NUMERICAL STUDY OF CURVED FLAMES UNDER CONFINEMENT

Dynamics of laminar flames in closed tubes is studied by means of two- dimensional numerical simulations taking into account thermal conducti on, fuel diffusion, viscosity and chemical kinetics. Development of th e hydrodynamic instability of a flame front is investigated for flames with chemical reactions of the first and the third order. We found th at for a flame with the first order reaction the hydrodynamic instbili ty is strongly reduced or even suppressed in sufficiently short tubes. Unlike this, in the case of a flame with the third order reaction the instability is enhanced due to significant increase of the normal vel ocity of the planar flame under confinement. The instability developme nt for flames of both first and third order reactions is strongly affe cted by acoustic waves generated by the flame in a closed chamber. Par ticularly, a weak shock colliding with the flame front may lead to tem porary stabilization of the flame instability. On the contrary, when f lame comes to the end of the tube the acoustic waves may cause signifi cant increase of the flame instability. We studied a possibility of th e detonation ignition ahead of the flame front as well. We found that the detonation can be ignited at the far end of the tube by the weak s hocks and sound waves generated by the flame in a closed tube. Trigger ing of the detonation ahead of the flame propagating in a closed tube is related to the knock problem in spark-ignition engines.