Continuous detonation in the air ejection mode. Domain of existence

Results of an experimental study of continuous and pulsed detonation of a hydrogen-air mixture in an annular flow-type combustor 306 mm in diameter with an expanding channel in the air ejection mode are reported. By varying the free-cross-sectional area of the slot for air supply, the number and cross-sectional area of the orifices of the fuel injectors, the size of the fuel receiver, and the initial pressure of the fuel, the domain of existence of detonation regimes in the coordinates “air ejection slot size versus the specific flow rate of hydrogen” is determined. An optimal air ejection slot width for the combustor and fuel used is found (10–12 mm); deviations from this slot width to either side reduce the domain of existence of detonation regimes. A necessity of making a step in the air supply path is found. It is also shows that there exists an optimal geometry of injector orifices, which expands the domain of existence of detonation regimes. Rough mixing of hydrogen with air, as well as too rapid mixing, makes the domain of detonation existence narrower. The following sequence of processes is found to occur as the hydrogen flow rate is increased: combustion transforms to longitudinal pulsed detonation, then to continuous spin detonation, then to pulsed detonation again, and finally to usual combustion. Experiments of long-time operation of the combustor without cooling are performed.