Flow Design Using CFD for a Constant-Section Recursive Sequential Combustor

The project MOeBIUS stands for MOmentum-Enhanced Blend of the reactants with recIrculated bUrnt gaseS. It is a new combustion concept based on the principle of recursive sequential combustion (RSC), as described in paper GT2021-59592. The aim is to assert the feasibility of a recursive sequential combustor using CFD simulations and to evaluate the most promising flow design for a 3D printed prototype. This paper focuses on the latest developments of the variant called constant section, with a short overview of the geometry’s design iterations. Based on previous simulation results the combustion chamber is torus-shaped with a double-spiral-like cross section. The simulated domain covers a sector of the torus, with interpolated results to augment the data points. Two air inlets and one fuel inlet (currently modelled with Methane) feed the combustion chamber to create a stable, lean, and continuous flame. Flue gas is partly fed back into the combustion process, this recirculation increases lean combustion robustness and decreases the amount of generated nitrogen oxides. The circular combustion chamber and guiding vanes in the in- an outlet pipes generate a flow dynamic that combines a swirling motion necessary to stabilise the flame to a flow circulation along the torus. This flow pattern is driven by the elevated momentum flux at the injection. The air outlet is designed to enforce interaction between outgoing burnt gasses and fresh inlets while facilitating the split of a fraction of the flue gas that follows the torus’ curvature. The simulations confirm the presence of a large swirl in the chambers section, as well as the maintenance of a circulation in the toroidal direction, which is essential to the concept. This is in good agreement with the desired flow design, and the constant section concept is therefore feasible and valid. Ongoing simulations implying fine-tuning of the parameters are carried out in 3D to ensure stable combustion behaviour and meet expectations in terms of functionality.