Airfoil air seal assembly

Abstract

An air seal assembly for a gas turbine engine the air seal comprises a first assembly and a second assembly. One of the first assembly and the second assembly is rotatable relative to the other of the first assembly and the second assembly. The second assembly is aligned annularly with the first assembly and includes a circumferential surface with an abradable coating disposed annularly adjacent to the first and second airfoil tips. The first assembly includes at least one first airfoil with a first tip having an abrasive coating, and at least one second airfoil with a second tip absent the abrasive coating, the at least one first airfoil co-aligned axially and intermingled with a respective at least one second airfoil around a periphery of the first assembly.

1 . An air seal assembly for a gas turbine engine the air seal comprising:
 a first assembly including at least one first airfoil with a first tip having an abrasive coating, and at least one second airfoil with a second tip absent the abrasive coating, each of the at least one first airfoil co-aligned axially and intermingled with a respective at least one second airfoil around a periphery of the first assembly; and   a second assembly aligned annularly with the first assembly, the second assembly including a circumferential surface with an abradable coating disposed annularly adjacent to the first and second airfoil tips, with one of the first assembly and the second assembly being rotatable relative to the other of the first assembly and the second assembly.   
     
     
         2 . The air seal assembly of  claim 1 , wherein the engine is operable in at least a run-in mode and an operational mode, the run-in mode including rotating the rotatable assembly intermittently to centrifugally expand the rotatable assembly for abrasively forming a circumferential seal groove into the abradable coating with the at least one first airfoil tip, and the operational mode including rotating the rotatable assembly continuously to centrifugally and thermally expand the rotatable assembly forming an air seal. 
     
     
         3 . The blade outer air seal assembly of  claim 1 , wherein the seal assembly is installed into a compressor section of the gas turbine engine. 
     
     
         4 . The air seal assembly of  claim 1 , wherein the at least one airfoil tip includes at least one squealer tip cut under the abrasive coating. 
     
     
         5 . The air seal assembly of  claim 4 , wherein the at least one airfoil tip includes a first squealer tip cut proximate the pressure surface and a second squealer tip cut proximate the suction surface. 
     
     
         6 . The air seal assembly of  claim 1 , wherein the abrasive coating comprises cubic boron nitride (CBN) suspended in a matrix. 
     
     
         7 . The air seal assembly of  claim 1 , wherein the abradable coating comprises a boro-nitride ceramic. 
     
     
         8 . The air seal assembly of  claim 1 , wherein the at least one first airfoil and the at least one second airfoil each comprise a titanium alloy. 
     
     
         9 . The air seal assembly of  claim 1 , wherein the first assembly is a rotor assembly and the second assembly is a stator assembly. 
     
     
         10 . The air seal assembly of  claim 9 , wherein the at least one first airfoil is intermingled with the respective at least one second airfoil based at least in part on results of a Monte Carlo simulation. 
     
     
         11 . The air seal assembly of  claim 9 , wherein the first and second airfoils are rotor blades integrally formed with a rotor disc. 
     
     
         12 . The air seal assembly of  claim 1 , wherein the first assembly is a stator assembly, and the second assembly is a rotor assembly. 
     
     
         13 . The air seal assembly of  claim 12 , wherein the first and second airfoils are cantilevered stator vanes. 
     
     
         14 . A rotor assembly comprising:
 a rotor disc;   at least one first rotor blade including a first airfoil tip with an abrasive coating; and   at least one second rotor blade including a second airfoil tip absent an abrasive coating, the at least one first rotor blade intermingled and co-aligned with a respective at least one second rotor blade axially around a periphery of the rotor disc.   
     
     
         15 . The rotor assembly of  claim 14 , wherein the at least one first rotor blade is intermingled with the respective at least one second rotor blade for rotational balance of the rotor assembly, the intermingling determined using a Monte Carlo simulation. 
     
     
         16 . The rotor assembly of  claim 14 , wherein a ratio of the at least one first rotor blade and the at least one second rotor blade is between about 1:12 and about 1:1. 
     
     
         17 . The rotor assembly of  claim 16 , wherein the ratio of the at least one first rotor blade and the at least one second rotor blade is between about 1:3 and about 1:9. 
     
     
         18 . The rotor assembly of  claim 17 , wherein the ratio of the at least one first rotor blade and the at least one second rotor blade is about 1:6. 
     
     
         19 . The rotor assembly of  claim 14 , wherein the at least one first rotor blade and the at least one second rotor blade are integrally formed with the rotor disc. 
     
     
         20 . The rotor assembly of  claim 14 , wherein the first airfoil tip includes at least one squealer tip cut under the abrasive coating.