THE BREAKUP ZONE OF A DIESEL SPRAY .1. LENGTH OF ZONE AND VOLUME OF UNATOMIZED LIQUID

A new conductivity probe technique is applied to high-speed, pulsed di esel sprays to measure the dimensions and time dependency of the break up zone. Variations are made of liquid properties, gas density, and or ifice size. A flat-plate probe is used to detect the contiguous liquid in the breakup zone. Breakup length is of the order 100 nozzle diamet ers at engine conditions of gas density, and a increases with increase of liquid viscosity and reduction of gas density. Typically, of the o rder of 1% of injected liquid is measured to be incompletely atomized at 100 diameters downstream. Some agreement with published correlation s for breakup length is found; however, a is shown that liquid viscosi ty should be included in correlations and analyses of breakup, and not simply the ratio of liquid and gas density as in some previous work. A revised correlation gives reasonable agreement with the new data. Th e breakup length is found to vary throughout the spray pulse, reflecti ng, in a complex manner, the time-varying flow rate produced by a conv entional injector and pump. Periodicity of the breakup zone structure is noted at frequencies of the order 10 kHz, and this appears to be in accordance with published results using photography and laser anemome try.