Spectral and Wavelet Vibration Analysis Applied for Detecting Afterburner Ignition

Reliable diagnostics of gas turbine engine (GTE) systems and components is a critical task in the field of engine engineering. This study addresses the activation process of the afterburner combustion chamber in a twin‐circuit turbojet engine. The aim is to investigate the vibration characteristics of turbine supports and to assess the feasibility of diagnosing afterburner activation using a standard GTE vibration sensor. The diagnostic component was identified at a frequency of 2.52 times the high‐pressure rotor speed, within the range of 750–850 Hz. The vibration velocity amplitude at the diagnostic frequency increases by 3–5 times during afterburner ignition compared to the non‐afterburner mode. It was established that the vibration‐based detection of afterburner ignition occurs on average 1.0–1.5 s earlier than the standard flame sensor response, while the detection of afterburner extinguishing occurs 2–3 s earlier, with the vibration velocity dropping from 15–17 to 2.5–5 mm/s. It is demonstrated that the appropriately processed signal from the standard GTE vibration sensor can be used either as an alternative to the flame sensor or as a complementary means to suppress its false activations, thereby enhancing the reliability of afterburner ignition without the need for additional sensing hardware. It was further established that both ignition and extinguishing of the afterburner can be identified by the vibration velocity amplitude obtained using a narrowband tracking filter at the diagnostic frequency. The study also demonstrates the potential of applying a continuous wavelet transform to the standard vibration sensor signal for the identification of afterburner operation. To the best of the authors’ knowledge, this is the first study to demonstrate the feasibility of using a standard GTE vibration sensor for real‐time identification of afterburner ignition and extinguishing through spectral and continuous wavelet transform analysis, offering a practical alternative to dedicated flame sensors.