Ansys Employee

Fluent has a limiter for pressure, temperature and turbulent itensity to avoid the solution reaching silly values without any warning. So, in your case the solver will be struggling, hit 1K which will mess with any temperature dependent properties, is then diverging and the final error is the floating point. I assume there are a load of multigrid messages in the TUI before the solver falls over?

The cause is likely mesh or boundary condition related, but then linked to time step. With three phases and combustion/phase change you're going to need to carefully look at the mesh and all settings.