Zero-crossing rate method as an efficient tool for combustion instability diagnosis

Abstract

A novel methodology based on the zero-crossing rate (ZCR) is introduced to diagnose combustion instability (CI) in a combustion system. This method can assess the combustion status by counting the number of points of dynamic pressure (DP) signals crossing zero in a cycle, and quantifies the cyclic variation of the number of crossing points. To validate the feasibility of this method, transition experiments were performed in a lab-scale gas turbine combustor. The performance of the ZCR method was compared with that of a conventional method based on the root mean square (RMS) and variance (VR) for the CI detection time and stability margin. The ZCR method detected the CI 0.84 s earlier, which is an 11.11% improvement compared to the RMS method. Additionally, the ZCR method provides information regarding the stability margin between the current combustion status and CI limit, which is a crucial parameter to ensure safe operation. Furthermore, in the ZCR method, the CI frequency can be derived without fast Fourier transform calculation by analyzing the periodic characteristics of DP. Moreover, this method can assess multi-mode and single-mode CI, which makes the ZCR a potential indicator for CI monitoring systems in gas turbine combustors.