Paroxysmal positional vertigo--a study of 255 cases.

Abstract

Surge is an aerodynamic flow instability which limits stable compressor operation for low mass flows. The stable operating region can be enlarged using so-called active control. In this study, plenum pressure measurements and a one-sided controlled bleed/recycle valve\nare used for active surge control in a laboratory-scale gas turbine installation. This control valve is nominally closed and only opens to stabilize the system in the nominal operating point. The influence of the control valve’s capacity and bandwidth on system performance\nis also examined. Using a bounded linear feedback controller, surge limit cycles are stabilized in the desired set-point, and stable operation can be sustained in this operating point with zero control valve mass flow. Surge point mass flow can be reduced significantly using this control strategy.