A vacuum pump generally comprises a low pressure portion and a high pressure portion separated by a gas impermeable partition. Gas molecules exit the low pressure portion through an opening in the partition and passively impinge on a featureless rotatable surface in the high pressure portion. A drive rotates the rotatable surface with tangential velocity in the supersonic range at multiple times the most probable velocity of the impinging gas molecules. Impinging gas molecules are ejected outwardly from the periphery of the rotatable surface generating a substantial net outward flow of gas and reducing the pressure in the low pressure portion. The vacuum pump is effective to reduce the pressure in the low pressure portion to a target minimum pressure without using seals to prevent gas molecules from leaking back to the low pressure portion and without using blades or vanes to actively impact the gas molecules.

A vacuum pump generally comprises a low pressure portion and a high pressure portion separated by a gas impermeable partition. Gas molecules exit the low pressure portion through an opening in the partition and passively impinge on a featureless rotatable surface in the high pressure portion. A drive rotates the rotatable surface with tangential velocity in the supersonic range at multiple times the most probable velocity of the impinging gas molecules. Impinging gas molecules are ejected outwardly from the periphery of the rotatable surface generating a substantial net outward flow of gas and reducing the pressure in the low pressure portion. The vacuum pump is effective to reduce the pressure in the low pressure portion to a target minimum pressure without using seals to prevent gas molecules from leaking back to the low pressure portion and without using blades or vanes to actively impact the gas molecules.

A mixed-flow compressor includes an impeller attached to a shaft and rotatable about a shaft axis. A vaneless diffuser is located axially downstream of the impeller and has a converging portion and a diverging portion. A vaned diffuser is located axially downstream of the vaneless diffuser.

A mixed-flow compressor includes an impeller attached to a shaft and rotatable about a shaft axis. A vaneless diffuser is located axially downstream of the impeller and has a converging portion and a diverging portion. A vaned diffuser is located axially downstream of the vaneless diffuser.

A transonic compressor of a turbomachine comprising exactly two or exactly three annular rows of rotor blades and respectively exactly one or exactly two annular rows of intermediate stator vanes interposed between two respective rows of rotor blades, wherein the flow velocity relative to the rotor downstream of the intermediate stator vanes is less than or equal to a Mach number of 0.9 over a radial portion of the blades extending over the radially inner 40% of the blades, and less than or equal to a Mach number of 1 over a radial portion extending over the radially inner 80% of the blades, and less than or equal to a Mach number of 1.05 over a radial portion extending over the radially outer 20% of the blades.

A transonic compressor of a turbomachine comprising exactly two or exactly three annular rows of rotor blades and respectively exactly one or exactly two annular rows of intermediate stator vanes interposed between two respective rows of rotor blades, wherein the flow velocity relative to the rotor downstream of the intermediate stator vanes is less than or equal to a Mach number of 0.9 over a radial portion of the blades extending over the radially inner 40% of the blades, and less than or equal to a Mach number of 1 over a radial portion extending over the radially inner 80% of the blades, and less than or equal to a Mach number of 1.05 over a radial portion extending over the radially outer 20% of the blades.

A centrifugal compressor includes a casing. An impeller is arranged within the casing. The impeller is rotatable about an axis. A diffuser section is arranged within the casing. The diffuser section is positioned axially downstream from an outlet of the impeller and includes a forward portion fixed relative to the impeller and an aft portion distinct from the forward portion.

A centrifugal compressor includes a casing. An impeller is arranged within the casing. The impeller is rotatable about an axis. A diffuser section is arranged within the casing. The diffuser section is positioned axially downstream from an outlet of the impeller and includes a forward portion fixed relative to the impeller and an aft portion distinct from the forward portion.

A vacuum pump generally comprises a low pressure portion and a high pressure portion separated by a gas impermeable partition. Gas molecules exit the low pressure portion through an opening in the partition and passively impinge on a featureless rotatable surface in the high pressure portion. A drive rotates the rotatable surface with tangential velocity in the supersonic range at multiple times the most probable velocity of the impinging gas molecules. Impinging gas molecules are ejected outwardly from the periphery of the rotatable surface generating a substantial net outward flow of gas and reducing the pressure in the low pressure portion. The vacuum pump is effective to reduce the pressure in the low pressure portion to a target minimum pressure without using seals to prevent gas molecules from leaking back to the low pressure portion and without using blades or vanes to actively impact the gas molecules.

A vacuum pump generally comprises a low pressure portion and a high pressure portion separated by a gas impermeable partition. Gas molecules exit the low pressure portion through an opening in the partition and passively impinge on a featureless rotatable surface in the high pressure portion. A drive rotates the rotatable surface with tangential velocity in the supersonic range at multiple times the most probable velocity of the impinging gas molecules. Impinging gas molecules are ejected outwardly from the periphery of the rotatable surface generating a substantial net outward flow of gas and reducing the pressure in the low pressure portion. The vacuum pump is effective to reduce the pressure in the low pressure portion to a target minimum pressure without using seals to prevent gas molecules from leaking back to the low pressure portion and without using blades or vanes to actively impact the gas molecules.