Fuel effects on NOx emissions in partially premixed flames

摘要: Abstract The requirement to significantly reduce NOx and particulate emissions while maintaining combustor performance is one of the main drivers for internal combustion engine research. Partially premixing using fuel blends represent two promising approaches reducing both from flames. This paper reports on results a numerical investigation effects different fuels in counterflow partially premixed investigated include methane, n-heptane, their with hydrogen. methane flame computed GRI-3.0 mechanism, n-heptane by combining Held et al. oxidation mechanism Li Williams mechanism. Results indicate that, regard characteristics, flames can be grouped into distinct regimes, namely double-flame regime, characterized high levels partial and/or low strain rates ( s ) physically separated reaction zones, merged-flame nearly merged zones. In first characteristics are strongly affected changes equivalence ratio (ϕ) rate, second they exhibit relatively weak dependence ϕ . addition, established under identical conditions widely emission behavior regime but qualitatively similar regime. Major differences (i) higher NO level index, (ii) much wider , (iii) dominance prompt over thermal entire (iv) noticeable reduction hydrogen addition compared These attributable pyrolysis/oxidation chemistry fuels, as consumption occurs mainly through C2 path, that C1 path. As result, amounts C2H2 and, consequently, CH radicals formed than those responsible observed fuels.