Final Report Summary - BTTMON (BLADE TIP TIMING MEASUREMENT TECHNIQUE FOR TURBINE MONITORING IN WORKING CONDITIONS)
The goal of this project is the development of technological basis and key components to realize new measurement systems for turbomachine blade vibration monitoring during operation by non contact and stationary sensors on the casing. This kind of measurement system are actually used for final testing of new turbomachines but till now never used for monitoring purposes.
The research activity carried out allow to obtain:
-some new sensors and a data acquisition and processing software;
-new mechanical modeling and data processing software/methods;
a new calibration and testing technique for development and performance analysis of this kind of measurement systems.
Blade tip sensors embedded in the engine case have been used for decades to measure blade tip clearance and blade vibration. Many sensing technologies have been used: capacitive, inductive, optical, microwave, infrared, eddy-current, pressure and acoustic. The most used are optical probes because of their best metrological performances, well suited for laboratory testing but not useful for engine monitoring because of durst, particle and oil that reduce their operability. The attempts done till now to use magnetic, eddy current, capacitive and similar kind of proximity sensor in order to overcome the problems of optical sensors has shown a reduction of accurate timing of blade tip arrival that cause a strong reduction of the resolution of the measurement technique in terms of minimum amplitude of blade tip vibration that can be measured. This cause a large soil level and a large uncertainty of the whole measurement system. Rotor blades are subject to flexural and/or torsional vibrations of amplitude of some mm (in long blades of the first compressor stages) down to some µm. What Is actually possible to measure by BTT technique is in between, certainly mm, not few µm.
The first result of the activity carried out in this project is the realization and testing of new prototype of magnetoresistive sensing element. Many configuration has been tested and compared in a test rig at hosting istitution with the most commonly sensor technology used till now. A first system with four digital sensing haed, with specific proicessing electronics, has been realized and tested at hosting institution.
The second result obtained is a simulation and processing software in order to generate with no electrical noise the sequence of pulses of the sensors on a generic rotor, rotating with an imposed irregularity, with a generic number of blades vibrating each accordingly with a simple and known model (amplitude and frequency). The software is useful to optimize sensor position in order to obtain an optimal sampling of blade vibrations, analyze the uncertainty given by the irregularity of rotation, test different pulse sequency data processing technique in order to choose the optimal one, by comparison with the known simulated blade vibrations.
The third result obtained was the realization of a new little and portabler test bench to be used as reference for calibration and testing of this kind of measurement system. In this test bench in order to have a suitable reference of vibration the relative motion between the blade (rotating and vibrating) and the sensor has been changed by realizing rigid tooth only rotating and fiving a vibration to the sensor. This allow to have a more easy to control and measure reference for testing and calibrating purpouses.
The research activity carried out allow to obtain:
-some new sensors and a data acquisition and processing software;
-new mechanical modeling and data processing software/methods;
a new calibration and testing technique for development and performance analysis of this kind of measurement systems.
Blade tip sensors embedded in the engine case have been used for decades to measure blade tip clearance and blade vibration. Many sensing technologies have been used: capacitive, inductive, optical, microwave, infrared, eddy-current, pressure and acoustic. The most used are optical probes because of their best metrological performances, well suited for laboratory testing but not useful for engine monitoring because of durst, particle and oil that reduce their operability. The attempts done till now to use magnetic, eddy current, capacitive and similar kind of proximity sensor in order to overcome the problems of optical sensors has shown a reduction of accurate timing of blade tip arrival that cause a strong reduction of the resolution of the measurement technique in terms of minimum amplitude of blade tip vibration that can be measured. This cause a large soil level and a large uncertainty of the whole measurement system. Rotor blades are subject to flexural and/or torsional vibrations of amplitude of some mm (in long blades of the first compressor stages) down to some µm. What Is actually possible to measure by BTT technique is in between, certainly mm, not few µm.
The first result of the activity carried out in this project is the realization and testing of new prototype of magnetoresistive sensing element. Many configuration has been tested and compared in a test rig at hosting istitution with the most commonly sensor technology used till now. A first system with four digital sensing haed, with specific proicessing electronics, has been realized and tested at hosting institution.
The second result obtained is a simulation and processing software in order to generate with no electrical noise the sequence of pulses of the sensors on a generic rotor, rotating with an imposed irregularity, with a generic number of blades vibrating each accordingly with a simple and known model (amplitude and frequency). The software is useful to optimize sensor position in order to obtain an optimal sampling of blade vibrations, analyze the uncertainty given by the irregularity of rotation, test different pulse sequency data processing technique in order to choose the optimal one, by comparison with the known simulated blade vibrations.
The third result obtained was the realization of a new little and portabler test bench to be used as reference for calibration and testing of this kind of measurement system. In this test bench in order to have a suitable reference of vibration the relative motion between the blade (rotating and vibrating) and the sensor has been changed by realizing rigid tooth only rotating and fiving a vibration to the sensor. This allow to have a more easy to control and measure reference for testing and calibrating purpouses.