NITROGEN-OXIDES (NOX) EMISSION CONTROL IN A LIQUID FUEL DIFFUSION FLAME USING ACOUSTIC EXCITATION

Nitrogen oxides (NOx) emission control will be a major issue in the up coming years in the development of domestic boilers as well as automot ive or aircraft engines. Pulsed combustion offers an alternative, low- energy solution. In this paper, we demonstrate the efficiency of this pollutant reduction technique when applied to a 20 kW boiler burning d omestic fuel oil. An actuator is located on the air duct. Two kinds of actuators have been successfully tested: a loudspeaker and a rotary v alve. Both produce frequencies ranging from 100 Hz to 1000 Hz. Nitroge n oxide emissions can be reduced up to 20%, The feasibility of this co ncept has been proven on a larger-scale device (840 kW, operating with liquid fuel). The mechanisms involved under excitation are examined u sing optical diagnostics. Results show a strong reorganization of the flow configuration and flame structure. An annular vortex is formed at each cycle at the trailing edge of the flame holder. This analysis pr ovides guidelines for a new, more effective NOx emission control using acoustic excitation.