GAS TURBINE ENGINE AIRFOIL MISTUNING
A circumferential airfoil array that provides a total airfoil count for the stage and that includes first and second sets of airfoils with different vibrational frequencies. First and second arcuate regions are arranged opposite one another and third and fourth arcuate regions are arranged opposite one another. The first set of airfoils has first primary, first secondary and first tertiary airfoil groups. The second set of airfoils has second primary, second secondary and second tertiary airfoil groups. The first primary airfoil group and second primary airfoil group are respectively arranged in the first and second arcuate regions. The first secondary airfoil group and second secondary airfoil group are arranged in the third arcuate region. The first tertiary airfoil group and the second tertiary airfoil group are arranged in the fourth arcuate region. The first and second arcuate regions provide greater than 50% of the total airfoil count.
1 . A stage for a gas turbine engine comprising:
a circumferential airfoil array providing a total airfoil count for the stage and that includes first and second sets of airfoils, the airfoil array has first, second, third and fourth arcuate regions, the first and second arcuate regions arranged opposite one another, and the third and fourth arcuate regions arranged opposite one another, the first set of airfoils includes a different vibrational frequency than the second set of airfoils, the first set of airfoils has first primary, first secondary and first tertiary airfoil groups, the second set of airfoils has second primary, second secondary and second tertiary airfoil groups, the first primary airfoil group and second primary airfoil group respectively arranged in the first and second arcuate regions, the first secondary airfoil group and second secondary airfoil group arranged in the third arcuate region, and the first tertiary airfoil group and the second tertiary airfoil group arranged in the fourth arcuate region, the first and second arcuate regions provide greater than 50% of the total airfoil count.
2 . The stage according to claim 1 , wherein the array is a stator vane stage, and the airfoils are vanes.
3 . The stage according to claim 2 , wherein the stator vane stage is arranged in one of a compressor section and a turbine section of the gas turbine engine.
4 . The stage according to claim 2 , wherein the vanes are integrated with an outer platform and are cantilevered.
5 . The stage according to claim 1 , wherein the first set of airfoils has a different characteristic than the second set of airfoils to provide the different vibrational frequency.
6 . The stage according to claim 5 , wherein the different characteristic is at least one of an airfoil thickness, an airfoil shape, an airfoil spacing, a platform endwall shape, an airfoil material and an airfoil weight.
7 . The stage according to claim 6 , wherein the different characteristic is the airfoil spacing.
8 . The stage according to claim 7 , wherein the first and second sets of airfoils each have an airfoil spacing based upon a simulated stage airfoil count within +/−10 airfoils of the total airfoil count.
9 . The stage according to claim 8 , wherein the first set of airfoils has an airfoil spacing based within +8 airfoils of the total airfoil count, and the second set of airfoils has an airfoil spacing based within −8 airfoils of the total airfoil count.
10 . The stage according to claim 1 , wherein the first primary group, the first secondary group, the first tertiary airfoil group, the second primary group, the second secondary group and the second tertiary airfoil group each include multiple airfoils.
11 . The stage according to claim 10 , wherein the multiple airfoils are arranged in clusters.
12 . The stage according to claim 1 , wherein the first secondary group, the first tertiary airfoil group, the second secondary group and the second tertiary airfoil group each include the same number of airfoils as one another.
13 . The stage according to claim 1 , wherein the first primary group and the second primary group each include a different number of airfoils than one another.
14 . The stage according to claim 1 , wherein the first primary group and the second primary group each include the same number of airfoils as one another.
15 . The stage according to claim 1 , wherein the total airfoil count is provided only by the first and second sets of airfoils.
16 . The stage according to claim 1 , wherein the airfoil array includes only the first, second, third and fourth arcuate regions.
17 . The stage according to claim 1 , wherein a sum of the first secondary airfoil group and second secondary airfoil group arranged in the third arcuate region provides less than 25% of the total airfoil count, and a sum of the first tertiary airfoil group and the second tertiary airfoil group provides less than 25% of the total airfoil count.
18 . The stage according to claim 1 , wherein the first and second arcuate regions provide greater than 75% of the total airfoil count.
19 . The stage according to claim 1 , where some of the airfoil groups contain a third or fourth set of airfoils within them.
20 . A stage for a gas turbine engine comprising:
a circumferential airfoil array providing a total airfoil count for the stage and that includes first and second sets of airfoils, the airfoil array has first, second, third and fourth arcuate regions, the first and second arcuate regions arranged opposite one another, and the third and fourth arcuate regions arranged opposite one another, the first set of airfoils includes a different vibrational frequency than the second set of airfoils, the first set of airfoils has first primary, first secondary and first tertiary airfoil groups, the second set of airfoils has second primary, second secondary and second tertiary airfoil groups, the first primary airfoil group and second primary airfoil group respectively arranged in the first and second arcuate regions, the first secondary airfoil group and second secondary airfoil group arranged in the third arcuate region, and the first tertiary airfoil group and the second tertiary airfoil group arranged in the fourth arcuate region, the first and second arcuate regions provide greater than 50% of the total airfoil count;
wherein the first set of airfoils has a different characteristic than the second set of airfoils to provide the different vibrational frequency, the different characteristic is an airfoil spacing;
wherein the first and second sets of airfoils each have an airfoil spacing based upon a simulated stage airfoil count within +/−10 airfoils of the total airfoil count;
wherein the first primary group, the first secondary group, the first tertiary airfoil group, the second primary group, the second secondary group and the second tertiary airfoil group each include multiple airfoils; and
wherein the first secondary group, the first tertiary airfoil group, the second secondary group and the second tertiary airfoil group each include the same number of airfoils as one another.
21 . The stage according to claim 20 , wherein the array is a stator vane stage, and the airfoils are vanes, the stator vane stage is arranged in one of a compressor section and a turbine section of the gas turbine engine.