Characterization of Detonation Waves with High-Speed Rayleigh Scattering and Single-Pulse Laser-Induced Fluorescence

This study characterizes a Chapman–Jouguet (CJ) hydrogen–air detonation using high-speed Rayleigh scattering and single-shot planar laser-induced fluorescence of nitric oxide (NO-PLIF). Firstly, we demonstrate that a Nd:YAG laser cluster can be employed to conduct high-speed (2.5 MHz) Rayleigh scattering visualizations of hydrogen–air detonations at 25 kPa. This multipulse Rayleigh scattering diagnostic is complementary to the existing techniques: 1) it enables the characterization of any detonation, from CJ to marginal detonations; 2) it is significantly less expensive than typical burst-mode lasers; 3) it has adjustable visualization frequency, which can go beyond 10 MHz with the same energy per pulse, and 4) it is easily applicable to higher initial pressures because the Rayleigh signal scales with number density. Secondly, we combine this multipulse Rayleigh scattering with NO-PLIF to complement the average speed and speed decay measurements with local induction zone length ([Formula: see text]) measurements. This five-beam configuration provides measurement capabilities similar to our previous three-beam configuration, outside of the local speed decay. Furthermore, a combined experimental and computational evaluation of the Rayleigh signals reveals that [Formula: see text] measurements appear theoretically possible from Rayleigh scattering visualizations, but these experimental measurements are challenging due to the limited image quality in the current multipulse configuration.