Drop size measurement is an important part in studying the atomization characteristics and spray behavior. Recently, the light diffraction method that do not interrupt the spray flow is being widely used. In the present study, a set of reticles(reference particles) with known size distributions, based on the Rosin-Rammler distribution function, were used to evaluate the measurement accuracy of the light diffraction method. The ranges of the distribution parameters, X and δ, tested were 50 ~ 80㎛ and 2 ~ 20, respectively.
Experimental results showed that Sauter mean diameter(SMD) measured by the laser diffraction particle analyzer were in good agreement with the true values within ±5% for the entire ranges of the distribution parameters. However, the relative span values were measured to be substantially different from the actual ones as the particle distribution became monodispersed. With δ not greater than 6, the measurement values of δ stayed within ±10% of the true ones. On the other hand, the measurement error appeared much larger as δ became larger than 6. This implies that the accurate values of the relative span and δ cannot be found by using the conventional approach, i.e., simply by minimizing the LD(log-difference) value. Thus, in the present work, functional expressions for δ and the relative span were proposed in terms of the peak height ratio obtained directly from the light energy distribution information.
