Localised forced ignition of globally stoichiometric stratified mixtures: A numerical investigation

Abstract

Localised forced ignition of globally stoichiometric stratified mixtures (i.e. < φ > =1.0) has been analysed here based on direct numerical simulations for different initial values of velocity and equivalence ratio fluctuations (i.e. u′ and φ′), and the Taylor micro-scale l_φ of equivalence ratio φ variation. The localised ignition is accounted for by a source term in the energy transport equation which deposits energy over a stipulated time interval. It has been found that combustion takes place predominantly under premixed mode in the case of successful ignition. The initial values of φ′ and l_φ have been found to have significant effects on the extent of burning of stratified mixtures following localised ignition. It has been found that an increase in u′(φ′) has adverse effects on the burned gas mass, whereas the effects of l_φ on the extent of burning are non-monotonic and dependent on φ′. Detailed physical explanations have been provided for the observed u′, φ′ and l_φ dependences on the extent of burning in stratified mixtures.

Keywords:

• stratified mixtures
• equivalence ratio
• localised ignition
• direct numerical simulation

Acknowledgements

This work made use of the facilities of N8 HPC provided and funded by the N8 consortium and Engineering and Physical Sciences Research Council (EPSRC) [grant number EP/K000225/1]. The Centre is co-ordinated by the Universities of Leeds and Manchester.

Additional information

Funding

The authors are grateful to Engineering and Physical Sciences Research Council (EPSRC), UK, for financial assistance [grant number EP/J003573/1].