  Accurate perception of the combustor thermal environment is crucial for
thermal protection design of a rotating detonation combustor (RDC). In this
study, a comprehensive analysis method is established to calculate the
non-uniform heat flux distribution of the RDC by utilizing the measured
temperature distribution of the combustor outer wall obtained by the high-speed
infrared thermal imager. Firstly, in order to determine the inverse heat flux
solving method, a physical model based on the geometric characteristics of the
RDC is constructed and its thermal conductive process is simulated, given by
different heat flux boundary conditions. Then the wall heat fluxes are
inversely calculated by the Levenberg-Marquardt (L-M) method based on the above
numerical data. Results show that the L-M method can obtain more accurate heat
flux distribution even in the zones with large heat flux gradients, considering
the axial heat conduction within the combustor outer wall caused by the
non-uniform heat flux. Finally, the wall heat flux distribution is analyzed
coupling the L-M method together with the experimental measurements in kerosene
two-phase RDC. The analyses show that the highest temperature of combustor
outer surface and the highest wall heat flux occurs within the region of 20mm
from the combustor head, which corresponds to nearly 14% of the combustor
length. With the increase of axial distance, the heat flux is rapidly reduced,
and then the heat flux distribution is more uniform at the downstream region of
the combustor. The heat flux peak and thermal heat rate are positively
correlated with the combustor equivalence ratio in the range between 0.44 and
0.64.
