Study On Structure Optimization Of Ejector For Aerosolizing Powdered Nanoparticles And Its Dispersion Mechanism

A combined experimental-numerical study was performed to reveal the mechanisms of powdered SiO₂?TiO₂ nanoparticle?NP?breakage and establish the relationship between the divergent angle???of a convergent-divergent?C-D?nozzle and nanoparticle size distribution.All distributions of aerosolized NPs obtained through ejectors with varied?were identically log-normal and unimodal.As?increased?from 8°to 20°?,there were identified decreases in GMD?from 216 nm to 189 nm?,mode diameter,and median diameter,while GSD increased slightly?from 1.59 to 1.65?.The parallel negative growth trends of D25 and D75,with slightly decreasing interquartile?D25–D75?ranges,indicated that an increase in?could result in a clear shift of PSDs toward smaller particle sizes.This implied that NP deagglomeration was strengthened and the ejector became more efficient as?increased.Three cross-sections including the C-D nozzle outlet?Section 1?,mixer tube inlet?Section 2?,and central section?Section 3?were selected to estimate the influence of shear stress?|?|?distribution in the ejector on NP aerosolization.Increasing?hardly changed the location of the two inner peaks,but it significantly decreased the values of inner peaks and smoothened|?|distributions.|?|in section 2 with different?exhibited a flat bimodal distribution and the two outer steep peaks?from section 1?disappeared.For|?₀|=0.5 Pa and|?₀|=1 Pa,the ratio of the|?|distribution range of|?|>|?₀|?0.5 Pa<|?₀|<5 Pa?to the entire section span,?,increased significantly as?increased.The growth rate of?decreased apparently for|?₀|ranging from 2 Pa to 4 Pa,but for|?₀|?5 Pa,?stopped growing in section 1.The maximum value of|?|exerted no significant influence on NP dispersion.The smoothness and flatness of the|?|distribution determined whether the powdered NPs could experience enough shear aerodynamics and be dispersed thoroughly.This played a crucial role in NP aerosolization.The mechanism of the effect of?on NP dispersion resulted in smooth and flat|?|distributions.This helped expand|?|distribution to increase the possibility of powdered NPs experiencing stronger shear flow as?increased.