www.pulse-jets.com

Hi all:

Today I performed the first tests of my latest valveless pulsejet, the M4E.

The results are a mixed bag (some good, and some not so good).

On the positive side, the engine started very easily and ran smoothly over a wide range of throttle settings. I'm quite pleased to have an engine that just started and ran well, the very first time. No teething problems there.

Max demonstrated thrust was 12 lbf, and minimum was 3.5 lbf. The max value is below what I had hoped for--but is still excellent for a combustor diameter of 73 mm, and a duct length of about 1500 mm.

The latest construction methods and mounting concepts were effective in keeping this engine from showing any deformation, in spite of extended hot runs with a lot of metal color showing.

On the negative side, the engine has very poor fuel specifics, compared to my expectations (and previous successful engines). The demonstrated TSFC at 5.5 lbf was about 3.0, and the TSFC at 8.5 lbf was about 3.9.

This engine has taught me more about the complex variables that dictate the operating qualities of a valveless pulsejet. I will be making substantial modifications to the design and I predict further success toward my goal of an efficient engine for aircraft application.

Bill H.
Acoustic Propulsion Concepts

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

Congratulations! Doesn't sound bad at all, except for fuel consumption. Bill, let us know when you have some idea on why the fuel consumption is so high.

Howly crap! And congratulations!

Cool, that the engine started and ran without any problems.

I think the thrust value of 12 lbf is pretty good for the size.

Did you also measure the TSFC for the original 1/4 Kentfield?

Bruno Ogorelec wrote:Congratulations! Doesn't sound bad at all, except for fuel consumption. Bill, let us know when you have some idea on why the fuel consumption is so high.

Well, yes--I'm sure I know what the problem is.

The evidence was pretty obvious--the so-called "combustion zone" extended too far down into the exhaust assembly (visual evidence in the metal heating pattern), and there was a distinct smell of unburned propane in the exhaust.

The engine isn't timed properly. That means the re-compression wave(s) aren't arriving to do their job, in coordination with the onset of the next combustion event.

I did a very rough "eyeball" estimate of the appropriate time for the onset of combustion--and it has come back to haunt me. It's yet another variable that UFlow isn't capable of handling.

The M2E would run, with the smaller of the 2 throttle valves just barely cracked open. This one needed both valves opened, quite a ways--so I knew the TSFC wasn't going to be very good.

It's all a learning experience.

On the bright side of the fueling situation, the choice and placement of the injectors appears to be nearly optimized--the engine starts easily and throttles well (and that's partly due to the injector situation). You'd be surprised how many mistakes it takes to get to that point!

My ratio of research and development, to actual running time--continues to be about 100:1. Some day soon I hope to reverse that number..........

Bill H.
Acoustic Propulsion Concepts

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

hinote wrote:
My ratio of research and development, to actual running time--continues to be about 100:1. Some day soon I hope to reverse that number..........

Bill, we all have the same problem !

Ed

Nice, Bill!

hinote wrote:
Max demonstrated thrust was 12 lbf, and minimum was 3.5 lbf.

I re-checked the calibration on the thrust stand, this afternoon.

The values are within about 1/2lbf of the original numbers; the variation would appear to be due to the smaller, lighter engine contributing less weight to the total. Still, the accuracy is within something like 5% or so of the original.

I'll post a photo tomorrow, of the M4E in the thrust stand.

M4E is a dead-end for my engine development, for the time being.

M2E3 is off the (virtual) drawing board, and I hope it will demonstrate my design intent--to operate an efficient pulsejet at part-throttle, and to maintain the desired max thrust output--all at the same time.

I'll be several weeks, due to social events, and fishing trips in the Eastern Sierras.

It's a tough life!!

Bill H.
Acoustic Propulsion Concepts

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

Bill
Looking forward to seeing the pictures and to reading more.
Take care of yourself. All that socialization and fishing can really get you down.
Dave

Dave wrote:Bill
Looking forward to seeing the pictures and to reading more.
Take care of yourself. All that socialization and fishing can really get you down.
Dave

Heheheh...

Yeah, enjoy your time apart from pulsejets. Necessary to refresh the mind somehow, IMHO.

hinote wrote: I'll post a photo tomorrow, of the M4E in the thrust stand.

OK, here's the photo.

The engine borrows several design cues from existing engines.

The most obvious is the "step" in the transiton cone behind the combustion chamber--from the Ecrevisse C.

The curved intake tube is formed from sections of exhaust u-tubes, of several diameters. The intake length is only .60 inches longer the the bend radii, so it's pushing the limit of do-ability. The front plate is formed from 10-gauge (.134 inches) mild steel.

The engine is mounted at one solid and 3 articulated points. No distortion was noted even after extended hot runs. The overall length of the engine increased by an estimated 1/2-inch during hottest operation.

This engine starts easily, using a modified leaf blower for auxiliary air (stationary unit with flex hose and small-diameter nozzle). After a short warmup period of about 10 seconds the engine transitions easily into resonance with increase of fuel feed.

Bill H.
Acoustic Propulsion Concepts

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

Thanks Bill!

Interesting what the Ecrevisse C shape does...

Interesting, I wonder if it is better to do away with the air gap in the rectifier?
Mark

Mark wrote:Interesting, I wonder if it is better to do away with the air gap in the rectifier?
Mark

Mark:

There's no rectifier.

The intake is curved around, 180 degrees.

If you're not sure about my statement above, let me know; I can post a drawing showing the concept.

Bill H.
Acoustic Propulsion Concepts


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

I was thinking it is an escopette without the air gap leading to the rectifier/elbow that redirects flow. You say the elbow is not a rectifier, well that's fine. In Foa's book he calls the escopette elbow a rectifier and has some other pictures of other examples.
Perhaps your interesting design can at least be seen as a branch off the escopette tree. It hadn't occurred to me to wonder why the French didn't just do away with the air gap. Good luck with it, I like the idea.
Here is a Logan I pondered that didn't work but I suppose the 90 degree "elbow" redirected flow concept would work with some tinkering.
Mark

Just wanted to add, I had hoped my elbow Logan would have run as brightly as the regular design. I didn't work with it for very long, so I feel the elbow Logan could still be a viable variation.
I guess you could say your engine has an elbow port on the end and the altered Logan, (and not yet run), a half elbow on the side.
Mark