Blade tip timing

摘要

A method of determining rotor blade axial displacement (bij). The rotor blade tip (34) comprises first and second measurement features (36, 38) arranged to make an acute angle therebetween. Measure time of arrival (tijk) of the once per revolution feature (1), first and second edges (40, 42) of the first measurement feature (36), and first and second edges (44, 46) of the second measurement feature (38), for at least two revolutions of the rotor (2). Convert these to circumferential distances (dijk) for each revolution. Calculate a feature angle (αijk) between each measurement feature (36, 38) and the once per revolution feature (1) for each revolution. Calculate blade untwist angle (φij) from the change in feature angle (αijk) between measured revolutions. Calculate the rotor blade axial displacement (bij) from the blade untwist angle (φij) and the circumferential distance (dijk) of the point from one of the measurement features (36, 38).

主权项

1. A method of determining rotor blade axial displacement (bij); the rotor blade mounted to a rotor having a once per revolution feature, the rotor rotating at a rotational speed (ω) about an axis; a radially outward tip of the rotor blade comprising a first measurement feature and a second measurement feature; the first and second measurement features arranged to make an acute angle (αijk) therebetween; the measurement features and the once per revolution feature monitored by a stationary timing probe; the method comprising steps to:
a) measure time of arrival (tijk) of the once per revolution feature, first edge of the first measurement feature, second edge of the first measurement feature, first edge of the second measurement feature and second edge of the second measurement feature, for at least two revolutions of the rotor; b) multiply the difference between pairs of time of arrival measurements (tijk) by the rotational speed (ω) and radial distance between the rotor axis and blade tip to calculate the circumferential distances (dijk) for each measured revolution; c) calculate a feature angle (αijk) between each measurement feature and the once per revolution feature for each measured revolution; d) calculate blade untwist angle (φij) from the change in feature angle (αijk) between measured revolutions; and e) calculate the rotor blade axial displacement (bij) at a point from the blade untwist angle (φij) and the circumferential distance (dijk) of the point from one of the measurement features.