Qunxing Huang

Efficient atomization of liquid fuels over a broad range of physical properties is important for practical utilization. However, the response of pressure-swirl atomization to substantial variations in liquid viscosity remains insufficiently understood, particularly the transition from a hollow-cone atomization to a degraded atomization regime. A volume-of-fluid numerical method is employed to investigate liquid-film formation and primary breakup in a pressure-swirl nozzle over a range of viscosities and surface tensions of waste-derived pyrolysis oils in this study. The results show that increasing viscosity substantially alters the liquid-film morphology, cone angle, and primary breakup behavior. At high Reynolds numbers, a hollow-cone liquid film develops and undergoes interfacial destabilization and breakup. As the Reynolds number decreases, the hollow-cone morphology is replaced by a spiral-blade morphology. The high-viscosity condition is accompanied by substantially weakened internal swirl and circumferential mixing, allowing the liquid streams originating from individual tangential slots to retain distinct spiral paths. Consequently, centrifugal expansion is suppressed and continuous liquid persists in the central region. These results clarify the flow characteristics associated with the viscosity-dominated transition from hollow-cone to spiral-blade atomization and provide insight into the pressure-swirl atomization of liquids with a broad range of viscosities.

Complete degradation of microplastics can be achieved within 2–4 minutes, with non-hazardous CO ₂ as nearly the only gas product.

The huge market demand, large annual yield, wide application, and massive discard of plastics and tires have brought severe environmental issues. It is urgent to find an efficient way to recycle waste plastics and tires as high-value chemicals and energy fuels. Pyrolysis has long been considered a clean and productive technology. However, waste polymers are complex mixtures. The co-pyrolysis of the mixture is difficult but essential for energy and material recovery. This study investigated the co-pyrolysis of PE, PS, PVC, and TW using Thermogravimetric analysis, Pyrolysis-Gas Chromatography/Mass Spectrometry, and lab scale experiments at 550°C. The results revealed significant synergistic effects between different polymers. The interaction effect was reflected by thermal behavior, product distribution, and product components. There were also differences between lab scale programmed heating pyrolysis and micro-scale fast pyrolysis. The interaction of PE/PVC and PE/TW improved olefin yield due to the synergistic effect. While aromatics formation was promoted by PS/TW and PVC/TW. It can be deduced that PE had a positive effect on chain scission reaction, while PS and PVC induced cyclization and aromatization reactions. The possible reaction pathways were proposed to get a better understanding of co-pyrolysis. Our study provided theoretical guidance for mixed polymer co-pyrolysis and product regulation.