Research On Phase Change Evaporation And Its Influence In The Interaction Of Plasma And Water Surface

Atmospheric pressure gas-liquid two-phase discharge has extensive applications in the fields of biomedicine,advanced material preparation,and environmental protection.Exploring the internal interaction mechanism of plasma gas-liquid two-phase discharge can provide important theoretical basis and guiding ideas for the development of applied research.In the gas-liquid two-phase discharge process,the change of water vapor generated by the liquid surface phase participates in the discharge process at all times.However,due to the unclear spatiotemporal behavior of water vapor,the experimental diagnosis and simulation of the gas-liquid two-phase discharge have meet great difficulties.The physical and chemical evolution mechanism leading to the current gas-liquid two-phase discharge is still unclear.Therefore,studying the phase transition process of the liquid surface,especially the temporal and spatial behavior of water vapor,will provide an important theoretical basis for exploring the complex interaction process between the plasma and the liquid surface.This paper focuses on the following aspects of research work around the gas-liquid two-phase discharge of a typical pin-water electrode structure at atmospheric pressure:1)A stable atmospheric pressure argon plasma generator based on a single-pin-water electrode structure is constructed.The device is excited by a high-voltage DC power supply.Based on the U-tube structure,it avoids the liquid level jitter caused by the peristaltic pump during the solution cycle that the stable Ar glow discharge can be maintained,which provides important support for accurately diagnosing the phase change evaporation behavior during the discharge process.2)Build a tunable diode laser absorption spectroscopy(TDLAS)diagnostic platform,and accurately detect the yield of water vapor produced by the discharge-induced liquid surface phase change.The effects of voltage polarity,discharge current,and solution temperature on the amount of water vapor generated are studied.Experiments show that the water vapor yield when the pin electrode is anode is distinctly higher than that of cathode,and this trend becomes more obvious with the rise of discharge current.The important contribution of positive ion bombardment inducing liquid surface phase change is determined,which accounts for more than 50%;at the same time,it is found that the lower the temperature of the solution,the less water vapor is generated,and the linear trend of liquid surface evaporation and solution temperature is obtained.3)Based on the laser Rayleigh scattering method,the gas temperature spatial distribution behavior in the vicinity of the liquid surface discharge area is quantitatively determined.The gas temperature obeys an obvious Gaussian distribution on the cross section of the plasma center.The maximum gas temperature is 600-700 K and 400-600K when the needle electrode is positive polarity and 400-600 K,and the profile increases with the increase of current.4)Based on the gas temperature distribution,combined with laser-induced fluorescence and broadband ultraviolet absorption methods,the absolute density of OH radicals and their spatial distribution behavior in the area close to the liquid surface discharge area are quantitatively determined;the results show that the density of OH radicals almost obeys the Gaussian distribution and reaches its maximum value at the discharge center,the density of OH radicals is positively correlated with the amount of water vapor generated,and the latter significantly affects the generation and distribution of the former.5)Based on the liquid phase chemical analysis,the important chemical components produced by the discharge induced liquid phase,including H₂O₂ and OH radicals,were quantitatively detected.The regular pattern of the impact of different experimental parameters on the production of chemical active ingredients were obtained;combined with the above diagnostic results in the gas phase region,the influence mechanism of the liquid surface phase change evaporation on the liquid active ingredients is revealed.It provides experimental support and improvement directions for exploring and constructing atmospheric pressure gas-liquid two-phase discharge theory system and promoting the development of practical applications.