Fluid-Induced Rotordynamic Instability in Rotary Atomizers

Abstract

A theory is presented for the calculation of rotordynamic coefficients for the fluid-rotor interaction in rotary atomizers, based on calculation of the fluid flow through a whirling atomizer wheel. The theory predicts potentially unstable rotor whirl in high-speed rotary atomizers. The whirl frequency can be that of the first critical forward or the first critical backward precession of the rotor, depending on atomizer wheel geometry, speed, fluid properties, and flow rate. The predicted whirl phenomena have been produced in an atomizer test stand. Both forward and backward precession have been observed to become unstable. The observed whirl directions and amplitudes are consistent with the calculated coefficients. Some design parameters are identified that can help control and suppress the whirl.