EFFECTS OF DIRECT CURRENT ELECTRIC FIELD ON THE BLOWOFF CHARACTERISTICS OF BLUFF-BODY STABILIZED CONICAL PREMIXED FLAMES

An experimental study was conducted on the stability enhancement of conical premixed flames by application of direct current electric fields. Turbulent conical premixed flames were stabilized at the tip of a circular cylindrical bluff-body flame holder. An electric field was set up between a positively charged upper electrode and a grounded flame holder to determine its effects on the lean limit stability characteristics. In these experiments, the flame blowoff equivalence ratios were determined as a function of mixture velocity, electric field strength, and the electrode configuration. It was found that the most pronounced effects were observed at the lowest mixture velocities in this study of about 5.0 m/s with the influence of the electric field virtually disappearing at higher velocities of 10 to 15 m/s. The maximum reduction in blowoff equivalence ratios was 4 to 5% at the low-velocity conditions. These findings are consistent with the estimates of the ionic wind velocities expected in hydrocarbon/air flames and point to the rather weak electric field effect for applications in high-speed premixed flame stabilization.