Understanding and analysis of wear in homogenizers for processing liquid food

摘要

The tribological research pertaining to homogenizers in processing liquid food has received much lessattention compared to its potential in enhancing the efficiency and durability of the homogenization processequipment. Homogenization is a process used to disrupt fat globules in dairy products to reduce theformation of creamy layer (separation) and also to enhance the viscosity of certain products. This processtakes place in a narrow gap in the homogenizer machine and this region is highly prone to wear. Theoccurrence of wear during processing not only impairs the homogenization effect but also leads to increaseddowntime of the machine.The aim of this work was to understand the occurrence of wear and wear mechanisms in the homogenizationgap using both experimental and analytical approaches. Two experimental test rigs were used to study thedifferences in wear during operation, i.e., with and without particles. The trajectory of the particles wassimulated without the influence of cavitation using a CFD-code to investigate whether the particles are thecause of the wear. The homogenizer gap has been simulated for a worn geometry to see how the occurrenceof wear affects the particle trajectories.The results show that the presence of particles accelerates wear and most important parameters are theparticle hardness and mass. When cavitation and particles are combined they create a synergistic effect on thewear. This can be explained by the fact that cavitation can accelerate particles in random directions throughthe imploding action of cavities. A change of impact angle increases the amount of wear significantly. CFDsimulationsand calculations show that the particles do not fully follow the streamlines and therefore createwear on the gap surfaces.