Effect of superheated fuel on air entrainment under GDI-relevant boundary conditions measured with FPIV

Bornschlegel S, Welß R, Durst A, Conrad C, Wensing M, Jestrovic S (2018)


Publication Language: English

Publication Type: Conference contribution, Conference Contribution

Publication year: 2018

Event location: Lissabon PT

URI: https://www.researchgate.net/publication/326579552_Effect_of_superheated_fuel_on_air_entrainment_under_GDI-relevant_boundary_conditions_measured_with_FPIV

Abstract

Fluorescent particle image velocimetry (FPIV) is used to examine the flow field around a single hole experimental injector under superheated and non-superheated conditions. The experimental injector is designed to match the behavior of a multi hole spray, that is common in modern gasoline direct injecting (GDI) engines. By its single hole design it eliminates the influence of jet-to-jet interaction and allows the isolated investigation of flashboiling effects on fuel sprays. Those effects occur, when fuel transits its boiling-curve during injection, leading to rapid evaporation at nozzle outlet. The air movement around the spray jet generally is found to be subdivided into three regions: In the displacement zone, air is pushed aside by the propagating spray front and its stagnation pressure. It is a function of spray front wid th, and spray front density. In this zone, the main momentum transfer with the surrounding air takes place, accelerating the captured air to spray velocity. Recirculation around the spray front takes place due to the pressure difference between the dynamic pressure of the spray front where the air is initially at rest, and the wake of the spray front where the air moves with spray velocity. It is therefore closely linked to air displacement. The stationary air entrainment equals the mass flow of air that is carried away with the stationary spray. Hence it is a function of the fuel-air ratio and the velocity in the spray. Flashboiling has different impact on those three air flow regimes. Both displacement and recirculation are increased significantly as, due to the evaporation of fuel, the spray front becomes wider and denser. Stationary air entrainment is increased too, but the effect is less pronounced, since the evaporating fuel replaces air in the spray jet and therefore partly counters the increase in spray volume, which leads to a moderately increased transport of air with the spray. It can be assumed that the reason for increased jet-to-jet interaction of flashboiling multi hole sprays, and the eventually resulting spray collapse, is not found in an significantly increased stationary air entrainment but rather in an overlap of the displacement zones of the individual jets and the resulting asymmetrical recirculation. 

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How to cite

APA:

Bornschlegel, S., Welß, R., Durst, A., Conrad, C., Wensing, M., & Jestrovic, S. (2018). Effect of superheated fuel on air entrainment under GDI-relevant boundary conditions measured with FPIV. In Proceedings of the 19th International Symposium on the Application of Laser and Imaging Techniques to Fluid Mechanics. Lissabon, PT.

MLA:

Bornschlegel, Sebastian, et al. "Effect of superheated fuel on air entrainment under GDI-relevant boundary conditions measured with FPIV." Proceedings of the 19th International Symposium on the Application of Laser and Imaging Techniques to Fluid Mechanics, Lissabon 2018.

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