Patent ID: 7597145

Claim:
An apparatus useful in combining at least two fluid streams of differing pressures, the apparatus comprising: a housing; a first rotor within the housing; a second rotor within the housing, the first rotor engaging the second rotor and both the first and the second rotors engaging the housing; a third rotor within the housing and engaging the first rotor; a fourth rotor within the housing and engaging the second rotor, the third rotor engaging the fourth rotor and both the third and the fourth rotors engaging the housing; wherein the first and the second rotors define a first input volume positioned and arranged to receive a first input stream having a first pressure; wherein the third and the fourth rotors define a second input volume positioned and arranged to receive a second input stream having a second pressure; wherein the first pressure differs from the second pressure; wherein the first and the third rotors define a first output volume; wherein the second and the fourth rotors define a second output volume; and wherein at least one rotor further comprises a means for sealing engagement, the means for sealing engagement comprising: a set of protrusions; a set of recesses between the protrusions; wherein the protrusions comprise sealing surfaces; wherein at least a portion of the protrusion sealing surface comprises a portion of a first circle; wherein the recesses comprise sealing surfaces; wherein at least a portion of the recess sealing surface comprises a portion of a second circle; wherein the first circle and the second circle are tangential; wherein the first circle and the second circle each have centers located on a circle having a center on an axis of the rotor.