A non-intrusive electrostatic induction sensor array for monitoring charged particles in gas turbine exhaust

Charged particles in gas turbine exhaust contain critical information for early fault diagnosis of gas-path components. Electrostatic sensing offers a non-contact, high-sensitivity approach for detecting such particles. However, conventional intrusive sensors suffer from structural degradation, particle adhesion, and limited spatial coverage under operating conditions. In this study, a non-intrusive electrostatic induction sensor array (NIEISA) with a four-probe circumferential flush-mounted design is proposed for harsh exhaust monitoring. The engineering novelty lies in the structural organisation and circumferential integration strategy of the sensing unit. A theoretical model describes the induction mechanism and analyses the effects of particle charge, spatial position, velocity, and probe geometry. Finite-element simulations are conducted to evaluate the spatial sensitivity distribution and parameter-dependent sensing characteristics. To validate the model, calibration experiments based on a controlled oil droplet system are performed, demonstrating consistent relationships between input charge and sensor response. Furthermore, comparative experiments on a micro turbojet engine test rig are carried out to evaluate the proposed sensor against a conventional intrusive sensor. The results show that the proposed NIEISA achieves improved circumferential sensing coverage and enhanced detectability of weak electrostatic signals. The present results support the mechanical installability and preliminary operational feasibility of the proposed configuration under representative exhaust conditions.