Is it the same as the black flame in that case ?
I don’t think so. And the sun wheel is neither a nazi symbol nor the black sun.
The black flame is what you kindle within yourself, I think of it as spiritual fire aligned to the potential in darkness.
The black sun, imo, is a gateway to the ‘infernal realms’ aka outer darkness across the abyss, but more usually energy and beings come through it to us rather than the other way around. The Seed of Darkness (a nonagram or nine pointed star with a pentagram in the middle) is also such a gateway.