Multi-stage inducer for centrifugal pumps

Abstract

An inducer assembly comprising at least two sets of rotating and non-rotating helical inducer vanes. As the fluid enters the inducer, the fluid moves up through a first set of rotating vanes, and gains rotational momentum. The fluid then enters a second set of non-rotating vanes that use the rotational momentum of the fluid to progress the fluid forward while removing the rotation and consequently decreasing the net positive suction head required. The inducer is positioned at the inlet of a cryogenic centrifugal pump. Embodiments of the cryogenic centrifugal pump use a vertical rotational axis and include a thrust equalizing mechanism device to balance hydraulic thrust.

1 . An inducer assembly for use on a pump inlet of a cryogenic centrifugal pump operating within a vessel containing a cryogenic fluid, comprising:
 a housing including an inlet, an outlet and an exterior housing having an interior wall;   a shaft with a vertical rotational axis, having an outer surface, and having a thrust load balanced by a thrust equalizing mechanism device;   at least two rotating helical blades affixed to the shaft that spiral in a first direction about the vertical rotational axis of the shaft, the at least two rotating helical blades occupying at least two first annular spaces formed between the interior wall and the outer surface, the at least two rotating helical blades rotating within the interior wall; and   at least two non-rotating helical blades in axial alignment with the shaft that spiral in a second direction that is in counter rotation to the first direction, the at least two non-rotating helical blades occupying at least two second annular spaces formed between the interior wall and the outer surface, the at least two non-rotating helical blades affixed to the interior wall, wherein interaction between the at least two rotating helical blades and the at least two non-rotating helical blades lowers a net positive suction head required of the cryogenic centrifugal pump and allows more of the cryogenic fluid to be removed from the vessel without allowing cavitation to occur within the pump.   
     
     
         2 . The inducer assembly as recited in  claim 1 , wherein a first rotating helical blade among the at least two rotating helical blades is affixed to the shaft near the inlet, and a first non-rotating helical blade among the at least two non-rotating helical blades is positioned along the vertical rotational axis next to the first rotating helical blade. 
     
     
         3 . The inducer assembly as recited in  claim 1 , wherein the at least two rotating helical blades and the at least two non-rotating helical blades alternate axial positions within the housing. 
     
     
         4 . The inducer assembly as recited in  claim 1 , wherein the at least two rotating helical blades have a first rotating blade pitch and the at least two non-rotating helical blades have a first non-rotating blade pitch, the first rotating blade pitch being dissimilar to the first non-rotating blade pitch. 
     
     
         5 . The inducer assembly as recited in  claim 1 , wherein the at least two rotating helical blades have a first rotating blade width and the at least two non-rotating helical blades have a first non-rotating blade width, the first rotating blade width being dissimilar to the first non-rotating blade width. 
     
     
         6 . The inducer assembly as recited in  claim 1 , wherein the at least two rotating helical blades have a first number of rotating blades and the at least two non-rotating helical blades have a first number of non-rotating blades, the first number of rotating blades being dissimilar to the first number of non-rotating blades. 
     
     
         7 . The inducer assembly as recited in  claim 1 , wherein a rotating helical blade of the at least two rotating helical blades and a non-rotating helical blade of the at least two non-rotating helical blades form a stage, and wherein a plurality of stages are positioned between the inlet and the outlet. 
     
     
         8 . The inducer assembly as recited in  claim 1 , wherein the at least two non-rotating helical blades are positioned around but are not affixed to the shaft. 
     
     
         9 . The inducer assembly as recited in  claim 1 , wherein the at least two non-rotating helical blades are formed from the interior wall. 
     
     
         10 . A cryogenic centrifugal pump with a vertical rotational axis operating within a vessel containing a cryogenic fluid, comprising:
 a motor shaft mounted on one or more first bearings in a motor housing, the motor shaft supporting a motor and rotating around the vertical rotational axis;   a pump shaft mounted on one or more second bearings in a pump housing, the pump shaft rotating around the vertical rotational axis, the motor shaft driving the pump shaft;   a thrust equalizing mechanism device balancing a thrust load of the pump shaft;   an impeller transferring a rotational energy from the pump shaft to the cryogenic fluid flowing through the cryogenic centrifugal pump; and   an inducer assembly positioned at a pump inlet lowering a net positive suction head required of the cryogenic centrifugal pump and allowing more of the cryogenic fluid to be removed from the vessel without allowing cavitation to occur within the cryogenic centrifugal pump, the inducer assembly including
 an inducer housing including an inlet, an outlet and an exterior inducer housing having an interior wall, 
 at least two rotating helical blades affixed to the pump shaft that spiral in a first direction about the vertical rotational axis of the pump shaft, the at least two rotating helical blades occupying at least two first annular spaces formed between the interior wall and an outer surface of the pump shaft, the at least two rotating helical blades rotating within the interior wall, and 
 at least two non-rotating helical blades in axial alignment with the pump shaft that spiral in a second direction that is in counter rotation to the first direction, the at least two non-rotating helical blades occupying at least two second annular spaces formed between the interior wall and the outer surface, the at least two non-rotating helical blades affixed to the interior wall. 
   
     
     
         11 . The cryogenic centrifugal pump as recited in  claim 10 , further comprising a magnetic coupling with two matching rotating parts, a first rotating part mounted on the motor shaft and a second rotating part mounted on the pump shaft next to each other and separated by a non-rotating membrane, the motor shaft rotating the first rotating part and transferring rotational power to the second rotating part through the magnetic coupling. 
     
     
         12 . The cryogenic centrifugal pump as recited in  claim 10 , wherein a first rotating helical blade among the at least two rotating helical blades is affixed to the pump shaft near the inlet, and a first non-rotating helical blade among the at least two non-rotating helical blades is positioned along the vertical rotational axis next to the first rotating helical blade. 
     
     
         13 . The cryogenic centrifugal pump as recited in  claim 10 , wherein the at least two rotating helical blades and the at least two non-rotating helical blades alternate axial positions within the inducer housing. 
     
     
         14 . The cryogenic centrifugal pump as recited in  claim 10 , wherein the at least two rotating helical blades have a first rotating blade pitch and the at least two non-rotating helical blades have a first non-rotating blade pitch, the first rotating blade pitch being dissimilar to the first non-rotating blade pitch. 
     
     
         15 . The cryogenic centrifugal pump as recited in  claim 10 , wherein the at least two rotating helical blades have a first rotating blade width and the at least two non-rotating helical blades have a first non-rotating blade width, the first rotating blade width being dissimilar to the first non-rotating blade width. 
     
     
         16 . The cryogenic centrifugal pump as recited in  claim 10 , wherein the at least two rotating helical blades have a first number of rotating blades and the at least two non-rotating helical blades have a first number of non-rotating blades, the first number of rotating blades being dissimilar to the first number of non-rotating blades. 
     
     
         17 . The cryogenic centrifugal pump as recited in  claim 10 , wherein a rotating helical blade of the at least two rotating helical blades and a non-rotating helical blade of the at least two non-rotating helical blades form a stage, and wherein a plurality of stages are positioned between the inlet and the outlet. 
     
     
         18 . The cryogenic centrifugal pump as recited in  claim 10 , wherein the at least two non-rotating helical blades are positioned around but are not affixed to the pump shaft. 
     
     
         19 . The cryogenic centrifugal pump as recited in  claim 10 , wherein the at least two non-rotating helical blades are formed from the interior wall.