A study of NOX production in air heated by laser discharges: Effect of energy, wavelength, multiple discharges and pressure

An experimental study on the production of NOX in air heated under the action of a concentrated laser beam is presented. In this experiment laser induced plasma was produced in air in a closed Teflon chamber of inner volume 1600 cm3 by focusing a laser beam with either the wavelength of 1064 or 532 nm from a Q-switched Nd:YAG laser. The NOX production was measured by chemiluminescence method and the possible effect of wavelengths, multiple discharges, and pressure on the yield of NOX was studied. The results show that within the studied plasma energy range of 26–253 mJ for 532 nm beam and 16–610 mJ for 1064 nm beam, the NOX production scales linearly with the dissipated plasma energy. For a given energy, 532 nm beam produces more NOX in air at atmospheric pressure than the 1064 nm beam. In an attempt to see the possible influence of multiple discharges on the production of NOX, discharges were created using 2–8 pulses with a repetition rate of 10 pulses per second in stationary air at atmospheric pressure. The results indicate that a certain amount of the NOX created by a given pulse is destroyed by the subsequent pulses. In order to study the pressure dependence of the NOX production, the pressure was varied from 16 to 100 kPa in the chamber and it was found that the NOX production efficiency scales linearly with pressure.