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Multi-hole DI injectors are being adopted in the advanced downsized DISI ICE powertrain in the automotive industry worldwide because of their robustness and cost-performance. Although their injector design and spray resembles those of DI diesel injectors, there are many basic but distinct differences due to different injection pressure and fuel properties, the sac design, lower L/D aspect ratios in the nozzle hole, closer spray-to-spray angle and hense interactions. This paper used Phase-Contrast X ray techniques to visualize the spray near a 3-hole DI gasoline research model injector exit and compared to the visible light visualization and the internal flow predictions using with multi-dimensional multi-phase CFD simulations. The results show that strong interactions of the vortex strings, cavitation, and turbulence in and near the nozzles make the multi-phase turbulent flow very complicated and dominate the near nozzle breakup mechanisms quite unlike those of diesel injections.

While the use of injection strategies utilizing multiple injection events for each engine cycle has become common, there are relatively few studies of the spray structure of split injection events. Optical spray measurements are particularly difficult for split injection events with a short dwell time between injections, since droplets from the first injection will obscure the end of the first and the start of the second injection. The current study uses x-ray radiography to examine the near-nozzle spray structure of split injection events with a short dwell time between the injection events. In addition, x-ray phase-enhanced imaging is used to measure the injector needle lift vs. time for split injections with various dwell timings. Near the minimum dwell time needed to create two separate injection events, the spray behavior is quite sensitive to the dwell time.