Pipewood Pulsejet build

[username]

Hi guys, just thought i'd share my Pipewood build. I've made a video of the process, maybe it can help someone else build their own Pipewood!

http://www.youtube.com/watch?v=MPZXXwuvxR8

As of yet it does not run, I have decided the problem is in my ignition system. I have been trying to start it by sticking a large wire connected to an electrical pulse generator down the intake, but the problem is this wire takes up 50% of the intake space. I am going to install a spark plug once I get the spark plug tap I ordered.

I am also going to reduce the size of the fuel injector to 3/32 of an inch, as currently I am using a way over sized copper pipe for injection, and it also takes up a lot of the intake space. 3/32" should be plenty large enough for fuel flow, and small enough to take up little room in the intake pipe.

I'll post more updates as I continue working on this jet, if anyone cares.

[username]

Well, here's part two.

http://www.youtube.com/watch?v=X6T80qJhFnw

[metiz]

That M40 is worth fixing - it will knock your socks off when it's going! cool pipejet build btw

[username]

So it is the M40, thanks metiz! That was a fun jet to build.

Holy crap, I don't know if my neighbors would tolerate the M40 running, after I just ran that little pipewood! First successful pulsejet run I have ever had, although it is only running on forced air right now.

Jesus man, I know people say pulsejets are loud, but I had no idea they would be this fricken loud. You can actually feel the concussions from the engine. Also, I may not be hearing for a few days now.

I'm definitely hooked, but now i'm worried about noise complaints from the neighbors!

[username]

It still isn't running without forced air

Part 3, where I attempt to solve it's sustain problems (and fail) :

http://www.youtube.com/watch?v=dKlGzaUAyQk

Here's what the jet looks like so far, after a forced air non-sustaining run:

On forced air, it sounds just like any pulsejet I have heard run. It noticeably runs better when the engine starts to get red hot. adding fuel when It gets to this stage kills the engine, and reducing the fuel puts the engine in "grumble" mode, where it will quietly roar, but is not technically "running" . When a large excess of fuel is added, the engine will not run at all, but rather violently explode every couple of seconds, without a continuation of combustion.

Any suggestions? I am soooo close to getting this thing to work. Will flaring the exhaust help? will making the flare on the intake even larger help? what about lengthening the intake, or even further lengthening the now rather long exhaust?

[metiz]

What's with the 90 degree bend on your injector? There's a good chance that's your problem. Just make a Rosscojector and use that. It's also a good idea to attach it to the intake with some hoseclamps so you have both hands free.

[username]

Hmm, well in this thread: viewtopic.php?t=1643&postdays=0&postorder=asc&start=0

Mike Everman said:

Stinger in the opening didn't work, but one that blew at 90deg, and put all the way down to the cc opening started right up, like, instant start. Nice throttleability, no visible flame. Coolish exhaust out the front.

Which is why I bent the end of the injector 90 degrees. I suppose I could try a straight injector, pushing fuel right into the combustion chamber. I have heard that you want to avoid "laminar flow" of your fuel, which means you want the fuel injection to be disrupted, not straight flowing, right?

Thank you for your help Metiz, you are a legendary jet builder, can't wait to see the M500 running

[metiz]

Legendary am I? WHERE'S MY WHEALTH AND FAME!?

if you try a rossco, don't stick it in realy deep into the intake, keep it shallow, like 10-20%

[username]

Haha! Success!

After modifying the injector as you said, I was able to get it to self-sustain with no forced air!

I made the injector point straight into the combustion chamber, with the tip of the injector only about one inch inside the intake from the venturi on the end. the injector was perfectly centered in the pipe, and it was a rossco style injector. When the propane was turned on, without a spark, you should be able to put your hand right in front of the intake and feel cool air being sucked in. if you put your hand on the exhaust, you feel propane coming out.

Engine is started as normal, with spark and air, and held at a loud roar until the whole engine is red hot. Once it is red hot, only then can you start to pull the air away, slowly and gently. (at least in my experience, it wouldn't self sustain unless red hot)

After that, it runs on it's own! I threw the air hose aside, pulled off the spark plug, and marveled at pure jet propulsion. Fuel goes in, thrust goes out!

I'll have a video of it running soon enough, thanks for your help metiz!

[metiz]

Good to hear you've got it running. Fun stuff right?