Investigation of flame acoustic excitation of a gas burner

Abstract

Combustion in ultrasonic field is a promising combustion technology as it provides high combustion efficiency and low pollutant emission. Imposing acoustic oscillations on flame front enhances the turbulent mixing, resulting in reduced NOxand CO emissions and reduced flame length. The acoustic field can be generated by using two types of devices: the piezoelectric devices and the sonic nozzle. In this paper, the combustion characteristics in ultrasonic field generated by a sonic nozzle attached to a gas burner have been experimentally and numerically studied. The acoustic intensity can be adjusted by modifying the pressure of feeding air or the nozzle size. The numerical model was validated against experimental data on CO concentration and temperature and was used to study the burner performance for different operation conditions (different air pressures and different nozzle sizes). For a given air pressure and nozzle size, the NOxemissions drop from 200 mg/Nm3 to 150 mg/Nm3, the CO emissions decrease from 125 mg/Nm3 to 100 mg/Nm3 and combustion efficiency increases from 94% to about 96%. The temperature field, with slightly lower temperatures, has more uniform distribution in the flame.

Keywords

• Combustion
• Ultrasonic field
• Annular sonic nozzle
• Burner performance