Numerical study of the inlet velocity effect on characteristics of Repetitive Extinction-Ignition Dynamics for lean premixed hydrogen-air combustion in a heated micro channel

In the present study, the effects of inlet velocity on characteristics of Repetitive Extinction-Ignition Dynamics are numerically investigated. Hydrogen-air mixture (with equivalence ratio = 0.5) enters into a heated micro channel with a prescribed wall temperature. Low Mach number approach is considered for governing equations in numerical simulation and also detailed chemistry, and different mass diffusivity of species is utilized. The dynamic behavior is studied by two parameter, amplitude and frequency. The results show that the amplitude of repetitive extinction-ignition dynamics increases with increasing the inlet velocity, while the frequency has a descending-ascending behavior. For detailed study of this phenomenon the chemical reaction approach is used by considering the reaction rate parameter. The results illustrate that for high inlet velocitis the reactions tend to produce light species such as O, H and OH. The effects of inlet velocity on flame propagation velocity are also studied. For lower inlet velocities, flame stays longer in an extinction-ignition period in the channel, while increasing the inlet velocity causes the flame to extinguish faster.