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• The flame and flow dynamics under air flow pulsations are resolved by performing validated LES and simultaneous OH-PLIF/PIV. • Temporal variations of stretch rate and heat release rate can be used as a criterion for flame extinction/reignition. • A novel decoupled simulation which integrates the plasma source terms and the CFD model is developed. • Thermal and kinetic effects of microsecond repetitively pulsed discharge on combustion are quantitatively interpreted. This paper intensively investigates the inlet pulsation-induced extinction of a premixed swirl flame (PSF) and its plasma-assisted stabilization using the microsecond repetitively pulsed (MRP) discharge. A well-designed low-frequency flow pulsation is applied to the air feedline for the mimicking of transient operations/disturbances in practical engines, which exhibits significant deterioration on the lean blowout (LBO) limit. The MRP discharge is utilized to improve the stability of perturbed flames. It extends the LBO limit at a proper time delay between the air flow pulsation and the discharge, with discharge power less than 1% of the combustion power. Further, the validated large-eddy simulations (LES) and the simultaneous OH planar laser-induced fluorescence/particle imaging velocimetry (OH-PLIF/PIV) measurements are performed to capture the unsteady evolution of flames approaching lean blowout. The nonlinear flame response to the flow pulsation quantitatively reveals the phase difference between the maximum local stretch rates (κ max) and volumetric heat release rates (q ̇ c). A combined effect of the excessive stretch and the reduction of heat release due to flow pulsation can be used to interpret the flame extinction. Finally, a novel LES-ZDPlasKin combined approach, which decouples the discharge and combustion processes, is dexterously developed to simulate plasma-assisted combustion behaviors. The reignition and stabilization due to the plasma effects are well reproduced in the predictive model, pronouncing the indispensable and synergistic thermal and kinetic effects of the MRP discharge on flame stabilization. [ABSTRACT FROM AUTHOR]

• A stable ethanol spray tubular flame is obtained with wide operation ranges and low emissions of CO and NO x. • The ethanol spray and flame structures are characterized by laser diameter analyzing and OH-PLIF imaging. • The flame lift-off characteristics are investigated under various tangential velocities, atomizing gases and ethanol flow rates. • The Damköhler numbers are theoretically assessed to analyze the flame lift-off behavior. This study proposes an efficient technique to burn ethanol spray in an intense swirling air flow and investigates the mechanism of flame lift-off. On the basis of typical tubular burners for gaseous fuels, ethanol spray was axially induced and mixed with the tangentially injected air under room temperature, yielding the ethanol spray tubular flames under various operating conditions. The results show that from an ultra-lean condition of global equivalence ratio of 0.1 to the rich condition, two typical flames, namely attached and lifted tubular flames, were established. Then, the structure of the ethanol spray tubular flame was specified by temperature measurements, OH-PLIF imaging, indicating its overwhelming aerodynamic and thermal stability with low pollutant emissions. Meanwhile, a flue gas analyzer was used to characterize the gas composition in the hot exhaust. It is found that the burner can achieve very low emissions of both CO and NO x , illustrating high combustion completeness under both attached and lifted flame conditions. To give a better understanding and make fully utilization of spray tubular flames, a parametric study was carried out to investigate the effects of the tangentially swirling air flow, the flow rate and oxygen concentration of atomizing gas, and the flow rate of liquid ethanol. Generally, an attached flame is lifted under a higher tangential velocity of air flow; increasing oxygen concentration of the atomizing gas flow leads to the height decrease of the flame lift-off, even the reattachment of the lifted flame; by raising the ethanol flow rate to exceed a critical value, the flame also lifts off. Furthermore, the evaporation time of droplets, residence time and chemical reaction time were calculated to quantify the flame lift-off behavior. The lifted flame can be established only when the evaporation time is larger than both the reaction time and the residence time. [ABSTRACT FROM AUTHOR]