Effects of the geometrical parameters of the injection nozzle on ethylene-air continuous rotating detonation

Compared with traditional isobaric combustion, continuous rotating detonation (CRD) has been theoretically proved to be a more efficient combustion mode with higher thermal cycle efficiency. However, the realization and stable operating of liquid kerosene detonation is still a challenge. As a major component of kerosene pyrolysis products after regenerative cooling, ethylene is a transitional hydrocarbon fuel from kerosene to hydrogen and it is worth studying. In this paper, a series of 2D numerical simulations are conducted to investigate the effects of the injection nozzle on the ethylene-air CRD. Three geometrical parameters of the nozzle are thoroughly tested including the distance between two neighboring nozzle centers, the nozzle exit width, and the slant angle of the nozzle. The results show that an ethylene-air detonation wave is realized and it propagates stably. A small distance between two neighboring nozzle centers is conducive to improving the strength of the CRD wave and leads to greater feedback pressure into the plenum. As the nozzle exit width increases, the strength of the CRD wave and the feedback pressure into the plenum both increase. The CRD wave propagation velocity is greatly improved and the feedback pressure into the plenum is significantly reduced when the slant angle of the nozzle is positive. By contrast, a sizeable reduction in velocity is found when the angle is negative. The co-rotating two-wave propagation mode is observed when the angle is 30 degrees, and the highest CRD propagation velocity and the lowest feedback pressure are both obtained when the angle is 60 degrees.