Evaluation of a novel curved vortex exhaust system for pollutant removal

Based on the principle of a column air vortex, a novel curved vortex exhaust system (CVES) is proposed in this study as an alternative for capturing pollutants when a canopy hood cannot be used. Experimental and numerical methods are used to investigate the curved vortex formation process and influencing factors of the CVES, and the effect of geometric parameters and the supply/exhaust flow ratios are investigated to optimise the pollutant capture performance. The evolution of the negative pressure distribution is used to investigate the formation process of the vortex in the CVES. The formation of the curved vortex in the CVES is found to be a top-to-bottom process, and there is a delay of a few seconds before the curved vortex is formed. According to the characteristics of the CVES, the effective pollution source area is proposed as an index to evaluate the performance of the CVES, and the effects of the arc baffle width, back plate angle, exhaust outlet position, and exhaust outlet area on the vortex flow characteristics and effective pollution source area are analysed. The relationship between the supply/ exhaust flow ratio and size of the effective pollution source area is investigated with different exhaust outlet flowrates. The results reveal that with an increase in the exhaust outlet flowrate, the optimal supply/exhaust flow ratio of the CVES gradually decreases from 0.4 to 0.2 and then remains stable. Meanwhile, a larger ventilation flowrate is beneficial for increasing the size of the effective pollution source area.