raging fire
煆 centers on a fierce, blazing fire: a raging, intense flame.
煆 combines 火 (fire) with 叚, which likely contributes the sound and may relate to the idea of intense heat or blazing.
The left side is fire 火, and the right side 叚 looks like a fierce, open-mouthed beast. Picture a raging fire roaring like a wild animal.
For カ, imagine a car engulfed in a raging fire: car -> カ, and the flames roar around it.