Dynamic Response Characteristics of Oblique Detonation Waves in Non-Uniform Inflows

In propulsion systems based on oblique detonation waves (ODWs), the airflow compressed by the inlet still has a very high velocity and the complete mixing of fuel and airflow is unattainable, which thus has a huge effect on wave systems of oblique detonations. In this paper, the ODWs in non-uniform inflows were considered as the object. By means of the evolutions of wave angles and displacement distances of wave front, the disturbance characteristics of ODWs were studied using the Euler equations coupled with the hydrogen-air detailed reaction model. The equivalence ratio was chosen as the representation variable of nonuniformity, and a disturbance region with a varying height was introduced into the incoming flow. The symbol φ_A was defined as the disturbance amplitude and the equivalence ratio distribution in the disturbance region was modeled using the sinusoidal function. It is found that with the decrease of φ_A, the wave angle decreases and the wave front moves downstream, the opposite trend is observed when the equivalence ratio increases. When φ_A is negative and small enough, a novel phenomenon characterized by the abrupt change of wave angle can be observed. Further analyses show that this phenomenon is due to ODW re-initiation under the influence of non-uniform equivalent ratio. When φ_A is posi-tive and large enough, the ODW angle of the disturbance region is in a non-equilibrium state. A larger equivalence ratio gradient results in a higher value than the theoretical wave front angle, while a smaller equivalent ratio gradient has a lower value than the theoretical one. Quantitative analyses of wave front positions show that the displacement distance of the wave front with φ_A is nonlinear when φ_A is positive, and linear when φ_A is negative. Meanwhile, the displacement distance is linear with the height of the disturbance region.