| Spray angle, penetration length, droplet size, and velocity measurements were taken under cold start conditions for a Direct Injection Spark Ignition engine to investigate the effect of transient conditions on spray development. The results show that during cold start, spray development depends primarily on fuel pressure, followed by Manifold Absolute Pressure (MAP). Injection frequency had little effect on spray development. The spray for this single hole, pressure-swirl fuel injector was characterized using high speed imaging and phase Doppler interferometry. The fuel spray was characterized by three different regimes. Regime 1 comprised fuel pressures from 75--175 psig, MAPs from 0--4.3 psig, and was characterized by a large pre-spray along with large drop sizes. The spray angle and penetration lengths were comparatively small and the spray profile resembled a solid cone. Regime 2 comprised fuel pressures from 425--550 psig and MAPs from -6.8---7.3 psig. A large pre-spray and large drop sizes were still present but reduced compared to Regime 1. The spray profile was mostly solid, but the spray angle and penetration lengths were typically larger then in Regime 1. Regime 3 comprised fuel pressures from 925--1470 psig and MAPs from -8---9.5 psig. The fuel spray had a fully developed hollow cone structure with recirculation vortices at the edges of the spray, which constricted the spray angle. The spray angle was similar to Regime 2, while the penetration length increased. The pre-spray and drop size were reduced compared to Regime 2. In all regimes, decreasing MAP enlarged the spray angle, while injection frequency was not a significant factor. Experimental verification of these variables is critical due to the subjectivity in taking such data. |
