In this paper we present the characterization of the flow unsteadiness upstream and downstream of divergent exhaust sections from rotating detonation combustors. Unsteady outlet conditions from a 2D rotating detonation combustor were used as periodic inlet condition for the nozzle evaluations. The methodology consists of a ID Euler approach where a specific Mach number of 2 was targeted at the outlet while trying to maximize damping of the flow fluctuations. Three nozzles were evaluated: a smooth divergent, convergent-divergent and front expansion divergent nozzle. The smooth divergent nozzle offered with 42 % of damping the best attenuation of fluctuations while maintaining a reasonable flow momentum increase. Several nozzle lengths were evaluated and an optimal length of 10 cm was found in terms of damping. Secondly, an analysis of the inlet flow fluctuation magnitude revealed better damping performance for large variations as opposed to small fluctuations. Finally, a 3D unsteady assessment of the smooth divergent nozzle was performed and the discrepancy between the Euler code and the 3D simulations was below 5 %. Additionally, the outlet maximum flow angle oscillation showed a decrease of more than SO %. The heat load within the channel was also quantified with three isothermal simulations. Similar levels of tangentially averaged heat flux were observed for the hub and the shroud, however peak heat fluxes at the shroud were 30 % higher than the hub, with values up to 15 MW/m~2. The adiabatic heat transfer coefficient achieved levels of 4000 MW/(Km2) at the inlet and decreased to 2000 MW/(Km~2) towards the outlet for both hub and shroud.
展开▼
