  We consider a one-dimensional (1D) autoignitive reaction wave in reactive
flow system comprising unburned premixed gas entering from the inlet boundary
and burned gas exiting from the outlet boundary. In such a 1D system at given
initial temperature, it is generally accepted that steady-state solutions can
only exist if the inlet velocity matches either the velocity of deflagration
wave, as determined by the burning rate eigenvalue in the subsonic regime or
the velocity of detonation wave as dictated by the Chapman-Jouguet (CJ)
condition in the supersonic regime. In this study, we developed the general
concept of "autoignitive reaction wave" and theoretically demonstrate that two
distinct regimes that can maintain steady-state solutions both in subsonic and
supersonic conditions. Based on this theory, we selected inlet velocities that
are predicted to yield either steady-state or flashback solutions, and
conducted numerical simulations. This novel approach revealed that steady-state
solutions are possible not only at the velocity of the deflagration wave in the
subsonic regime and the velocity of the detonation wave in the supersonic
regime, but also across a broad range of inlet velocities. Furthermore, we
identify a highly stable "autoignitive reaction wave" that emerges when the
inlet velocity surpasses the velocity of detonation wave, devoid of the typical
shock wave commonly seen in detonation waves. This "supersonic autoignitive
reaction wave" lacks the instability-inducing detonation cell structure,
suggesting the potential for the development of novel combustor concepts.
