Q's: Brauner Design

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tony
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Q's: Brauner Design

Post by tony » Sat Oct 09, 2004 10:41 pm

Greets all. I'm new here, and new to pulse engines.. am having a start with the E. Brauner plans. Have the intake nozzle (venturi) made and hope to include a picture here.

my assumption here is that all of you have access to this drawing.

questions: parts 1 and 2 on the brauner plans show the air and fuel nozzles (i believe) .. how are these two connected? and are they in the same plane?

my guess is that part 1 is the air inlet. it is in the same plane as 2, the fuel inlet. incoming air is blown across the small (through) hole in part 3 and draws fuel out.

second question: how do i light this baby? can i add a spark plug anywhere in the CC? or should i get my road flare out?

last q for the night: 100psi compressed air line to the air inlet and suction feed (or gravity feed?) line from a 1gallon bucket of gas to the fuel inlet? fire it up and hope it works?

thanks,
-tony
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Mark
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Re: Q's: Brauner Design

Post by Mark » Sun Oct 10, 2004 12:44 am

A quart tank should be quite ample for testing. A hundred psi might be a little overkill but shouldn't hurt. A few short puffs of air using a clear or translucent fuel tubing will indicate the fuel level and as you puff in bursts of starting air, you should see the fuel being drawn into the throat from the lower pressure produced. I like to set the gas tank so that the fuel level is a half inch or so below entry into the fuel metering jet. That way you don't flood the engine or have an annoying drip, drip of gasoline that on occasion with a backfire, a flame can sneak by the reeds, light the gasoline and start to then melt your fuel line, light the floor on fire and other attention getting events.
I'd use a spark plug but you could try a propane torch angled at the tail end a few inches back of it, while puffing in air/fuel in the throat.
With time and patience, you will happen upon the interesting phenomenon that has from time to time entranced all of us here in pulsejet land, that being a deafening roar you will probably tire of well before your quart is gone. It only takes a few seconds to feel the thrill. It's as much or more fun to stop the engine and reflect on what just happened as it is to listen to it wail on and on. I once ran a homemade Dynajet sized engine for 5 minutes straight and it seemed a long, long time.
Mark

tony
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Re: Q's: Brauner Design

Post by tony » Sun Oct 10, 2004 2:07 pm

despite missing a few details, i've pressed on. the valve plate turned
out (seemingly) ok.. though my arm hurts from all the filing.

the brauner plans show a threaded tail pipe but no shoulder to actually
hold the valveplate in the intake nozzle. i've turned a small threaded
retaining ring to which i plan to tig weld a stainless CC and exhaust.

the retaining ring has a 1mm shoulder that snugs the valve plate
into the nozzle when screwed on.

-tony
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Mark
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Re: Q's: Brauner Design

Post by Mark » Sun Oct 10, 2004 4:14 pm

If you have any specific questions, I'd be glad to help. Once the jet starts, it will feed itself from the suction in the throat; you can cup your hand over the intake a little and feel an impressive vacuum when the jet pops and stutters during starting. You don't need a gravity feed and at the same time, don't expect it to suck fuel too far up if your gasoline level is very low, just keep it around the same height as your engine, a little lower of course so it doesn't drain out during starting.
It looks good so far.
Mark

tony
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Re: Q's: Brauner Design

Post by tony » Sun Oct 10, 2004 5:57 pm

mark,
thanks for the feedback.
i've got the valve backing finished (the rounded washer thing).. and
now will be starting work on the venturi nozzles for fuel and air.

they look like they'll be the toughest bits.

do you have a copy handy of the brauner design? i'm talking
about part numbers 2 and 3. here is an external link to the print:
http://home.earthlink.net/%7Efamcaine/p ... brauna.gif

looks like parts 2/3 make up a needle valve. so i'm guessing this
is where i plug my fuel line into (planing on using gasoline). looks as
if fuel enters from the line into part #2.

part #1 seems to be the air delivery. air blown over #3 draws fuel out.

specific question: how are the air nozzle (1) and needle valve (2/3) connected??

if i use a blow gun, from a compressor, do i need part #1? once the engine is running (knock on wood) i no longer need to feed air.. hence #1 becomes obsolete?

-tony

Mark
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Re: Q's: Brauner Design

Post by Mark » Sun Oct 10, 2004 6:34 pm

Yes, part # 1 becomes obsolete once the engine starts sucking it's own air. On my Dynajet I tried to loosen the metering jet/air injector unit and broke off my air injector. It's just welded/tacked on to the metering jet which is essentially just a tube with two holes, one on either side.
The metering jet is threaded and screws into the center of the pulsejet head. On my Dynajet there is a sub-fitting,(tube with tinier hole) in the metering jet that breaks up the fuel as it is aspirated the rest of the way down the metering jet to the two fuel holes, where fuel is misted out into the throat.
Since I broke off the air injector on my Dynajet accidentally by trying to loosen it when the head was still hot, I just angle in the starting air 90 degrees to the two holes or try to simulate how the air injector would direct air over the holes. You don't want to inject air at any other angle or else it will push the fuel back down the fuel line as you can see if you use clear fuel line. But when you angle it just right, it draws the fuel out and also starts the jet machine gunning and getting hot whereupon it soon starts. Sometimes on a cold day, the heat of several false starts helps to vaporize the gasoline, if the jet is being fussy.
One time on my smaller Tigerjet, I slid a silicone tube with methanol fuel over the blow pipe and disregarded the fuel metering jet because it was too small for the greater flow of methanol needed over the recommended gasoline. Anyway, by puffing in air from a compressor it started and ran fine even with this crude off-center fuel spraying/feeding into the throat via the air injector.
On my first homemade pulsejet I just elbowed a piece of copper tubing into the throat and primed the engine with a spray bottle, having the fuel level sitting right at the top of the lip of the tubing so it would quickly be ingested. In some ways pulsejets can tollerate a lot of bumbling and still do ok.
Mark

