Velocity and Concentration Studies of Flowing Suspensions by Nuclear Magnetic Resonance Imaging

摘要

Nuclear magnetic resonance imaging (NMRI) techniques were developed to study concentrated suspension flows. Some of the proposed tasks were completed and others partly completed before the funding was terminated. The tasks completed were (1) materials selection for imaging of both particle and fluid components, (2) pipe flow measurements, and (3) flows in complex geometries. The task tackled with good progress is to develop rapid imaging techniques by analog compensation of eddy currents generated by the gradient pulses and real-time image reconstruction from the rapidly obtained data. The most suitable combination of materials arrived at is pharmaceutical beads in silicon oil. Their relaxation times T, are sufficiently different to permit imaging the two components separately. The pipe flow experiment used 3 mm, neutrally buoyant, plastic particles, up to 40% by volume, in 80-90W transmission oil flowing in a 5 cm diameter pipe. A series of distances ranging from 60 cm to 6 m downstream from a commercial mixer was studied. The flow is fully developed at 6 m and the velocity and concentration profiles agree with the earlier lower resolution experiments. The eddy current compensation scheme works well for two channels and is being extended to eight channels including the uniform field compensation term. In addition, we have implemented a rapid reconstruction hardware that processes and displays images in a fraction of a second.