Rotor with asymmetric blade spacing

Abstract

A turbine apparatus comprises a rotor with a hub section defined about a rotational axis and a plurality of blades attached to the hub section. The plurality of blades comprises a first group having a first angular spacing in a first circumferential sector of the rotor, and a second group having a second angular spacing in a second circumferential sector of the rotor. The first angular spacing is different from the second angular spacing, and the rotor blades are asymmetric about the rotational axis.

1 . A turbine apparatus comprising:
 a rotor having a hub defined about a rotational axis, the hub having first and second circumferential sectors; and   a plurality of blades attached to the hub and extending radially therefrom, the plurality of blades comprising a first group of blades having a first angular spacing in the first sector and a second group of blades having a second angular spacing in the second sector;   wherein the first angular spacing is different from the second angular spacing, and the rotor blades are asymmetric about the rotational axis.   
     
     
         2 . The turbine apparatus of  claim 1 , wherein the plurality of blades comprises an odd number N of blades, the first group of blades comprising (N−1)/2 of the N blades and the second group of blades comprising (N+1)/2 of the N blades. 
     
     
         3 . The turbine apparatus of  claim 2 , wherein the first angular spacing is approximately 360°/(N−1) and the second angular spacing is approximately 360°/(N+1). 
     
     
         4 . The turbine apparatus of  claim 1 , wherein the plurality of blades comprises an even number N of blades, the first group of blades comprising N/2−1 of the N blades and the second group of blades comprising N/2+1 of the N blades. 
     
     
         5 . The turbine apparatus of  claim 4 , wherein the first angular spacing is approximately 180°/(N/2−1) and the second angular spacing is approximately 180°/(N/2+1). 
     
     
         6 . The turbine apparatus of  claim 1 , further comprising a plurality of splitters attached to the hub section and disposed between the plurality of blades. 
     
     
         7 . The turbine apparatus of  claim 6 , wherein the plurality of splitters comprises a first group of splitters having the first angular spacing in the first circumferential section and a second set of splitters having the second angular spacing in the second circumferential section. 
     
     
         8 . The turbine apparatus of  claim 1 , wherein the rotor comprises an impeller and further comprising a compressor rotor rotationally coupled to the impeller, the compressor rotor comprising:
 a compressor hub defined about the rotational axis, the compressor hub having a first and second circumferential sectors;   a second plurality of blades attached to the second hub and extending radially therefrom, the second plurality of blades comprising a first group of blades having the first angular spacing in the first sector of the second hub and a second group of blades having the second angular spacing in the second sector of the second hub.   
     
     
         9 . An auxiliary power unit comprising the turbine apparatus of  claim 8 , and further comprising a curvic coupling for rotationally coupling the second rotor to the first rotor. 
     
     
         10 . An auxiliary power unit comprising the turbine apparatus of  claim 8 , wherein the first rotor is clocked with respect to the second rotor such that the first plurality of blades is out of phase with respect to the second plurality of blades. 
     
     
         11 . An impeller comprising:
 a hub section defined about a rotational axis, the hub section comprising first and second circumferential sectors;   a first set of blades extending radially from the first sector of the hub section, the first set of blades having a first angular spacing; and   a second set of blades extending radially from the second sector of the hub section, the second set of blades having a second angular spacing;   wherein the first angular spacing is different from the second angular spacing, such that the first and second sets of blades are asymmetric about the rotational axis.   
     
     
         12 . The impeller of  claim 11 , wherein the first set of blades comprises an odd number of blades N 1  and the first angular spacing is about 180°/N 1 . 
     
     
         13 . The impeller of  claim 12 , wherein the second set of blades comprises an even number of blades N 1 +1 and the second angular spacing is about 180°/(N 1 +1). 
     
     
         14 . The impeller of  claim 12 , wherein the second set of blades comprises an odd number of blades N 1 +2 and the second angular spacing is about 180°/(N 1 +2). 
     
     
         15 . An auxiliary power unit comprising the impeller of  claim 11 . 
     
     
         16 . The auxiliary power unit of  claim 15 , further comprising a compressor rotor rotationally coupled to the impeller, the compressor rotor comprising:
 a compressor hub defined about the rotational axis, the compressor hub comprising first and second circumferential sectors;   a third set of blades extending radially from the first sector of the compressor hub, the third set of blades having the first angular spacing;   a fourth set of blades extending radially from the second sector of the compressor hub, the fourth set of blades having the second angular spacing.   
     
     
         17 . A turbomachine comprising:
 a load impeller circumferentially divided into first and second sectors, the first sector of the load impeller having a set of blades with a first angular spacing and the second sector of the load impeller having a set of blades with a second angular spacing;   a power head impeller circumferentially divided into first and second sectors, the first sector of the power head impeller having a set of blades with the first angular spacing and the second sector of the power head impeller having a set of blades with the second angular spacing; and   a rotational coupling between the load impeller and the power head impeller, the coupling defining a rotational axis;   wherein the first angular spacing and the second angular spacing are different, such that the load impeller and the power head impeller are asymmetric about the rotational axis.   
     
     
         18 . The turbomachine of  claim 17 , wherein the load impeller is clocked about the rotational axis with respect to the power head impeller, such that the load impeller is out of rotational phase with respect to the power head impeller. 
     
     
         19 . The turbomachine of  claim 17 , wherein the load impeller and the power head impeller each comprise an equal, odd number of blades N, and wherein the first angular spacing is about 360°/(N−1) and the second angular spacing is about 360°/(N+1). 
     
     
         20 . The turbomachine of  claim 17 , wherein the load impeller and the power head impeller each comprise an equal, even number of blades N, and wherein the first angular spacing is about 180°/(N/2−1) and the second angular spacing is about 180°/(N/2+1).