OH Chemiluminescence Characteristics of the RP‑3 Fueled Dual-Swirl Direct-Mixing Combustor

The flame structure characteristics of the RP-3 fueled dual-swirl direct-mixing combustor are studied experimentally. The flame shape is marked by the OH* radical, which is captured by a CMOS camera with an image intensifier. The flow fields and spray distributions are obtained by particle image velocimetry. The variation of pilot/main-stage flame structure with global fuel-air ratio (FAR), fuel ratio (FR), pilot/main-stage swirl numbers (S p and S m), and Δp/p (total pressure loss coefficient) is further investigated. The typical flame structure, consisting of two main-stage combustion zones (pilot-stage and main-stage combustion zones), is first analyzed. Then, according to the relationship between integral OH* intensity and global heat release rate, increasing swirl number will weaken the effect of strain rate on OH* chemiluminescence. The global FAR has little impact on the flame structure, while modifying the FR will alter the flame mode. The influence of the S p on the flame structure is more significant than that of the S m. Within the range of experimental conditions, the greater the swirl number, the smaller the Δp/p is required to obtain the maximum OH* radical intensity. The addition of non-swirl flow in the main-stage swirler can improve the stability of the pilot-stage flame. The equivalent swirl number is further evaluated by the neural network.