No Hit - no Extra Damage
The incorporeal description says:
MM v.3.5: An incorporeal creature has no physical body. It can only be
harmed by other incorporeal creatures, magic weapons or creatures that
strike as magic weapons, and spells, spell-like abilities, or
supernatural abilities. It is immune to all non-magical attck forms.
All of the spells you mentioned depend on hitting the opponent.
Burning Sword (Spell Compendium):
The enchanted weapon deals an extra
1d6 points of fire damage on a successful hit. Also, on a critical
hit, the weapon deals additional fire damage [...]
If there is no hit there is no additional damage.
Mighty wallop increases the damage of a bludgeoning melee weapon
by one size category without increasing the dimensions or weight of
If the weapon does not deal damage there is nothing to be increased.
This transmutation doubles the threat range of the weapon.
A weapon not capable of hitting the enemy cannot deal crits - thus doubling the threat range would have no effect.
The only question is, whether the spells transform the weapon to a magic weapon.
The description of Mighty Wallop or Burning Sword in no way imply transforming a mundane or masterwork weapon to a magic weapon. These are clearly useless in this case.
There is an ambigous description in Keen Edge:
This spell makes a weapon magically keen, improving its ability to
deal telling blows.
While this does not exactly state "The weapon in question is transformed to a magic weapon" it could be implied. Lasting magic properties can only be added to magic weapons. On the other hand we are not talking about creating a magic weapon but about a spell effect. A spell effect can be added to a mundane weapon. Thus, I would judge a mundane weapon with keen edge still a mundane weapon and thus unsuited to harm an incorporeal creature, but I'd say this is a DM's call.