High performance rotor monitoring

This paper describes the development of a high bandwidth, capacitive sensing system to monitor blade tip clearance, system vibration, blade time-of-arrival, blade vibration and detection of low cycle fatigue cracking on aircraft engines and industrial machinery. All measurements are fused into a single sensor and single channel of electronics. The paper describes the development of the multielement capacitive sensor and high bandwidth preamplifier, presents results from tests conducted in a spin pit, and compares their time-of-arrival performance to the current non-intrusive strain measurement system being developed by the Propulsion Instrumentation working Group. The system measures the clearance between the tip of each blade on a rotating disk and a thin multi-element capacitive sensor mounted close to the rotating part. The sensor is coupled to a very high bandwidth and high signal-to-noise preamplifier that allows detection of individual blades in real-time and the use of narrow striped capacitive sensors for increased resolution. The device can be used as the heart of a rotor health monitoring system for detection of high cycle fatigue blade vibration, low cycle fatigue disk cracking active tip clearance control input, blade damage from foreign objects, and monitoring of system vibration and speed.