Spontaneous ignition of methane–air mixtures in a wide range of pressures

The ignition delay in methane–air mixtures $(\varphi = 0.5)$ within the range of temperatures of $1200$–$1700$ K and pressures of $3$–$450$ atm behind reflected shock waves in a shock tube is measured on the basis of emission of the electron-excited $\mathrm{OH}$ radical (transition $A^2\Sigma^+-X^2\Pi$) at the wavelength of $306.4$ nm and on the basis of absorption corresponding to the component $F_1^{(2)} (\nu_3 = 1)\leftarrow F_2^{(2)}(\nu_3=0)$ of the $P(7)$ line of the $\nu_3$ mode of the $\mathrm{CH}_4$ molecule at the wavelength of $3.3922$ $\mu$m. The measured ignition delays are compared with those calculated by the GRI-Mech $3.0$ mechanism; good qualitative agreement of results is obtained in a wide range of pressures.