I messed with a few properties and went through the trouble of rendering it out… but can’t upload it as I’m a new user here.
It looks like it let me upload an animated gif !? animation|690x388
The important changes were to the ReactionSpeed, timescale and Fuel settings. I’m sure you can fine tune it and get it performing better yet. You might also want to play with the vortex setting.
Domain changes:
ReactionSpeed 1.5 -> 2
Timescale -> 0.1
FlameSmoke -> 0.12
Emitter:
Sampling Substeps -> 10
Fuel -> 0.13
Initial Velocity: all to 0, set Z to 15
I also set the Vertex Group to one which included the top 4 faces of the mesh.
It’s a little fast… but looks ok? Lowering the initial velocity might be better yet.