Multi-stage radial turbine

Abstract

A multi-stage radial turbine that is capable of reducing the number of bearings and of improving the conversion efficiency is provided. Provided are a plurality of radial turbine rotor blades ( 5 ) that are attached at intervals to a single rotating shaft ( 3 ); a plurality of nozzles ( 19 ) that are individually installed on an upstream side of each of the radial turbine rotor blades and that accelerate a flow of fluid; a connecting channel portion ( 9 ) that connects gas an outlet portion ( 23 ) of the radial turbine rotor blade ( 5 ) on the front stage side and an upstream side of the nozzle ( 19 ) on the rear stage side, the connecting channel portion ( 9 ) being provided with a U-shaped bent portion ( 25 ) that deflects outward in the radial direction the flow of fluid that is made to flow out from the radial turbine rotor blade ( 5 ) in the shaft direction; a vane portion having a plurality of deflecting vanes ( 27 ) that deflect the flow of fluid inward in a rotation direction (R) while guiding the flow of fluid from the U-shaped bent portion ( 25 ) outward in the radial direction; and a return bent portion ( 31 ) that deflects inward in the radial direction the flow that is made to flow out from the vane portion ( 29 ) while swirling outward in the radial direction.

1 . A multi-stage radial turbine comprising:
 a single rotating shaft;   a plurality of radial turbine rotor blades that are attached at intervals to the rotating shaft and that cause a flow of fluid that flows in from an outer peripheral side in a radial direction to flow out in substantially a shaft direction;   a plurality of nozzles that are individually installed on an upstream side of each of the radial turbine rotor blades and that accelerate the flow of fluid in a rotation direction;   a connecting channel portion that connects an outlet portion of the radial turbine rotor blade on a front stage side and an upstream side of the nozzle on a rear stage side,   the connecting channel portion being provided with a U-shaped bent portion that deflects outward in the radial direction the flow of fluid that is made to flow out from the radial turbine rotor blade in the shaft direction;   a vane portion having a plurality of deflecting vanes that deflect the flow of fluid in the rotation direction of the radial turbine rotor blades while guiding the flow of fluid from the U-shaped bent portion outward in the radial direction; and   a return bent portion that deflects inward in the radial direction the flow that flows out from the vane portion while swirling outward in the radial direction.   
     
     
         2 . A multi-stage radial turbine according to  claim 1 , wherein the U-shaped bent portion is configured such that a downstream-portion channel area at an end portion closer to the vane portion is made smaller than an upstream-portion channel area at an end portion closer to the radial turbine rotor blade. 
     
     
         3 . A multi-stage turbine according to  claim 2 , wherein the downstream-portion channel area is set to be equal to or less than 0.8 to 0.9 times the size of the upstream-portion channel area. 
     
     
         4 . A multi-stage radial turbine according to  claim 1 , wherein the deflecting vanes are configured to form involute curves. 
     
     
         5 . A multi-stage radial turbine according to  claim 2 , wherein the deflecting vanes are configured to form involute curves. 
     
     
         6 . A multi-stage radial turbine according to  claim 3 , wherein the deflecting vanes are configured to form involute curves.