Quantify the slow decay of conversion with increasing gap distance

Establish a quantitative explanation for the observed slow decay of relative n-butane conversion with increasing surface dielectric barrier discharge (SDBD) electrode gap distance when energy density is held constant, and identify the additional contributing factors beyond the measured middle-gap vorticity that account for this behavior.

Background

The study compares volatile organic compound (VOC) conversion data with flow-field characteristics induced by a surface dielectric barrier discharge (SDBD). Using particle image velocimetry (PIV), the authors analyze vorticity and turbulent kinetic energy (TKE) to correlate fluid structures with conversion behavior. They find local peaks in conversion around 16–22 mm gap distance and observe that integrated absolute vorticity in a fixed middle-gap window decays rapidly beyond ~20 mm.

While the vorticity in the analyzed region decreases faster than the conversion, suggesting enhanced gas mixing effects, the authors note that the slower decay of conversion compared to vorticity is not quantitatively understood. They hypothesize that other factors (e.g., increased vortex velocities at larger gaps) may influence conversion, but explicitly state that the slow decay cannot yet be fully quantified.