Working in Blender 2.91
Preview shows much bigger flames than render, both in Cycles and Eevee. I have increased the smoke domain to a very large size, but the flames don’t seem to get much bigger.
Below are the screenshots. I am unable to share the .blend file at the moment, as this is a joint project in progress. But I have shared the physics tab and shader screenshots.
Preview, fire filling the whole camera view and far beyond:
Render in Cycles, only a small fire around the emitting object:
Render in Eeevee, fire is bigger, but still nowhere close the preview:
Physics tab settings for emitter:
Physics tab settings for smoke domain:
Smoke domain shader: