Common envelope evolution occurs when one star in a binary system unstably fills its Roche lobe, and the other star's orbit shrinks into the expended envelope. This process typically causes the ejection of the envelope, leading to a close binary or stellar merger. The outflowing envelope is not symmetrical, so it may break the symmetry of any subsequent faster wind, such as that produced during the planetary nebula phase. Previous work has shown that the dense material ejected in the common envelope phase can explain the bipolar shape of such nebulae. To study this process, we have produced two common-envelope progenitor systems of planetary nebulae. Each enters common envelope evolution at a different evolutionary phase with a different amount of available recombination energy. This can help us understand how recombination energy affects the evolution of planetary nebulae.
