Effects of Engine Speed on Spray Behaviors of the Engine Combustion Network “Spray G” Gasoline Injector

Non-reacting spray behaviors of the Engine Combustion Network “Spray G” gasoline fuel injector were investigated at flash and non-flash boiling conditions in an optically accessible single cylinder engine and a constant volume spray chamber. High-speed Mie-scattering imaging was used to determine transient liquid-phase spray penetration distances and observe general spray behaviors. The standardized “G2” and “G3” test conditions recommended by the Engine Combustion Network were matched in this work and the fuel was pure iso-octane. Results from the constant volume chamber represented the zero (stationary piston) engine speed condition and single cylinder engine speeds ranged from 300 to 2,000 RPM. As expected, the present results indicated the general spray behaviors differed significantly between the spray chamber and engine. The differences must be thoughtfully considered when applying spray chamber results to guide spray model development for engine applications. Overall, increases in engine speed correlated well with enhanced vaporization, loss of distinct plume structure, and enhanced spray collapse which led to reductions in wetted-footprint area. Furthermore, while loss of distinct plume structures appeared to be strongly dependent on ambient thermodynamic conditions, the relative impact of the spray collapse on wetted-footprint area was small. Of practical importance, while the spray chamber results indicated a consistent increase in wetted-footprint area through the end of injection, sprays in an engine underwent significant spray collapse and resulted in a parabolic area time history, with maximum values far less than the spray chamber values. These data will be made publicly available, in order to facilitate improved modeling efforts at realistic engine conditions as part of the objectives of the Engine Combustion Network.