- Previous Article
- Next Article
- Table of Contents
Atomization and Sprays, Vol.19, No.6, 583-595, 2009
SENSITIVITY OF PULSATING ORGANIC GEL POLYDISPERSE SPRAY DIFFUSION FLAMES TO EVAPORATION FREQUENCY DROPLET-SIZE DEPENDENCY
There is recent experimental evidence that organic gellant-based fuel droplets, under appropriate ambient thermal conditions, evaporate and burn in a pulsating manner This unusual behavior is incorporated phenomenologically in a model of a two-dimensional polydisperse gel fuel spray flame. In keeping with the observations the frequency of oscillatory evaporation/burning is assigned a droplet-size dependence, rather than a single average value for all droplets. An analytical/numerical solution of the governing equations is utilized to examine the way in which the frequencies of oscillatory evaporation influence the combustion field for different initial polydisperse droplet size distributions. It is shown that the droplet-size-dependent frequency of evaporation of the burning gel droplets can have a strong impact on the thermal field downstream of the homogeneous spray diffusion flame front. Nevertheless, the greater the reduction in the oscillatory evaporation frequency with increasing droplet size, the more the characteristics of the gel spray flames resemble those of a liquid spray flame. Hot spots of individual (or clusters of) burning droplets can be created downstream and, under certain operating conditions, can lead to higher temperatures than experienced in the main homogeneous flame. This can be extremely important in realistic combustion settings in which hot spots in undesirable regions can damage the structural integrity of the chamber These effects point to the fact that despite the attractive safety features of gel fuel sprays, it is crucial that careful control of the operating conditions must be exercised in order not to detract from attaining the desired combustion performance.