Utilization of pyrometer data to detect oxidation

#This invention generally relates to turbine buckets. More specifically, the invention relates to a method for determining conditional based maintenance of first stage turbine buckets.

#A gas turbine engine is an air-dependent device that uses exhaust-gas-driven turbine wheels to drive a compressor, making continuous operation of the engine possible. Turbines extract kinetic energy from the expanding gases as the gases exit from the burners. The turbines convert this energy into shaft horsepower to drive the compressor and engine accessories. Turbines typically used for power generation are comprised of multiple stages, each stage having fixed partitions and a plurality of turbine buckets, also known as blades, mounted on rotatable turbine wheels.

#Turbines are subjected to high speeds and high temperatures. These high speeds result in high centrifugal forces. Turbines must operate close to temperature limits that, if exceeded, lower the strength of the materials used to form the turbine components. Turbine buckets undergo distortion or lengthening known as “creep.” Creep, which is a cumulative condition, refers to stretching or elongation of the bucket. The rate of creep is determined by the load imposed on the turbine, and the strength of the bucket. The strength of the bucket is in turn determined by the temperature within the turbine. Since changes in pitch and creep are more pronounced if engine operating limits are not respected, the temperature and RPM limits stipulated by the manufacturer must be followed.

#These and other features and advantages of the present invention will become more apparent in view of the following detailed description in conjunction with the accompanying drawings, of which:

#FIG. 1 is a section view of an optical pyrometer system in accordance with the present invention that may be used to acquire temperature data, shown installed on a turbine;

#FIG. 2 is a perspective view showing the line of sight viewed by the pyrometer of FIG. 1;

#Numerous embodiments of the present invention are possible and will be apparent to those skilled in the art given the benefit of this disclosure. The detailed description herein, for convenience, will focus on certain illustrative and exemplary embodiments.

#In accordance with preferred embodiments, a method is provided to predict intervals for servicing first stage turbine buckets. This method may be based on numerous parameters including oxidation of the buckets, reduction in power output, irregular operation, and other parameters indicative of turbine and turbine bucket failure. Most preferably, the oxidation data is obtained from temperature measurements using a temperature sensor such as a pyrometer. One skilled in the art would recognize that other devices, such as thermometers, thermocouples, or other devices that measure resistance and convert the resistance to a temperature value, may be used to determine the temperature within the bucket.

#In accordance with preferred embodiments, pyrometer data can be used to detect and track oxidation of the buckets. The data obtained from the pyrometer measurements are evaluated using a technique of relative temperature measurement. Relative temperature measurement is performed using temperature data from a bucket that has no oxidation at the leading edge or mid chord locations. The temperature data obtained from a bucket without oxidation is used as a baseline, and is subtracted from all other temperature data to obtain relative temperature data.