Variable displacement flutter damper for a turbofan engine
Disclosed is a flutter damper, including a chamber having an internal space, a movable diaphragm disposed at least partially within the chamber, the diaphragm separating the chamber into a first chamber and a second chamber, the second chamber forming an acoustic volume, wherein a size of the acoustic volume configures the chamber for peak acoustical energy absorption at a frequency range that is associated with one or more fan flutter modes, and a biasing member that moves the diaphragm responsive to a signal from an aircraft or engine electronic control (EEC) unit, wherein movement of the diaphragm increases or reduces the size of the acoustic volume of the second chamber.
1. A flutter damper, comprising:
a chamber having an internal space;
a movable diaphragm disposed at least partially within the chamber, the diaphragm separating the chamber into a first chamber and a second chamber, the second chamber forming an acoustic volume, wherein a size of the acoustic volume configures the chamber for peak acoustical energy absorption at a frequency range that is associated with one or more fan flutter modes; and
a biasing member that moves the diaphragm responsive to a signal from an aircraft or engine electronic control (EEC) unit, wherein movement of the diaphragm increases or reduces the size of the acoustic volume of the second chamber; wherein
the biasing member is an inflatable and deflatable bladder disposed in the first chamber, the diaphragm includes a parameter seal to fluidly seal the first chamber from the second chamber, and
the flutter damper further includes:
a pressurized fluid supply fluidly connected to the bladder and a first valve controlled by the electronic engine control to enable or prevent fluid from flowing to the bladder, the pressurized fluid being air;
a vent and a second valve controlled by the electronic engine control to enable or prevent air from venting from the bladder;
a sensor in electronic communication with the electronic engine control that detects the position of the diaphragm in the chamber; and
a spring to counter-bias the diaphragm to an opened state that increases the acoustic volume.
2. The flutter damper of claim 1 , wherein the chamber is box or rectangular shaped.
3. The flutter damper of claim 1 , including an acoustic liner having a perforated radial inner face sheet and a radial outer face sheet, wherein the chamber is secured to the outer face sheet and is in fluid communication with the acoustic liner.
4. The flutter damper of claim 1 , wherein the chamber is a metallic material, including aluminum, or a plastic or a composite, or a hybrid metallic and non-metallic material.
5. A gas turbine engine comprising:
a nacelle; and
a flutter damper secured to the nacelle, the flutter damper including:
a chamber having an internal space;
a movable diaphragm disposed at least partially within the chamber, the diaphragm separating the chamber into a first chamber and a second chamber, the second chamber forming an acoustic volume, wherein a size of the acoustic volume configures the chamber for peak acoustical energy absorption at a frequency range that is associated with one or more fan flutter modes; and
a biasing member that moves the diaphragm responsive to a signal from an aircraft or engine electronic control (EEC) unit, wherein movement of the diaphragm increases or reduces the size of the acoustic volume of the second chamber; wherein
the biasing member is an inflatable and deflatable bladder disposed in the first chamber, the diaphragm includes a parameter seal to fluidly seal the first chamber from the second chamber, and
the flutter damper further includes:
a pressurized fluid supply fluidly connected to the bladder and a first valve controlled by the electronic engine control to enable or prevent fluid from flowing to the bladder, the pressurized fluid being air;
a vent and a second valve controlled by the electronic engine control to enable or prevent air from venting from the bladder;
a sensor in electronic communication with the electronic engine control that detects the position of the diaphragm in the chamber; and
a spring to counter-bias the diaphragm to an opened state that increases the acoustic volume.
6. The gas turbine engine of claim 5 , wherein the chamber is box shaped or rectangular shaped.
7. The gas turbine engine of claim 5 , wherein the chamber is a metallic material, including aluminum, or a plastic or a composite, or a hybrid metallic and non-metallic material.
8. A method of providing flutter damping to a gas turbine engine, comprising:
determining with an electronic engine control that an acoustic volume in a chamber should change by being increased or decreased, wherein a size of the acoustic volume configures the chamber for peak acoustical energy absorption at a frequency range that is associated with one or more fan flutter modes; and
actuating a biasing member to increase or decrease the acoustic volume,
wherein,
the biasing member is an inflatable and deflatable bladder, and the method includes: actuating a fluid vent valve to deflate a bladder in the chamber to move a diaphragm so as to increase the acoustic volume, or actuating a fluid supply valve to inflate the bladder in the chamber to move the diaphragm so as to decrease the acoustic volume; and
the flutter damper includes a sensor in electronic communication with the electronic engine control that detects the position of the diaphragm in the chamber, and the chamber includes a spring to counter-bias the diaphragm to an opened state that increases the acoustic volume.
9. The method of claim 8 , wherein the chamber is box or rectangular shaped.
10. The method of claim 8 , further including damping, within an acoustic liner, the acoustic liner having a perforated radial inner face sheet and a radial outer face sheet, wherein the chamber is secured to the outer face sheet and is in fluid communication with the acoustic liner.