Investigation of Combined Neutron Scattering and Neutron Radiography Techniques for Measurement of Gas-Liquid Two-Phase Flow

Neutron radiography has the ability to differentiate between a gas and liquid in two phase flow due both to the density difference and the affinity of Hydrogen to scatter the neutrons. The neutron radiography technique has the additional benefit of visualizing through metal walls due to the low probability of neutron interactions with most metals which has resulted in significant studies using neutron radiography for the measurement of two-phase flow. The studies have shown that both real-time and high-speed imaging of two-phase flow is possible for the measurement of void distribution in air-water, steam-water, and gas-liquid metal flow. However, since neutron radiography is a planar method, full three dimensional capability of two-phase flow has not yet been demonstrated. The purpose of this work is to investigate if neutron scattering could provide additional information to supplement the information obtained in real-time neutron radiography. Experiments are performed with a real-time neutron radiography system which provides the two-dimensional information. A turntable is used to evaluate the 3D structure of a non-moving two-phase system to identify the three dimensional structure. Additional thermal neutron detectors are placed at the periphery of the neutron beam to detect the scattered neutrons. The detector response as a function of the location of a gas-liquid interface rotated through the third dimension can be obtained. The neutron radiography technique was able to resolve the interface. The location of the interface could be observed to move as the object was rotated in the beam yet the location of the interface along the neutron beam axis could not be determined by radiography alone as expected. The neutron scattering technique did provide additional information in the third dimension and thus it was possible by using both techniques to locate the gas-liquid interface.Copyright © 2008 by ASME