Vaneless multistage pump

In a centrifugal, multistage pump having an input state, an outlet stage and a plurality of intermediate stages, the improvement wherein each of said intermediate stages comprises:

• an impeller;
• a divider plate serving to separate said stage from the next and formed with an inclined oval opening extending therethrough to provide undisturbed fluid flow between said stages;
• a center plate interposed between said divider plate and the divider plate of the preceding stage and having a front surface and a rear surface;
• a first recess formed in said rear surface of said center plate having a central portion shaped to mate with said impeller, a second portion extending radially outward from the exit portion of said impeller, a groove extending about the periphery of said second portion and gradually increasing in depth and width through approximately 360.degree. and having a final curved portion formed to direct fluid flow through the oval opening in the subsequent divider plate;
• and
• a second recess formed in said front surface of said center plate having a curved portion formed to receive fluid flow from the oval opening in the preceding divider plate, a helical portion of substantially constant cross-sectional area spiralling inwardly through approximately 360.degree., and an axially diverting portion which continues to spiral inwardly through approximately another 360.degree. while gradually deflecting the fluid flow axially rearward to deliver said fluid flow to the input of said impeller.