Interference effects between multiple bluff body flameholders

A general program was undertaken to determine the interference effects between multiple bluff body flameholders. The flameholders used for these experiments were 1/4 inch diameter water cooled cylinders tested in a 1 by 4 inch combustion chamber. Stability limits, flame geometry, and relative combustion efficiency were determined as functions of flameholder spacing and number. The results of the tests showed that the maximum blowoff velocity decreased as the number of flameholders increased. This reduction was primarily due to the increase in the blockage ratio. In addition, a reduction in maximum blowoff velocity occurred when the flameholders were moved from the symmetrical arrangement in the duct. A combustion instability characterized by a loud, high frequency noise occurred over well defined ranges of fuel air ratio, gas velocity, and flameholder spacing. The recirculation zone length and flame widths were primarily functions of blockage ratio, modified slightly by flameholder separation. No large scale interaction occurred between the wakes of adjacent flameholders. Combustion efficiency increased with the number of flameholders and was little affected by flameholder separation