Two-phase PIV to investigate spray/flow interaction in Gasoline Direct injection engine
Résumé
This paper focus on the influence of the injection on the internal aerodynamic in an engine. Firstly, velocity measurements have been performed in an optical mono-cylinder engine with fuel injection through a solenoid multihole injector using Particle Imaging Velocimetry (PIV) technique. Only gaseous phase is studied in the engine for acquisition timings for which fuel droplets are totally evaporated. Results indicate that the injection impacts the incylinder flow by several means. The tumble position and intensity are modified. Injection reduces the cycle-to-cycle variations of the tumble and maintains it around the chamber mid-height until 100 BTDC. The tumble intensity is also almost twice less important with injection. The velocity magnitude is globally lower and less fluctuating during the cycle. The turbulence is also reduced in the presence of the injection and velocity fluctuations are more spatially homogeneous than without injection. Secondly, a two-phase PIV diagnostic is settled in order to enable a simultaneous measurement of the velocities of liquid and gaseous phases when both are present. Validations of the technique are performed in a static chamber with the same injector than for the study on the engine bench. The two phases are separated during the acquisition using fluorescence signal of two different dyes, recorded on two cameras with filters. The use of a second laser is proposed for this diagnostic to enable to adjust two PIV delays to overcome the difference of velocity range between both phases. The gas velocities measurement has been validated. Finally, this paper highlights two points: (1) injection in the engine clearly impacts the stability of the internal aerodynamic; (2) two-phase PIV using dyes succeeds separating phases to provide well-separated instantaneous velocity fields during injection phase.
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