Fuel system using dual pressure hi-speed centrifugal pump arrangement

Abstract

An improved system for providing fuel uses a centrifugal pump arrangement that provides dual pressure. The dual pressure pump assembly includes a centrifugal pump for supplying pressurized fluid to an associated downstream use, and an auxiliary pump stage for selectively boosting pressure of delivered flow. The auxiliary pump stage in one preferred arrangement includes a start and turbo-pump stage where inlet fuel from an associated airframe is fed to a centrifugal pump portion of the turbo-pump that outlets to an inlet of the centrifugal pump. The auxiliary pump stage in another arrangement includes a recirculation passage communicating with the outlet of the high-speed centrifugal pump and the turbine, and the outlets from the start and turbo-pump stage feed an inlet of the high speed centrifugal pump, and a flow valve is disposed in the recirculation passage. In still another arrangement, the auxiliary pump stage includes an electric motor for start-up.

I claim: 
     
         1 . A dual pressure pump assembly for a fuel system comprising:
 a centrifugal pump for supplying pressurized fluid to an associated downstream use; and   an auxiliary pump stage operatively associated with the centrifugal pump for selectively boosting pressure of delivered flow to the associated downstream end-use.   
     
     
         2 . The dual pressure pump assembly of  claim 1  wherein the auxiliary pump stage includes a start and turbo-pump stage where inlet fuel from an associated airframe is fed to a second centrifugal pump that outlets to an inlet of the centrifugal pump. 
     
     
         3 . The dual pressure pump assembly of  claim 2  wherein the start and turbo-pump stage includes a recirculation passage communicating with the outlet of the turbo-pump to feed an inlet of the start stage. 
     
     
         4 . The dual pressure pump assembly of  claim 3  wherein the start and turbo-pump stage includes a valve in the recirculation passage to selectively control flow from the high-speed centrifugal pump outlet to a turbine portion of the turbo-pump stage. 
     
     
         5 . The dual pressure pump assembly of  claim 2  wherein the auxiliary pump stage includes an electric motor for start-up. 
     
     
         6 . A method of selectively boosting pressure of delivered flow to an associated downstream end-use using a dual pressure pump assembly for a fuel system that includes a centrifugal pump and an auxiliary pump stage, the method comprising
 supplying pressurized fluid to the associated downstream use from the centrifugal pump; and   selectively boosting pressure of delivered flow from the centrifugal pump with the auxiliary pump stage.   
     
     
         7 . The method of  claim 6  wherein the auxiliary pump stage includes a start and turbo-pump stage, and the method further includes feeding inlet fuel from an associated airframe to a second centrifugal pump that outlets to an inlet of the centrifugal pump. 
     
     
         8 . The method of  claim 7  wherein the start and turbo-pump stage includes a recirculation passage, and the method further includes communicating with the outlet of the turbo-pump to feed an inlet of the start stage. 
     
     
         9 . The method of  claim 8  wherein the start and turbo-pump stage includes a valve in the recirculation passage, and the method further includes selectively controlling flow from the high-speed centrifugal pump outlet to a turbine portion of the turbo-pump stage. 
     
     
         10 . The wherein the auxiliary pump stage includes an electric motor, and the method includes using the electric motor for start-up.