A rotating detonation engine is an engine using continuous detonation in an annular combustor, and make thrust. Because detonation wave propagates in supersonic and in very small region, the combustor can be shortened. Programs in the combustor are high pressure loss when propellant is injected and necessity of cooling due to high heat flux. However, the physics of detonation combustion in an annular combustor is still not clear. Especially combustion efficiency, influence of injector shape of a rotating detonation combustor are not reported a lot. This paper reports measurement result of combustor stagnation pressure and influence of injector on characteristic velocity efficiency. Then convergent-divergent nozzle was used to increase thrust efficiency. In addition we measured temperature of the combustor and estimated heat flux.