Flow-field characteristics and spray characteristics of medical air-compressing nebulizer

A medical air-compressing nebulizer used for inhalation therapy is a special type of two-fluid atomizer. Although two-fluid nebulizers have been studied for decades, the flow-field and spray characteristics of medical air-compressing nebulizers used for aerosol drug delivery remain underexplored. This study aimed to investigate the interaction between airflow and liquid as well as the effects of different structural parameters on the velocity distribution, pressure distribution, gas flow rate, water flow rate, gas-liquid ratio, spray concentration, and aerosol size through numerical simulations and spray experiments. It primarily focused on three structural parameters: orifice diameter (0.4, 0.6, 0.8, 1.0 mm), baffle width of the atomizing core (1.0, 2.0, 3.0, and 5.0 mm), and distance between the baffle and orifice (1.0, 1.5, 2.0, 2.5 mm). Numerical simulations were performed to evaluate the atomization process and flow-field characteristics, and spray experiments were conducted to assess the spray characteristics. We found that the atomization process is characterized by periodic pulsations, and the shear and impact forces between the gas and liquid are the primary causes of atomization. Furthermore, the gas-liquid ratio is the main factor affecting the aerosol size when the baffle width is constant, whereas the baffle width becomes dominant when it is changed. In the structural design of this type of nebulizer, the orifice diameter should be minimized to reduce the energy consumption while meeting the basic output-flow requirements. An appropriate increase in the baffle width facilitated a reduction in the aerosol size. A higher spray concentration was obtained by controlling the distance between the baffle and orifice at 1.5 mm. This study provides theoretical guidance for the structural design of medical air compression nebulizers. The recommended parameters can effectively reduce the aerosol size, increase the spray concentration, and improve the overall performance of medical nebulizers.