FLAME-OUT DETECTION FOR GAS TURBINE ENGINES BASED UPON THERMOCOUPLE SIGNAL ANALYSIS

摘要

This paper describes an experimental study to examine the potential of using Exhaust Gas Temperature (EGT) thermocouples for prompt flame-out detection in gas turbine engines. The approach taken involved accelerating the response of a shielded, slow response thermocouple using electronic processing of the signal. Thus, the abrupt drop in temperature characteristic of a flame-out could be detected within a much shorter time period than would be possible through a conventional thermocouple temperature measurement method. This was intended to provide a robust alternative to existing optical flame-out sensors which have fast response but can be susceptible to false flame-out indications due to window sooting. A production EGT thermocouple with online electronic processing was compared with a production optical flame sensor from a GE F-404 and a laboratory photodiode sensing system. The devices were tested in a full scale GE J-85 combustion chamber sector rig with optical access. The results showed that the thermocouple flame sensor had a response time to flame-outs of less than 100 ms. This was much faster than a conventional thermocouple, but still an order of magnitude longer than the optical flame sensor. However, whereas the optical flame sensor could yield ambiguous results about the presence of flame under some conditions, the thermocouple flame sensor provided a clear indication of flame-out events for all the conditions that were tested.