摘要：

A technique for planar measurement of size, velocity and liquid volume or surface area of droplet clusters in sprays and the identification of fluid flow structures, which may be responsible for droplet clustering, is reported. The technique was applied in water sprays with added Rhodamine dye at appropriately adjusted concentration to ensure volume dependency of the fluorescence intensity. The spray was injected in a liquid-fuelled burner for a domestic boiler. Combined droplet laser induced fluorescence and Mie scattering images were recorded, using two CCD cameras and appropriate optical filtering, and the ratio of the two light intensity images allowed measurement of instantaneous spatial distribution of droplet Sauter mean diameter (SMD). It was found that droplet clusters formed in regions of high droplet density, but low SMD values compared to the surrounding spray. The identified droplet clusters were tracked between time delayed images and cross-correlation techniques quantified the instantaneous cluster velocity. In the vicinity of droplet clusters, flow structures are identified, using Particle Image Velocimetry, which may be responsible for the formation of droplet clusters. The droplet velocity field was measured by cross-correlation techniques from the Mie scattering and Fluorescence images and agreed well with the velocity of mean droplet diameters corresponding to the Area Mean Diameter (D20) and Volume Mean Diameter (D30) respectively, as measured with the Phase Doppler technique. 2002 by L. Zimmer, Y. Ikeda, R. Domann and Y. Hardalupas. Published by the American Institute of Aeronautics and Astronautics, Inc.

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