Variable-pitch nozzle for a radial turbine, in particular for an auxiliary power source turbine

Abstract

A radial turbine nozzle of a turbine engine rotating about a central axis includes a first annular array of fixed blades and a second annular array with a same number of variable-pitch blades. The blades have pressure and suction surfaces. Each variable-pitch blade is connected to cups and is configured to be rotated by a controller about a geometric axis connecting centers of the cups. Each variable-pitch blade is mounted at a distance from the axis of the cups such that this axis of rotation is positioned facing the suction surface of the blade and substantially closer to a trailing edge than to a leading edge of that blade. The nozzle can modify the reduced flow admitted by a radial turbine in accordance with requirements of a thermodynamic cycle and produce a seal in an area of maximum load of the nozzle blades.

1 - 8 . (canceled) 
     
     
         9 . A radial turbine nozzle for a turbine engine, rotating about a central axis, comprising:
 a first annular array of fixed blades and a second annular array with a same number of variable-pitch blades, the fixed blades and variable-pitch blades including pressure and suction faces,   each variable-pitch blade of the second array is rigidly connected to cups extending at each end of the variable-pitch blade, is configured to be driven in rotation by control means about a geometric axis connecting centers of the cups, and includes a trailing edge and a leading edge of gas flows linked to the suction and pressure faces,   wherein each variable-pitch blade is mounted at a distance from an axis of rotation of the cups such that the axis of rotation is positioned facing the suction face of the variable-pitch blade and substantially closer to the trailing edge than the leading edge of the variable-pitch blade.   
     
     
         10 . A radial turbine nozzle according to  claim 9 , wherein the leading edge of each variable-pitch blade is located substantially in a wake of a fixed blade so as to guide the gas flows radially towards a central axis of rotation of the turbine. 
     
     
         11 . A radial turbine nozzle according to  claim 9 , wherein the leading edge of each variable-pitch blade has a thickness substantially greater than that of the trailing edge and an aerodynamic curved shape optimized for absorption of a wake of air generated by a fixed blade of the fixed array facing it. 
     
     
         12 . A radial turbine nozzle according to  claim 9 , wherein an average thickness of a portion of a variable-pitch blade between the mounting cups is substantially less than a thickness of a remainder of the variable-pitch blade located on a leading edge side. 
     
     
         13 . A radial turbine nozzle according to  claim 9 , wherein the variable-pitch blades are configured to pivot between two extreme positions about a reference position corresponding to 100% of an aerodynamic flow area, a closed position cutting off air flow, corresponding to 0% of the reference flow area, and an open position of maximum air-flow opening, corresponding to 150% of the reference flow area. 
     
     
         14 . A radial turbine nozzle according to  claim 9 , wherein the fixed-pitch blades are thick enough to ensure passage of structural loads. 
     
     
         15 . A radial turbine nozzle according to  claim 9 , wherein the radial turbine is one of a turboshaft engine turbine, an auxiliary power source of an aircraft, or a turbocharger. 
     
     
         16 . A radial turbine nozzle according to  claim 9 , wherein the radial turbine is fitted with a volute, a diameter of which decreases between its inlet and its end at vanes.