Abstract: A rotating detonation combustor with the outer diameter100mm, the inner diameter 80mm and the axial length 117 mm for the detonation channel was designed. There is no exhaust nozzle attached to the combustor. Numerical and experimental studies were carried out to study combustion and flow characteristics under different equivalence ratio conditions. The air flows into the combustor through 60 orifices each with 2mm in diameter, and the hydrogen gas flows into the combustor through an annular channel with 2mm in width. The maximum total pressures of hydrogen and air can be 12 and 10.5MPa, respectively. When the equivalence ratio is greater than 2, deflagration occurs outside the combustor. When the equivalence ratio is close to 1, multiple counter-rotating detonation waves move in the combustor and the average detonation velocities are lower than 1000m/s. When the equivalence ratio is less than 0.58, only one detonation wave rotates. The detonation velocity is 1274m/s for the equivalence ratio 0.55. The rotating detonation engine without cooling ran for 17 seconds at the equivalence ratio 1 and apparent erosion wasn't found. Three detonation waves are co-rotating with velocities 1998m/s near the outer wall for the mass flow rate 400 g/s in the numerical study.