SYSTEMATIC DESCRIPTION OF SPRAY TIP PENETRATION FOR SEVERAL KINDS OF ENGINE INJECTORS

There are many spray types for applications, such as internal combustion engines, agriculture, and spray coating. In internal combustion engines, the fuel injection system plays an important role in efficient fuel supply. A systematic approach for understanding the spray formation process requires consideration of differences in injection modes and atomization mechanisms. This research aims to clarify the spray structure for several kinds of engine conditions, such as injector specifications and injection conditions. In this paper, a prediction model of spray tip penetration is proposed for the spray injected from hole nozzles in several kinds of engine injectors. The spray droplets' velocity and internal gas flow velocity of the spray are also estimated. The prediction model of spray tip penetration considers the atomization and spray-droplet momentum exchange. The analysis results were compared with experimental measurements, which were breakup length, spray tip penetration, and the droplet velocity. The prediction method provided a time-series variation; the errors of spray tip penetration at 1.0 ms after the start of injection were 10.8% for port fuel injection (PFI), 3.0% for direct injection spark ignition (DISI), and 1.5% for diesel condition. Using this proposed model, the features of spray development and the structure for each engine condition were discussed. The time exponential value was nearly 1.0 at the PFI, which is different from the DISI and diesel conditions. The time delay, which for the internal gas flow velocity equals the droplet velocity in the spray, was the dominant factor for the spray structure, and there is a difference between diesel, DISI, and PFI sprays.