Airflow control for air turbine starter

Abstract

An example arrangement for cooling a gas turbine engine includes an air turbine starter having a turbine section for rotationally driving a compressor through rotation of a shaft. An starter air valve is configured to control a flow of pressurized air that flows downstream towards turbine blades of the air turbine starter. An airflow adjustment device (AAD) is configured to adjust the flow when a manual override feature of the starter air valve is engaged based on a rotational speed of one of the shaft and an additional shaft that is driven by the compressor. A governor is configured to control a degree to which the AAD adjusts the flow. The governor is mechanically linked to the shaft through one or more gears and configured to adjust the AAD such that a rotational speed of said one the shafts does not exceed a predefined threshold during a particular operating mode.

What is claimed is: 
     
         1 . An arrangement for cooling a gas turbine engine comprising:
 an air turbine starter comprising a turbine section for rotationally driving a compressor of a gas turbine engine through rotation of a shaft that connects the turbine section to the compressor;   a starter air valve configured to control a flow of pressurized air along a flow path that flows downstream towards turbine blades of the turbine section, the starter air valve having a manual override feature that allows manual opening of the starter air valve;   an airflow adjustment device configured to adjust the flow of pressurized air along the flow path when the manual override feature is engaged based on a rotational speed of one of the shaft and an additional shaft that is driven by the compressor; and   a governor configured to control a degree to which the airflow adjustment device adjusts the flow, the governor mechanically linked to the shaft through one or more gears and configured to adjust the airflow adjustment device such that a rotational speed of said one of the shafts does not exceed a predefined threshold during a particular operating mode.   
     
     
         2 . The arrangement of  claim 1 , wherein the governor is configured as a fluid motor that controls a degree to which the airflow adjustment device adjusts the flow by adjusting a pressure in a pressure-based control line that connects the governor to an actuator for the airflow adjustment device. 
     
     
         3 . The arrangement of  claim 1 , comprising a governor shutoff device configured to disable the governor by disengaging the governor from the shaft or adjusting a pressure in a pressure-based control line that connects the governor to an actuator for the airflow adjustment device. 
     
     
         4 . The arrangement of  claim 1 , wherein:
 the airflow adjustment device includes an additional valve; and   the governor is configured restrict the flow of pressurized air by adjusting a position of the additional valve.   
     
     
         5 . The arrangement of  claim 4 , wherein the additional valve includes an active bleed valve configured to selectively release pressurized air from the flow path. 
     
     
         6 . The arrangement of  claim 4 , wherein the additional valve includes a shutter valve having a central aperture and configured to adjust the flow of pressurized air to the turbine blades by altering a flow area defined by the central aperture. 
     
     
         7 . The arrangement of  claim 4 , wherein the additional valve includes a butterfly valve. 
     
     
         8 . The arrangement of  claim 1 , wherein:
 the airflow adjustment device includes an air shutter situated in the flow path between the source of pressurized air and the turbine section, the air shutter including two discs; and   the governor is configured to control a degree to which the airflow adjustment device adjusts the flow by controlling a degree to which airflow holes in the two discs are misaligned.   
     
     
         9 . The arrangement of  claim 1 , wherein:
 the turbine section includes a plurality of turbine blades that extend radially outward from a central longitudinal axis;   the air turbine starter includes an inlet duct that fluidly connects the plurality of turbine blades to the source of pressurized air; and   the airflow adjustment device includes an inner wall of the inlet duct that is movable along the central longitudinal axis to adjust a volume of the inlet duct.   
     
     
         10 . The arrangement of  claim 1 , wherein the airflow adjustment device includes a sync-ring, and rotation of the sync-ring about a central longitudinal axis of the air turbine starter adjusts vane angles of a plurality of variable vanes of the air turbine starter that are upstream of the turbine blades. 
     
     
         11 . A method of cooling a gas turbine engine, comprising:
 delivering a flow of pressurized air along a flow path to turbine blades of a turbine section of an air turbine starter, the flow path passing through a starter air valve, the pressurized air causing the air turbine starter to rotate a compressor of a gas turbine engine through rotation of a shaft that interconnects the turbine section and the compressor; and   controlling a degree to which an airflow adjustment device adjusts the flow of pressurized air to the turbine section when the starter air valve is manually opened based on a rotational speed of one of the shaft and an additional shaft that is driven by the compressor, said controlling includes utilizing a governor mechanically linked to the shaft through one or more gears and configured to adjust the airflow adjustment device such that a rotational speed of said one of the shafts does not exceed a predefined threshold during a particular operating mode.   
     
     
         12 . The method of  claim 11 , wherein said controlling includes the governor adjusting a pressure in one or more pressure-based control lines that connect the governor to an actuator for the airflow adjustment device to control a degree to which the airflow adjustment device adjusts the flow. 
     
     
         13 . The method of  claim 11 , comprising:
 disabling the governor by utilizing a governor shutoff device to disengage the governor from the shaft or adjust a pressure in a pressure-based control line that connects the governor to an actuator for the airflow adjustment device.   
     
     
         14 . The method of  claim 11 , wherein:
 said airflow adjustment device includes an additional valve; and   said controlling a degree to which the airflow adjustment device restricts the flow of pressurized air includes adjusting a position of the additional valve.   
     
     
         15 . The method of  claim 14 , wherein the additional valve includes an active bleed valve. 
     
     
         16 . The method of  claim 14 , wherein the additional valve includes a shutter valve having a central aperture and configured to adjust the flow of pressurized air to the turbine blades by altering a flow area defined by the central aperture. 
     
     
         17 . The method of  claim 14 , wherein the additional valve includes a butterfly valve. 
     
     
         18 . The method of  claim 11 , wherein:
 the airflow adjustment device includes an air shutter situated in the flow path between the source of pressurized air and the turbine section, the air shutter including two discs; and   said controlling a degree to which the airflow adjustment device restricts the flow of pressurized air includes the control device selectively restricting the flow of pressurized air through misalignment of airflow holes in the two discs.   
     
     
         19 . The method of  claim 11 , wherein:
 the airflow adjustment device includes a movable inner wall of an inlet duct of the air turbine starter that is in fluid communication with the turbine section; and   said controlling a degree to which the airflow adjustment device reduces the flow of pressurized air includes adjusting a volume of the inlet duct by moving the inner wall along a central longitudinal axis of the air turbine starter.   
     
     
         20 . The method of  claim 11 , wherein:
 the airflow adjustment device includes a sync-ring; and   said controlling a degree to which the airflow adjustment device restricts the flow of pressurized air includes rotating the sync-ring about a central longitudinal axis of the air turbine starter to adjust vane angles of a plurality of variable vanes of the air turbine starter that are upstream of the turbine blades.