A rotating detonation engine using methane-ethylene mixture and air

Most of hydrocarbon fuels often have larger methane numbers than hydrogen. It is more difficult to detonate the mixture of hydrocarbon fuels and air at room temperatures in non-premixed engines since the mixing is slower than hydrogen-air mixing and the mixing is slower at lower temperatures. Ethylene-air rotating detonation operations have been successful, but methane-ethylene-air mixture at room temperatures is more difficult to detonate for rotating detonation engines since methane is more chemically stable. The hollow combustor channel here had an outer diameter of 220 mm and a length of 163 mm. Methane-ethylene mixture was injected axially into the combustor from cylindrical orifices in a diameter of 0.8 mm, and air was injected radially through a convergent-divergent circular channel with a throat width of 0.8 mm. Non-premixed rotating detonation waves were obtained for methane-ethylene-air mixture at total temperatures of 280-285 K in the present study. Both high-speed images and pressure traces show that three-wave mode has a higher detonation speed than five-wave mode. The rotating detonation speed is increased with the increased detonation height.