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Abstract
A recent research program has identified the possibility of using the analysis of casing wall pressures in the direct measurement of gas turbine rotor blade vibration amplitudes. Currently the dominant method of non-contact measurement of gas turbine blade vibrations employs the use of a number of proximity probes located around the engine periphery measuring the blade tip (arrival) time. Despite the increasing ability of this method there still exist some limitations, ie. the requirement of a large number of sensors for each engine stage, sensitivity to sensor location, difficulties in dealing with multiple excitation frequencies and sensors being located in the gas path. Analytical modelling of the casing wall pressures and reconstruction of rotor blade vibration amplitudes from the analysis of these simulated pressure signals has shown significant improvement over current non-contact rotor blade vibration measurement limitations by requiring only a limited number of sensors and providing robust rotor blade vibration amplitude estimates in the presence of simulated measurement noise. However, this modelling was conducted with some fundamental assumptions about the casing wall pressures being made. One of these assumptions presumed that during blade motion the pressure profile around the rotor blades follows the blade’s motion while it oscillates around its equilibrium position. This assumption is investigated in this paper through the numerical modelling of the fully coupled two-way rotor blade motion and fluid pressure interaction.
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Notes on contributors
G L Forbes
Gareth Forbes is currently a Lecturer at Curtin University in Perth, Western Australia. His research interests are in the area of structural dynamics and signal processing. Of particular interest is the dynamics of structures under simultaneous spatially and temporally varying loads, signal processing in mechanical systems and gas turbine blade vibration measurement, on which he has authored over 10 peer-reviewed publications. He has completed both a Bachelor of Engineering, and a PhD degree from the University of New South Wales. Between studying for these two degrees he worked for the engineering consultancy firm KBR.
O N Alshroof
Osama Alshroof is currently a Senior Research Engineer at AECOM Consultation Company in Sydney, Australia. His research interests are in Computational Fluid Dynamics including heat transfer and fluid structures, also fluid structure interaction. Osama has authored over 5 peer-reviewed publications. He has completed a Bachelor of Engineering from The University of Jordan, and both a masters and a PhD degree from the University of New South Wales.
R B Randall
Bob Randall is a visiting Emeritus Professor in the School of Mechanical and Manufacturing Engineering at the University of New South Wales (UNSW), Sydney, which he joined as a Senior Lecturer in 1988. Prior to that, he worked for the Danish company Bruel & Kjaer for 17 years, after 10 years’ experience in the chemical and rubber industries in Australia, Canada and Sweden. He was promoted to Associate Professor in 1996 and to Professor in 2001. He has degrees in Mechanical Engineering and Arts (Mathematics, Swedish) from the Universities of Adelaide and Melbourne, respectively. He is the invited author of chapters on vibration measurement and analysis in a number of handbooks and encyclopaedias, and a member of the editorial boards of four journals including Mechanical Systems and Signal Processing and Trans. IMechE Part C. His book Vibration-based Condition Monitoring was recently published by Wiley. He is the author of more than 190 papers in the fields of vibration analysis and machine diagnostics, and has successfully supervised 14 PhD and three Masters projects in those areas. Since 1996, he has been Director of the Defence Science and Technology Organisation’s Centre of Expertise in Helicopter Structures and Diagnostics at UNSW.