Internal and Near-Nozzle Flow in a Multi-Hole Gasoline Injector Under Flashing and Non-Flashing Conditions 2015-01-0944

A computational and experimental study was performed to characterize the flow within a gasoline injector and the ensuing sprays. The computations included the effects of turbulence, cavitation, flash-boiling, compressibility, and the presence of non-condensible gases. The flow domain corresponded to the Engine Combustion Network's Spray G, an eight-hole counterbore injector operating in a variety of conditions. First, a rate tube method was used to measure the rate of injection, which was then used to define inlet boundary conditions for simulation. Correspondingly, injection under submerged conditions was simulated for direct comparison with experimental measurements of discharge coefficient. Next, the internal flow and external spray into pressurized nitrogen were simulated under the base spray G conditions. Finally, injection under flashing conditions was simulated, where the ambient pressure was below the vapor pressure of the fuel. The results elucidate the similarities and differences between the internal and near-nozzle flow amongst the three simulated scenarios: submerged conditions, injection into a pressurized nitrogen atmosphere, and flashing conditions. The injector's discharge coefficient was remarkably consistent amongst all three conditions. Close observation of cavitation formed in the nozzles shows that vapor persists downstream and occupies a significant volume of the counterbore, suggesting that the counterbore further expands the two-phase fuel flow. Downstream, large amounts of vapor are generated under flashing conditions, however this vapor represents only a trivial amount of mass.