Abstract: A gas turbine engine has a fan section including a fan, a compressor section including a low pressure compressor and a high pressure compressor, a turbine section including a low pressure turbine and a high pressure turbine, and a gear reduction. The low pressure compressor and the low pressure turbine have a number of blades in each of at least one of a plurality of blade rows. The blades are rotatable at least some of the time at a rotational speed in operation. The number of blades in at least one row and the rotational speed are such that the following formula holds true for at least one row of the compressor rotor turbine: 5500?(number of blades×rotational speed)/60?10000, the rotational speed being in revolutions per minute.

Abstract: A gas turbine engine has a fan section including a fan, a compressor section including a low pressure compressor and a high pressure compressor, a turbine section including a low pressure turbine and a high pressure turbine, and a gear reduction. The low pressure compressor and the low pressure turbine have a number of blades in each of at least one of a plurality of blade rows. The blades are rotatable at least some of the time at a rotational speed in operation. The number of blades in at least one row and the rotational speed are such that the following formula holds true for at least one row of the compressor rotor turbine: (number of blades×rotational speed)/60s?5500 Hz, and the rotational speed is in revolutions per minute.

Abstract: A fan section for a gas turbine engine according to an example of the present disclosure includes, among other things, a fan rotor having fan blades, and a plurality of fan exit guide vanes positioned downstream of the fan rotor. The fan rotor is configured to be driven through a gear reduction. A ratio of a number of fan exit guide vanes to a number of fan blades is defined. The fan exit guide vanes are provided with optimized sweep and optimized lean.

Abstract: Disclosed is a flutter damper including a first plurality of chambers configured for peak acoustical energy absorption at a frequency range that is associated with a first fan flutter mode, the first plurality of chambers in fluid communication with a flow surface, and a second plurality of chambers configured for peak acoustical energy absorption at a frequency range that is associated with a second fan flutter mode, the second plurality of chambers in fluid communication with the flow surface, and wherein the first plurality of chambers and second plurality of chambers are disposed in a grid pattern.

Abstract: A gas turbine engine according to an exemplary aspect of the present disclosure includes, among other things, a turbine section including a fan drive turbine, a compressor section driven by the turbine section, a geared architecture driven by the fan drive turbine, and a fan driven by the fan drive turbine via the geared architecture. At least one stage of the turbine section includes an array of rotatable blades and an array of vanes. A ratio of the number of vanes to the number blades is greater than or equal to about 1.55. A mechanical tip rotational Mach number of the blades is configured to be greater than or equal to about 0.5 at an approach speed.

Abstract: A gas turbine engine according to an exemplary aspect of the present disclosure includes, among other things, a turbine section including a fan drive turbine, a geared architecture driven by the fan drive turbine, and a fan driven by the fan drive turbine via the geared architecture. At least one stage of the turbine section includes an array of rotatable blades and an array of vanes. A ratio of the number of vanes to the number blades is greater than or equal to about 1.55. A mechanical tip rotational Mach number of the blades is configured to be greater than or equal to about 0.5 at an approach speed.

Abstract: In accordance with one aspect of the disclosure, a gas turbine engine, method of using and designing such is disclosed. The gas turbine engine may comprise a fan including a plurality of blades, and a variable area fan nozzle. The fan may be configured to have a design point fan tip leading edge relative flow angle ?ADP, and may be further configured to have an off-design point fan tip leading edge relative flow angle ? at an off-design fan operating point. The variable area fan nozzle may be configured to manipulate the amount of air flowing through the fan so that the absolute value of a difference between the design point fan tip leading edge relative flow angle ?ADP and the off-design point fan tip leading edge relative flow angle ? is in a specified range.

Abstract: Disclosed is a flutter damper, including an acoustic liner having a perforated radial inner face sheet and a radial outer back sheet, the acoustic liner being configured for peak acoustical energy absorption at a frequency range that is greater than a frequency range associated with fan flutter, a chamber secured to the radial outer back sheet, the chamber being in fluid communication with the acoustic liner, and the chamber being configured for peak acoustical energy absorption at a frequency range that is associated with one or more fan flutter modes, and at least one stiffening structure connected to a top surface of the chamber that tunes the top surface out of the frequency range associated with one or more fan flutter modes.

Abstract: Disclosed is flutter damper including a first cavity having a radially inner side in fluid communication with a flow path, and a second cavity having a radially inner side in fluid communication with a radially outer side of the first cavity, and the flutter damper having an impedance characteristic at one or more target frequencies defined as ftarget=fS,ND+?·ND wherein fS,ND is a resonance frequency corresponding to a structural mode of a rotating component, ND is a nodal diameter count of the structural mode, and ? is a rotational speed of the rotating component, and wherein the flutter damper has the following impedance characteristic at the one or more targeted frequencies R?2?c ?3?c?X??0.6?c wherein R is the real part of the impedance characteristic, X is the imaginary part of the impedance characteristic, ? is air density, and c is speed of sound.

Abstract: A flutter damper is disclosed, which includes a chamber configured to fluidly communicate with a gas flow, the chamber being filled with an open celled foam bulk damper, and wherein the chamber is configured for peak acoustical energy absorption at a frequency range that is associated with one or more fan flutter modes.

