Turbomachine with reduced leakage penalties in pressure change and efficiency

Abstract

A turbomachine is provided having at least one row of blades oriented at a predetermined stagger. Casing grooves are provided proximate to at least a portion of the tip of the blades. The grooves are oriented substantially normal to the stagger of the blades. The normal of the blade is determined from a chord of the blade. The chord may be taken across a pair of corresponding points one the upstream and downstream end of the blade, hence across the extent of the cross-sectional shape of the blade. Alternatively, a blade chord may be determined over only a portion of the blade, for instance, from a point along the centerline of the upstream end of the blade to a second point on the centerline midway down the blade from the upstream end. Optimally, the grooves are positioned adjacent to the upstream half of the blades, but may continue across the axial extent of the blades. The spacing between grooves can be optimized for blade stagger in order to find an optimal number of grooves that concurrently cross the blade. Additionally, obtaining an optimal groove depth for a particular turbomachine requires knowing only the tip clearance gap as groove depth is directly related to the tip clearance. Furthermore, since the groove may be substantially smaller than prior art casing treatments, fluid recirculation is reduced. The blade-normal groove may take a variety of cross-sectional shapes. Optimally, the aft surface of the groove will have less than a 45° incline to the radial at that point.

1 . A turbomachine with reduced leakage penalties in pressure change and efficiency comprising:
 a plurality of blades, each of said plurality of blades extending substantially radially from a rotational axis and terminating in a blade tip and having a forward facing surface and an opposite facing surface which join together at an upstream extent of the blade and at a downstream extent of the blade, and each said plurality of blades having a cross-sectional shape defined between the forward facing surface and the opposite facing surface; and   a casing, said casing having an inner surface surrounding the plurality of blades, and a plurality of casing grooves in said inner surface, said plurality of casing grooves being oriented in a direction normal to an orientation of the plurality of blades.   
   
   
       2 . The turbomachine recited in  claim 1 , wherein the direction normal to an orientation of the plurality of blades further comprises, a direction normal to a point on one of the forward facing surface and the opposite facing surface. 
   
   
       3 . The turbomachine recited in  claim 1 , wherein the direction normal to an orientation of the plurality of blades further comprises, a direction normal to a point on a mean line between the forward facing surface and the opposite facing surface. 
   
   
       4 . The turbomachine recited in  claim 1 , wherein the direction normal to an orientation of the plurality of blades further comprises, a direction normal to a point on a chord line which intersects a mean line defined between the forward facing surface and the opposite facing surface. 
   
   
       5 . The turbomachine recited in  claim 2 , wherein the plurality of casing grooves being substantially linear. 
   
   
       6 . The turbomachine recited in  claim 2 , wherein the plurality of casing grooves being curvilinear. 
   
   
       7 . The turbomachine recited in  claim 2 , wherein each of the plurality of casing grooves is defined by a first groove wall and a second groove wall. 
   
   
       8 . The turbomachine recited in  claim 2 , wherein a cross-sectional shape of each of the plurality of casing grooves is triangular. 
   
   
       9 . The turbomachine recited in  claim 2 , wherein a cross-sectional shape of each of the plurality of casing grooves is rectangular. 
   
   
       10 . The turbomachine recited in  claim 2 , wherein a cross-sectional shape of each of the plurality of casing grooves is trapezoidal. 
   
   
       11 . The turbomachine recited in  claim 2 , wherein each of the plurality of grooves being defined by an upstream extent and a downstream extent. 
   
   
       12 . The turbomachine recited in  claim 11 , wherein said upstream extent of the plurality of grooves is downstream from the upstream extent of the plurality of blades. 
   
   
       13 . The turbomachine recited in  claim 12 , wherein said downstream extent of the plurality of grooves is upstream from the downstream extent of the plurality of blades. 
   
   
       14 . The turbomachine recited in  claim 1 , wherein the direction normal to an orientation of the plurality of blades being between a minimum tangential angle at any point on said forward facing and opposite surfaces, and a maximum tangential angle at any other point on said forward facing and opposite facing surfaces. 
   
   
       15 . The turbomachine recited in  claim 14 , wherein each of said plurality of blades having a camber line defining blade orientation, and each of said plurality of casing grooves having a shape defined by at least a portion of said camber line. 
   
   
       16 . The turbomachine recited in  claim 8 , said casing further comprises a surface portion between each of the plurality of grooves. 
   
   
       17 . The turbomachine recited in  claim 8 , said casing further comprises a peak between each of the plurality of grooves. 
   
   
       18 . The turbomachine recited in  claim 1  further comprises:
 a plurality of vanes, each of said plurality of vanes extending substantially radially from the casing and terminating in a vane tip and having a forward facing surface and an opposite facing surface which join together at an upstream extent of the blade and at a downstream extent of the vane, and each said plurality of vanes having a cross-sectional shape defined by the forward facing surface and the opposite facing surface;   a hub, said hub having an outer surface, said outer surface adjoining the plurality of blades; and   a plurality of hub grooves within the hub surface, said plurality of hub grooves being oriented in a direction normal to the plurality of vanes.   
   
   
       19 . The turbomachine recited in  claim 1 , wherein the turbomachine is one of an axial flow machine and a non axial flow machine. 
   
   
       20 . The turbomachine recited in  claim 1 , wherein the turbomachine is one of a turbine, compressor, fan, blower and pump.