At a given power level, lean premixed (DLE) gas turbines vary equivalence ratio (ϕ) for optimal performance. This range is usually determined by variations in ambient conditions, acoustic response of the system, and emissions trade-off (e.g. between NOx and CO). In this work, the effects of ϕ variation on premixed jet flame lengths are investigated, by modeling the pressurized jet experiments of Griebel et al. [1]. While previous modeling of these experiments focused on a priori tabulated chemistry based methods, in this work we investigate an approach that represents finite-rate effects explicitly using skeletal chemistry (16 species, 41 reactions) in RANS and LES. Two equivalence ratios (ϕ = 0.56 and ϕ = 0.43) corresponding to the two extremes of flame lengths are chosen from the experimental database for 673K mixture preheat, 5 bar and 40 m/s jet velocity. A better correspondence with the experimentally measured flame length was achieved for ϕ = 0.43 than for ϕ = 0.56 indicating that the model is suitable when finite-rate effects are dominant but requires extensions for flames closer to the flamelet regime. It was found, further, that the RANS-EDC models failed to predict the confined turbulent jet development, as well as the flame lengths accurately, and demonstrated that scale resolution is required even for a relatively simple configuration.
CFD modeling of pyrolysis oil combustion using finite rate chemistry
