Liquid Particle Dynamics and Rate of Evaporation in the Rotating Field of Centrifugal Compressors

Abstract

A model is presented which consists of injecting a liquid coolant into the gas or superheated vapor of centrifugal compressors via slots in the rotating blades. The aim of the injection is minimization of required compression work. The three-dimensional analysis determines the relative velocities and trajectories of the liquid particles, and their rate of vaporization as a function of the prevailing flow field and inlet conditions. Inertia, viscous drag, centrifugal and Coriolis forces are all included. The analysis rests on the assumption of low volumetric liquid/gas ratios so that the aerodynamics of the flow is not appreciably disturbed. The computer-obtained results show that for optimum conditions, and to avoid collision with the blades, it is desirable that injection occur at the suction side of the blades and close to the hub, that low rather than high initial particle velocities are preferred, and that small droplet sizes are required both to avoid blade erosion and to assure the highest rate of vaporization.