The Great War mod is a total conversion modification for Napoleon: Total War. It creates an authentic representation of World War 1-era tactics, strategies and general warfare within the game. Including stunning new visuals that include entirely new models and textures for equipment, vehicles and more, the mod immerses you into the era with brand new gameplay unlike anything you've experienced in Total War before.
This is the height of the explosion. It dwarfs the surrounding units.
It looks like the carcass shot incendiary shell (from vanilla) is ised to create the flames.
I tried using that but it didn't work as expected so instead I used the ship magazine explosion effect instead.