Premixed flames are highly sensitive to changes in pressure. It is found that following the passage of a shock wave, a conventional diffusion-reaction deflagration can accelerate to become a fast convection-reaction driven flame that itself can further markedly accelerate. An induction zone is formed between the shock and the combustion wave. This is a relatively long region in which small changes in the dependent variables occur. Treating these as asymptotic perturbations, an intermediate zone that connects the rear of the induction zone to the front of the fast flame must also be considered. Matching conditions between the zones and boundary conditions at the shock and piston are calculated and the evolution of the shock wave, induction zone, and fast flame system is investigated. Across the induction zone there is strong acoustic coupling such that the resulting behavior of the combined system leads to thermal runaway. The time for this blow up to occur is investigated as a function of initial mass flux through the fast flame and initial shock Mach number. It is also shown that there is the possibility of hot spots occurring in the induction zone which then leads to secondary ignition ahead of the fast flame. We have also investigated the effect on primary and secondary ignition of the activation energy of the simple one-step chemistry used in this work.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Fuel Technology
- Energy Engineering and Power Technology
- Mechanical Engineering
- Physical and Theoretical Chemistry
- Fluid Flow and Transfer Processes