Influences of different diluents on ignition delay of syngas at gas turbine conditions: A numerical study

Ignition delay of syngas is an important factor that affects stable operation of combustor and adding diluents to syngas can reduce NOx emission. This paper used H2O, CO2 and N2 as diluents and calculated ignition delay of syngas in temperature range of 900-1400 K and at pressures of 10 and 30 atm respectively. In high temperature range, comparing with N2 dilution, adding H2O and CO2 can significantly inhibit autoignition of syngas because they have higher collision efficiencies in reaction H + O2 (+ M) = HO2 (+ M). As for low temperature conditions, adding H2O can increase reactivity of syngas, especially under high pressure, because of its high collision efficiency in reaction H2O2 (+ M) = 2OH (+ M). Comparing with different dilution rates shows that for syngas and operating conditions in this paper, adding N2 mainly influences temperature rising process of syngas combustion, thus inhibiting reactivity of syngas. In addition, this paper calculated ignition delay of syngas at different equivalence ratios (φ = 0.5, 1.0). Higher equivalence ratio (φ ≤ 1) means that less air (especially N2) needs to be heated, thus promoting ignition of syngas.