.

Wish I could say the same for this effort--it's payback time, I guess.

Bill H.
Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."

Re: M1E Preview

Posted: Sat Oct 02, 2004 3:52 pm
by Graham C. Williams
Dear Bill.
That's what it's all about.
What are you trying to do?
If it's just a case of getting some sort of resonance you could start with a long induction pipe. That is 2 induction pipe resonance cycles timed to equal the length of the induction period as controlled by the exhaust pipe so that the end of the second induction pipe resonance cycle corresponds with the lowest pressure in the combustion chamber. Make the extension from thin material so that you can squash the open end of the induction pipe to increase the resistance to back flow until it shows signs of wanting to start. Use this as a starting point to develop towards the configuration you want.

Why did you move away from the flat plate entry to the combustion chamber?

Best Regards
Graham.

P.S. You could also try blanking off 1/2 the induction pipe area with a lump of wood.

Re: M1E Preview

Posted: Sat Oct 02, 2004 3:58 pm
by hinote
Graham C. Williams wrote:
Why did you move away from the flat plate entry to the combustion chamber?
Graham:

Thanks for your suggestions.

The flat front plate appeared (in Uflow) to be more effective, giving a sharper cutoff for the intake gases (turbulence) and possible aiding in rectification at the intake.

But it's more critical to find the correct intake length with a flat front--and I'm already in trouble with finding the right value for that.

I need all the help I can get.

Also, it's a great place to mount the fuel injectors.

BTW I'm getting enough induction effect from the propane nozzles to eliminate the need for any starting air. Just turn on the spark, and valve-up the propane, and she lights every time.

When I get this thing running, we can plug-in the results and see how it conforms with the rest of the model.

Bill H.
Acoustic Propulsion Concepts


".......some day soon we'll be flying airplanes powered by pulsejets."