Abstract: A gas turbine engine according to an exemplary aspect of the present disclosure includes, among other things, a fan, a compressor section having a low pressure compressor and a high pressure compressor, a combustor section, and a turbine section having a low pressure turbine, the low pressure turbine for driving the low pressure compressor and the fan; a gear reduction effecting a reduction in the speed of the fan relative to a speed of the low pressure turbine and the low pressure compressor; and at least one stage of the compressor section having a ratio of vanes to blades that is greater than or equal to 1.8. The corrected tip speed of the blades is greater than or equal to 480 ft/sec at an approach speed.

Abstract: A turbine section including a high pressure turbine, an intermediate pressure turbine and a fan drive turbine, the fan drive turbine driving a gear reduction to in turn drive a fan, and effecting a reduction in the speed of the fan relative to an input speed from the fan drive turbine and said high pressure turbine driving a high pressure compressor, and the intermediate pressure turbine driving a low pressure compressor, with the intermediate pressure turbine having a number of turbine blades in at least one row, and the turbine blades operating at least some of the time at a rotational speed, and the number of turbine blades in the at least one row, and the rotational speed being such that the following formula holds true for the at least one row of the intermediate pressure turbine: (number of blades×speed)/60?5500 Hz.

Abstract: A turbine section including a high pressure turbine, an intermediate pressure turbine and a fan drive turbine, the fan drive turbine driving a gear reduction to in turn drive a fan, and effecting a reduction in the speed of the fan relative to an input speed from the fan drive turbine and said high pressure turbine driving a high pressure compressor, and the intermediate pressure turbine driving a low pressure compressor, with the intermediate pressure turbine having a number of turbine blades in at least one row, and the turbine blades operating at least some of the time at a rotational speed, and the number of turbine blades in the at least one row, and the rotational speed being such that the following formula holds true for the at least one row of the intermediate pressure turbine: (number of blades×speed)/60?5500 Hz.

Abstract: A fan section for a gas turbine engine according to an example of the present disclosure includes, among other things, a fan rotor having fan blades, and a plurality of fan exit guide vanes positioned downstream of the fan rotor. The fan rotor is configured to be driven through a gear reduction. A ratio of a number of fan exit guide vanes to a number of fan blades is defined. The fan exit guide vanes are provided with optimized sweep and optimized lean.

Abstract: A gas turbine engine has a fan section including a fan, a compressor section including a low pressure compressor and a high pressure compressor, a turbine section including a low pressure turbine and a high pressure turbine, and a gear reduction. The low pressure compressor and the low pressure turbine have a number of blades in each of at least one of a plurality of blade rows. The blades are rotatable at least some of the time at a rotational speed in operation. The number of blades in at least one row and the rotational speed are such that the following formula holds true for at least one row of the compressor rotor turbine: (number of blades×rotational speed)/60 s?5500 Hz, and the rotational speed is in revolutions per minute.

Abstract: A gas turbine engine has a fan section including a fan, a compressor section including a low pressure compressor and a high pressure compressor, a turbine section including a low pressure turbine and a high pressure turbine, and a gear reduction. The low pressure compressor and the low pressure turbine have a number of blades in each of at least one of a plurality of blade rows. The blades are rotatable at least some of the time at a rotational speed in operation. The number of blades in at least one row and the rotational speed are such that the following formula holds true for at least one row of the compressor rotor turbine: 5500?(number of blades×rotational speed)/60?10000, the rotational speed being in revolutions per minute.

Abstract: Disclosed is a flutter damper including a first plurality of chambers configured for peak acoustical energy absorption at a frequency range that is associated with a first fan flutter mode, the first plurality of chambers in fluid communication with a flow surface, and a second plurality of chambers configured for peak acoustical energy absorption at a frequency range that is associated with a second fan flutter mode, the second plurality of chambers in fluid communication with the flow surface, and wherein the first plurality of chambers and second plurality of chambers are disposed in a grid pattern.

Abstract: Disclosed is flutter damper including a first cavity having a radially inner side in fluid communication with a flow path, and a second cavity having a radially inner side in fluid communication with a radially outer side of the first cavity, and the flutter damper having an impedance characteristic at one or more target frequencies defined as ftarget=fS,ND+?·ND wherein fS,ND is a resonance frequency corresponding to a structural mode of a rotating component, ND is a nodal diameter count of the structural mode, and ? is a rotational speed of the rotating component, and wherein the flutter damper has the following impedance characteristic at the one or more targeted frequencies R?2?c ?3?c?X??0.6?c wherein R is the real part of the impedance characteristic, X is the imaginary part of the impedance characteristic, ? is air density, and c is speed of sound.

Abstract: A flutter damper is disclosed, which includes a chamber configured to fluidly communicate with a gas flow, the chamber being filled with an open celled foam bulk damper, and wherein the chamber is configured for peak acoustical energy absorption at a frequency range that is associated with one or more fan flutter modes.

Abstract: Disclosed is a flutter damper, including an acoustic liner having a perforated radial inner face sheet and a radial outer back sheet, the acoustic liner being configured for peak acoustical energy absorption at a frequency range that is greater than a frequency range associated with fan flutter, a chamber secured to the radial outer back sheet, the chamber being in fluid communication with the acoustic liner, and the chamber being configured for peak acoustical energy absorption at a frequency range that is associated with one or more fan flutter modes, and at least one stiffening structure connected to a top surface of the chamber that tunes the top surface out of the frequency range associated with one or more fan flutter modes.