Effects of pre-injection parameters on spray characteristics of high-pressure common rail diesel engines.

This article focuses on investigating the effects of multiple injection strategies—specifically pre-injection parameters—on diesel fuel spray development and atomization characteristics under high-temperature (800 K) and high-pressure (6 MPa) conditions typical of direct-injection, turbocharged, high-speed automotive diesel engines. Using a verified computational fluid dynamics (CFD) spray model validated by high-speed Schlieren optical experiments in a constant volume bomb, the study analyzes how variations in pre/main-injection interval time and pre-injection fuel ratio influence spray morphology, penetration distances, spray width, turbulent kinetic energy, temperature distribution, and fuel concentration fields. Key findings include that increasing the pre/main-injection interval time tends to increase gas-phase penetration distance but decrease spray width and high-temperature spray volume, while increasing the pre-injection fuel ratio has the opposite effect; moreover, adjusting the pre-injection ratio more strongly affects spray width and temperature-related parameters, whereas interval time more significantly influences penetration distance. The research provides quantitative insights for optimizing multiple injection strategies in high-pressure common rail diesel engines to improve fuel–air mixing and combustion efficiency.