Hysteresis and bifurcation of flow in fuel injection nozzles

Abstract

Separated flows due to cavitation and attached flows with and without cavitation are investigated for sharp-edged nozzles. The influence of the nozzle diameter, length—diameter ratio and Reynolds number on the bifurcation between the two states of flow is determined. A zone of hysteresis is seen to be present in small sharp-edged nozzles having length—diameter ratios of about 1.5—5 owing to a delayed bifurcation from cavitated flow to attached flow. The role of nozzle diameters and imperfections in the sharp-edged entry is determined. The onset of separated flows arising from cavitation and subsequent reattachment due to cessation of cavitation occur at threshold values of the cavitation number which vary with the nozzle diameter and the length—diameter ratio. The time for transition from cavitated flow to attached flow is discussed.

Keywords

fuel injection nozzles flow separation cavitation hysteresis

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