Continuous detonation of methane/hydrogen–air mixtures in an annular cylindrical combustor

Regimes of continuous detonation of methane/hydrogen-air mixtures in spin and opposing transverse detonation waves are obtained for the first time in a flow-type annular cylindrical combustor 503 mm in diameter. A two-component (methane/hydrogen) fuel with the H$_2$ mass fractions of 1/9–1/2 in the range of specific flow rates of the mixture from 64 to 1310 kg/(s $\cdot$ m$^2$) and the fuel-to-air equivalence ratio $\phi$ = 0.78–1.56 is considered. In methane/hydrogen-air mixtures with two compositions of the fuel (СН$_4$ + 8Н$_2$ и СН$_4$ + 4Н$_2$) one-wave and two-wave regimes of continuous spin detonation are obtained; the frequency of rotation of transverse detonation waves is 0.56–1.66 kHz at $\phi$ = 0.78–1.02. For the fuel compositions СН$_4$ + 2Н$_2$ и СН$_4$ + 1.5Н$_2$, continuous multifront detonation with two opposing transverse detonation waves rotating with the frequency of 0.86–1.34 kHz at $\phi$ = 1.0–1.23 is obtained. For the СН$_4$ + Н$_2$ + air mixture, both combustion in the chamber and continuous spin detonation outside the combustor with transverse detonation waves rotating with the frequency of 1.01–1.1 kHz are observed. The lean limits of continuous detonation are obtained in terms of the specific flow rate of the mixture: 64, 100, 200, and 790 kg/(s $\cdot$ m$^2$) for the fuel compositions СН$_4$ + 8Н$_2$, СН$_4$ + 4Н$_2$, СН$_4$ + 2Н$_2$, and СН$_4$ + 1.5Н$_2$, respectively, for the mass fraction of hydrogen in the methane/hydrogen fuel of $\approx$ 0.16. Violation of regularity of the continuous detonation wave structure and the wave velocity with a decrease in the fraction of hydrogen in the two-component fuel is detected.