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Atomization and Sprays
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ISSN Druckformat: 1044-5110
ISSN Online: 1936-2684

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Atomization and Sprays

DOI: 10.1615/AtomizSpr.2013006775
pages 983-995

FLOW-FIELD INVESTIGATION OF MULTI-HOLE SUPERHEATED SPRAYS USING HIGH-SPEED PIV. PART I.
CROSS-SECTIONAL DIRECTION

Ming Zhang
Magneti Marelli (China) Co., Ltd.
Min Xu
School of Mechanical Engineering, Shanghai Jiao Tong University, National Engineering Laboratory of Electronic Control Technology, Shanghai, 200240, China
Yuyin Zhang
School of Mechanical Engineering, Shanghai Jiao Tong University, National Engineering Laboratory of Electronic Control Technology, Shanghai, 200240, China
Gaomimg Zhang
School of Mechanical Engineering, Shanghai Jiao Tong University, National Engineering Laboratory of Electronic Control Technology, Shanghai, 200240, China
David J. Cleary
General Motors Global Research and Development, China Science Lab, Shanghai, 201206, China

ABSTRAKT

Superheated sprays are expected to improve the spray atomization and evaporation processes owing to the flash-boiling effects. However, the breakup mechanism and evaporation processes of superheated sprays have not been fully understood. In this study, a multi-hole spray flow-field on three cross-sectional planes was investigated by using high-speed particle image velocimetry (PIV) in a well-controlled high-pressure constant-volume chamber. Firstly, the spray structure under various superheated degrees was examined: As the superheat degree (SD) starts to increase, the eight individual circular plumes expand; then the expanded plumes gradually move towards the spray axis, connect with adjacent plumes, and form a donut-shaped spray pattern. With further increase of the superheat degree, the spray becomes a pancake-shaped pattern; as the fuel spray enters the fully flashing zone, an octopus-arms spray pattern can be observed. To elucidate the mechanism driving such dramatic change of the spray pattern with superheated degree, the interactions among spray plumes under various superheated conditions were investigated based on PIV data. A mixing zone is formed in between spray plumes when spray plumes approach each other. The dynamic variation of this mixing zone was analyzed through the flow-field measurement results. It is shown that the magnitude of the velocity vector in the mixing zone increases with the superheat degree, and this magnitude can be higher than that in the spray plumes' main stream, as can be observed under fully flashing conditions. The results provide insight into the spray-collapse processes and the interaction between the spray plumes. It is proven that the superheat degree is the predominant factor influencing the structure and the flow-field of the spray.