Thrust-balancing contra-rotating system
A contra-rotating compressor includes a first shaft assembly disposed in a housing, the first shaft assembly including an outer shaft, and a first plurality of impellers coupled to the outer shaft, wherein the outer shaft includes a final stage that includes a final impeller of the first plurality of impellers, a second shaft assembly disposed in the housing and rotatable about the longitudinal axis, the second shaft assembly including a second plurality of impellers, 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 the 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.
1 . 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.
2 . The contra-rotating system of claim 1 , wherein the final stage comprises:
the first cylindrical member;
the second cylindrical member comprising the outlet port;
an annular shoulder extending between the first cylindrical member and the second cylindrical member; and
an annular channel formed between the first cylindrical member and the second cylindrical member and terminating the annular shoulder, wherein the final blade is positioned in the annular channel.
3 . The contra-rotating system of claim 1 , wherein a first radial end of the final blade is coupled to the first cylindrical member of the final stage, and a second radial end of the final blade is permitted to flex relative to the second cylindrical member of the final stage.
4 . The contra-rotating system of claim 1 , wherein the final stage comprises an outlet port in the second cylindrical member.
5 . The contra-rotating system of claim 1 , wherein the pressure balancing circuit further comprises a third pressure balancing passage extending through the housing.
6 . The contra-rotating system of claim 5 , wherein the third pressure balancing passage comprises a plurality of circumferentially spaced pressure balancing passages disposed in the housing.
7 . The contra-rotating system of claim 1 , wherein the pressure balancing circuit has the second pressure balancing passage extending through the final blade.
8 . The contra-rotating system of claim 1 , wherein the pressure balancing circuit has the second pressure balancing passage extending through the second shaft assembly.
9 . The contra-rotating system of claim 1 , further comprising a barrier fluid system that comprises:
a first barrier fluid seal assembly positioned around the first shaft assembly and configured to receive a barrier fluid at a first pressure;
a second barrier fluid seal assembly positioned around the second shaft assembly and configured to receive the barrier fluid at the first pressure.
10 . The contra-rotating system of claim 1 , wherein the first pressure balancing passage comprises a plurality of circumferentially spaced pressure balancing passages disposed in the first cylindrical member.
11 . A method, comprising:
flowing an inlet flow of a fluid into a housing at an inlet pressure;
rotating a first shaft assembly disposed in the housing and comprising a first plurality of blades about a longitudinal axis in a first rotational direction;
rotating a second shaft assembly disposed in the housing and comprising a second plurality of blades interleaved with the first plurality of blades about the longitudinal axis in a second rotational direction opposite the first rotational direction; and
applying an axially directed pressure force to each end of the second shaft assembly with the fluid at the inlet pressure.
12 . The method of claim 11 , wherein applying the axially directed pressure force comprises:
communicating the fluid at the inlet pressure to a chamber positioned axially between the first shaft assembly and the second shaft assembly.
13 . The method of claim 12 , wherein applying the axially directed pressure force comprises:
communicating the fluid at the inlet pressure through a passage extending through at least one of the first plurality of blades.
14 . The method of claim 12 , wherein applying the axially directed pressure force comprises:
communicating the fluid at the inlet pressure through a passage extending through the second shaft assembly.
15 . The method of claim 12 , further comprising:
flowing an outlet flow of the fluid from the housing at an outlet pressure;
leaking a portion of the outlet flow into the chamber; and
recirculating the leaked portion of the outlet flow to the inlet flow.
16 . 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;
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 first pressure balancing passage extending through the housing; and
a second pressure balancing passage extending through the final stage;
wherein the first shaft assembly is allowed to be rotated in a first rotational direction;
wherein the second shaft assembly is allowed to be rotated in a second rotational direction opposite to the first rotational direction.
17 . The contra rotating system of claim 16 , wherein the contra-rotating system is configured to receive a multiphase, gas-liquid and wet gasses in a subsea environment.
18 . The contra rotating system of claim 16 , wherein a radially first radial end of the final blade is coupled to a first cylindrical member of the final stage, and a radially second radial end of the final blade is permitted to flex relative to a second cylindrical member of the final stage.