I've faced some unexpected issue: the fire is becoming blocks, but only in specific frames, not the whole simulation. The voxel size in pyrosolver is 0.08, so it is enough for this small object (22 mil. voxels)


The viewport and rendered picture (Karma)

Blocks can be the results of pushing the density too high in the shader. Try pushing density at the simulation level instead.

Enivob
Blocks can be the results of pushing the density too high in the shader. Try pushing density at the simulation level instead.

Thanks for your answer. It seems that the density is right (I've pushed it in simulation), but fire voxels are still look blocks at the small density value. I found a possible solution, but I'm not sure is it right.

So, The flame and density sources have been animated to spawn it on some frames (scr.1). Also, changed the flame intensity scale on the Karma pyroshader to 10 (scr.2) and it became blocks. To avoid it I added pyropostprocess and everything became okay.