2022/10/09 by Qiuxiao Wang, Wang, Qiuxiao, Yongzhi Ren +11
Chemical Engineering · Engineering · #Advanced Combustion Engine Technologies #Combustion and flame dynamics #FOS: Physical sciences #Fluid Dynamics (physics.flu-dyn) #Radiative Heat Transfer Studies
paper · pdf · doi:10.48550/arxiv.2210.04181
openalex publication_date 2022/10/09 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
This paper presents an experimental study on the emergence of the central recirculation zone (CRZ) in a V-shaped premixed swirling flame, using simultaneous measurement of particle image velocimetry (PIV) and CH* chemiluminescence. The results show that either increasing the Reynolds number (Re) or decreasing the equivalence ratio (Φ) would facilitate the emergence of CRZ. Further analysis demonstrates that the CRZ characteristics and its emergence are strongly influenced by the inner shear layer (ISL) surrounding the CRZ, while the swirl intensity remains unchanged. Dimensional analysis is performed to understand the underlying mechanism, suggesting the CRZ emergence is controlled by a non-dimensional parameter, Res=|γ|max D/νs, defined based on the maximum ISL intensity (|γ|max), the exit diameter (D), and the kinematic viscosity (νs) of the burnt gas. By estimating the temperature and viscosity with a simple heat-loss model, we show in the |γ|max D-νs regime diagram that the cases with and without CRZ are separated by a single boundary line, corresponding to a critical Res of about 424. This verifies the applicability of the proposed Res criterion to lean-premixed V-shaped swirling flames under various conditions. Unlike most previous works that attribute the CRZ of swirling flames to vortex breakdown, the present work reveals the non-negligible effect of the ISL, especially the CRZ suppression when the ISL is weakened by flame heating.