Hydrogen-air, ethylene-air, and methane-air continuous rotating detonation in the hollow chamber

A series of hydrogen-air, ethylene-air, and methane-air continuous rotating detonation (CRD) tests are performed in the hollow chamber with the variations on nozzle contraction ratio and equivalence ratio. Hydrogen-air, ethylene-air, and methane-air CRDs are achieved with low velocity deficit and high stability in the same laboratory hollow chamber. Larger combustor width, flame stabilization and mixing quality promotion benefited from the hollow chamber, and the prolongation of residence time impacted by the hollow chamber and nozzle are key factors for significant enhancement. Generally, the operating range, propagation frequency, propagation velocity/C-J detonation velocity; and stability increase with the fuel detonability increasing. The quantitative analysis approaches, the integral of chemiluminescence intensity and axial distribution of chemiluminescence intensity ratio on high-speed photography images, and flowfield reconstruction based on the time difference calculation method, are proposed and applied. Multiple analysis approaches all show that the length of CRD wave increases with the fuel detonability decreasing, which is mainly attributed to that the hydrocarbon fuels release heat in longer axial distance with relatively lower intensity. In addition, two dominant peak one-wave mode is verified as the single wave coupled with the reflected shock wave, which propagates upstream from nozzle to combustor forepart. (C) 2020 Elsevier Ltd. All rights reserved.