Farzad Hemmati
Farzad Hemmati, University of British Columbia, Canada
Biography
Farzad Hemmati has his research mainly focused on dynamic characteristic problems of high-speed turbomachinery. Continuous online monitoring is necessary to assess health conditions, to enable early detection of operation problems and to reduce possibility of downtime. Destructive excessive vibrations in rotor supported oil film journal bearing systems are mainly caused by misalignment, unbalance, and oil-induced instability phenomenon known as whirl. In many of the published works, the predictions of the instability threshold speed and dynamic response of the rotor supported by fluid-film journal bearings are based on the linearized stiffness and damping coefficients. Nevertheless, the fluid forces generated in fluid-film journal bearings are highly nonlinear so that bifurcation exists around the instability threshold speed.