A high sensitivity inductive sensor for blade tip clearance measurement

Abstract

A multiplexed inductive sensor consisting of multiple mini-sized planar spiral coils for detecting multiple tip clearances of rotor blades is presented. The sensor measures the tip clearances by monitoring the inductance changes of planar spiral coils caused by the passage of the rotor blades. A resonance frequency division multiplexing technique and parallel LC resonance measurement were applied to the multiple sensor coils, making it feasible to measure multiple tip clearances using only one set of measurement electronics with high sensitivity and resolution. The results from tests conducted on a bench-top test rig have demonstrated that the sensor is capable of simultaneously measuring multiple tip clearances from 0 to 5 mm with a 10 μm resolution at a high rotary speed up to 80 000 RPM. With its high resolution, high sensitivity and capability of monitoring a large number of tip clearances simultaneously, this sensor can potentially be used for advanced active tip clearance control in turbine machinery.

Experimental Investigation of High Temperature-Resistant Inductive Sensor for Blade Tip Clearance Measurement

“…The study result of Du L. et al [20] indicated the planar coil had simple geometry, intensive magnetic field and fast response speed, its sensitivity and range satisfied the turbine tip clearance measurement requirement. Thus, the sensor in this paper is also planar coil without iron core, that is to say the minimum h equals to the wire diameter and the compact method is adopted to wrap coils to permit more turns for the given coil size and generate higher magnetic flux density.…”

“…Du L. and Zhu X.L. et al [20,21] verified the eddy current method in laboratory with 3000 rpm revolution and 1300 K temperature.…”

An Inductive Sensor for Real-Time Measurement of Plantar Normal and Shear Forces Distribution

“…Four rubber blocks [10 mm (length) × 10 mm (width) × 10 mm (height)] with durometer hardness 40 A were used to obtain linear deformation by forces ranging from 0 to 800 N. Each planar coil was designed to be 10 mm in outer diameter and 0.8 mm in inner diameter. Such a design ensures the coil is sensitive to the Z d up to 10 mm [18]. We tested magnet wires with different diameters and found that a wire with 0.2 mm in diameter generated the highest sensitivity.…”

Tip-Clearance Measurement in the First Stage of the Compressor of an Aircraft Engine

“…Besides, they provide a limited spatial resolution as compared to optical sensors, and it is not an economical technology [13]. Another option are eddy-current (inductive) sensors, which have the advantage of not requiring a direct view of the blade tip, so the sensor is not exposed to the harsh conditions of the engine [14], but their calibration is highly dependent on the tip shape and temperature [15]. Finally, optical sensors offer multiple inherent advantages [16] and that is the reason why they are being more and more employed in the aircraft industry [17,18,19].…”