STRUCTURE OF UNSTEADY VORTICAL WAKES BEHIND BLADES OF MUTUAL-MOVING ROWS OF AN AXIAL TURBOMACHINE

Abstract

At research of effects of mutual circumferential shift of stators in system of rows stator-rotor-stator of an axial turbomachine (clocking effects, [1–3]) significant periodic velocity pulsations were found out in the field of turbulent vortical wakes behind rotor blades [3]. The basic frequency of these pulsations is equal to stators vanes passing frequency past rotor blade, and the amplitude of velocity pulsations essentially depends from stators clocking position. According to the Thomson theorem it is necessary to expect that the specified pulsations are caused by the free vortexes, descending from rotor blades owing to change on them of flow velocity circulation at interaction of rows. Clearly, that presence in vortical wakes of progressing waves of vorticity causes acoustic disturbances and additional aerodynamical losses owing to energy dissipation. As dissipative function depends on distribution of vorticity, for an estimation of the losses, caused a rotor-stator interaction, the description of vortical wakes structure at presence in them of free vortexes is necessary.