The FOAM file format has not changed from version 2.0 in many years and so there
is no longer a need for the 'version' entry in the FoamFile header to be
required and to reduce unnecessary clutter it is now optional, defaulting to the
current file format 2.0.
XiEngineFoam is a premixed/partially-premixed combustion engine solver which
exclusively uses the Xi flamelet combustion model.
engineFoam is a general engine solver for inhomogeneous combustion with or
without spray supporting run-time selection of the chemistry-based combustion
model.