Experimental investigation of inner flow of a throatless diverging rotating detonation engine

Kotaro Nakata, Kazuki Ishihara, Keisuke Goto, Noboru Itouyama, Hiroaki Watanabe, Akira Kawasaki, Ken Matsuoka, Jiro Kasahara, Akiko Matsuo, Ikkoh Funaki, Kazuyuki Higashino, James Braun, Terrence Meyer, Guillermo Paniagua

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


The inner flow containing the ignition process of a throatless and diverging (constant diverging angle α=5 deg) rotating detonation engine (RDE) was experimentally investigated by both optical observation and pressure measurement. An RDE that had an acrylic engine wall with a length of 70 mm and an inlet diameter of 20 mm was tested under a low back pressure condition using gaseous C2H4−O2 as the propellants. A high-speed camera captured the ignition process, of which there were two types: deflagration-to-detonation transition and direct initiation. In addition to the visualizations of the inner flow, the pressure values in an RDE with an acrylic wall were compared with those of an RDE having a stainless steel wall with 8 pressure ports in the axial direction. The comparison revealed that the RDE exhaust flow was supersonic. A strong self-luminescence and CH* luminosity area near the injector surface during combustion suggested that the short completion of detonation combustion enabled the thermal choking of the subsonic propellant gases even when the channel was diverging. Moreover, the axial position of the erosion in the acrylic wall indicated that the heat release region was near the injector surface. Finally, a theoretical flow model for the RDE was compared to the experimental data, and the results suggested that the inner flow in the RDE can be reasonably described as a quasi-one-dimensional steady flow.

Original languageEnglish
Pages (from-to)3073-3082
Number of pages10
JournalProceedings of the Combustion Institute
Issue number3
Publication statusPublished - 2023 Jan


  • Detonation
  • Rotating detonation engine without inner cylinder
  • Thermal choke

ASJC Scopus subject areas

  • General Chemical Engineering
  • Mechanical Engineering
  • Physical and Theoretical Chemistry


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