Ingestion blocking endwall feature

Abstract

An endwall of a gas turbine engine section comprises a flow path surface and a wall. The flow path surfaces defines an inner diameter of a main flow path through the gas turbine engine section, and terminates in an aft waterfall step. The wall extends substantially radially inward from the waterfall step, and defines a blockage feature that impedes airflow from the main flow path to a secondary air cavity situated inward of the waterfall step.

1 . An endwall of a gas turbine engine section, the endwall comprising:
 a flow path surface defining an inner diameter of a main flow path through the gas turbine engine section, and terminating in an aft waterfall step; and   a wall extending substantially radially inward from the waterfall step, and defining a blockage feature that impedes airflow from the main flow path to a secondary air cavity situated inward of the waterfall step.   
     
     
         2 . The endwall of  claim 1 , wherein the wall is formed via a triangular cross-section widening of a region of the endwall near the waterfall step. 
     
     
         3 . The endwall of  claim 2 , wherein the triangular cross-section widening comprises a substantially triangular cross-section portion of additional material extending from an endwall into the secondary air cavity. 
     
     
         4 . The endwall of  claim 3 , wherein the substantially triangular cross-section portion has a substantially right triangle cross-section. 
     
     
         5 . The endwall of  claim 1 , wherein the substantially radial wall is radially thicker than an adjacent forward region of a second gas turbine engine section immediately downstream of the gas turbine engine section. 
     
     
         6 . The endwall of  claim 5 , wherein the gas turbine section includes a cooling air inlet into the secondary air cavity. 
     
     
         7 . The endwall of  claim 1 , wherein the gas turbine engine section is a vane section. 
     
     
         8 . The endwall of  claim 1 , wherein the flow path surface is substantially frustoconical, such that the flow path defined by the flow path surface extends radially outward as it extends axially aft. 
     
     
         9 . A gas turbine engine comprising:
 a first gas turbine section with a first platform defining an inner diameter of a main gas turbine flow path in a first region;   a second gas turbine section situated immediately aft of the first gas turbine section, and having a second platform defining an inner diameter of the main gas turbine flow path in a second region; and   an annular secondary air cavity situated at an aft inner diameter of the first platform, between the first and second gas turbine sections;   an ingestion reduction feature disposed to reduce airflow from the main gas turbine flow path to the annular secondary air cavity, the ingestion reduction feature comprising:
 a waterfall step at an aft end of the first platform higher than an adjacent forward end of the second platform; and 
 a wall extending substantially radially inward from the waterfall step, into the annular secondary air cavity. 
   
     
     
         10 . The gas turbine engine of  claim 9 , wherein the wall has radial wall thickness greater than a radial thickness of an adjacent forward tip of the second endwall. 
     
     
         11 . The gas turbine engine of  claim 10 , wherein the wall extends from an outer radial extent radially outward from an outer radial extent of the adjacent forward tip, to an inner radial extent radially inward from an inner radial extent of the adjacent forward tip. 
     
     
         12 . The gas turbine engine of  claim 9 , wherein the first turbine section is a turbine exhaust case, and the second turbine section is a power turbine. 
     
     
         13 . The gas turbine engine of  claim 9 , wherein the first platform and the second platform are both stationary endwalls. 
     
     
         14 . The gas turbine engine of  claim 9 , further comprising a cooling air inlet into the annular secondary air cavity. 
     
     
         15 . The gas turbine engine of  claim 9 , wherein the wall is formed via a triangular cross-section widening of the first platform at the aft end of the first platform. 
     
     
         16 . A method for reducing combustion gas ingestion into a secondary air cavity of a gas turbine engine, the method comprising:
 directing substantially laminar flow along a frustoconical flow path surface terminating in a waterfall step disposed radially outward of an adjacent tip of a downstream vane platform, such that the combustion predominantly jumps from the frustoconical flow path surface to the downstream vane platform without being ingested therebetween; and   impeding radially inward backflow between the waterfall step and the downstream vane platform via a radial wall extending radially inward from the waterfall step, and into the secondary air cavity.   
     
     
         17 . The method of  claim 16 , wherein the radial wall extends from a radial location radially outward of an outer radial extent of the adjacent tip, to a radial location radially inward of an inner radial extent of the adjacent tip. 
     
     
         18 . The method of  claim 16 , wherein a downstream projection of the frustoconical surface extends radially outboard of an adjacent tip.