High-Fidelity Simulation for the Lean Blow-Out Analysis of an Industrial Burner Operated with Artificial Exhaust Gas Recirculation

In this paper an enhanced thickened flame model (TFM) capable of accounting for both premixed and nonpremixed combustion regimes is leveraged to reproduce the extinction limit of an industrial burner operating at atmospheric pressure with a vitiated oxidizer. CO2 is employed to dilute the air, simulating the effects of the exhaust gas recirculation (EGR). The CO2 content in the oxidizer is progressively increased until the occurrence of lean blow-out (LBO). Due to practical constraints, the numerical procedure consists of an acceleration of the experiment trend of O2 depletion. In this context, a dedicated strategy for the dynamic calculation of the laminar properties of the flame—i.e., the laminar flame speed (LFS) and laminar flame thickness (LFT)—as a function of the local elemental mass fraction is used. This quantity evolves during the simulation in response to the time-dependent boundary conditions. It will be demonstrated that the proposed approach is capable of successfully capturing the flame characteristics of both the stable conditions and the transient phase leading to blow-out. In fact, it is found that the adopted combustion model is able to predict the LBO at the same oxidizer composition detected experimentally. Moreover, as extinction is approached, the numerical model reproduces the same dynamics observed during the reactive test. A detailed comparison between the numerical results and experimental measurements during this phase is presented and discussed.