EFFECTS OF TURBULENT MIXING ON SPRAY IGNITION IN SPRAY SYSTEM

When a column of droplets freely falling from an ultrasonic atomizer w as ignited behind a reflected shock, no ignition occurred at a tempera ture below 1100 K, even if the pressure was as high as IMPa. Although, a higher temperature condition ensured ignition, no luminous flame wa s observable by high-speed photography, and even if a luminous flame l ump appeared at an extremely high temperature, it disappeared without spreading over the entire column of droplets in this case. It is known however that, if a fuel is injected into a diesel cylinder or an elec tric furnace, ignition occurs even at a temperature as low as 650 K wi th a luminous flame spreading over the entire spray. These differences could be caused by the effects of turbulent mixing between fuel dropl ets and hot air, in fact, turbulence-generating rods were placed on th e upstream side of the spray column. Experimental results indicates th at the ignition limit was lowered to 840 K, and the ignition delay per iod was decreased by increasing the intensity of turbulence. Furthermo re, the light emission of the flame was intensified, and normal spray combustion was maintained in the low-temperature atmosphere after the shock tube ceased its operation.