Optically Based Temperature Sensing of Rotating Detonation Engine Combustor Internal Wall

An optically based temperature sensor was designed for determining the temperature of a rotating detonation engine (RDE) combustion chamber internal wall with the capability to resolve highly transient behavior. The temperature was interpreted with a multi-spectral pyrometric technique by collecting radiation emissions at carefully selected wavelength bands in the visible and near-infrared spectrums. A water-cooled combustion chamber center body and internally mounted optical equipment were designed, fabricated, and installed in a laboratory RDE. This equipment was tested in long-duration engine runs and was able to withstand the high temperatures and pressures of the RDE combustion chamber during sustained operation. The ability to make temperature measurements of the internal combustor wall with microsecond level time resolution was demonstrated. Measured transient temperature fluctuations were found to be approximately +/- 30˚C around an average temperature of 1044˚C at the end of tests near stoichiometric conditions and determined to have similar frequency characteristics to wave dynamics within the combustion chamber, indicating that they were correlated to gas dynamics and heating effects associated with internal wave dynamics within the combustor.