Numerical Analysis of Flame Shape Impact On the Performance of Fuel Staging in a Lean-Burn Aeronautical Burner

Abstract The BIMER combustor is a lab-scale burner investigating fuel staging techniques as a stabilisation strategy for lean premixed prevaporized combustion for aeronautical applications. Two stages compose its injection system: the pilot and the multipoint stages. The staging factor is defined as the ratio of fuel mass flow rate injected through the pilot stage over the total one. As three flame shapes were found experimentally, Large-Eddy Simulations are performed in this study to assess the impact of the flame shape on the combustion regime and stability of the burner. Two operating conditions were explored experimentally (pilot-only and multipoint-dominated) to validate the simulations and compare the three flames. An additional multipoint-only condition is also investigated for the V flame. The burning regimes (premixed and non-premixed) and noise signatures (as a function of fuel staging) were compared to check whether these flames could benefit from the staging strategy. The M and Tulip flame combustion regimes are little affected by fuel staging, remaining mostly premixed and non-premixed, respectively, regardless of fuel staging. In opposition, the V flame changes from being mostly non-premixed to completely premixed when the injection is changed from pilot-only to multipoint-only. For the same staging evolution, the V flame also emits less noise for the investigated points. These results show that the V flame shape is the only one that allows this burner to benefit from an efficient fuel staging strategy.