A comparison of spray characteristics between an air-assisted fuel injector and a high-pressure swirl injector for gasoline direct-injection engine application

The spray characteristics of two preferred injection tools for gasoline direct-injection (DI) application were compared. An air-assisted fuel injector (AAFI) and a high-pressure swirl injector (HPSI) were designed and fabricated, and the characterization strategies and processes for both injector sprays were arranged in parallel. In this article, the overall spray characteristics, defined as spray pattern, penetration, internal spray structure, atomization performance and drop size distribution, are discussed. A spray shape factor is introduced to describe the development of intermittent sprays ftom both injectors. Axialpenetration appears to be almost linear in the case oftbeAAFT, while its instantaneous speed continuously decreases with time in the HPSI. Large droplets are distributed at the tail end of the AAFI spray, while they are concentrated on the head portion of the HPSI spray. From the viewpoint of mean drop diameter, feasible ranges of injection and of ambient pressure are found to be broader in the HPSI. Drop size distributions of the HPSI are found to be more uniform than those of the AAFI.