1995-02-01

Estimates of Fuel Evaporation: Bench Experiments and In-Cylinder 950446

A relatively simple, commercially available, PC-based, dilute-spray model called TESS (Trajectory and Evaporation of Spray Systems) has been used to estimate methanol evaporation rates and drop-size evolution in bench experiments, and compared with measurements by McDonell and Samuelsen(1). Using measured initial conditions, the TESS model correlates well with the drop-size evolution for instruments using both number-flux-weighted sampling and number-density-weighted sampling, except close to the atomizer where the dilute spray assumptions do not apply. The amount of fuel evaporated at 100 mm from the atomizer is over-predicted (as expected for a dilute spray model) by 29 percent, but is within the experimental measurement error. The model is then used to estimate ethanol spray behavior in an intake manifold of a spark-ignition engine during cold-start. Ethanol fuel drops from an air-assist injector smaller than 20 or 30 micrometers are predicted to follow the airstream into the cylinder of a 3.0-liter Ford V-6 during low-temperature cranking. Finally, the TESS code is integrated with a cycle simulation model and used estimate ethanol spray evaporation in-cylinder during low-temperature cranking.

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