A rotary engine where the rotor cavity has a peripheral inner surface having a peritrochoid configuration defined by a first eccentricity and the rotor has a peripheral outer surface having a peritrochoid inner envelope configuration defined by a second eccentricity larger than the first eccentricity. Also, a rotary engine where the rotor cavity has a peripheral inner surface having a peritrochoid configuration defined by an eccentricity, and a rotor with a peripheral outer surface between adjacent ones of the apex portions being inwardly offset from a peritrochoid inner envelope configuration defined by the eccentricity. The engine may have an expansion ratio with a value of at most 8. The rotary engine may be part of a compound engine system.

A rotary piston and cylinder device (1) comprising a rotor (2), a stator (4) and a rotatable shutter (3), the rotor comprising a piston (5) which extends from the rotor into a working chamber, the rotor and the stator together defining a working chamber, the shutter arranged to extend through the working chamber and forming a partition therein, and the shutter comprising a slot which allows passage of the piston therethrough, a bearing (20) which mounts the rotor relative to the stator, the rotor comprising a formation (12; 30) which extends substantially axially away from the chamber, and the formation being radially outward of the bearing and extending around the axis of rotation, and the formation comprising a surface which at least in part defines a space between the rotor and the stator, and at least part of that space and/or the formation overlaps in an axial direction with the bearing.

A screw rotor which is hollow has improved performance against heat, pressure, rust, and the like. A screw rotor includes a screw portion of which an outer periphery has teeth and grooves having a helical shape and extending by a predetermined length in an axial direction. A radial cross section of at least a part of the screw portion includes a cross section of an outer surface portion forming the teeth and the grooves, a cross section of an axial center portion, a cross section of a support portion that connects an axial center side of the outer surface portion and an outer diameter side of the axial center portion, and a cross section of a hollow portion formed by the support portions adjacent to each other in a rotational direction and an axial center side inner surface of a tooth bottom or a tooth tip. In at least the radial cross section of the screw portion, different members are continuously joined as an integral structure in a cross section of at least one of the axial center portion and the support portion and the outer surface portion.

A displacement device including an inner rotor and an outer rotor with meshing projections. Points on each rotor trace a hypotrochoidal path relative to the other. The tips of the outer rotor projections may contact the inner rotor at Top Dead Center (TDC) and Bottom Dead Center (BDC) to form higher and lower pressure regions. Various elements may shape other elements to form seals.

A rotary piston and cylinder device comprising a rotor (2), comprising a rotor surface (2a), a stator (4), a rotatable shutter (3), a piston (5) which extends from the rotor surface, the rotor surface and the stator together defining an annular chamber, and the piston arranged to rotate, through the annular chamber, and the rotor surface being orientated at an incline to a plane (P-P) substantially perpendicular to the axis of rotation (A-A) of the rotor and the rotor surface faces generally away from, or outwardly of, the axis of rotation of the rotor.

A rotary machine, for directing a quantity of fluid from an inlet to an outlet, comprises one or more elliptical or near-elliptical rotors having planetary rotation within a housing. The interior cavity of the housing comprises an inverse apex region that is in contact with the rotor during its rotation. In various embodiments the rotor and housing can be symmetric or asymmetric in cross-section. Features are described that can improve the operation of the machine for various end-use applications. Such features include cut-outs that are fluidly connected to the inlet or outlet ports of the machine, mechanisms for reducing variation in output flow rate from the rotary machine, linings for the interior cavity of the housing, pressure relief mechanisms, dynamic apex seals and other sealing mechanisms.

This screw compressor is provided with a screw rotor, a casing accommodating the screw rotor, and a liquid feed mechanism for feeding a liquid into an operating chamber enclosed by the casing, wherein the pitch of the screw rotor changes in the axial direction from a suction end surface toward a discharge end surface.

Rotary positive displacement machines based on trochoidal geometry, that comprise a helical rotor that undergoes planetary motion within a helical stator are described. The rotor can have a hypotrochoidal cross-section, with the corresponding stator cavity profile being the outer envelope of the rotor as it undergoes planetary motion, or the stator cavity can have an epitrochoidal cross-section with the corresponding rotor profile being the inner envelope of the trochoid as it undergoes planetary motion. In some embodiments, the geometry is offset in a manner that provides structural and/or operational advantages in the rotary machine.

A compressor, more particularly, a scroll compressor provides structures that may enhance centrifugal stiffness at a contact point between a fixed scroll and an orbiting scroll. The compressor may include an orbiting scroll having an orbiting scroll wrap wound around a radial-direction inner area from a radial-direction outer area; and a fixed scroll having a fixed scroll wrap wound around the radial-direction inner area from the radial-direction outer area. A surfacing part may be configured to narrow a distance between the orbiting scroll wrap and the fixed scroll wrap may be formed in a predetermined section of the orbiting scroll or fixed scroll wrap.

Provided is a rotor structure of a screw compressor and an inverter screw compressor with the same. The rotor structure includes: a female rotor including a female rotor body, wherein the female rotor body includes a plurality of female teeth, and a tooth profile is formed between tooth crests of two adjacent female teeth of the female rotor body, and the tooth profile is formed by sequentially connecting an arc segment a.sub.1b an envelope bc, an arc segment cd, an arc segment de, an arc segment ea.sub.2, an arc segment a.sub.2a.sub.3 from front to rear along a counterclockwise direction, wherein centers of the arc segment cd and the arc segment de are respectively located on both sides of the tooth profile.