Interakce mezi kapalinou a plynem ve spreji trysek s vnitřním směšováním

Gas-Liquid Interaction in Internally Mixed Twin-Fluid Atomization

abstrakt

en

Twin-fluid atomizers with internal mixing, such as effervescent atomizers, are based on mixing of a gas with the sprayed liquid prior to discharge. Near nozzle two-phase flow undergoes fragmentation process, mixing with surrounding air and gas expansion leading to a complex character of flow field. We first generally describe the interaction between droplets and gas jet using simple theoretical models, following with elucidation of dynamics of droplets in an effervescent spray using experimental data. Spatially resolved data were acquired using Phase Doppler anemometry for a range of operation conditions. Significant discrepancy between real spray and the model predictions was found and related to spray unsteadiness, break-up of the liquid, dense flow and a highly complex three-dimensional character of the jet with turbulent flow and mixing with ambient air. Velocity field of the droplets is affected by the gas less than predicted by simple models and the difference between predictions and real situation depends on character of the internal flow. Particle velocity close the spray centreline depends on discharge conditions. Gas flow affects strongly small particles near the nozzle and also larger particles with increasing axial distance. Near the spray edge mixing of the spray mass with surrounding air takes place which leads to selective deceleration of small particles.

Interakce mezi kapalinou a plynem ve sprejích trysek s vnitřním směšováním je komplexní proces, který zahrnuje vnitřní dvoufázový tok, výtok směsi, primární a sekundární atomizaci. Příspěvek jej analyzuje teoreticky a experimentálně s využitím dat z fázové dopplerovské anemometrie.

Twin-fluid atomizers with internal mixing, such as effervescent atomizers, are based on mixing of a gas with the sprayed liquid prior to discharge. Near nozzle two-phase flow undergoes fragmentation process, mixing with surrounding air and gas expansion leading to a complex character of flow field. We first generally describe the interaction between droplets and gas jet using simple theoretical models, following with elucidation of dynamics of droplets in an effervescent spray using experimental data. Spatially resolved data were acquired using Phase Doppler anemometry for a range of operation conditions. Significant discrepancy between real spray and the model predictions was found and related to spray unsteadiness, break-up of the liquid, dense flow and a highly complex three-dimensional character of the jet with turbulent flow and mixing with ambient air. Velocity field of the droplets is affected by the gas less than predicted by simple models and the difference between predictions and real situation depends on character of the internal flow. Particle velocity close the spray centreline depends on discharge conditions. Gas flow affects strongly small particles near the nozzle and also larger particles with increasing axial distance. Near the spray edge mixing of the spray mass with surrounding air takes place which leads to selective deceleration of small particles.

Interakce mezi kapalinou a plynem, sprej, atomizace, trysky s vnitřním směšováním

Twin-fluid atomizers with internal mixing, effervescent atomizers, Gas-Liquid Interaction

20.11.2012

University of Auckland

Auckland, Nový Zéland

Symposium handbook of 23rd International Symposium on Transport Phenomena

173–178

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