Accretion detection systems and associated methods for gas turbine engines

1. An assembly for a gas turbine engine comprising:

at least one rotatable airfoil;

at least one vibration sensor operable to detect vibration of the at least one rotatable airfoil at one or more rotational frequencies; and

a controller operatively coupled to the at least one vibration sensor, wherein the controller is configured to determine an accretion level associated with accretion of glass on the at least one rotatable airfoil in response to comparing vibration of the at least one rotatable airfoil at the one or more rotational frequencies to a vibratory pattern associated with accretion of glass,

wherein the vibratory pattern is associated with the one or more rotational frequencies and one or more respective vibration thresholds,

wherein the controller is configured to determine the accretion level in response to comparing at least one amplitude associated with vibration of the at least one rotatable airfoil at the respective rotational frequency to the respective vibration threshold; and

wherein the vibratory pattern is established based on different amounts of accretion of glass and associated vibration for each of the amounts of accretion of glass at the one or more rotational frequencies.

2. The assembly as recited in claim 1 , wherein the controller is configured to cause an indicator to be generated in response to determining that the accretion level meets an accretion threshold.

3. The assembly as recited in claim 1 , wherein the controller is configured to cause excitation of the at least one rotatable airfoil to release debris associated with the accretion level in response to determining that the accretion level meets an accretion threshold.

4. The assembly as recited in claim 3 , wherein the controller is configured to cause excitation of the at least one rotatable airfoil by causing a rotational speed of the at least one rotatable airfoil to approach a resonant frequency of the at least one rotatable airfoil.

5. The assembly as recited in claim 1 , wherein the one or more rotational frequencies includes a plurality of rotational frequencies associated with the vibratory pattern, the one or more vibration thresholds includes a plurality of vibration thresholds associated with the respective rotational frequencies, the at least one amplitude includes a plurality of amplitudes associated with the respective rotational frequencies, and the controller is configured to determine the accretion level in response to determining that the respective amplitudes meet the respective vibration thresholds.

6. The assembly as recited in claim 1 , wherein the controller is configured to determine the accretion level in response to determining a best fit of vibration at the one or more rotational frequencies to a set of vibratory responses associated with the vibratory pattern and respective amounts of accretion.

7. The assembly as recited in claim 1 , wherein:

the at least one rotatable airfoil is a propulsor blade for generating thrust.

8. A gas turbine engine comprising:

a propulsor section including a propulsor;

a compressor;

a turbine that drives the propulsor;

a plurality of airfoils rotatable about an engine axis;

at least one vibration sensor operable to detect vibration and configured to generate a signal associated with detected vibration of one or more airfoils of the plurality of airfoils at one or more rotational frequencies; and

a controller operatively coupled to the at least one vibration sensor, wherein the controller is configured to determine an accretion level associated with accretion of glass on the one or more airfoils in response to comparing the signal to a vibratory pattern associated with accretion of glass,

wherein the vibratory pattern is associated with the one or more rotational frequencies and one or more respective vibration thresholds,

wherein the controller is configured to determine the accretion level in response to comparing at least one amplitude of the signal associated with vibration of the one or more airfoils at the respective rotational frequency to the respective vibration threshold; and

wherein the vibratory pattern is established based on different amounts of accretion of glass and associated vibration for each of the amounts of accretion of glass at the one or more rotational frequencies.

9. The gas turbine engine as recited in claim 8 , wherein: the one or more rotational frequencies include a plurality of rotational frequencies associated with rotation of the plurality of airfoils about an engine axis of the gas turbine engine; the vibratory pattern is associated with the plurality of rotational frequencies and a plurality of respective vibration thresholds; and the controller is configured to determine the accretion level in response to comparing respective amplitudes of a plurality of amplitudes of the signal respectively associated with the plurality of rotational frequencies to the respective vibration threshold associated with the respective rotational frequency.

10. The gas turbine engine as recited in claim 8 , wherein the controller is configured to cause excitation of one or more of the plurality of airfoils to remove glass on the one or more airfoils in response to determining the accretion level.

11. The gas turbine engine as recited in claim 8 , wherein the controller is configured to cause a change in a rotational speed of the plurality of airfoils such that the rotational speed approaches a resonant frequency of the plurality of airfoils.