PROGRESS ON COMBINED OPTIC-ACOUSTIC MONITORING OF COMBUSTION IN A GAS TURBINE

The need for better combustion monitoring in gas turbines has become more acute with the latest technical requirements, standards, and policies in terms of safety, environment, efficiency, operation flexibility and operation costs. This paper reports on a concept for gas turbine combustion monitoring using multiple probes that combine optical and acoustical measurements. The motivation of the project is twofold. On the one side, one wants to exploit the radiative feature of the flame and transform it into a piece of reliable information about the combustion status. On the other side, this information can be useful in terms of data interpretation or data reconciliation with other information coming from further sensors such as temperature probes, fast pressure probes or accelerometers. For this purpose, a set of multiple Rayleigh Criterion Probes (RCPs) combining optical and acoustical sensors is used. Detailed information about the RCP can be found in paper GT2017-63626, [1]. The focus is put on the detection of the flame, on the monitoring of the ignition process, on the quality assessment of combustion based on its spectral contents (including soot formation) and on the detection of possible combustion instabilities. The novel test rig used for validation of this advanced combustion monitoring concept is introduced, and minimal instrumentation including three probes is recommended. The split in red, green and blue (RGB) light components and their further analysis allows mapping the different types of operation. Solutions are proposed to bring the optical interface as near as possible to the flame and make it operational and reliable despite prevailing heat. The paper closes with a description of the ongoing tests on a pressurized combustion facility, and a sketch for a 3-RCPs based compact combustion monitoring system. The advantages of selected chromatic spectral bands are discussed, as well as the remaining challenges towards a full demonstration.