Abstract
On research of plasma assisted combustion, effects of electric and plasma discharges in DC, AC and pulse forms on reattachment of a lifted flame have attracted extensive attention. However, the detailed plasma assisted reattachment process and mechanism and roles of induced corona discharge and corona-induced ozone on the reattachment process are still unclear and undocumented. The forced reattachment process of a lifted diffusion jet flame by repetitive DC electric pulse discharges was experimentally investigated in this study using high-speed flame imaging, conditioned particle image velocimetry (PIV), and planar ozone concentration imaging. The forced reattachment process can be divided into three stages in sequence: ionic wind prior to corona initiation, corona initiation, and corona enhancement propagation. The conditioned PIV results showed that the instantaneous flame base propagation velocity is sufficiently enhanced beyond the laminar burning velocity for high pulse-repetition-frequency (PRF) cases at the instant of pulse discharge (on pulse) due to the enhanced oxidation of the corona induced ozone. By observing the dynamic flame-base behavior and evolution characteristics of the short-lived corona induced ozone for various PRFs, the novel forced reattachment process and mechanism of a lifted jet flame induced by repetitive DC electric pulse discharges is proposed.
Highlights
Fuel lean combustion of low carbon-content fuel can provide high energy efficiency and emit low carbon pollution, it generally produces NOx emission
The variation of mean liftoff heights with pulse repetition frequencies (PRFs) for various Ve cases is shown in Figure 2, which is to compare with the data obtained from natural lifted jet flame without pulsed discharges (PRF = 0 Hz) represented by the hollowed symbols
According to the lifted propane-jet diffusion flame by a repetitive directive current (DC) pulsed discharge with a proposed results of ozone density distribution in the corona enhancement stage, the considerable single-electrode configuration have been experimentally investigated in this study
Summary
Fuel lean combustion of low carbon-content fuel can provide high energy efficiency and emit low carbon pollution, it generally produces NOx emission. The second enhancement pathway is that high energy electrons, ions, and molecules produced from plasma lead to the subsequent production of active radicals and reactive species in the fuel and air streams. Plasma generated ionic wind and flow motion via the Coulomb and Lorentz forces provides hydrodynamic enhancement by changing local velocity [4]. Since these effects are coupled to combustion system, it is difficult to isolate them and clearly describe the progressive mechanisms individually
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