Parameters of continuous multifront detonation of a methane mixture with heated air in an annular cylindrical combustor

Regimes of continuous multifront detonation in a methane mixture with heated air in a flow-type annular combustor 503 mm in diameter are obtained and studied for the first time. Air is preheated by straight firing from 600 to 1200 K in the settling chamber by means of burning a stoichiometric hydrogen-oxygen mixture entering the combustor; the air flow rate is 6–20.9 kg/s. The fuel (methane)-to-air equivalence ratio is 1.15 $\pm$ 0.1. The influence of the air heating level on the domain of continuous detonation, pressure in the combustor, and specific impulse is analyzed. Regimes of continuous multifront detonation with one pair of colliding transverse waves with a frequency of 1.2 $\pm$ 0.1 kHz are observed in all experiments at air temperatures ranging from 600 to 1200 K. Based on the stagnation pressures measured at the combustor exit, the specific impulse of continuous detonation is determined as a function of the air flow rate and its temperature. As the air heating temperature increases, the specific impulse of the thrust force is found to decrease owing to the increase in the degree of dissociation of the detonation products. The maximum specific impulse with allowance for the heated air energy, equal to 1630 s, is obtained for the air temperature in the settling chamber equal to 600 K.