Hybrid test results.

[DYI]

I just noticed something: your post says the chamber is 750 mL, which is equal to 750 cc, or about 116 ci, which is the volume of a 2" diameter chamber about 35" long. Are you sure that your measurement is correct?

[spanerman]

im pretty sure it is as his fueling would be waaay off

[noname]

You stole my idea, except I'm using 1.5" cell core ABS!
Now people can believe me when I say 8x is fine for steel.

[Fnord]

750 ml = 45.7678081 cubic inches

Also, in response to previous posts, I have no idea where I'm going to get a decent peak pressure gauge. I'm betting mcmaster has them, but I really don't want to spend more than $20 on one. I haven't found anything on ebay, and none of my hardware stores sell them

[DYI]

1cc = 1mL
2.54cm x 2.54cm x 2.54cm = 16.387064cc = 1ci
750/16.387064 =45.767808071
Muhahaha! Google is wrong...
But so was I. I must have forgotten to do something the first time.

[jackssmirkingrevenge]

lol this is coming from the guy who took pvc to 400pi

and who also has all his fingers and a distinct lack of razor-sharp PVC fragments in his gut

[dongfang]

Hi,

Great work! Always nice when somebody gets about to actually verify things, while the rest of just go on with assumptions and blah-blah

_Fnord, in the Spudfiles threads as I see them, the more recent posts appear below the less recent ones... so I see your example as normal system behavior.

Regards
Soren

[jackssmirkingrevenge]

_Fnord, in the Spudfiles threads as I see them, the more recent posts appear below the less recent ones... so I see your example as normal system behavior.

That's what I was thinking, I don't see the anomaly.

[Fnord]

That's what I was thinking, I don't see the anomaly.

I just realised what was going on a little while ago. It was my mistake, partially due to small text/bad eyes
See original post.

[clide]

I'm not sure if you were trying to initiate DDT or not, but wouldn't having the spark at one side of the chamber be more prone to DDT than a spark in the middle? Thats how I understood it anyway.

Also did you vary the fuel mixture at all? I've also heard that lean mixtures are more likely to transition to detonation.

Pretty good test, but like others have said, a measure of peak pressure would have been nice

[Fnord]

I wasn't really trying to get ddt, as I don't think I can with my current setup. There just isn't enough run-up distance in the pipe.

The fuel mixture probably varied slightly, but if it did it was in error.

I don't know where to get a peak pressure gauge in my area. If you can find one relatively cheap online I might get it.

[frankrede]

pressure gauge+ 1/4" inline check valve.
The gauge may go bad after a while so a manifold of some type might be needed.

or perhaps this
mcmaster item #4031K44 or 4031K54

[jimmy101]

I can't say for sure, as I don't have a peak pressure gauge that goes that high. 2" threaded sch40 steel has an estimated burst pressure of ~1300 psi.
Someone needs to do some gaseq number punching.

Nice work _Fnord!

For propane + air at 11x GasEq puts the pressure at 1274 PSIA.
Getting pretty close to the estimated burst pressure of ~1300 PSI.

I don't think you'll be able to get a closed pipe to DDT with propane + air unless you get the initial pressure and temperature up near autoignition conditions. According to GasEq, the speed of sound in your chamber at the end of combustion is ~900m/s (~Mach 3 compared to air at STP).

[jimmy101]

It's amazing, spudders go months (years) without any interesting new data then we get two posts, on two different boards, within 24 hours of each other on high pressure tests in hybrids.

Check out http://www.spudcom.com/forums/showthread.php?t=75. "Noname" is measuring peak pressures in a burst disk hybrid. At 6x he is getting ~650 PSI. Since Noname is using a burst disk gun the maximum pressure in the chamber is limited by the failure pressure of the burst disk.

[noname]

I may need to get a check valve to make operation easier and more accurate, but those were the general numbers I got out of it.