Combustion dynamic stability analysis in stratified-rotation ethanol/air flame

The flame-dynamic stability and internal mechanism in a stratified-rotation ethanol/air flame are investigated through the utilization of a stratified vortex-tube combustor based on an advanced numerical calculation method. The performance of flame-dynamic and combustion stability is examined by evaluating the stability limit, pressure fluctuation, and flame topology. Results demonstrate that the stratified vortex-tube combustor exhibits excellent combustion and flame-dynamic stabilities, with the lean stability limit consistently below 0.2 and pressure fluctuations within 2000 Pa, accompanied by a uniform flame topology without significant temporal variations over time. The burning velocity displays good adaptability to flow field disturbances, aligning well with the normal flow velocity on the flamelet throughout time. Slight variations in flame topology result in weak heat release fluctuations, effectively suppressing fluid disturbances in the post-flame zone. Decreased momentum flux and its alterations in the post-flame zone play a crucial role in achieving flame-dynamic stability due to intense momentum exchange within this highly rotating reactive flow environment. The Rayleigh parameter and flame transfer function are employed to quantify flame-dynamic stability, revealing that both weak thermo-acoustic coupling degree and limited response level of heat release rate fluctuations to fluid fluctuations significantly contribute to maintaining stable flames. These findings systematically elucidate underlying mechanisms responsible for achieving robust flame-dynamic stability observed within this highly rotating reactive environment.