Measurement of out-of-plane vibrations of a rotating bladed disk using Blade Tip Timing measurement method

The Blade Tip-Timing (BTT) method is largely used to measure vibrations of rotating turbomachinery bladed disks under operating conditions. Other measurement methods, for example strain gauges, might be intrusive, or unsuitable because of inadequate optical access such as is required by Scanning Laser Doppler Vibrometer (SLDV) systems which may be commonly used in laboratory-based rotating test rigs. This paper presents the use of BTT method for measuring out-of-plane vibrations of a rotating 24-bladed disk and the design of mechanical components to accommodate BTT probes. Examples of measured data, using both BTT and SLDV system, will be presented.