Laser-induced spark ignition of pulsed methane jets in homogeneous and isotropic turbulence without mean flow
Author(s)
Chen, Chaoxu
Charalampous, Georgios
Shi, Zhengjie
Hardalupas, Ioannis
Type
Conference Paper
Abstract
The influence of surrounding air turbulence on laser-induced spark ignition of a pulsed methane jet was investigated
in an air environment where the turbulence is homogeneous and isotropic without mean flow. The methane jet
Reynolds number (Rejet) was set at 160, while the surrounding air turbulent Reynolds number was varied in the range
of Reλ = 0 - 220. Minimum Ignition Energy (MIE) was evaluated at four ignition locations by measuring the ignition
probability and correlated with the local equivalence ratio (Φ) measured at three ignition locations using Laserinduced Breakdown Spectroscopy (LIBS) technique. The relationship between MIE and the local equivalence ratio
obtained in quiescent air environment was similar to that reported in premixed methane/air mixtures. The impact of
the surrounding air turbulence on MIE varies for different ignition locations, because the turbulence not only affects
the mixing process and thereby the local equivalence ratio, but also increases the heat loss from the ignition point.
The MIE decreased with increasing level of air turbulence, when the effect of local mixture composition becoming
closer to stoichiometry was more significant than the adverse effect of increasing heat loss. Otherwise, the MIE
increased with the level of air turbulence due to the dominance of the enhanced heat loss. The rate of increase in MIE
became higher, if the local mixture composition moved further away from stoichiometry when turbulence was
present. Successful ignition was also observed at locations where the mixture is relatively difficult to be ignited (Φmean
= 2.38 and Φmean = 0.02), which may be attributed to the finite size of the plasma.
in an air environment where the turbulence is homogeneous and isotropic without mean flow. The methane jet
Reynolds number (Rejet) was set at 160, while the surrounding air turbulent Reynolds number was varied in the range
of Reλ = 0 - 220. Minimum Ignition Energy (MIE) was evaluated at four ignition locations by measuring the ignition
probability and correlated with the local equivalence ratio (Φ) measured at three ignition locations using Laserinduced Breakdown Spectroscopy (LIBS) technique. The relationship between MIE and the local equivalence ratio
obtained in quiescent air environment was similar to that reported in premixed methane/air mixtures. The impact of
the surrounding air turbulence on MIE varies for different ignition locations, because the turbulence not only affects
the mixing process and thereby the local equivalence ratio, but also increases the heat loss from the ignition point.
The MIE decreased with increasing level of air turbulence, when the effect of local mixture composition becoming
closer to stoichiometry was more significant than the adverse effect of increasing heat loss. Otherwise, the MIE
increased with the level of air turbulence due to the dominance of the enhanced heat loss. The rate of increase in MIE
became higher, if the local mixture composition moved further away from stoichiometry when turbulence was
present. Successful ignition was also observed at locations where the mixture is relatively difficult to be ignited (Φmean
= 2.38 and Φmean = 0.02), which may be attributed to the finite size of the plasma.
Date Acceptance
2018-03-13
Citation
Proceedings of the 19th International Symposium on Applications of Laser and Imaging Techniques to Fluid Mechanics, pp.1-15
ISBN
978-989-20-9177-8
Start Page
1
End Page
15
Journal / Book Title
Proceedings of the 19th International Symposium on Applications of Laser and Imaging Techniques to Fluid Mechanics
Identifier
https://www.lisbonsimposia.org/blank-cjg9
Source
19th International Symposium on the Application of Laser and Imaging Techniques to Fluid Mechanics
Start Date
2018-07-16
Finish Date
2018-07-19
Coverage Spatial
Lisbon, Portugal