Studies on waterjet impact forces in the hydroentanglement process

Abstract

In the hydroentanglement process, high velocity multiple waterjets are generated through the nozzles before impinging on the hydroentangling belt or fibre-web and exert an impact force. In this study, a technique to measure important characteristics of the waterjets, namely, the coefficient of velocity, Cv, and coefficient of discharge, Cd, is proposed. The technique offers a simple and practical method to determine the energy transfer efficiency from the manifold to the waterjets. The measured Cv and Cd values were observed to decrease with an increase in waterjet pressure, which implied higher energy losses at higher waterjet pressures. These results were then used in the next experiment to measure the waterjet impact force. The waterjet impact force was measured using a Tensiometer-R2000 fixed on a vibration-free stand at different waterjet pressures, varied from 30 to 120 bar. It was observed that the waterjet impact forces were equal across the width of the machine at a given pressure, but increased proportionally with the increase in the waterjet pressure. When the empirical relation was fitted between experimental and theoretical values of waterjet impact force, it was found that theoretical values were overestimated.