Optimized single-step (OSS) chemistry for auto-ignition of heterogeneous mixtures

A new method for systematic 1-step chemistry reduction applied to hydrocarbon combustion

“…Let us now illustrate the difficulty of using single-step chemistry for ignition events. As Carbajal-Carrasco et al remind in [27] , the asymptotic analysis describes the dependence of the ignition delay time or autoignition time as…”

“…As duly noted in the literature, chemical timescales associated with ignition are different from those of premixed flame propagation and tackling both phenomena with a single step is non-trivial [8,27,28] . It is well understood that the ignition process can be well represented by chained reactions building up a radical pool, which eventually will trigger heat-releasing reactions [21,22,29,30] .…”

“…Two main strategies to circumvent this issue may be found in the literature. One strategy consists in fitting two sets of rates ( K V L for flame propagation, K ig for ignition), and switching smoothly between the two based on, e.g., the fresh gases reconstructed temperature [27] . Nonetheless, transitioning between the two can be tricky, and no complex configuration including simultaneously propagation and ignition modes is reported [19,27] .…”

“…One strategy consists in fitting two sets of rates ( K V L for flame propagation, K ig for ignition), and switching smoothly between the two based on, e.g., the fresh gases reconstructed temperature [27] . Nonetheless, transitioning between the two can be tricky, and no complex configuration including simultaneously propagation and ignition modes is reported [19,27] . This approach remains appealing, as numerical boundedness of mass fractions is trivial when a single progress variable is considered.…”

Premixed flame heat release-based optimum global single-step chemistry for H$$_2$$, CH$$_4$$, and C$$_3$$H$$_8$$ mixtures with air

“…Optimized single-step chemistry models have also been developed to reproduce the burned gases temperature, the laminar flame speed and the laminar flame thickness based on the temperature gradient for the simulation of turbulent premixed flame propagation [10]. This has also been applied for studies of auto ignition of heterogeneous mixtures, where the objective is to determine the ignition delay [6]. These studies also provide an ample discussion on the different requirements that simplified chemical models should satisfy.…”