Thrust-balancing contra-rotating system

A contra-rotating system, comprising:

• a first shaft assembly disposed in a housing and rotatable about a longitudinal axis, the first shaft assembly comprising an outer shaft, and a first plurality of blades coupled to the outer shaft, wherein the outer shaft comprises a final stage that includes a final blade of the first plurality of blades, wherein the final blade is disposed between first and second cylindrical members;
• a second shaft assembly disposed in the housing and rotatable about the longitudinal axis, the second shaft assembly comprising a second plurality of blades interleaved with the first plurality of blades, wherein the first and second plurality of blades are disposed in a flow path of a fluid;
• a pressure balancing circuit configured to be in fluid communication with an inlet flow of the fluid at an inlet pressure, wherein the pressure balancing circuit comprises:
• a first pressure balancing passage extending through the first cylindrical member of the final stage;
• a second pressure balancing passage extending through at least one of the final blade or the second shaft assembly;
• and
• a chamber positioned axially between the final stage and the second shaft assembly;
• a first pair of annular seals between the final stage and an inner surface of the housing, the pair of annular seals being configured to permit relative rotation between the final stage and the housing;
• and
• a third annular seal positioned between an outer surface of the final stage and an inner surface of the second shaft assembly, the third annular seal configured to permit contra-rotation between the final stage and the second shaft assembly.