Method for protecting a gas turbine engine against high dynamical process values and gas turbine engine for conducting the method

1. A method for protecting a gas turbine engine, the gas turbine having a compressor, a combustor, and a turbine, against high dynamical process values, including combustor/flame pulsations, the method comprising:

a) measuring pulsations of the combustor with a sensor;

b) dividing the frequency spectrum of the measured pulsation signal up into pre-defined band pass sections;

c) computing the root mean square (rms) of the signal for each band;

d) weighting the computed frequency/frequency band rms with predetermined weighting factors;

e) cumulating the weighted frequency/frequency band rms values to get a Pulsation Limit Criterion (PLC) value;

f) comparing the PLC value with at least one reference value; and

g) operating the gas turbine engine according to the result of said comparing,

wherein said weighting factors are predetermined based on a structural model for a complete structure of the combustor and other affected components, and by computing the stresses as a response to the acoustic load resulting from pulsations in the combustor.

2. The method according to claim 1 , further comprising:

forcing Hot Gas Parts of the combustor structure with a broadband frequency signal, thereby simultaneously exciting multiple structural eigenmodes;

inputting structural stresses from said forcing as a function of the Hot Gas Part eigenmodes, pulsation load amplitude, and pulsation load frequency/frequency band for a frequency bandwidth to a lifetime model;

predicting achievable lifetime of the components over the frequency bandwidth of interest; and

capturing a sensitivity of the Hot Gas Parts to the frequency/frequency band by weighting the frequency/frequency band as the result of the frequency/frequency band forcing calculation with said weighting factors.

3. A method according to claim 1 , further comprising:

defining a recommended maximal PLC value for the operation, PLC operation ; and

operating the gas turbine engine such that PLC≦PLC operation .

4. A method according to claim 3 , wherein the PLC value is in the range of 0.6-0.9 of the PLC operation .

5. A gas turbine engine comprising:

a compressor;

a combustor;

a turbine;

a gas turbine control unit having an input;

a signal processing unit;

at least one sensor configured and arranged to measure pulsations within the combustor and generate a pulsation signal, said at least one sensor being connected to the signal processing unit;

wherein the signal processing unit is configured and arranged to divide the frequency spectrum of the measured pulsation signal up into pre-defined band pass sections;

compute the root mean square (rms) of the signal for each band;

weight the computed frequency/frequency band rms with predetermined weighting factors;

cumulate the weighted frequency/frequency band rms values to derive a Pulsation Limit Criterion (PLC) value,

wherein said weighting factors are predetermined based on a structural model for a complete structure of the combustor and other affected components, and by computing the stresses as a response to the acoustic load resulting from pulsations in the combustor; and

a comparing device configured and arranged to receive said derived Pulsation Limit Criterion (PLC) value from said signal processing unit and compare the PLC value to a reference value and generate an output, and the output of the comparing device is connected to the input of the gas turbine control.