Entrainment studies in inverse jet flame port burner

Abstract

The present investigation aims to investigate the fundamental understanding of entrainment characteristics of a Circumferentially Arranged Fuel Port Inverse Jet Flame Burner (CAFP IJF). The high-speed flame Schlieren visualization is carried out experimentally for 8, 18 and 32 port CAFP IJF burner for varying air–fuel operating conditions to visualize the entrainment characteristics. The region of fuel entrainment is found to occur within the base region whereas intense mixing and combustion is observed in transition and main flame region respectively. The 32 port CAFP IJF burner exhibits enhanced entrainment characteristics and augmented ambient air–jet interactions for similar operating conditions as compared to a lesser number of circumferential fuel ports. The jet breakup length is employed to identify the interaction of ambient air with the combustion driven vorticial structures. The steady laminar flamelet model is used to investigate the entrainment characteristics of a 32 port CAFP IJF burner. The calculated entrainment coefficients at different operating conditions for reacting and non-reacting CAFP IJF indicate that the entrainment rate for reacting jet is lower due to the diminution of density across the flame cross-section at each axial plane. The strong ambient air entrainment is observed within the interstitial space between consecutive fuel ports which promote air–fuel mixing. Additionally, unlike in Normal Jet Flame (NJF), a clear distinction between air and fuel entrainment is found to be essential for the current CAFP IJF burner configuration.