Experimental Investigation of the Drop Size Distribution of Sprays Produced by A Low-Velocity Netwonian Cylindrical Liquid Jet

摘要

The origin of the critical point of a cylindricalliquidjet,first maximum of the stability CUMIe, is not fully understood so far. In a previoUs experimental investigation, three different jet regimes of atomization were defined according to the influence of the gas density on the jet critical velo- city. Whether a jet is in a given regime was found to be a function of a parameter Pa 0, equiva- lent to a density. In the present investigation, the relevance of this parameter is considered and jet atomization processes are studied through the analysis of the evolution of the drop size distri- bution in the vicinity of the critical condition. A (Pa 0, Z) map is derived from the analysis of a large amount of experimental results found in the literature. This map is of practical interest, as it helps in presupposing the behavior of a liquid jet. The analysis of the drop size distribution reveals that the instability that develops when the critical velocity is reached may be a subcritical or a supercritical instability, according to the jet regime of atomization. When a subcritical instability develops, the disintegration process is controlled by capillary instability even for velocities greater than the critical velocity, and the breakup length varies according to the initial conditions. It was found that the develop- ment of such instabilities has no effect on the relative drop size distribution width, 'Which seems therefore to be mainly a function of the perturbation growth process. When a supercritical insta- bility develops, the development of the criticalpointis due to the action of the aerodynamicforces, 'Which increases the temporalgrowth rate of the instability as the velocity increases.