Droplet Behavior in Counterflowing Streams

Single droplets of n-heptane fuel are observed in two countcrflowing laminar streams with well-defined velocity and state fields. The simpler of the two involves identical isothermal streams of nitrogen and nonevaporating droplets. The second consists of a non-premixed flame leading to droplet evaporation on both sides of the reaction zone and to combustion when oxygen and suitably high temperatures exist in the ambient surrounding the droplet. In both flows the droplet trajectory and in the flame the radius history are observed by photographic means. The measurements are compared with engineering models for the drag and heat and mass transfer of droplets.Significant discrepancies between the data and predictions in both flows arc found. Particularly interesting is the magnitude of the lift that the droplets experience and the extent of the modification of droplet drag by acceleration.