Analyse numérique de l'interaction entre une chambre de combustion rotative à détonation et une turbine axiale

A Rotating Detonation Combustor (RDC), where one or several detonation waves are rotating around a typically annular combustion chamber, may be an alternative combustion technology for gas turbines, with perspectives of reducing fuel consumption, increasing thermal efficiency and reducing emissions. Among numerous additional challenges, thepossibly detrimental interaction of the unsteady, high-enthalpy combustor exhaust gas with the downstream located axial turbine is a largely unresolved issue. To facilitate this coupling, installing an ejector between RDC and turbine is a viable option. In the current work, three separate ejector configurations are investigated using a Large-Eddy Simulation(LES), Reynolds-Averaged Navier-Stokes (RANS) simulations and 1D modeling, and the potential for integration with an RDC is evaluated. The analysis revealed that both the internal flow field and the design requirements are considerably different between a conventional ejector and an ejector coupled to an RDC. The study showed that integrating an ejector with an RDC renders the exhaust gas much more admissible for turbine entry by reducing fluctuations, mean velocity and mean temperature. Nevertheless, the presence of the ejector in the thermodynamic cycle led to performance penalties, compared to a reference cycle without an ejector present. The ejector entrainment ratio was determined as a crucial parameter controlling both dampening characteristics and global cycle performance: Small values provided for high cycle efficiency but low dampening (and vice versa). A detailed analysis of local entropy generation in the ejector showed that under RDC-representative conditions, thermal losses show the highest contribution, followed by viscous dissipation losses. The majority of losses concentrated in the shear layer between the RDC exhaust gas and the entrained secondary flow. Based on a design study using steady RANS, a preliminary set of design guidelines could be established for an annular ejector coupled to an RDC. The work showed that a minimal secondary flow passage, and a relatively long constant-area mixing chamber are beneficial. In addition, it was asserted that 1D and RANS modeling are useful in preliminary design, but that an unsteady approach such as LES is necessary afterwards to capture the essential flow physics. The presented work showed both a methodology to evaluate integrated ejector performance, and a possible final annular ejector that can be readily coupled to an RDC.