In a fluid energy machine, such as an exhaust gas turbocharger of an internal combustion engine of an automobile, with a casing accommodating a rotor wheel that is rotatable about a first axis of rotation extending in the axial direction of the casing, an inlet flow passage which extends generally in a flow direction at an angle relative to the axial and the radial directions to the housing, the flow passage is formed by spaced insertion elements with spherical sections that have a common center of curvature disposed on the first axis of rotation and guide vanes are supported between the spaced spherical wall sections of the insertion elements so as to be rotatable about a second axis of rotation which extends through the common center of curvature, and have opposite axial end walls also curved spherically with a center of curvature coinciding with the center of curvature of the insertion elements thereby to be pivotable between the two spaced spherical wall sections of the insertion elements with minimal clearance.