Mass flow rate measurement in heterogeneous diphasic flows by using the slurry pumps behavior

This study lies within the scope of a European project, with the objective of studying and designing a tunnel boring machine able to function in continuous mode. This operating mode allows reduction of discontinuities of excavation in order to obtain greater efficiency by reducing the excavation time. The extraction of rubble is carried out by means of a hydraulic circuit composed of a set of special pumps for slurry and of a horizontal hydraulic pipe. The optimal control of the whole installation, pumps included, requires continuous assessment of the mass flow rate of the solid-liquid mixture. During this study, we aimed to develop a methodology of mass flow rate measurement to replace the existing limited method of gamma-densitometer, as the irregularities noticed during various phase measurement reduce the reliability of this technique. This paper presents a theoretical and experimental study which will make it possible to improve the accuracy of measurement carried out by the gamma-densitometer and the development of a method based on the power consumed by the engines driving the pumps. (C) 2002 Published by Elsevier Science Ltd.