Effect of humidity on atmospheric pressure humid air discharge—interpretation from the perspective of detachment reactions

Abstract

Abstract Detachment reactions have an important influence on the decreasing trend of electron density after high-field excitation, yet existing studies on humidity’s impact on discharge have failed to address this issue. To bridge this gap, we utilize a validated global model to explore how species density changes during humid air discharge corona inception. Our results indicate that humidity influences the detachment reaction rate by altering the negative ion composition. In dry conditions, the primary species involved in detachment reactions is O− ions. However, in environments with higher water vapor density, O− ions primarily react with water molecules, depleting O− ions. This change results in H− ions becoming the main detachment negative ions during the pulse. The greater the rate of the Detachment reaction the slower the decrease in electron density, and a rise in humidity causes the Detachment reaction to peak at a higher value and have a shorter duration, thus causing the electron density to decrease more rapidly. This discovery offers fresh insights into humidity’s effect on discharges. Additionally, we introduce the concept of the average negative ion detachment reaction rate constant, denoted as k d, to quantify the impact of detachment reactions within the three-element model.