Comparison of droplet dynamics in low-speed gaseous counterflow: Pressure-swirl and twin-fluid spra

article in a collection out of WoS and Scopus

en

CO2 release into the atmosphere, responsible for global warming, can be reduced by spray scrubbing. Sprays are deployed to create an interfacial area for efficient gas-liquid contact in the spray column. The counter-flow of air interacts with the spray and causes droplet deceleration, momentum transfer, and air/droplet entrainment. Understanding the spray/air flow interaction can improve the pressure loss and droplet entrainment models, improve the estimation of entrained air velocity, and provide better insight into the spray column function. Twin-fluid effervescent atomizers, operated at injection pressure of 0.025 MPa and GLR ratios of 2.5 and 5%, were compared with hollow-cone and full-cone atomizers, operated at injection pressures of 0.05 and 0.2 MPa, under the counter-flow conditions. A vertical wind tunnel was used to simulate counter-flow conditions with an air flow velocity ranging from 0 to 1 m/s. The flow was seeded with water mist, generated by the ultrasonic atomizer, so that the velocity of the continuous and discrete phase could be resolved. Simultaneous velocity and droplet size measurement was performed, at various radial positions ranging from Z = 0 mm (atomizer tip position) to Z = 600 mm, with a 1D Phase Doppler anemometer. The spray causes a large distortion of the counter-flow velocity near the atomizer and displaces most of the air towards the walls. Entrained droplet computed using the superficial counter-flow velocity (not influenced by the spray) yield significant errors compared to estimation using the maximum air velocity mainly for sprays with higher momentum. Higher liquid velocity causes larger air entrainment and complicated vortex structure, which govern the air velocity near the atomizer.

CO2 release into the atmosphere, responsible for global warming, can be reduced by spray scrubbing. Sprays are deployed to create an interfacial area for efficient gas-liquid contact in the spray column. The counter-flow of air interacts with the spray and causes droplet deceleration, momentum transfer, and air/droplet entrainment. Understanding the spray/air flow interaction can improve the pressure loss and droplet entrainment models, improve the estimation of entrained air velocity, and provide better insight into the spray column function. Twin-fluid effervescent atomizers, operated at injection pressure of 0.025 MPa and GLR ratios of 2.5 and 5%, were compared with hollow-cone and full-cone atomizers, operated at injection pressures of 0.05 and 0.2 MPa, under the counter-flow conditions. A vertical wind tunnel was used to simulate counter-flow conditions with an air flow velocity ranging from 0 to 1 m/s. The flow was seeded with water mist, generated by the ultrasonic atomizer, so that the velocity of the continuous and discrete phase could be resolved. Simultaneous velocity and droplet size measurement was performed, at various radial positions ranging from Z = 0 mm (atomizer tip position) to Z = 600 mm, with a 1D Phase Doppler anemometer. The spray causes a large distortion of the counter-flow velocity near the atomizer and displaces most of the air towards the walls. Entrained droplet computed using the superficial counter-flow velocity (not influenced by the spray) yield significant errors compared to estimation using the maximum air velocity mainly for sprays with higher momentum. Higher liquid velocity causes larger air entrainment and complicated vortex structure, which govern the air velocity near the atomizer.

PDA, spray column, counter-flow, pressure-swirl atomizer, effervescent atomizer

23.06.2024

ICLASS 2024

Shanghai

10