Measurement of Drop-Size Distribution by a Light-Scattering Technique

Although a light-scattering technique, using a single-element photomultiplier tube, has proved to be an accurate tool for determining the Sauter mean diameter (SMD) of a liquid fuel spray, it has been generally considered unsuitable for the measurement of drop-size distribution. Usually, a photomultiplier tube on the receiving side of the optical system is traversed in a direction at right angles to the optical axis, and the scattered light intensity due to the passage of a monochromatic laser beam through the spray is plotted against radical distance to provide a measurement of SMD. In the present study it is shown that this same light intensity profile can be also converted into an energy distribution which is uniquely related to drop-size distribution. Values of SMD obtained with this technique show good agreement with corresponding values as determined by a photographic method. Moreover, the drop-size distribution calculated by the proposed method is found to be almost identical to the distribution exhibited by a standard calibration reticle. Typical examples of SMD and drop-size distribution for sprays produced at various test conditions are presented.