Intrinsic instability of different fuels spherically expanding flames: A review

Premixed flames have wide-ranging intrinsic instabilities which have been considerably investigated recently. Intrinsic instability is a classical area in combustion science, it is of essential interest to the combustion community and engine researchers, and has many practical consequences in internal combustion engines (ICEs). Intrinsic instability can increase the combustion intensity and enhance ICEs performance. Also, it can cause unexpected explosions in combustion devices due to the rapid acceleration of the flame. Therefore, a deeper mechanistic understanding of intrinsic instability dynamics of different fuels premixed flames is noteworthy for ICEs. This review summarizes and provides intrinsic instability investigations on hydrocarbons, hydrogen, and syngas spherically expanding flames. The experimental, theoretical, and numerical investigations on intrinsic thermal-diffusion and hydrodynamic instabilities of the various fuels premixed flames are presented. The effects of various physicochemical parameters and initial conditions on the intrinsic instability of the fuels premixed flames are discussed. Amongst the physicochemical characteristics, pressure and equivalence ratio significantly influence intrinsic instability. Finally, the inconsistencies in the evaluation of Lewis number, activation energy, and flame thickness used in the theoretical analysis of intrinsic instability cause a considerable difference between the theoretical, numerical and experimental results.

Automated summary

This article summarizes the experimental, theoretical, and numerical investigations on the intrinsic instability of different fuels premixed flames. Physicochemical parameters such as pressure and equivalence ratio have significant effects on instability. However, inconsistencies in the evaluation of certain parameters in the theoretical analysis cause differences between theoretical, numerical, and experimental results.