有限长度斜劈对燃烧室斜爆震波起爆结构影响研究

Effects of Finite Length Wedge on the Initiation Structure of Oblique Detonation Waves in Combustor

斜爆震发动机利用斜劈在超声速可燃混气中产生的斜爆震波实现快速高效的燃烧,在更高马赫数吸气推进领域极具应用潜力。面向斜爆震发动机工程应用,首先需要明确飞行条件下燃烧室内斜爆震波的起爆结构特征。但以往的研究大多采用无限长斜劈假设,不能真实反映实际燃烧室中有限长斜劈下的斜爆震燃烧特性。基于此,本文针对斜劈长度和斜劈后壁面倾斜角度两个关键设计参数,研究了在飞行马赫数8~10条件下,有限长度斜劈对斜爆震波起爆结构的影响。结果表明,对于不同高空飞行工况对应的不同起爆区结构斜爆震波,均存在一个临界斜劈长度,只有当斜劈长度缩短至临界斜劈长度时,斜爆震结构才会明显改变。相反,有限长度斜劈末端产生的膨胀波不会影响斜劈表面热释放和压缩波的汇聚过程,因此不会影响斜爆震波起爆结构。通过分析斜劈表面热释放过程,提出了一种理论的临界斜劈长度预测方法,其在不同飞行工况下的计算结果与仿真结果吻合较好。

The oblique detonation engine(ODE)uses the oblique detonation wave(ODW)generated by a wedge in supersonic combustible mixtures to achieve fast and efficient combustion,which is more applicable to air-breathing hypersonic aircraft with higher flight Mach numbers than a conventional scramjet.Prior to the practical application of ODE,it is first necessary to clarify the initiation structure characteristics of ODWs in the combustor under flight conditions.However,previous studies usually used the infinite length wedge hypothesis which cannot really reflect the flow and combustion characteristics of finite length induced ODW in the actual combustor.Two key design parameters,i.e.,the wedge length and end inclination angle,are used to investigate the effects of finite length wedge on the initiation structure of ODW in an ODE at different flight Mach numbers.Results show that there is a critical wedge length for different ODW initiation structures corresponding to different flight conditions.Only when the wedge length is shortened to the critical length,the ODW initiation structure will change significantly.When the wedge length is equal to or less than this critical length,both the wedge length and end inclination angle will affect the structure.On the contrary,the expansion wave generated at the end of the wedge cannot affect the heat release and compression wave convergence on the wedge,so it will not affect the ODW initiation process and structure.By analyzing the heat release process on the wedge,a theoretical method for predicting the critical wedge length is proposed to contribute to the combustor design.The calculated results under different flight conditions are in good agreement with the simulation results.