Rotor with balancing features and balancing method

A fluid charger device comprising:

• a housing;
• a rotor supported for rotation within the housing for rotation about an axis of rotation;
• a wheel of the rotor with a face that extends out in a radial direction from the axis of rotation and terminates in the radial direction at an outer rim edge of the wheel, the wheel including a plurality of blades that extend from the face, the wheel defining a direction of rotation about the axis of rotation;
• an inter-blade area of the face with an inter-blade area surface defined circumferentially between a first blade and a second blade of the plurality of blades with respect to the axis of rotation;
• and
• a balancing mark recess on the face of the wheel and within the inter-blade area, the balancing mark recess being recessed in an axial direction along the axis of rotation into the inter-blade area surface, the balancing mark recess defined by an outer perimeter edge that is continuous at the inter-blade area surface, the balancing mark recess defined by a smooth interior surface that is bordered by the outer perimeter edge, the outer perimeter edge including an inboard edge portion and an outboard edge portion, the balancing mark recess being elongate and arcuate along a length direction directed between a first end and a second end of the balancing mark recess, the first end and the second end spaced apart across the face, the first end and the second end being recessed and defining respective portions of the outer perimeter edge, the balancing mark recess having a depth that is measured in the axial direction from a surrounding area of the face surrounding the balancing mark recess, the depth varying gradually as the balancing mark recess extends in the length direction the balancing mark recess having a width that is measured in the radial direction between the inboard edge portion and the outboard edge portion, the width varying gradually as the balancing mark recess extends in the length direction the first end and the second end being cupped, an entirety of the outer perimeter edge of the balancing mark recess being spaced apart inwardly in the radial direction from the outer rim edge of the wheel;
• the first blade including a pressure side and the second blade includes a suction side with respect to the direction of rotation, the pressure side facing toward the suction side across the inter-blade area, the first end being disposed proximate the pressure side of the first blade, and the second end being disposed proximate the suction side of the second blade, the depth at the first end being greater than the depth at the second end, and the width at the first end being greater than the width at the second end;
• and
• the balancing mark recess extending in the length direction along an arcuate axis between the first end and the second end, and the arcuate axis being centered substantially on the axis of rotation.