A STUDY OF NOX REDUCTION BY ACOUSTIC EXCITATION IN A LIQUID FUELED BURNER

This paper presents the results of a controlled acoustic excitation of a liquid fueled nonpremixed flame as a means of nitric oxide reductio n. The experimental burner is a domestic hot-water heater provided by Viessmann. An actuator is located on the air duct and comprises two pe rforated plates. By changing the speed of rotation of the rotor it is possible to achieve a single frequency excitation of the burner cavity . The industrial version of the burner already features low NOx exhaus t levels (82 ppm at 0% O-2) and satisfies the current European regulat ions concerning pollutant emissions. Its operating point corresponds t o an equivalence ratio of 0.82. It is shown that for a broad range of frequencies (100 Hz to 700 Hz) the overall nitric oxide emissions are reduced up to 15%. Radical imaging of the excited dames shows strong e ffects of the excitation on the dame geometry, especially on the flame length, and gives guidelines to a new, more effective, NOx emission c ontrol using acoustic excitation.