Chemiluminescence tomography reconstructs volumetric structure of spinning detonation waves at 1 MHz

The experiment recorded simultaneous line-of-sight images through the cylindrical section, applied a custom ray-tracing calibration for refraction, and inverted the projections to obtain an effective emission source term at 1 MHz. Reconstructions captured a persistent single-head spin, a decaying spin that failed to re-initiate, and counter-propagating transverse waves, yielding direct measurements of axial and azimuthal speeds plus cell geometry.

Prior line-of-sight or planar techniques could not separate overlapping fronts inside the volume; the new data show that apparent transverse wave angles inferred from end-on imaging deviate by up to 18 degrees from the true three-dimensional trajectories. This resolves long-standing discrepancies between smoked-foil records and optical measurements.

The work extends earlier MHz-rate chemiluminescence imaging in rectangular channels by adding full volumetric capability, yet remains limited to ethylene mixtures at 1 atm and cannot yet quantify species concentrations without additional spectral filtering. Extension to methane-oxygen at elevated pressure would require only modest changes to the optical train and inversion algorithm.

Next steps include coupling the tomography with laser-induced fluorescence to obtain simultaneous temperature and OH fields, enabling quantitative comparison against high-fidelity detonation simulations.