Ignition of methane and propane in high-temperature oxidizers with various oxygen concentrations

In this investigation, ignition processes of methane (CH₄ > 98%) and propane (C₃H₈ > 95%) using a high-temperature oxidizer (T_oxi > T_ai) with a varying oxygen concentration (zO2=0.05÷0.21), applying two types of experimental installations, viz. a constant-volume bomb (CVB) and a co-flow reactor (CFR) were investigated. The influence of the initial temperature of the oxidizer (for methane T_oxi = 960 ÷ 1234 K and for propane T_oxi = 803 ÷ 1055 K), the equivalence ratio and oxygen concentration in the oxidizer on ignition of gaseous fuels is analyzed and discussed. It is shown that in order to achieve an effective reaction of ignition (taking into account the minimum value of ignition delay time τ_ig and maximal value of the increment of temperature ΔT) the oxidizer temperature need not be maximized. There are optimal values of temperature of the oxidizer (for methane T_oxi ≈ 1100 K and for propane T_oxi ≈ 950 K) in which the parameters mentioned above reach their extreme values.