59103 - Characterisation And Validation Of An Optical Pressure Sensor For Combustion Monitoring At Low Frequency 

This paper introduces a novel approach to better monitor fast pressure dynamics in turbomachinery, including combustion. This innovation is motivated by the need expressed by machine OEMs and end-users to better analyze steady-state and transient phenomena in a continuous flow machine, and more precisely in its hot core. This improved monitoring system will support an optimization of the machine performance, leading to a safer, cleaner, more flexible and more cost-efficient operation for the end-user.

While the piezoelectric technology is commonly used in fast pressure measurement, a new paradigm based on optical interferometry was developed by Meggitt. The upside of such a development is threefold. First, the novel system is designed to provide a larger range of measurement frequencies with much better stability, especially in the lower frequency range, i.e., less than 10 Hz. This unique feature allows the quasi-real-time observation of precursors, such as the specific noise of a low frequency flame dynamic, which is a characteristic of an imminent LBO. It is intrinsic to the optical-based principle, which exposes only the passive sensor to harsh environmental conditions, while the active elements are located remotely at room conditions. Second, the measurement is independent from temperature and static pressure at the measurement point. Finally, the measurement is intrinsically insensitive to vibrations or EMI perturbations.

The novel measurement system was characterized under non-reactive and reactive conditions within the frame of a joint study with Combustion Bay One e.U. and FH Joanneum GmbH. The technology is first described, including the relevant hardware and software aspects of the measurement chain. After that, the different experimental set-ups and conditions are presented. The paper finally ends with test results, validating all the advantages stated, and a discussion on the merits of a fleet deployment.