Pressure Swirl Spray Characteristics Under Cross-flow

article in a collection out of WoS and Scopus

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The pressure swirl atomizers (PSAs) are used in a wide range of agriculture and combustion applications where ambient flow applies. The PSAs form a hollow cone-type spray, with high concentration of droplets at spray periphery, where droplets appear in a wide size range (1 – 100 µm). The spray quality (e.g. droplet size) is governed by the liquid sheet thickness at its breakup position. The sheet thickness reduces with the breakup length increase and thus the spray quality is expected to improve. A smooth and undistorted liquid sheet breaks up at a large distance from the nozzle under still ambient air conditions. The liquid sheet formation under the cross-flow condition differs from that in still conditions. The flowing air increases the relative sheet-air velocity with two consequences: 1) it reduces the primary breakup length as the disrupting forces on the sheet increase, and 2) it promotes the secondary liquid breakup and intensifies the spray mixing so the droplet size reduces. The present study aims to investigate the spill-return pressure swirl spray with optical diagnostic tools such as PDA and high-speed visualization. The effects of 1) the inlet pressure (Pin = 0.25, 0.5 and 1 MPa), 2) the Spill-to-feed ratio, SFR (defined as a ratio of the flow rate through the spill-line to the flow rate through the inlet ports and 3) the cross–flowing air (0 – 35 m/s) on the spray were investigated.

The pressure swirl atomizers (PSAs) are used in a wide range of agriculture and combustion applications where ambient flow applies. The PSAs form a hollow cone-type spray, with high concentration of droplets at spray periphery, where droplets appear in a wide size range (1 – 100 µm). The spray quality (e.g. droplet size) is governed by the liquid sheet thickness at its breakup position. The sheet thickness reduces with the breakup length increase and thus the spray quality is expected to improve. A smooth and undistorted liquid sheet breaks up at a large distance from the nozzle under still ambient air conditions. The liquid sheet formation under the cross-flow condition differs from that in still conditions. The flowing air increases the relative sheet-air velocity with two consequences: 1) it reduces the primary breakup length as the disrupting forces on the sheet increase, and 2) it promotes the secondary liquid breakup and intensifies the spray mixing so the droplet size reduces. The present study aims to investigate the spill-return pressure swirl spray with optical diagnostic tools such as PDA and high-speed visualization. The effects of 1) the inlet pressure (Pin = 0.25, 0.5 and 1 MPa), 2) the Spill-to-feed ratio, SFR (defined as a ratio of the flow rate through the spill-line to the flow rate through the inlet ports and 3) the cross–flowing air (0 – 35 m/s) on the spray were investigated.

Conical liquid sheet, subsonic cross-flow, pressure swirl atomizer, Laser Doppler diagnostics

06.09.2022

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