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In this paper, six kinds of two-stage ESPs with various ratios of charger and collector units are designed to research the capture enhancement mechanism of submicron particles. The working conditions are optimized by studying the influence of gas velocity, charger current, and electric field strength of collector. Results show that the electrostatic field characteristics of the two-stage ESP with Ra = 1/6 is beneficial to improve the collection efficiency while slightly less stable. The indicator factor of particle charging enhancement effect of two-stage ESP with Ra = 6/1 fluctuates between 0.06 and 0.1, which suggests that the two-stage ESP with a higher proportion of charger units cannot achieve the satisfying performance for the limitation of ionic wind effect. Under comprehensive consideration of ionic wind effect and ozone emission, the two-stage ESP with Ra = 2/5 is selected at the first priority by exerting the advantages of fully particle charging and enough collection space, which has a strong potential in both particle charging enhancement and electric field enhancement. However, for improving the collection efficiency of submicron particle with a size ranging from 0.2 to 0.5 µm which suffers from both of weak particle charging and agglomeration effect, the two-stage ESP with Ra = 4/3 is not recommended. [Display omitted] • Submicron particles with the lowest collection efficiency are selected as target. • Capture enhancement mechanism is investigated by designing two-stage ESPs. • Working conditions are optimized by studying the effect of operating parameters. • The electrostatic capture equipment with appropriate unit proportion is selected. [ABSTRACT FROM AUTHOR]

[Display omitted] • Operando observation system is constructed to make in situ test on lab-on-a-chip. • Image processing method is developed based on automatic object detection. • It is first-time visualization of dynamic deposition process of submicron particle. • The growth site and direction of particle chain are investigated systematically. • This work confirms the effect of drag force on ultimate height of particle chain. Submicron particle is a harmful air pollutant due to size effect, gathering characteristic and biological activity, which not only causes a serious threat to human health and public sanitary security, but also is difficult to capture with lowest removal efficiency. Here, Operando investigation system is constructed to explore deposition characteristics of submicron particles in electric-flow coupled fields through combining microfluidic technology for forming micro electric field on the lab-on-a-chip with micro-visualization technology for capturing dynamic deposition process. Besides, based on object detection and deep learning, an image processing method is developed which can realize automatic object detection and rapid extraction of required information. Results show that particle chain grows preferentially from the convex position to prove the influence of electrode surface roughness on the growth site. The global electric field has a positive effect on keeping particle chain growing up at upright direction, and the growth process of particle chain is proposed: forming growth site stage, grow fast stage and fluctuation stage. Particle velocity in the airflow direction presents a decrease trend during the process particle migrates towards to electrode surface, which proves the direct influence of boundary layer effect on the ultimate height of particle chain. [ABSTRACT FROM AUTHOR]

In this paper, aiming at PM 1, namely submicron particles which are the most difficult to remove in traditional purification technologies, it tries to improve their removal efficiency depending on collision enhancement and agglomeration effect. The effect of electric field and plate structure on collision enhancement is studied. Besides, a novel structure of corrugated plate is put forward and its removal performance is compared with parallel plate. Results show that it confirms the key function of the external electric field on the enhancement of particle collision through the trajectory visualization of particle streams with different polarity charging types. The intense turbulence quickens the particle collision and agglomeration in corrugated plate, and the enhancement of electric field around the bend can bring a quick capture firstly, and then the nonuniformity of electric field also leads to the positive effect of particle collision. Corrugated plate can achieve a 12% improvement of removal efficiency for PM 1 compared with traditional parallel plate, under consideration of collision enhancement brought by the airflow arrangement and agglomeration effect under Coulomb force between positive and negative particles. [Display omitted] • Collision enhancement in external electric field is investigated through visualization and simulation. • Corrugated plate proves to achieve a 12% improvement of removal efficiency for submicron particles. • Collision model based on Coulomb force is developed to study agglomeration effect. [ABSTRACT FROM AUTHOR]