The common envelope (CE) phase is important for the evolution of close binary
systems with compact stars. In the past, most 3D hydrodynamic simulations of the
CE phase have failed to explain how the envelope is ejected. For a long time, it
has been discussed if energy from recombination of H and He may help ejecting
the envelope. Here, I present 3D hydrodynamic simulations of the CE phase of a
two solar mass red giant with different companions including the release of
recombination energy. I will show that releasing recombination energy helps
ejecting the envelope: after the rapid spiral-in releases orbital energy and
lifts large parts of the envelope to larger radii, recombination energy is
released during expansion, largely unbinding the envelope during the simulated
time. Moreover, I will show that convergence can be achieved in this type of
simulations by increasing the resolution around the red giant core and the
companion. I will also present first light curves computed from the simulations
and compare the luminosities and colors to observations of luminous red novae
and to analytical models.