Experimental Measurement of Alford’s Force in Axial Flow Turbomachinery

Abstract

This paper presents the results of experimental measurements made on a small, high-speed, axial-flow test apparatus to verify the existence of Alford’s force and to investigate the validity of his mathematical prediction model. The measurements show that the cross-coupled aerodynamic force is linearly proportional to rotor eccentricity, and to stage torque, as predicted by Alford’s theory. However, it was found that the force is also speed-dependent, and that the inlet flow conditions to the stage have a pronounced effect. For some special combinations of rotor speed and stage torque, the direction of the force is reversed.