Measurement of the vapor-phase and liquid-phase fuel distributions downstream of an integrated flameholder in heated stream

Understanding the vapor-phase and liquid-phase fuel distributions are necessary for conducting combustion performance research, especially under high-temperature inflow or fuel conditions. In this study, we propose physical and optical quantitative methods for measuring the total fuel distribution in the dual-modal (after-burner/ramjet) combustor with an integrated flameholder. The vapor-phase equivalence ratio is deduced from the n-decane (C10H22) concentration (determined using an n-decane detector). Raw images of the fuel spray field are captured using a high-speed camera. The droplets Sauter mean diameter (SMD) can be obtained using an image processing technology. The liquid-phase equivalence ratio is further derived by analyzing the droplet size and distribution. Finally, the total equivalence ratio can be obtained by adding the equivalence ratios of the vapor and liquid phases. The vapor-phase and liquid-phase fuel distributions were measured on different cross-sections downstream of an integrated flameholder. The global equivalence ratio, inflow velocity, inflow temperature, and fuel temperature were set to empty set=0.3-0.6, V-1 = 50m/s, T-1 = 450K, and T-f = 373K, respectively. Further, the vapor- and liquid-phase equivalence ratios for the measurement points increased and decreased, respectively, with increasing flow distance. The flow characteristics and the vapor-phase fuel distribution were consistent behind the flameholder, confirming the rationality of deducing the vapor-phase fuel concentration from the n-decane concentration. The maximum error of the SMD obtained using the image processing technology was lower than the value reported in the literature (5.1%). Finally, the total equivalence ratio was almost conserved along the flow distance, proving the credibility of the proposed measurement methods.