دانلود رایگان مقاله شبیه سازی ناخالصی فرومغناطیس در دیسک توربین موتور با مغناطیس سنج فلوکس گیت

Abstract

In this paper, ferromagnetic impurities in paramagnetic aeroengine turbine disks are investigated. Because such inclusions represent a significant threat in aviation, a detailed analysis is required for impured turbine disks. For this purpose, sensitive fluxgate magnetometers are used. After a premagnetisation, this sensor is able to detect small ferromagnetic particles by recording the variation of the magnetic flux density while the disk rotates below the sensor head. This trajectory creates a unique signature. However, the measured signatures are often distorted. A main reason for these distortions is that the particles are not oriented in axial direction (in the direction of the disks axis). Up to now, it was not possible to interpret the measured signatures. Thus, a simulation tool has been developed that provides a catalogue of different magnetic flux density distributions of typical orientations, positions and various distances to the fluxgate magnetometer position. For these simulations, the particles are assumed to be dipoles. As part of impurities are not caused by concentrated particles but by elongated ones, so-called or dipole lines, the model has been expanded for these cases by using numerical integration techniques. Measurements verify the assumption to approximate impurities by dipoles.

5. Conclusion

In this case study, ferromagnetic inclusions on aeroengine turbine disks have been investigated. Three high sensitive and low-noise fluxgate magnetometers have been interconnected to a gradiometer second order to remove any magnetic background fields. This sensor is located above the turbine disk that rotates on a turn table. Depending on the orientation, size, position and elongation of the impurities, various signatures are obtained during the rotation. In order to solve the inverse problem – to gain information of the impurities based on the measured flux densities – the simulation results of different measurement configurations are stored in a catalogue. For these simulations, the impurities are modelled as simple magnetic dipoles or dipole lines. Real measurements show the very good agreement between the model and the reality. In future, intelligent pattern recognition algorithms can be implemented to select that curve out of the catalogue that fits best to the measured data.