Flow Regulators for Metering Propane

[mark.f]

I simply ask this because I've seen flow regulators everywhere, and their cheap. There are both the fixed kind, and the adjustable kind like you find at Home Depot next to the regular pressure regulators.

Anyways, I was thinking something like this.

You have a fixed flow regulator. It delivers a flow-rate of 0.1 gallons per minute.

So, that's 378.5 mL per minute, or 6.3 mL per second.

So, if you have a 2L combustion chamber, then for a 4.2% propane to air mixture, you would simply open the valve before the flow regulator for 13-1/3 seconds.

Makes sense?

[JDP12]

yea it makes sense......but the tricky part is timing it right.... i mean how do you time 13-1/3 sec?

[mark.f]

Counting. I can count pretty accurately in my head. I used to use a little propane stove regulator and count a little over seven seconds when fueling one of my old launchers.

[homedepotpro]

yes but the flow is also going to change with the pressure in the tank right, so when your fuel is running low on pressure you won't get as much fuel it your 13 sec fill

[mark.f]

Good point. Then you'd need some sort of primary regulator to bring it down to a lower fueling pressure...

So nevermind.

[noname]

I found that funny. Also, the only flow regulators I can find are $20, the same as pressure regulators. Instead of getting a flow regulator, you can always use 1 ball valve as a "meter" and time the seconds.

[paaiyan]

I don't know about y'all but the propane tanks i get for my gas grill have a 10 PSI flow regulator on them... Just an idea.

[jimmy101]

The simplest "flow regulator" is just the standard benzomatic torch head. Unscrew the burner/mixer assembly (not the pipe to valve junction). You'll see a tiny hole. Not exactly sure how small the hole is but a piece of 30G wire won't fit into it so it is less than 0.01 inch in diameter.

(Ignore the syringe etc., just look at the "unscrew".)

Rough measurment of the flow into a syringe puts the flow rate at 5~10cc/second. WAG estimate for a 100in³ chamber would be 5~10 seconds.

As folks have pointed out, the flow will change with the ambient temperature. So, if 4 seconds works at 90F it will take longer at 50F.

A flow regulator should never be used with high pressure gases (like CO2) or in a situation where the chamber being filled is actually being pressurized in the process. A flow regulator between two closed chambers will eventually equilibrate the pressure in the two chambers.