Flow-field Evaluation of Superheated Fuel Sprays using High-Speed PIV

Spray atomization and evaporation are expected to be improved by injecting fuel at a superheated state. However, the breakup mechanism and evaporation processes of superheated sprays have not been clarified. In previous studies [1], the multi-hole spray flow-field on the vertical plane through the spray axis was investigated by using high-speed particle image velocimetry (PIV). The results showed that the spray plumes collapse to the spray axis under high superheat conditions. It's also proven that the superheat degree is the predominant factor influencing the structure and the flow-field of the spray. To further understand this process, the interaction among spray plumes on three cross-sectional planes under various superheated conditions is investigated. In this study, n-hexane sprays generated from an eight-hole DI injector were measured using a high-speed PIV system. The results provide insight to the spray-collapse processes and the interaction between the spray plumes. As the superheat degree (SD) starts to increase, the eight individual circular plumes expanded. Then the expanded plumes gradually move towards the spray axis form a donut shape pattern. Further increasing the superheat degree, the spray becomes a pancake shape pattern. The detailed cross-sectional flow-field was analyzed to illustrate the dynamic variation of the spray and interaction among the spray plumes.