Mark
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Re: Q's: Brauner Design

Post by Mark » Sun Oct 10, 2004 6:47 pm

This is a picture of my Dynajet on the right, you would normally be able to see a little bit of the air injector blow pipe. On the left you can see the off-centered blow pipe on my Tigerjet. On the Dynajet the broad end of the air injector is the same as any threaded tire valve stem, it's made for attaching a bicycle pump to to start the pulsejet with.
Mark
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Mark
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Re: Q's: Brauner Design

Post by Mark » Sun Oct 10, 2004 7:11 pm

Here's my parts from both jets, note the similarity.
Mark
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Mark
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Re: Q's: Brauner Design

Post by Mark » Sun Oct 10, 2004 7:31 pm

Here's a simple 3 inch diameter pulsejet design I made, dressed up nicely with Larry's lines of instruction. Note the fuel metering jet is just some common brass fitting, I drilled 6 holes into the flat sides for the fuel to wisp out of.
This is the baby that I love to hear start instantly, from dead silence to instant roar. Not that it always is so easy but from time to time a single spark makes it look effortless.
Mark
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Mark
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Re: Q's: Brauner Design

Post by Mark » Sun Oct 10, 2004 8:01 pm

A constellation.
Mark
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tony
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Re: Q's: Brauner Design

Post by tony » Sun Oct 10, 2004 10:06 pm

mark,
thanks for the wealth of information! are those anodized aluminum heads
on the pulsejets? nice.

one last question (for now)... on fuel metering.

upon closer inspection, i have NO idea how metering is accomplished in
the brauner plans. looks like, once assembled, there is a 1mm through hole down the entire lenght of fuel nozzle.. and then it splits into two 0.8 mm holes where the fuel is actually drawn out of.

turning the screws would not affect metering, would it? all it would do is change the length of the nozzle.. but there is still only a 1mm hole.

is there a needle in there? am i missing something?

thanks again for the photos... 1000words, as they say.

-tony

Mark
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Re: Q's: Brauner Design

Post by Mark » Sun Oct 10, 2004 11:09 pm

It's kind of a tube within a tube for the metering jet. Imagine a smaller straw inside a larger straw. That's really all that is going on inside. The smaller straw,(the part you hook or sleeve a fuel line over), threads into a larger tube so that the fuel is away from its original walls and is droplet fed into the larger tube which leads to the two holes where the fuel is misted into the throat. Fuel metering is set and there is only one speed, full grease. The nippled fuel feed into the the main body of the metering jet just helps to atomize the droplets before they exit the two holes. You saw how I didn't screw in the tinier part into the main part of the metering jet. There is a very tiny hole at the end of the first section of the metering jet, especiallly for my Tigerjet, the hole is very minute as the gasoline passes through on its way to the two exit holes.
There is no needle valve, in fact I think you could get away with a single tube with a hole drilled in its side all the way through to form two holes as in the design, I don't know how the Brauner Jet is designed, if it stages the fuel metering jet in two parts or not. I don't think it is that critical, as long as the jet can suck in fuel and air, that's all that's needed, these two things keep the reeds calm, cool, and collective or better said prevented from warping with the benefit of cold fuel and air flowing over them. That's something neat about a valved jet, it is its own fuel pump and this simplicity too cools the reeds with the vaporizing fuel and air flowing over the singing petals, in a Dyna-Jet the reeds "purr" 220-240 times a second. A valved jet snaps the gate closed suddenly, you get good compression and it's in a small streamline package. And it's fun to see grown men cower from a meager 1 pound engine, as if their life or limb where in danger. I guess it is the sound and simplicity that makes a pulsejet mysteriously entertaining.
Mark

tony
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Re: Q's: Brauner Design

Post by tony » Mon Oct 11, 2004 5:40 pm

dang, i can't get this build fast enough. i'm spending way too many
happy hours in the shop.

got the nozzles done and they're installed... this thing is starting to
look mean. part of me will feel bad when it all turns black and lights
on fire. but i guess thats the whole point.

tried to make the valve leaf today.. the 'flower' ... all i can get my
hands on is 0.010" spring steel. is that gonna be too rigid??

cut it out with a cad print and a dremel tool. thought i did a good job, but
nothing lined up right. will try again tomorrow.

do the petals actually have to be rounded at the ends? what if i just
cut radial slits??

-tony

tony
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Re: Q's: Brauner Design

Post by tony » Tue Oct 12, 2004 5:37 pm

well, here it is. pix posted.

couldn't get it lit. got a pop or two using starter fluid in the nose, but no go.
the venturi pulls gasoline in like crazy.

i'm pretty sure its my valve.. my stock is too thick at a little over .010"
the petals are hard to open even with 100psi airgun at 6"

i bent them open a bit, hoping it would work, but no go. blowing in
from the tailpipe doesn't close them. (ie air comes out the front)

i'm using a chainsaw to drive the sparkplug. i get nice fat blue sparks.

if i wanted to start this with propane, where would i inject it?

-tony (thanks for your help so far everyone)
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tony
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Re: Q's: Brauner Design

Post by tony » Tue Oct 12, 2004 5:38 pm

ps.. the thing that looks like a wing is a standoff.. so i can tackweld
the PJ to my workbench for testing.

-tony
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