Mistuned concentric airfoil assembly and method of mistuning same

An airfoil assembly for a gas turbine engine, comprising:

• an annular shroud having a radially inner face and a radially outer face opposing the radially inner face;
• a radially inner array of airfoils extending from the radially inner face;
• a radially outer array of airfoils extending from the radially outer face;
• wherein the radially inner array of airfoils are configured to guide flow within a radially inner bypass flow passage, the radially inner bypass flow passage bypassing and being radially outward of a compressor section;
• wherein a plurality of airfoils of the radially inner array of airfoils on a first side of a horizontal midline of the assembly are circumferentially aligned with a corresponding airfoil in the radially outer array of airfoils;
• and
• wherein at least one airfoil of the radially inner array is circumferentially misaligned with the airfoils of the radially outer array.

An airfoil assembly for a gas turbine engine, comprising:

• a shroud having a radially inner face and a radially outer face opposing the inner face;
• a radially inner array of airfoils extending from the radially inner face;
• and
• a radially outer array of airfoils extending from the radially outer face, wherein a distance varies between circumferentially adjacent airfoils of the radially inner array of airfoils or between circumferentially adjacent airfoils in the radially outer array of airfoils;
• wherein a total number of airfoils in the radially inner array of airfoils is greater than a total number of airfoils in the radially outer array of airfoils;
• and
• wherein one airfoil of the radially inner array of airfoils is circumferentially aligned with a corresponding airfoil in the radially outer array of airfoils, and the remaining airfoils of the radially inner array of airfoils are circumferentially misaligned with all airfoils in the radially outer array of airfoils.

A method of reducing a vibratory response of airfoils that support a shroud for a gas turbine engine, comprising:

• circumferentially aligning at least one airfoil in a radially inner array of airfoils with a corresponding airfoil of a radially outer array of airfoils;
• circumferentially misaligning the remaining airfoils in the radially inner array of airfoils with all airfoils of the radially outer array of airfoils;
• and
• guiding flow through a radially inner bypass flow passage using the radially inner array of airfoils, the radially inner bypass flow passage bypassing and being radially outward of a core flow passage;
• and
• wherein a distance varies between circumferentially adjacent airfoils of the radially inner array of airfoils or between circumferentially adjacent airfoils in the radially outer array of airfoils.