Question

Why does Flame Expand? Use science Direct thesis papers to explain why does flame expansion occur ?

Answer 1

When flame burns, it heats the surrounding atmosphere causing the air to expand and becomes less dense. The pull of gravity draws colder, denser air down to the base of the flame, displacing the hot air, which rises. This convention process feeds fresh oxygen to the force, which burns until it runs out of the fuel. The upward flow of air is what gives a flame it's tear drop shape and causes it to flicker, this is what happens on earth.

But odd things happen in space where gravity looses it's grip on solids, liquids and gases. Without gravity hot air expands but doesn't move upward. The flame persists because of diffusion of oxygen, with random oxygen molecules drifting into the fire. Absence of upward flow of hot air, fires in microgravity are some shaped or spherical.