After failing to construct a test burner mechanism today, I decided to do another barebones "shavings in a dish" combustion experiment with Magnesium. Here's some of the things it reminded me of:
- Without active ventilation, oxide ash *will* cover the active combustion zone.
- Ash covering the combustion zone will lead to reduced airflow, creating a "smoldering pile" phenomenon rather than a flame.
- When magnesium does flare up, it is *bright*
- Flames are hyperlocal, but intense
Mg combustion notes
The takeaway from this for me is that an effective magnesium burner for reliable, high energy release, needs systems for actively separating the ash from the flame zone while ensuring high availability of oxidizer. Given the high localization of the flames and the deliberate energy input needed to light the fuel, thought must be given to how the fuel will be held and how the flame will be continued if being passed from one piece to the next to ensure flame continuity.
Mg combustion notes
I'm interested in capturing these notes because it would seem that deriving functional combustion systems for the fuel will require some novel thinking that hasn't been needed with liquid or gaseous fuels. While these novel problems are likely trivial, they will need to be solved. Mechanical waste removal which takes advantage of the weak granular ash consistency seems to be a promising avenue to pursue.
Mg combustion notes
@radehi Another aspect to consider is that there's a decent thermal gap between the melting point of magnesium and its vaporization temperature, which is right around where combustion initiates for magnesium. Aerosolization too early would probably lead to a decent fraction of unignited fuel being sputtered and cooled by the oxidizer flow. 🤔 Lots of things to validate.
Mg combustion notes
@ACTupper I meant aerosolizing molten magnesium, for example by blasting air up through it or through a venturi over it.
Mg combustion notes
@ACTupper I strongly concur with shying away from powdered magnesium ;)
Mg combustion notes
@radehi I think it's fair to say some sputtering may happen, and ultimately the degree to which that's desirable probably needs to be determined experimentally. The induced shear forces are going to be controlled by oxidizer flow rate, so there's probably a sweet spot to be found there. Powder aerosolization is a possibility, but at the moment I've been shying away from powdered magnesium due to fuel stability/safety concerns.