An exhaust debris monitoring method for gas turbine PHM by using a planar array of hemisphere-shaped electrostatic sensors

The exhaust debris of gas turbines contains important information about deterioration and faults of the gas path components. Electrostatic monitoring, which has advantages of real-time, robustness and low cost, is efficient in detecting the debris, making it a promising method for gas turbine PHM. However, electrostatic monitoring systems with a single sensor have a significant shortcoming of inhomogeneous and localized special sensitivity, which would affect the monitoring accuracy. To solve this problem, an exhaust debris monitoring method by using a planar array of hemisphere-shaped electrostatic sensors is discussed in this paper. Firstly, a spatial sensitivity model of the planar array is built based on the Poisson equation. Then, as for abnormal debris, a component extraction-based algorithm is proposed to achieve fast processing of the array signals. In the end, accuracy of the models and efficiency of the algorithm are validated by FEM and numerical simulations. The results indicate that the models built in this paper are accurate. In addition, as for an electrostatic monitoring system, the array signal processing algorithm makes a significant contribution to improving the homogeneity of its sensitivity, thus the sensing accuracy is improved remarkably, especially in the central zone of the exhaust pipe.