Flame-Generated Turbulence for Flame Acceleration and Detonation Transition

Detonations are a supersonic mode of combustion witnessed in a variety of applications, from next-generation propulsion devices to catastrophic explosions and the formation of supernovas. Detonations are typically initiated through the deflagration to detonation transition (DDT), a detailed process where a subsonic flame undergoes rapid acceleration increasing compressibility until a hotspot forms on the flame front inciting a detonation wave to form. Due to the complex nature of the phenomena, DDT is commonly investigated in three stages – (i) preconditioning, (ii) detonation onset, and (iii) wave propagation and stability. The research presented explores each of these stages individually, with a focus on preconditioning, to further resolve the governing mechanisms needed to initiate and sustain a detonation. More specifically, this work seeks to investigate the flow field and flame characteristics in reactions with increasing compressibility. Additionally, the research examines detonation onset and wave propagation to attain an all-encompassing concept of the DDT process. The work uses simultaneous high-speed diagnostics, consisting of particle image velocimetry (PIV), OH* chemiluminescence, schlieren and pressure measurements, to experimentally examine the preconditioning stage. Through the comprehensive suite of diagnostics, this research deduces the role of turbulence in detonation onset to an ongoing cycle of flame generated compression that amplifies until the hotspot ignites.