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A PLIF measurement system was designed and applied for imaging direct-injected stratified charge fuel preparation. An extensive measurement plane was achieved through novel design features in the system. Measurement and processing uncertainties were assessed at ±15% for the semi-quantitative fuel density. Tracer selection among suggested iso-octane candidates was found not to have a significant effect on PLIF results under the conditions tested. Stratified charge fuel distribution images were acquired for three piston and fuel injector combinations. The effect of piston design in guiding the fuel mixture position was most notable. Fuel distribution features correlated reasonably well with measured data from a thermodynamic engine of similar design.

In modeling of engine fuel-air mixing, it is desired to be able to predict fuel spray atomization under different injection and ambient conditions. In this work, a previously developed sheet atomization model was studied for this purpose. For sprays from a pressure-swirl injector, it is assumed in the model that the fuel flows out the injector forming a conical liquid film (sheet), and the sprays are formed due to the disintegration of the sheet. Modified formulations are proposed to estimate sheet parameters including sheet thickness and velocity at the nozzle exit. It was found that the fuel flow rate of a swirl injector satisfied the correlation well. Computations of correlation well. Computations of the sprays injected in an engine with a side-mounted injector were performed for conditions that duplicated a set of experiments performed in an optical engine. The computed results were compared with the spray images obtained from the optical engine using elastic (Mie) scattering.