Senior Project FWEVIII Rev 8

Moderator: Mike Everman

crazycorkey
Posts: 13
Joined: Thu Feb 18, 2010 8:42 pm
Antipspambot question: 125

Senior Project FWEVIII Rev 8

Post by crazycorkey » Sun May 23, 2010 5:51 pm

Hi guys,

First I want to thank Graham for getting me all the info to build this little guy.

Unfortunately I am having trouble getting it started. For the injectors I am using 1/4" OD copper tubing with 1/8" ID and just flattened the end with pliers. It has maybe a 1/32" gap.

The propane setup does have a regulator on it and when we did get it to start for a second (see video) it was turned down all the way and then slowly opened.
It was hard even to get flames to catch and burn. Maybe we need a stronger spark.

Any advice would be appreciated.
Pulsejet-002_web.jpg

[The extension avi has been deactivated and can no longer be displayed.]


metiz
Posts: 1522
Joined: Fri Apr 21, 2006 6:34 pm
Antipspambot question: 125
Location: Netherlands

Re: Senior Project FWEVIII Rev 8

Post by metiz » Sun May 23, 2010 6:57 pm

I think you need to increase the gap in your injectors. .7mm is way to thin I suspect. This may also acount for the fact that the fuel does not ignite properly: it's simply going to fast.

You also need to get rid of your regulator. I think it will run with a regulator but not a whole lot harder, if any, then idle and this makes starting a lot harder to.

finally, make sure that the engine is build to specifications with deviations of no more the 1mm for length and maybe .5 for width. Also check that non of your welds have penetrated to the other side of the seem making a blob. That may prevent this engine form running (properly) if the blob(s) is/ are big enough.
Quantify the world.

crazycorkey
Posts: 13
Joined: Thu Feb 18, 2010 8:42 pm
Antipspambot question: 125

Re: Senior Project FWEVIII Rev 8

Post by crazycorkey » Tue May 25, 2010 2:23 am

Thanks, I'll have to try that tomorrow.

I looked at the hardware store for some fittings to go without the regulator and all I found where BBQ LP regulators that had the correct connections which made me realize you might think thats what I have which I don't. Its a full regulator with adjusting screw like those used on a flame cutting setup.

What would a typical opening be for the squashed end type fuel injectors?

metiz
Posts: 1522
Joined: Fri Apr 21, 2006 6:34 pm
Antipspambot question: 125
Location: Netherlands

Re: Senior Project FWEVIII Rev 8

Post by metiz » Tue May 25, 2010 9:34 am

make it about 1mm, maybe a bit bigger. I don't know if there's a specific injector you have to use for this engine but small engines line that usually don't need a Rosscojector. (if it does, flattening a pipe on the end to a slit does not make a Rosscojector)

If no injector was specified, try using a simple open tube as injector.
Quantify the world.

Viv
Posts: 2158
Joined: Sat Oct 04, 2003 2:35 pm
Antipspambot question: 125
Location: Normandy, France, Wales, Europe
Contact:

Re: Senior Project FWEVIII Rev 8

Post by Viv » Tue May 25, 2010 1:20 pm

Hi

Just as a belt and braces check would you do a water test to see if you have any in pin hole leaks in your weld joints, small engines can be very sensitive to this problem, just put a bit of duct tape over the inlets to block them off then fill the engine with water via the exhaust, you will soon see if you have any small holes on the weld joints.

Takes five minutes and will save you hours in testing

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

Viv's blog

Monsieur le commentaire

James D
Posts: 86
Joined: Sun Jan 16, 2005 9:14 pm
Antipspambot question: 0
Location: England

Re: Senior Project FWEVIII Rev 8

Post by James D » Wed May 26, 2010 8:08 pm

Hi,
I’ve attached some photos of the fuel pipes I used; they were about 1/8” OD. I just flattened the ends completely, ground the corners at an angle and drilled four 1mm holes in the end.

The position of the sparkplug makes getting the initial ignition tricky, as you noted, but assuming you can live with that the main piece of advice I can give is to begin with very low gas pressure, try to get it howling with a smallish blue flame from the tailpipe, keep it like that until the pulsejet is getting visibly hot and then gradually increase the gas and air until it locks into resonance.

Hope that helps.
Attachments
fuel-pipe.jpg
Fuel pipe detailz
fuel-pipe.jpg (11.54 KiB) Viewed 4888 times
Pipe-Position.jpg
Fuel pipe position (on the inside;>)
Image

crazycorkey
Posts: 13
Joined: Thu Feb 18, 2010 8:42 pm
Antipspambot question: 125

Re: Senior Project FWEVIII Rev 8

Post by crazycorkey » Sat May 29, 2010 4:24 am

Thanks for the replies!

I was confident (maybe over confident) in my welds and too lazy to unbolt it from the test stand to full it with water before trying to run it today.

And the hardware store didn't have any 1/8" OD tubing BUT I did get a much better ignition system setup.

