An intershaft seal assembly for maintaining separation between a piston ring and a pair of mating rings is presented. The assembly includes a piston ring interposed between forward and aft mating rings and a plurality of hydrodynamic grooves disposed along a sealing face of each mating ring. Each hydrodynamic groove further includes at least two adjoining steps wherein each step is defined by a base wall arranged to decrease depthwise in the direction opposite to rotation of an inner shaft. Two adjoining base walls define a base shoulder which locally redirects potion of a longitudinal flow within the groove to form an outward flow in the direction of the piston ring. Base walls are bounded by and intersect a pair of side walls with at least one side shoulder thereon which narrows the groove widthwise and locally redirects portion of the longitudinal flow to form a lateral flow from one side wall toward another side wall. Outward and lateral flows cooperate, with or without the longitudinal flow, to increase fluid pressure and maintain separation between the piston ring and the mating rings.

A gas dynamic pressure bearing includes a shaft centered on a central axis extending in an up-down direction, and a sleeve that faces at least a portion of the shaft in a radial direction. The portion in which the sleeve and the shaft face each other in the radial direction includes a first dynamic pressure portion at each of both ends in the axial direction, and a second dynamic pressure portion between the first dynamic pressure portions. In the first dynamic pressure portion, one of the sleeve and the shaft includes dynamic pressure grooves arranged in a circumferential direction. A sum of center angles of groove widths of the dynamic pressure grooves in a cross-section cut along a plane orthogonal to the central axis is about 144 or more and about 216 or less.

A motor assembly includes a rolling bearing installed on a rotation shaft between an impeller and a rotor to support a first support of the rotation shaft, and a motor housing having a stator. The motor housing has a gas bearing bracket for accommodating a second support of the rotation shaft disposed at a side opposite to the first support with respect to the rotor. The motor assembly includes a gas bearing assembly in the gas bearing bracket to support rotation of the second support of the rotation shaft. The gas bearing assembly includes a gas bearing for surrounding the second support. The gas bearing is spaced apart from the second support of the rotation shaft to define a gap therebetween when the rotation shaft rotates. The gas bearing assembly includes an elastic member interposed between the gas bearing bracket and the gas bearing to elastically support the gas bearing.

Embodiments of a damper assembly are disclosed. In some embodiments, the damper assembly includes a damper housing, a damper plunger and a support spring. The damper plunger is disposed at least partially within the housing and movable within to define a first primary damper cavity and a second primary damper cavity. A damper cavity restrictive clearance is defined between the first primary damper cavity and the second primary damper cavity. The damper cavity restrictive clearance includes an elliptical damper orifice having a major-axis and a minor-axis at a mid-plane of the damper cavity restrictive clearance and is oriented perpendicular to a direction of a vibrational force imposed on the damper assembly.

An aerostatic bearing includes a slider that is guidable on a guide surface. The slider has an inner, conical sliding surface of an inner air bearing facing the guide surface with a central compressed air supply. The conical sliding surface is attached by first joints to the central compressed air supply and by second joints to a base of the slider arranged on a side of the slider facing away from the guide surface, such that a cone angle of the conical sliding surface is variable. The conical sliding surface is surrounded by an annular sliding surface of an outer air bearing having an annular compressed air supply.

A gas dynamic bearing includes a shaft extending along a central axis extending vertically, and a sleeve with a hole opening at least at one end of the sleeve in an axial direction, at least a portion of the shaft housed inside the hole. The sleeve includes dynamic pressure grooves in an inner peripheral surface of the hole. The shaft includes a core portion, and a protective portion that is disposed on an outer peripheral surface of the core portion and that includes at least a portion facing the inner peripheral surface of the hole in a radial direction. The protective portion includes a first protective portion and a second protective portion. The first protective portion is at least above or below the second protective portion in the axial direction, and includes at least a portion with a thickness in the radial direction more than a thickness of the second protective portion in the radial direction.

A gas dynamic pressure bearing includes a shaft centered on a central axis extending in an up-down direction, and a sleeve that faces at least a portion of the shaft in a radial direction. The portion in which the sleeve and the shaft face each other in the radial direction includes a first dynamic pressure portion at each of both ends in the axial direction, and a second dynamic pressure portion between the first dynamic pressure portions. In the first dynamic pressure portion, one of the sleeve and the shaft includes dynamic pressure grooves arranged in a circumferential direction. A sum of center angles of groove widths of the dynamic pressure grooves in a cross-section cut along a plane orthogonal to the central axis is about 144 or more and about 216 or less.

A rotation system (10) containing a housing (11), a shaft (12) rotatable relative to the housing (11), and at least one bearing assembly (51) which has a first region (52) supporting the shaft (12) by a radial gas bearing. An air gap is formed between the bearing assembly (51) and the shaft (12). The first region (52) contains or is formed by a tubular radial bearing bushing (55). An inside of the radial bearing bushing (55) has a bearing surface (66) which supports the shaft (12) in the radial direction. The bearing assembly (51) has a third region (54) which is held by or integrated on or in the housing (11) and a second region (53) connects the first region (52) to the third region (54). The second region (53) is more elastic than the first region (52) due to its shape or the shape of the first region (52).

A circumferential seal assembly capable of separating a gas into two separate flow paths before communication between a rotatable runner and a pair of seal rings is presented. The seal assembly includes an annular seal housing, a pair of annular seal rings, a rotatable runner, and a plurality of groove structures. The seal housing is interposed between a pair of compartments. The seal rings are separately disposed within the seal housing and separately disposed around the rotatable runner. The groove structures are disposed along an outer annular surface of the rotatable runner. A gas is communicable onto the groove structures. Each groove structure includes at least two hydrodynamic grooves that separate and communicate the gas onto the seal rings. Each groove includes steps whereby the depth of at least one adjoining step decreases in the direction opposite to rotation with or without the depth of another adjoining steps increasing in the direction opposite to rotation.

A circumferential seal assembly capable of dividing a gas into separate flow paths before communication between a rotatable runner and a pair of seal rings is presented. The assembly includes an annular seal housing, a rotatable runner, a pair of annular seal rings, and a plurality of groove structures. Each groove structure separates a source flow communicated into a feed groove so that a portion enters at least two grooves to form a longitudinal flow therein. Each groove includes at least two adjoining steps defined by base walls. The base walls are arranged along the groove to decrease depthwise opposite to rotation of the rotatable runner. Two adjoining base walls are disposed about a base shoulder. Each base shoulder locally redirects the longitudinal flow to form an outward radial flow in the direction of one annular seal ring. The base walls are bounded by and intersect a pair of side walls. Each side wall includes at least one side shoulder which narrows the groove widthwise and locally redirects the longitudinal flow away from the side wall to form a lateral flow in the direction of the other side wall. Each reduction to the volume of the gas at the downstream end of each groove structure increases pressure and enhances the stiffness of a thin-film layer between each annular seal ring and the rotatable runner.