Evaluation of Mixing Processes in a Non-Premixed Rotating Detonation Engine Using Acetone PLIF

Abstract

The fuel and air mixing processes in an optically accessible non-premixed rotating detonation engine (RDE) are visualized using acetone planar laser induced fluorescence (PLIF) imaging. The acetone PLIF images are used to observe the transient fuel injection processes and evaluate the extent of partial premixing upstream of the detonation wave. The acetone PLIF images complement past OH* chemiluminescence images which showed the instantaneous size and shape of the detonation structure, oblique shock wave, and possible presence of deflagration between the fuel-fill zone and expansion region containing detonation products. The acetone PLIF data presented in this work represents a recent and ongoing experimental investigation that provides insightful information on the transient processes in the RDE. The acetone PLIF images of the non-reacting flow show an impinging jet in crossflow consistent with the fuel injection scheme of the current RDE design. A recirculation zone with minimal fuel concentration is observed in the outer corner near the fuel injection surface of the annular detonation channel. The acetone PLIF images of the reacting flow indicate that there is a purging period (60 – 75 μs corresponding to 18 – 22 % of the cycle) in which fuel is not being injected into the channel after the detonation wave travels past a particular fuel jet. This observation suggests that the high-pressure detonation wave inhibits the inflow of fuel during the purging period. The application of established experimental techniques such as acetone PLIF and OH* chemiluminescence imaging is providing new insights into RDEs. The results provide benchmark measurements that are useful for evaluating RDE models and simulations, improving fundamental understanding of the detonation structure in RDEs, and identifying critical design parameters that influence RDE operation and performance.