Huge blue sparks crackling continuously. And with that SUCCESS!

Check out the video!
Attachments

[The extension avi has been deactivated and can no longer be displayed.]


metiz
Posts: 1522
Joined: Fri Apr 21, 2006 6:34 pm
Antipspambot question: 125
Location: Netherlands

Re: Senior Project FWEVIII Rev 8

Post by metiz » Sat May 29, 2010 10:08 am

good shit! see if you can get a thrust test
Quantify the world.

nickwilson
Posts: 52
Joined: Tue Feb 02, 2010 8:44 am
Antipspambot question: 125

Re: Senior Project FWEVIII Rev 8

Post by nickwilson » Mon May 31, 2010 5:57 am

hi crazycorkey nice name i can not watch your video but i was wondering what kind of ignition you are using i have a weedeater engine with drill hooked to it just wondering what you found good job on the build thanks nick

PyroJoe
Posts: 1743
Joined: Wed Aug 29, 2007 5:44 pm
Antipspambot question: 125
Location: Texas

Re: Senior Project FWEVIII Rev 8

Post by PyroJoe » Tue Jun 01, 2010 1:50 pm

Was it loud? Ha

Good to see she is up and running.
If valveless pulse jets had a linear relationship between thrust and sound, I figure these little beauties should be pushing several hundred pounds of thrust. Something to experience.
Good job.
Joe

larry cottrill
Posts: 4140
Joined: Sun Oct 05, 2003 1:17 am
Antipspambot question: 0
Location: Mingo, Iowa USA
Contact:

Re: Senior Project FWEVIII Rev 8

Post by larry cottrill » Thu Jun 03, 2010 4:25 pm

corkey -

CONGRATULATIONS!

Looks like a nice build and nice run for a nice loud lady. My experience with regulators has always been good, because I always get nice big ones with plenty of flow capacity.

Yes, your next homework assignment is definitely to do whatever it takes to get a thrust figure.

L Cottrill

crazycorkey
Posts: 13
Joined: Thu Feb 18, 2010 8:42 pm
Antipspambot question: 125

Re: Senior Project FWEVIII Rev 8

Post by crazycorkey » Thu Jun 03, 2010 7:57 pm

nickwilson wrote:hi crazycorkey nice name i can not watch your video but i was wondering what kind of ignition you are using i have a weedeater engine with drill hooked to it just wondering what you found good job on the build thanks nick
The ignition setup is a Bendix Aircraft starting vibrator 12V DC 215A and a high voltage Ford ignition coil. I'm not sure what power supply its hooked up to (borrowing it from another school experiment) but I'll try to find out.
Pulsejet Experiment 001.JPG
PyroJoe wrote:Was it loud? Ha
YES! With both the ear plugs and earmuffs! haha

crazycorkey
Posts: 13
Joined: Thu Feb 18, 2010 8:42 pm
Antipspambot question: 125

Re: Senior Project FWEVIII Rev 8

Post by crazycorkey » Mon Jun 07, 2010 1:02 am

crazycorkey wrote:
nickwilson wrote:hi crazycorkey nice name i can not watch your video but i was wondering what kind of ignition you are using i have a weedeater engine with drill hooked to it just wondering what you found good job on the build thanks nick
The ignition setup is a Bendix Aircraft starting vibrator 12V DC 215A and a high voltage Ford ignition coil. I'm not sure what power supply its hooked up to (borrowing it from another school experiment) but I'll try to find out.
The setup uses a car battery quick charger 12V 10Amp.



Finally got some thrust data!

The "pulses" in the graph are not the individual pulses of the pulsejet but are due to the pulsing and the system noise. Thanks Viv for informing me that our load cell was not fast enough to capture discreet pulses. The data aquisition system has quite a bit of noise in it. You can see it clearly at the end at 0lbs of thrust where it should be a steady 0 since the pulsejet is no longer running. Also all this data is after an exponentially weighted moving average in an attempt to smooth out the noise.
run1.jpg
run2.jpg

Viv
Posts: 2158
Joined: Sat Oct 04, 2003 2:35 pm
Antipspambot question: 125
Location: Normandy, France, Wales, Europe
Contact:

Re: Senior Project FWEVIII Rev 8

Post by Viv » Mon Jun 07, 2010 3:19 pm

Hi Mate

Good work and well done, just as an after thought did you stop your ignition during the recording run? high voltage sparks tend to bleed over every thing so that could also add to your noise problems

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

Viv's blog

Monsieur le commentaire

crazycorkey
Posts: 13
Joined: Thu Feb 18, 2010 8:42 pm
Antipspambot question: 125

Re: Senior Project FWEVIII Rev 8

Post by crazycorkey » Wed Jun 09, 2010 2:36 pm

Viv wrote:Hi Mate

Good work and well done, just as an after thought did you stop your ignition during the recording run? high voltage sparks tend to bleed over every thing so that could also add to your noise problems

Viv
Yes we started collecting data after I disconnected the ignition wires.

Post Reply