Does anyone have experience making small atomizing jet nozzles? Im not talking about the smash the stainless tube type. I need to make a few injector jets for an experiment out of something like stainless. I am almost certain the brass ones for carburetors that you can buy will melt and the smallest drill wire we have in the shop is still to big.

Any ideas on how to make tiny hole and shape the spray?

thanks

What about some type of fuel injector? Automobile ones I am guessing would be too big.
Not sure but I bet those high performance motorcycles may have something smaller.

some newer ATVs are injected, those injectors are prob small enuff??

Some nitrous systems use injector spray nozzels. That may work for what I think you are going for However, I think most are made of aluminum, that may not cut it.

Maybe diesel engine injectors from some small automobile? I guess they would need very high pressure though.

Lars

Well, only something like 800-1100 bar. For making synthetic diamonds you need about 50-100 kBar...

Hmmm, I guess I need to provide some detail.. all the ideas offered are good but to massive. I am trying not to use the name of what I am trying to build, because you all know what the missing part of my jet luge show is already and I don't need more attention till it works. For the ones that dont know... you will have to wait... There are far to many intellegent people on this forum for me not to tap the brain trust.

I am looking to surface mount 3 small jet nozzles to the exhaust cone in the wide area before it compresses the gases. I need the nozzle / orface to spray through a hole under the surface mount into the exhaust cone. I need to MAKE or find something as small as a carburetor jet orface, that won't melt and is threaded from the front side, not the back. The nozzle must atomize at 30 to 40 psi. The trick to making it is knowing how to form a tiny ass hole like .004 to .04 inches in diameter

Question. what is used inside these engines for fuel injection? Smashed tubes?


thanks
bob

Some (maybe all???)Home built turbines use hypodermic needles.

Inconel hyperdermic needle stock. At that location on a turbine, it has to be inconel - stainless will also crap out after a while. I don't know where they source the tubes from (medical supply?), but that's what they use on the fuel ring of turbines. You just need to size it up from there.... By the way, you can get drill bits that small, but they're expensive and I can't imagine how they'd do in a high alloy material.

Good luck - can't wait to see the finished product!

Yo Bob -

I think most of the more informed people here know what you want to do. Smart not to mention it here, though in your application it's fine.

Most injector rubes are made from stainless tubing that is crimped to seal the end and have the injector holes drilled in them. You can get very small decimal drills in the sizes you need from McMaster-Carr or an industrial tool supply shop.

It's tough to drill stainless, especially with small drill sizes. Try this...take your injector tube and insert a solid rod of the appropriate OD (even slightly smaller). Use a very sharp narrow angle punch (I made my own from 1/8" music wire) and lightly punch a dimple or even hole in the tubing. Remove the rod and final drill to size (use drill lube). You can bend the tube to shape after the drilling is done, seal the end of the tube by double rolling and crimping it.

What I can't answer is how you are going to retain it in the exhaust cone. I know I could not weld something that thin!

Here's an idea...AMT has some small stainless compression fittings welded into the tailcone of some of their engines to retain the thermocouple wire. These fittings might work OK if you could find them and drill the ID to the appropriate size to fit your injector tubing....good luck!

Barry

How about a refrigeration capillary tube .

http://www.airtoi.com/special/spec2.htm

http://www.skypipe.de/index.php?site=turbinen

Nachbrenner=afterburner

Schub, Nachbrenner nicht gezündet: 68 N
Schub, Nachbrenner gezündet: 105 N
Restschub, Nachbrenner nicht gezündet: 4 N
Drehzahl max, Nachbrenner nicht gezündet: 117.000 U/min
Drehzahl max, Nachbrenner gezündet: 113.000 U/min

I'm sure a laser will "drill" the correct size hole and it would be clean.

Dave

Close, but no cigar...

i hope you figur this out that would be sweeeeeeeeeeeeeet

I used to make small nozzles out of nickel tubing, it as drilled way oversize and then rotary formed using a ruby to "clse up" the end.. a carefull setup and a chase with the apropriate drill works..

I also made custom pen tubes using a spin forming technique.. a turn tool wth a "bald" bump kurl mounted at an angle to the spindle CL and a small wire in the drill quill to maintain the ID.. the pin was turned out of drill rod then flamed quick and dirty (only made these 2 dozen at a time).. get the slimeyest goopy oil you can find (100 weight+) slop it on there insert the ID mandrel and form the OD and ID from the cross slide.... the bald knurl can be substituted for a nice polished chunk of carbide or something else suitably hard (I have hijacked the dressing diamond from the surface grinder in a pinch)

just keep the chuck length short, even think about using x nose collets for this one

I also had ruby forming tools made.. trying to find those

Actually, I'm not so sure that the existing smoke tubes would not work. The heat is not going to go "up" the tube. And the tube is already at the hottest point behind the turbine. It would not scare me in the least bit to put some say, 50/ 50 mix of Kerosene and Diesel in the smoke tank and see what you get. You might want to even put some salt peter and sugar rockets on the side of your luge. That would give a lot of initial boost as well. Sort of the Fat Boy take off so to speak. You could also add a little bit of gas, say 5 percent to start into the diesel/ kero mix as well.

