Gas Metering Pumps

[Speedy]

Gas Metering Pumps - are there such things ?

We have an application that requires 2 combustible gases (fuel gas and Oxygen)to be mixed in-line and then filled into a chamber where the mix is ignited. Not only should the volume ratio be accurately controlled but also the degree of mixing.
We currently use pre-charge chambers, which we fill to a set pressure and discharge simultaneously - these work fine but a little on the slow side.
I was thinking that in-line metering devices like Gear Pumps could also work. Anyone know of any?
We have also tried fixed orifices but results were poor.

 

[handleman]

There are companies (Thermco is one) that make gas mixers for a living. They also work on the principle of a fixed orifice, but they control pre- and post-orifice pressure. They also make mixture analyzers to verify that the mix is as set. I don't think a gear pump would work. Those work because liquid is (essentially) incompressible.

-handleman, CSWP (The new, easy test)

 

[zdas04]

I'm surprised that the fixed orifice has provide poor results. Was the upstream pressure high enough to result in critical flow? In a choked-flow situation there are few devices more accurate than a fixed orifice.

Normally this is done with a series of pressure regulators that put the right partial pressure of the two streams together just before the combustion chamber. This seems to allow pretty precise control in millions of engines.

David

 

[Speedy]

The problem is the flow is not steady state.As expected the down stream presure increases as the chamber is filled. Also the gases are not mixed until the inlet of the chamber.
Upstream pressure to the supply regulators may also fluctuate. Flow is also only on for only a few secs.

 

[HDS]

http://www.google.com/search?as_epq=mass flow controller