A system includes a gearbox having an external surface; a fan or impeller constructed to generate a first cooling airflow when rotated; a shroud operative to guide and discharge the first cooling airflow over the external surface and cool the gearbox, wherein at least a portion of the shroud is spaced apart from the gearbox and disposed radially outward of the external surface; and a flow entrainment structure coupled to the gearbox and/or the shroud, wherein the flow entrainment structure is constructed to entrain a second cooling airflow and combine the second cooling airflow with the first cooling airflow to form a combined cooling airflow directed across the external surface to cool the gearbox.