Detonation Combustion of Carbon-Free Ammonia/Hydrogen–Air Mixtures

Continuous spin and multifront detonations of carbon-free ammonia/hydrogen–air mixtures are obtained for the first time in an annular cylindrical combustion chamber with a diameter of 503 mm. Binary ammonia/hydrogen fuel with a mass fraction of $${{{\text{H}}}_{{\text{2}}}}$$ in the fuel ranging from 0.105 to 0.485 is investigated at specific mixture flow rates of $$22{-} 347$$ kg/(s m2) and a fuel equivalence ratio $$\phi = 0.47{-} 1.55$$ . Single-wave and double-wave continuous spin detonation regimes with a velocity of $$1.15{-} 1.59$$ km/s and a wave rotation frequency of $$0.73{-} 1.81$$ kHz at $$\phi = 0.73{-} 1.2$$ are obtained in ammonia/hydrogen–air mixtures with three fuel compositions: $${\text{N}}{{{\text{H}}}_{3}} + 8{{{\text{H}}}_{{\text{2}}}}$$ , $${\text{N}}{{{\text{H}}}_{{\text{3}}}} + 4{{{\text{H}}}_{{\text{2}}}}$$ , and $${\text{N}}{{{\text{H}}}_{3}} + 2{{{\text{H}}}_{{\text{2}}}}$$ , and continuous multifront detonation with two opposing transverse detonation waves with a rotation frequency of approximately 1.0 kHz at $$\phi = 0.72{-} 1.0$$ is achieved for the $${\text{N}}{{{\text{H}}}_{{\text{3}}}} + {{{\text{H}}}_{{\text{2}}}}$$ composition. The regions of continuous spin detonation and continuous multifront detonation regimes are determined as functions of the ammonia content in the binary fuel and the air manifold pressure. The pressure profiles in the air manifold and in the region of rotation of transverse detonation waves in the combustion chamber are measured using high-frequency sensors. Thrust forces and specific impulses are determined. The maximum thrust impulses obtained in the combustion chamber are 2300, 1500, 1350, and 900 s for binary fuel mixtures with a hydrogen mass fraction of 0.485, 0.32, 0.19, and 0.105, respectively.