Characteristics of Induction-Type Electrostatic Water Mist and Its Suppression Performance on Methane Diffusion Flames

In response to the problems of poor atomization quality and limited fire suppression efficiency in conventional water mist fire suppression systems, electrostatic water mist fire suppression technology significantly enhances flame suppression performance through electrohydrodynamic effects and represents a key technology for achieving efficient and precise fire suppression. In this study, an induction-type charging system with a needle – ring electrode configuration was employed to investigate the effects of key factors such as voltage, electrode geometric parameters, and atomization pressure on the characteristics of electrostatic water mist. A comprehensive experimental platform was established, incorporating droplet size analysis, surface tension measurement, mass flux density determination, temperature field monitoring, and thermal radiation detection. Suppression experiments on methane diffusion flames were conducted within an electrostatic voltage range of 0–14 kV. Building upon existing research that characterizes mist field properties using single electrical parameters such as droplet charge-to-mass ratio, this study further establishes a multi-parameter evaluation system for mist fields. This system comprehensively characterizes droplet size distribution, spatial structure of mist cones, and evolution characteristics of mist flux, enabling multidimensional analysis of the coupling characteristics between electrostatic fine water mist fields and flames. The optimal operating parameters of the electrostatic water mist system were determined as follows: voltage of 8–10 kV, electrode ring diameter of 80–90 mm, needle – ring spacing of 15–20 mm, and spray pressure of 0.8–1.0 MPa. The results indicate that, under optimal operating conditions, the median droplet diameter (D50) decreased by 34.07%, surface tension was reduced by 15%, the effective spray cone angle increased by 10°, and the peak flux density increased by approximately 11.3%. Driven by Coulomb forces, the charged water mist was directionally transported toward the flame root, enabling precise fire suppression, with the extinction time reduced by approximately 69% and the radiative heat flux reduction reaching about 75–80%. The electrohydrodynamically enhanced water mist fire suppression mechanism was revealed: the electric field induces negative charges on the droplets and accelerates their directional transport toward the reaction zone under EHD effects; electrostatic attraction with the positively charged flame ion region promotes droplet enrichment in the flame core, thereby reducing temperature and weakening reaction rates through enhanced evaporative heat absorption. The synergistic action of multiple mechanisms ultimately achieves efficient fire suppression. The results of this study provide experimental references for mechanism investigation and system optimization of electrostatic water mist fire suppression.