Method and system for monitoring a status of a reducer of a gas turbine
A method for monitoring a status of a reduction gear of a gas turbine includes the steps of: obtaining measurements of parameters accomplished during an operating phase of the gas turbine, these parameters including temperatures of a lubricating oil of the reduction gear at the inlet and at the outlet of the reduction gear, a parameter representing a speed of the gas turbine, as well as at least one context parameter; selecting measurements; normalizing temperatures of the lubricating oil using the measurements of the context parameter; evaluating a thermal efficiency of the reduction gear by using a physical model defining the thermal efficiency based on a difference between the temperature of the lubricating oil; and determining a status of the reduction gear depending on a step of comparing the evaluated thermal efficiency with respect to a reference signature.
1. A method for monitoring a status of a reduction gear of a gas turbine comprising, for at least one duty cycle of the reduction gear:
a step of obtaining at least one set of measurements of a plurality of parameters accomplished over at least one time interval of a determined duration during at least one operating phase of the gas turbine, said parameters being measured by sensors carried in the gas turbine and comprising operating parameters of the reduction gear including temperatures of a lubricating oil of the reduction gear at an inlet and at an outlet of the reduction gear, and operating parameters of the gas turbine including at least one parameter representing a speed of the gas turbine, and at least one context parameter representing an environment wherein said reduction gear is located;
a step of selecting, among said at least one set of measurements obtained for said at least one operating phase, of a set containing measurements that are stable with regard to a predetermined stability criterion;
a step of normalizing temperatures of the lubricating oil at the inlet and at the outlet of the reduction gear of the set of selected measurements by using the measurements of the context parameters of the set of selected measurements;
a step of evaluating, based on the set of selected measurements wherein said temperatures of the lubricating oil have been normalized, a thermal efficiency of the reduction gear by using a physical model defining the thermal efficiency based on a difference between the temperature of the lubricating oil at the outlet of the reduction gear and the temperature of the lubricating oil at the inlet of the reduction gear;
a step of comparing the thermal efficiency evaluated for said at least one duty cycle of the reduction gear with respect to at least one reference signature representing an operational behavior or a faulty behavior of the reduction gear;
a step of determining a status of the reduction gear depending on the result of the comparison step; and
a step of replacing the reduction gear based on the status of the reduction gear.
2. The monitoring method according to claim 1 , wherein the context parameters comprises a temperature and/or an ambient atmospheric pressure.
3. The monitoring method according to claim 1 , wherein the operating parameters of the reduction gear also comprise a pressure of the lubricating oil of the reduction gear.
4. The monitoring method according to claim 1 , wherein the step of selecting the set of measurements comprises a step of evaluating, for several sets of measurements corresponding to a time interval with said determined duration:
of a first score called stability equal to a weighted sum, evaluated over the operating parameters, of the proportion of the measurements of each operating parameter in the set in question located in a predefined range of values for this operating parameter;
of a second stability score, equal to a weighted sum evaluated over the operating parameters, of the proportion of the measurements of each operating parameter in the set in question having a determined theoretical dispersion for this operating parameter;
said set of measurements selected during the selection step corresponding to the set of measurements maximizing a weighted sum of the first stability score and of the second stability score.
5. The monitoring method according to claim 1 , also comprising a step of evaluating at least one health indicator of the reduction gear among at least:
a heating margin indicator of the temperature of the lubricating oil between the inlet and the outlet of the reduction gear;
a margin indicator of the temperature of the lubricating oil at the outlet of the reduction gear;
an operating temperature margin indicator of the reduction gear under worst case conditions;
a pressure margin indicator of the lubricating oil during a predetermined operating phase of the gas turbine; and
a thermal efficiency margin indicator of the reduction gear;
and wherein the step of determining the status of the reduction gear also takes into account said at least one evaluated health indicator.
6. The monitoring method according to claim 1 , comprising a step of evaluating at least one trending indicator characterizing one use of the reduction gear among at least:
an indicator representing a number of duty cycles of the reduction gear and/or a number of duty cycles of the reduction gear since a maintenance operation carried out on the reduction gear;
an indicator representing an operating time of the reduction gear and/or an operating time of the reduction gear since a maintenance operation carried out on the reduction gear;
an indicator representing a number of duty cycles of the reduction gear since a maintenance operation carried out on the gas turbine;
an indicator representing an operating time of the reduction gear at high temperature;
an indicator representing an operating time of the reduction gear with a high particle level in the lubricating oil of the reduction gear; and
wherein the step of determining the status of the reduction gear also takes into account said at least one evaluated trending indicator.
7. The monitoring method according to claim 1 , comprising:
a step of detecting whether the measurements obtained of the temperature at the inlet and of the temperature at the outlet of the reduction gear comprise outliers; and
a step of eliminating said outliers;
wherein:
an outlier is detected for a said temperature when it is inconsistent with a theoretical value determined for this temperature depending on the speed of the gas turbine; and/or
an outlier is detected for the temperature at the inlet of the reduction gear when this value has a deviation greater than a predetermined threshold with respect to a measurement of the ambient temperature; and/or
an outlier is detected for the temperature at the outlet of the reduction gear when this value has a deviation greater than a predetermined threshold with respect to a reference temperature; and/or
an outlier is detected for the temperature at the outlet of the reduction gear when this value is less than the value of the temperature at the inlet of the reduction gear.