Gas turbine engine airfoil frequency design

A method of repairing an airfoil comprising the steps of:

• providing an airfoil having pressure and suction sides spaced apart from one another in a thickness direction and joined to one another at leading and trailing edges, the airfoil extending in a radial direction of a span that is in a range of 4.47-4.77 inch (113.5-121.2 mm), and a chord length extending in a chordwise direction from the leading edge to the trailing edge at 50% of the span is in a range of 2.57-2.87 inch (65.3-72.9 mm), wherein the provided airfoil has at least one unrestored mode frequency that is attributable to damage to the airfoil;
• and
• repairing the airfoil to provide at least two of:
• a first mode has a frequency of 297 up to ±10% Hz;
• a second mode has a frequency of 1035 up to ±10% Hz;
• a third mode has a frequency of 1488 up to ±10% Hz;
• a fourth mode has a frequency of 1524 up to ±10% Hz;
• a fifth mode has a frequency of 2855 up to ±10% Hz;
• and
• a sixth mode has a frequency of 4462 up to ±10% Hz;
• wherein at least one of the first mode frequency, second mode frequency, third mode frequency, fourth mode frequency, fifth mode frequency, and sixth mode frequency corresponds to a restored mode frequency that supersedes the unrestored mode frequency, wherein the frequencies are at zero speed and ambient conditions, and the frequency of any given mode does not exceed the frequency of a higher order mode;
• wherein the first mode is a 1EB mode, the second mode is a 1T mode, the third mode is a SWB mode, the fourth mode is a 2EB mode, the fifth mode is a 2T mode, and the sixth mode is a CWB mode, the 1EB and 2EB modes correspond to deflections parallel to the thickness direction, the SWB and CWB modes correspond to bending that is normal to the thickness direction and along the chordwise direction, and the 1T and 2T modes corresponds to twisting about the radial direction;
• wherein the airfoil is part of an integrally bladed rotor;
• wherein the airfoil is a titanium-based alloy, the titanium-based alloy has a density of 0.16 lb/in3 (4.4 g/cm3), the titanium-based alloy has a modulus of elasticity of 16-17 Mpsi (110-117 GPa) at room temperature.

A turbofan engine comprising:

• a fan section;
• a compressor section arranged fluidly downstream from the fan section;
• a turbine section arranged fluidly downstream from the compressor section;
• a combustor arranged fluidly between the compressor and turbine sections;
• and
• an airfoil in at least one of the fan, compressor and turbine sections, the airfoil having:
• pressure and suction sides spaced apart from one another in a thickness direction and joined to one another at leading and trailing edges, the airfoil extending in a radial direction of a span that is in a range of 4.47-4.77 inch (113.5-121.2 mm);
• a chord length extending in a chordwise direction from the leading edge to the trailing edge at 50% of the span is in a range of 2.57-2.87 inch (65.3-72.9 mm);
• and
• at least two of:
• a first mode has a frequency of 297 up to ±10% Hz;
• a second mode has a frequency of 1035 up to ±10% Hz;
• a third mode has a frequency of 1488 up to ±10% Hz;
• a fourth mode has a frequency of 1524 up to ±10% Hz;
• a fifth mode has a frequency of 2855 up to ±10% Hz;
• and
• a sixth mode has a frequency of 4462 up to ±10% Hz;
• wherein the frequencies are at zero speed and ambient conditions, and the frequency of any given mode does not exceed the frequency of a higher order mode;
• wherein the first mode is a 1EB mode, the second mode is a 1T mode, the third mode is a SWB mode, the fourth mode is a 2EB mode, the fifth mode is a 2T mode, and the sixth mode is a CWB mode, the 1EB and 2EB modes correspond to deflections parallel to the thickness direction, the SWB and CWB modes correspond to bending that is normal to the thickness direction and along the chordwise direction, and the 1T and 2T modes corresponds to twisting about the radial direction;
• wherein the airfoil is provided in the compressor section, the compressor section includes a low pressure compressor fluidly upstream from a high pressure compressor, and the airfoil is in the low pressure compressor, the low pressure compressor includes three stages, the airfoil is part of an integrally bladed rotor;
• wherein the airfoil is a titanium-based alloy, the titanium-based alloy has a density of 0.16 lb/in3 (4.4 g/cm3), the titanium-based alloy has a modulus of elasticity of 16-17 Mpsi (110-117 GPa) at room temperature.