Rotating Detonation Engines (RDEs) represent a relatively new concept in pressure gain combustion, where a detonation wave (DW) formed from injected mixture, travels circumferentially within an annular channel. The DW compresses the fuel to much higher pressures, resulting in the extraction of additional work and efficiencies not accessible through the conventional Brayton cycle. Unlike conventional engine designs, RDEs have no moving parts, making their manufacturing simpler, while their compact design increases their payload carrying capacity. RDEs can play a pivotal role in making hypersonic travel a reality.
Mode transition in RDEs refers to an abrupt change in the number of detonation waves due to a change in inlet conditions such as the injected fuel reactivity and total pressure. Our simulations of the gas-phase rotating engine have highlighted the possibility of a new pathway to mode transition, in which the number of detonation waves can change abruptly, based on inlet conditions and impacting the performance of the engine. We find mode transition in RDEs can occur when the reactivity of the inlet mixture is varied (say through Nitrogen dilution) leading to the formation of local deflagrations which transition to detonation waves.
Figure: Temperature contours from FLASH simulations of an RDE showing mode transition from 1 to 4 detonation waves, following a corresponding decrease in the inlet diluent concentration from 4 moles of Ar to 0 moles.
- P. Tarey, P. Ramaprabhu, D.A. Schwer and J.A. McFarland, “Numerical simulations of mode transition in rotating detonation engines”, AIAA 2023-1294, (2023). https://doi.org/10.2514/6.2023-1294
- P. Tarey, P. Ramaprabhu, J.A. McFarland, and P. Bigdelou, “Investigation of mode transition in rotating detonation engines using detailed numerical simulations”, AIAA 2020-3726, (2020); https://doi.org/10.2514/6.2020-3726