Gas turbomachine including a purge flow reduction system and method

Abstract

A gas turbomachine includes a turbine portion including at least one turbine wheel, and a wheel shaft operatively connected to the at least one turbine wheel. The wheel shaft includes an outer surface. A stationary member includes an inner surface positioned outward of the outer surface of the wheel shaft to form a purge flow passage. A bearing housing is linked to the stationary member and spaced radially outward of the wheel shaft. The bearing housing includes at least one purge flow passage configured and disposed to guide a purge flow toward the wheel shaft. At least one of the outer surface of the wheel shaft and the inner surface of the stationary member includes a roughness inducing coating configured and disposed to increase drag and residence time of purge flow in the purge flow passage.

What is claimed is: 
     
         1 . A gas turbomachine comprising:
 a turbine portion including at least one turbine wheel;   a wheel shaft operatively connected to the at least one turbine wheel, the wheel shaft including an outer surface;   a stationary member including an inner surface positioned outward of the outer surface of the wheel shaft to form a purge flow passage; and   a bearing housing linked to the stationary member and spaced radially outward of the wheel shaft, the bearing housing including at least one purge flow passage configured and disposed to guide a purge flow toward the wheel shaft,
 wherein at least one of the outer surface of the wheel shaft and the inner surface of the stationary member includes a roughness inducing coating configured and disposed to increase drag and residence time of purge flow in the purge flow passage. 
   
     
     
         2 . The gas turbomachine according to  claim 1 , wherein the roughness inducing coating is provided on the outer surface of the wheel shaft. 
     
     
         3 . The gas turbomachine according to  claim 1 , wherein the roughness inducing coating comprises a flame sprayed coating. 
     
     
         4 . The gas turbomachine according to  claim 1 , wherein the wheel shaft includes an axial portion and an angled portion, the angled portion being angled relative to the axial portion and operatively connected to the at least one turbine wheel. 
     
     
         5 . The gas turbomachine according to  claim 4 , wherein the roughness inducing coating is provided on the angled portion of the wheel shaft. 
     
     
         6 . The gas turbomachine according to  claim 5 , wherein the roughness inducing coating is provided on each of the angled portion of the wheel shaft and the inner surface of the stationary member. 
     
     
         7 . A turbomachine system comprising:
 a rotating component including an outer surface;   a stationary member including an inner surface positioned outward of the outer surface of the rotating component to form a fluid flow passage; and   a bearing housing linked to the stationary member and spaced radially outward of the rotating component adjacent the stationary member, the bearing housing including at least one fluid flow passage configured and disposed to guide a fluid flow toward the fluid flow passage,
 wherein at least one of the outer surface of the rotating component and the inner surface of the stationary member includes a roughness inducing coating configured and disposed to increase drag and residence time of fluid flow in the fluid flow passage. 
   
     
     
         8 . The turbomachine system according to  claim 7 , wherein the roughness inducing coating is provided on the outer surface of the rotating component. 
     
     
         9 . The turbomachine system according to  claim 7 , wherein the roughness inducing coating comprises a flame sprayed coating. 
     
     
         10 . The turbomachine system according to  claim 7 , wherein the roughness inducing coating is provided on each of the outer surface of the rotating component and the inner surface of the stationary member. 
     
     
         11 . A method of decreasing purge flow in a gas turbomachine, the method comprising:
 guiding a purge flow into a purge flow passage defined between a rotating component and a stationary component; and   inducing drag in the purge flow through an interaction with a roughness inducing coating provided on one of the rotating component and the stationary component, the drag leading to an increased temperature and residence time of the purge flow in the purge flow passage that decreases an amount of required purge flow.   
     
     
         12 . The method of  claim 11 , wherein inducing the drag in the purge flow includes passing the purge flow across a flame sprayed coating on an outer surface of the rotating component. 
     
     
         13 . The method of  claim 11 , wherein inducing the drag in the purge flow includes passing the purge flow across a flame sprayed coating provided on an outer surface of the rotating component and an inner surface of stationary component.