Effect of humidity on gas temperature in the afterglow of pulsed positive corona discharge

The effects of humidity on gas temperature in the afterglow of a pulsed positive corona discharge are studied. The gas temperature is measured using the laser-induced fluorescence (LIF) of NO molecules. The discharge occurs in a 13 mm point-to-plane gap under atmospheric pressure. When the water vapor concentration in air is increased from 0.5% to 2.4%, the temperature increases from 550 to 850 K near the anode tip, and from 350 to 650 K at a position 2.5 mm from the anode tip. The gas heating in the humid environment is due to the fast vibration-to-vibration processes of the O 2 –H 2 O and N 2 –H 2 O systems and the extremely rapid vibration-to-translation process of the H 2 O–H 2 O system. These processes accelerate the transfer of energy from O 2 ( v ) and N 2 ( v ) to translational energy. Measurements of the LIF of O 2 ( v = 6) show that the decay rate of O 2 ( v ) density is increased by humidification.