I know it's a long long.. looong post, but I hope you read it through before asking "how it works" and "what it does"..
Some of you know me and many does not, but I have been member of spudgun forums for over 10 years. I have used RDX name earlier here and also in spudtech and others that don't even exist anymore.. So hello everyone

I had a problem when building a large piston valved hybrid that needed to be fueled fast and with a "push of a button", without too complicated electrical stuff or programming. First I did try manometeric fueling but I had problems with low mixes, like the 4x mix that I had been using. Most problems I had was because of large chamber and low mix = I didn't get the air and propane to mix well.
I did not want to put chamber fan inside, I don't trust them to work long time in that use

Then I searched for gas mixing devices and found thing called "Static gas mixer". It's a tube filled with helical elements that mix two gases when they flow through the tube. I was like.. that's what i need to use ! ...But then I ran in to next problem, how to fill low pressure propane and relatively high pressure air at the same time and make sure that the air pressure doesn't fill the chamber before all propane is fed in ? ..only suitable thing that came to mind was to force that propane in the chamber with higher pressure, doing it by pump, little bit like syringe fueling.
Many weeks after and I had a "Hybrid gas meter pump / static mixer" setup ready test.. and BANG..it worked the first time !
I think this is not best suitable for small hybrids (because it needs lot of space), but it's very well suitable for larger hybrids like mine that have problems with mixing the gases.
I wanted to get this here fast, so a little of MS Paint and that's it

It works so that you only have to fill it with air and it "loads" simultaneously air and propane in chamber through the static mixing tube. Then you remove the air source (or vent the pressure) from the pneumatic cylinder inlet and it automatically fills the pump again with propane and cylinder moves back to normal position. The flow adjusting valve is there for adjusting the airflow to be in proportion to propane flow so that both are fed same time in the mixing tube. Propane does not need any other valves than the check valve and the poppet valve.
You should also be sure to have some kind of safety valve at the low pressure side, if the isolation valve leaks and flame ignites the mix in the static mixer ! Or you could use flame arrester, but those are not cheap. I used a 100bar rated high quality stainless steel valve with PTFE seals for isolation and it works well.
Pressures mentioned in the picture are of course only for my setup and mix, you would have to calculate different pressures for yours. Selecting right size cylinder is same as selecting right size of metering pipe.. know your volume and pressure and then few calculations and that's it. (pneumatic cylinder can be also replaced with any kind of pump tube, even home made one).
And the real setup.. (sorry for the bad picture)
There you can see the pneumatic cylinder that is used as a propane meter and pump.
All feed back and questions are welcome


-Matti