Active flow control intake for a gas turbine engine

Abstract

Intakes of gas turbine engines are subject to cross winds and high incidence cross flows which can affect the stability of air to the propulsive fan. An active flow control arrangement for an intake comprises a compressed gas supply pipe, a valve arrangement, a controller, and a compressed gas distribution pipe. The supply pipe is fluidly connects between a compressed gas source and the valve arrangement. The distribution pipe fluidly connects between the valve arrangement and intake surface for supply of compressed gas thereto. The active flow control arrangement is operable to supply compressed gas to the intake surface to prevent separation of a main air flow passing through the intake from the inlet surface thereby maintaining stability of the intake air flow to the fan.

1 . A gas turbine engine comprising an intake defining an inlet surface, a compressed gas source and an active flow control arrangement;
 the active flow control arrangement comprising a compressed gas supply pipe, a valve arrangement, a controller, a compressed gas distribution pipe;   the supply pipe is fluidly connects between the compressed gas source and the valve arrangement and the distribution pipe fluidly connects between the valve arrangement and intake surface for supply of compressed gas thereto;   the active flow control arrangement is operable to supply compressed gas to the intake surface to prevent separation of a main air flow passing through the intake from the inlet surface.   
     
     
         2 . A gas turbine engine as claimed in  claim 1  wherein the compressed gas source is any one or more or combination of a low, intermediate or high pressure compressor. 
     
     
         3 . A gas turbine engine as claimed in  claim 1  wherein the intake comprises a lip region, a throat region and a diffuser region, the active flow control arrangement comprises ducting to supply compressed gas to the intake surface in any one or more of the lip region, the throat region and the diffuser region. 
     
     
         4 . A gas turbine engine as claimed in  claim 1  wherein the intake comprises circumferential regions, the active flow control arrangement comprises ducting to supply of compressed gas to the intake surface in any one or more of the circumferential regions. 
     
     
         5 . A gas turbine engine as claimed in  claim 4  wherein the circumferential regions comprise a lower region, side regions and an upper region. 
     
     
         6 . A gas turbine engine as claimed in  claim 1  wherein the active flow control arrangement comprises a valve arrangement and a controller; the controller controls the valve arrangement to control the supply of compressed gas to the intake surface. 
     
     
         7 . A gas turbine engine as claimed in  claim 6  wherein the active flow control arrangement comprises at least one sensor positioned within the intake, the sensor is connected to the controller; the controller controls the valve arrangement to control the supply of compressed gas to the intake surface. 
     
     
         8 . A gas turbine engine as claimed in  claim 6  wherein the active flow control arrangement comprises an array of sensors; the array of sensors having at least one sensor positioned relative to a number of axial and/or circumferential regions of the intake. 
     
     
         9 . A gas turbine engine as claimed in  claim 1  wherein the intake comprises a lining having a surface liner, a spacer and a backing; the surface liner comprises perforations through its thickness and defines at least a part of the intake surface and the spacer comprises a cellular material. 
     
     
         10 . A gas turbine engine as claimed in  claim 9  wherein the distribution pipe fluidly connects to the cellular material, allowing compressed gas to the surface through the surface liner. 
     
     
         11 . A method of operating a gas turbine engine comprising a compressor, an active flow control arrangement and an intake defining an inlet surface and over which a main air flow passes;
 the active flow control arrangement is configured to blow compressor gas onto the surface,   the method comprises the steps of   determining a possible formation of separation of the main air flow from the surface; and   blowing compressor gas onto the surface or into a boundary layer adjacent the surface to prevent separation of the main air flow from the surface.   
     
     
         12 . A method of operating a gas turbine engine as claimed in  claim 11  wherein the step of blowing compressor gas onto the surface or into a boundary layer adjacent the surface to prevent separation of the main air flow from the surface comprises,
 determining an axial and/or a circumferential location(s) of a possible formation of separation of the main air flow from the surface. 
 
     
     
         13 . A method of operating a gas turbine engine as claimed in  claim 11  wherein the active flow control arrangement comprises located in the intake and a controller;
 the step of determining a possible formation of separation of the main air flow from the surface comprises the steps of 
 sensing the pressure of the main gas flow over the surface, and 
 comparing the sensed pressure to a predetermined value where possible formation of separation of the main air flow from the surface may occur. 
 
     
     
         14 . A method of operating a gas turbine engine as claimed in  claim 11  wherein the active flow control arrangement and a controller;
 the step of determining a possible formation of separation of the main air flow from the surface comprises the steps of 
 the controller receiving engine operational parameter(s), and 
 comparing the engine operational parameter(s) to a predetermined value where possible formation of separation of the main air flow from the surface may occur. 
 
     
     
         15 . A method of operating a gas turbine engine as claimed in  claim 14  wherein the engine operational parameter(s) comprise any one or more or combination of a flight cycle condition, an airspeed, an angle of incidence, an engine throttle position, cross-wind strength and direction and weight on wheels. 
     
     
         16 . A method of operating a gas turbine engine as claimed in  claim 11  wherein the method comprises the step of pulsing the compressed gas.