Mixer Mechanical Design - Fluid Forces

Abstract

This paper describes the mechanical design of a mixer with the emphasis on the fluid forces that are imposed on the impellers by the fluid continuum in the mixing vessel. The analysis shows that the forces are a result of transient fluid flow asymmetries acting on the mixing impeller. These loads are dynamic and are transmitted from the impeller blades to the mixer shaft and gear reducer. A general result for the form of the fluid force equation can be developed. The importance of the mechanical interaction of the mixing process with the mixing vessel and impeller is stressed. This interaction is shown in a number of examples. Fluid force amplification resulting from system dynamics of the mixer and tank configuration are addressed. The role of computational fluid dynamics in mixer process and mechanical design is shown. Several experimental techniques are described to measure the fluid forces and validate mixer mechanical design practice.