www.pulse-jets.com

/me edge of seat.

Fantastic! - got your propane and ignitor ready for a test run? -- we need a video!!

Here you go, Simon, bananarama:

Wow that's a lot smaller than I thought! Looks great. Can't wait for the first run.

Well, only one didn't have support material in the CC.
And the fueling holes are clogged with support material too.
I’ve gotten it just far enough to try the starting stinger: Need to find my dinky drills. I think a good starting point for this stinger is .5 mm…
Any ideas or examples for nozzle shapes that promote entrainment?

I see a 10 mm CM-6 spark plug found a home. Seems I remember a pocket for scale one time. Guess you can do some vibration testing soon. Just wondering how the sintered powder method will hold up.
It will be neat to see it run and how you use it. It's pretty just as an art form and the texture appealing.

Mike Everman wrote: ↑

Sun Mar 13, 2022 9:14 pm

Any ideas or examples for nozzle shapes that promote entrainment?

I've never found anything that works better than a rosscojector.

Yeah, I’ll do a few tests at nipping it to make a Rosscojector, but when you think about the area we are talking, the holes i was experimenting with were around .5mm. A nip or slit just seems too hard to replicate, or hit any specific area in production. Maybe it’s not that finicky…. I’m pointing down the centerline, which makes me think a straight across nip…
And then, if I hold a stinger candidate in my hand, with a flame going, what shape os flame should I be looking for do you think? Messy, broad, narrow? Maybe the closer the flame to the nozzle means it’s mixing sooner?

Yeah Mark, good ol’ cm6 looks big on here. I just found some 1/4-20 ones for RC motors.

I was wondering how many bananas does it weigh?

Mark wrote: ↑

Tue Mar 15, 2022 5:21 am

I was wondering how many bananas does it weigh?

Hi Mark,
It is approximately 3.5 bananas, if bananas are 3/lb. ha

So, I've got the 5 fueling access ports tapped and pluggable, and now I'm down to selecting the fueling hole diameter that will shoot inward at a 45 deg angle. Too big and I can't fix it, so I'm torn. I've taken to thinking I want tiny holes, but stiff jets seems disruptive inside, as much as I want good mixing, I don't want to shoot entirely across the incoming flow. I wonder if big holes is better as the feed connector area is no where near as big as the five holes combined. So I'm thinking big holes will have the fuel come out lazy and be obliterated by the incoming flow.

If I go to big, I can't fix or reduce, so, guess I need to start small, and test again with a bit larger to see if it trends better... if it doesn't, I've screwed up the only one that is clear of obstructions. gaaa Oh, wait, guess I could open those up and tap them for orifice inserts.

I was wondering what exactly is the situation with the internal support material, is it like a banana in the tailpipe or can you use a laparoscope, dremel, and three medical doctors to fix it?

That is I couldn't tell if you were saying some support material was not removed and creating a possible air flow drag or if there wasn't enough for things like tapping a thread.
"Well, only one didn't have support material in the CC."

Great news that the jets have arrived - looking superb too!

Mike - what is the support material made from or is it more SS?
Just wondering if a "hatch" could be cut in the side of the CC to remove the support material then tig welded back up again?

on the edge of my seat waiting for some start ups!

Great work!

Cheers

Nick

Mark, if you look at the first photo, they are freshly printed and still in the powder bed. The support is the comb like support features that must be removed by hand.
Nick, yes it is the same material.
They printed the “stomach” (tough not to call it that now!) u-bend up, and so I find support ribs in this area. I can allow some distortion, so I wonder if they can turn support material off.

So, about to drill five fueling holes in the CC. I’m torn between tiny, like .03”, but my 1/16” drills look quite tiny as well. I don’t think it is any simple area/flowrate calc, because the fuel jet velocity is a huge variable.

The question is:
Better to be smaller, energetic and turbulent delivery, or
Bigger holes with less disturbance?

Complicating factor is I only have one of the tiny drill bits and several of the 1/16. And I must do this this weekend. Ha, there are worse ways to make decisions….