关键词: 富燃燃气, 常温空气, 同轴剪切, 旋转爆震, 燃烧模态, 速度亏损

Abstract: To reveal the characteristics of rotating detonations utilizing kerosene fuel-rich gas and ambient air under a coaxial shear injection configuration, experimental research was conducted in a hollow cylindrical rotating detonation combustor with varying air slit widths. Results show that stable single-wave rotating detonation propagation was achieved with slit widths of 0.5 mm, 1.0 mm, and 1.5 mm, within a detonable equivalence ratio range of 0.4~1.0. In contrast, only deflagration combustion was observed when the slit width was increased to 2.0 mm and 2.5 mm. Analysis indicates that the degree of air choking within the slit is the key factor determining the combustion mode. Rotating detonation occurred primarily under choked air conditions, where the detonation wave velocity matched the Chapman-Jouguet theoretical value. A significant velocity deficit, up to 25%, was observed in the few single-wave cases without choked air. Since the air mass flowrate simultaneously affects both the choking condition and the global equivalence ratio, wider slits make it more difficult to satisfy both the choking requirement and a suitable equivalence ratio simultaneously, thereby being more prone to deflagration. Quantitative analysis reveals that the degree of air choking influences the rotating detonation characteristics on two levels: injection stiffness and coaxial shear mixing effectiveness. In the present experiments, forming a rotating detonation required an air momentum flux greater than 40 kg·m/s2. Under this prerequisite, the air-to-fuel momentum ratio further determines the velocity deficit. When the momentum ratio is between 26 and 42, the velocity deficit decreases in a nearly linear trend as the ratio increases. For momentum ratios greater than 42, the mixing effectiveness of the coaxial shear injection reaches its optimum, and the velocity deficit remains below 2% without significant further variation.

Key words: Fuel-rich gas, Ambient air, Coaxial shear injection, Rotating detonation, Combustion mode, Velocity deficit