Plasma-Assisted Stabilization of Lifted Non-premixed Jet Flames

Abstract

The present study experimentally investigates the effects of plasma discharges on the stabilization of lifted non-premixed jet flames in a stream of co-flow air. The plasma discharge is produced on the sharp edge of the fuel nozzle exit, facilitating its impact on flame stabilization. It is observed that the application of plasma discharges has an impact on the enhancement of flame lift-off velocity, lift-off height, and hysteresis phenomenon and leads to plasma-attached flames, plasma-enhanced lifted flames, and plasma-ineffective lifted flames, depending on flame lift-off conditions. A maximum enhancement of approximately 84% is observed for the flame lift-off velocity when the co-flow velocity is sufficiently low. As the co-flow velocity or the jet Reynolds number is low, the flame is anchored at the nozzle by the discharge. As the co-flow velocity or the jet Reynolds number is increased, the flame detaches but with a decrease in lift-off height compared to the flame without the discharge. If the co-flow velocity of the jet Reynolds number is continuously increased such that the flame lift-off height is beyond a critical value, the effect of plasma discharges diminishes and the flame lift-off height becomes comparable to that without plasma discharges. In flame hysteresis studies, both of the flame lift-off and reattachment velocities are increased with 2-fold enhancement when the discharge is present. Spectroscopic study shows that the emission characteristics, particularly for those between 400 and 800 nm, in flames are intensified with the presence of plasma discharge, consistent with the flame luminosity visualization, probably due to the reduced lift-off height that leads to reduced air premixing, resulting in increased soot formation.

Recent Advances in Ammonia Combustion Technology in Thermal Power Generation System for Carbon Emission Reduction

“…Recently, research on stabilization of ammonia flame through plasma has also been conducted [90]. This is a usual method for flame stabilization that has been performed for a long time [91][92][93][94][95][96]. However, in this study, it was experimentally demonstrated that flame stabilization and NOx generation could be simultaneously reduced through plasma-assisted combustion.…”

Experimental and Computational Study of the Combustion Characteristics of Dual-Stage Lean Premixed Flame

“…It should be noted that although most flames in industrial combustors are turbulent, 28 the research should start from laminar conditions. This is for the purpose of avoiding influence from turbulent fluctuation and capturing more accurately the burning information.…”

Investigation on the Regulation of the Combustion Characteristics of a Propane/Air Mixture by Repetitive nSDBD Pretreatment

“…Nonequilibrium plasma has the characteristics of low overall temperature, high utilization of discharge energy, and an obvious activation effect, which can generate a large number of active atoms and groups. Experiments in a continuous-flow combustion reactor had shown that the nonequilibrium plasma generated by continuous discharge could expand the lean burn limit and enhance flame stability. − Therefore, nonequilibrium plasma has significant advantages in stabilizing combustion and improving mixture activity.…”

“…Experiments in a continuous-flow combustion reactor had shown that the nonequilibrium plasma generated by continuous discharge could expand the lean burn limit and enhance flame stability. 18 − 20 Therefore, nonequilibrium plasma has significant advantages in stabilizing combustion and improving mixture activity.…”