  From experimental spark ignition (SI) engine studies, it is known that the
slow-down of early flame kernel development caused by the
($\mathrm{Le}>1$)-property of common transportation-fuel/air mixtures tends to
increase cycle-to-cycle variations (CCV). To improve the fundamental
understanding of the complex phenomena inside the flame structure of developing
flame kernels, an engine-relevant DNS database is investigated in this work.
Conclusive analyses are enabled by considering equivalent flame kernels and
turbulent planar flames computed with $\mathrm{Le}>1$ and $\mathrm{Le}=1$. In
Part I of the present study (Falkenstein et al., Combust. Flame, 2019), a
reduced representation of the local mixture state based on the parameters local
enthalpy, local equivalence ratio, and H-radical mass fraction was proposed for
the purpose of this analysis. Here, a coupling relation for the
diffusion-controlled mixture parameter local enthalpy with local flame geometry
and structure is derived, characterized by the key parameters $\kappa$ and ${\
|\nabla c \ t|/\ |\nabla c \ |_{\mathrm{lam}}}$. The analysis shows that the
large positive global mean curvature intrinsic to the flame kernel
configuration may detrimentally affect the local mixture state inside the
reaction zone, particularly during the initial kernel development phase.
External energy supply by spark ignition may effectively bridge over this
critical stage, which causes the impact of global mean flame kernel curvature
to be small under the present conditions compared to the overall effect of
$\mathrm{Le}\neq1$. Once ignition effects have decayed, the mixture state
inside the reaction zone locally exhibits an identical dependence on $\ |\nabla
c \ |$ as in a strained laminar flame. This implies that differential diffusion
effects under engine-typical Karlovitz numbers are not weakened by small-scale
turbulent mixing.