Since there is no oxygen in the line, it should not burn up the tube.

To anwer your question what's inside.

It's little tubes in a ring, about 1/16 diameter. The fuel enters the engine, goes straight down to the back near the turbine blade and splits off at a T into a circle around the Circ of the engine. Every CM or so, there is another T that comes forward towards the front of the engine.

That tube comes to a point where you have basically a hypodermic type needle. Where the fuel is atomized into the comb chamber.

Those tubes are far too small to be pushing liquid through at the exhaust of the engine and get anything worth while. They are really tiny.

By the way, your pressure ratings are quite good. I used to move smoke through a solenoid valve off of pressure from the on board propane tank. Once I was out of smoke fluid, the remaining propane would flow through the system and burn up in an "afterburner" type burn off.

That pressure is about 40 PSI.

LugeBob, Have your nozzles made at a machine shop out of inconel 718 and then have them EDM the hole dia that you will need.

kinda like this>

Bob, I know that you are probably looking for something easy and very produce-able, but think about this:

In these turbines the fuel tubes point into the sides of the fuel sticks (tubes) in such a way as to spray fuel into the tube's ID. The tube is glowing red hot when the turbine is running and therefore vaporizes the fuel upon contact. That allows a very well mixed air/fuel mix to enter the primary combustion zone.

Perhaps a similar strategy would work here. I would make as small a hole as you can in whatever tubing-end you use. This could be set in a recessed fitting that is welded into the tailpipe's wall. The spray is pointed at a button/tab/piece of stainless/Inconel that is exposed to/flush with the flow in the exhaust. This button/tab/piece is glowing VERY hot, due to the flow just aft of the turbine wheel. Your injected flow would vaporize immediately and mix well. As it exits the nozzle, into O2 rich ambient air.... VIOLA! Desired effect occurs!!! You could mount two or three of these equally spaced around the circumference.

I agree with Sean that the lack of O2 in the pipe will prevent any issues of flame front travel in the perilous direction.

Just like the real one work Wocketman

Wow, Lots of replies... exciting stuff. I never thought of "rolling / knurling" a pen type tube nozzle.
More details. I am not really looking for more BOOST in this experiment. I have a second engine for that and it burns less fuel that what you guys are thinking Im up to. For now I want to simulate the jet car fire show before I blast off.
I have tried many experiments external to the exhaust cone and none light off on demand and when it does it looks awful. The problem, with at least the engines I have, is the exhaust velocity is to high even at idle to light and sustain flame. Sure I can get the smoke / diesel coming out of the smoke tube to light 50% of the time.... but only before the engine gets to idle RPM and the start is a little wet and studders it's start. I need to make the exhaust wet on demand before the exiting gasses compress to a higher velocity in the exhaust cone. The Jet Car guys call it a Hot Streak. With a good tongue of fire on demand I should be able to light off just about anything a few feet back with the engine at idle. I do not plan on using the injector at any rpm above idle..... I will need to experiment with RPM, but must be cautious of any back pressure to the turbine section.

Although I could roll my own purpose built AB cone, the calculations show the entire engine Starter to tip of AB section to be like 3 foot long.... that is to big and out of the question. My intentions are to not insert anything inside the already small exhaust cone, except a tiny nub just up stream of where the flush mount jet nozzle would be. I plan on welding a threaded block to the exterior of the cone so I can change nozzle sizes till I get it right. I will be plumbing it with stainless smoke tubing running downhill to a one-way check valve, to a fuel solenoid on an adjustable timer relay (about .6 seconds) , to the tank that will be pressurized by the case bleed air.

I have a guy at work that can weld just about anything I throw at him so I dont need to learn that part for now.

The track owners want more excitement beyond the initial WOW when they see me run. It is time to turn up the heat... so to speak.

I would like to see something similar to what is in the picture, but on demand. This happened on it's own with a bad start in in 110 degree humid air. With a flame like this I could light off what ever I spray out of the smoke tubes...


********* Wow lots of good posts while I was writing this one.... Wocketman and I are thinking alot alike... I see. thanks for the confirmation on pressures Sean,