Measurements of n-Heptane Liquid Length and Spray Cone Angle for Low-Temperature, Low-Density Conditions in an Optically Accessible Flow Vessel

The purpose of this study was to measure global properties of n-heptane sprays using high-speed spray visualization in a newly developed constant-pressure flow vessel. Liquid-phase fuel penetration distance and cone angle were determined for low-density and low-temperature ambient conditions, which are increasingly relevant due to the advent of early direct-injection low-temperature combustion. Results indicated that fuel sprays under these conditions do not behave as predicted by established models. Penetration distances increased steadily throughout and after injection, and liquid-phase fuel persisted long after end of injection. Results suggest that these sprays vaporize extremely slowly and could cause wall-wetting issues.