In some embodiments, a plenum of an apparatus for transferring energy between a rotating element and a fluid may include a through hole disposed through the plenum; a plurality of inlet guide vanes disposed proximate a peripheral edge of the through hole, the plurality of inlet guide vanes comprising a first group of inlet guide vanes having a symmetrical profile, a second group of inlet guide vanes, and a third group of inlet guide vanes, wherein each inlet guide vane of the second group and third group have a cambered profile, and wherein each inlet guide vane of the third group has a different cambered profile from each other inlet guide vane of the third group.