Initiation characteristics of oblique detonation waves from a finite wedge under argon dilution

In this paper,the flow field characteristics of Oblique Detonation Waves(ODWs)induced by a finite wedge under argon dilution are studied by solving the Euler equations with a detailed chemical model of hydrogen and air.First,the effects of the expansion waves,argon concentration,geometric parameters,and Mach number on the ODW are discussed.The results show that the changes of these parameters may make the oblique detonation not be initiated.Then,the ODW initiation criterion of the finite wedge is summarized,as the characteristic length of the induction zone LCand the characteristic length of the oblique wedge LWmeet the condition LC/LW<1,the initiation of the ODW occurs;otherwise,it does not occur.What’s more,the Constant Volume Combustion(CVC)theory is applied to study the characteristic length of induction zone.It is found that CVC theory is more suitable for the“smooth transition”type of ODW flow field,the theoretical and numerical characteristic length in induction regions are in good agreement.This work is of great significance for the design of oblique detonation engines for hypersonic vehicles.

Influence of process parameters on the microstructural evolution of a rear axle tube during cross wedge rolling

In the shaping process of cross wedge rolling（CWR）, metal undergoes a complex microstructural evolution, which affects the quality and mechanical properties of the product. Through secondary development of the DEFORM-3D software, we developed a rigid plastic finite element model for a CWR-processed rear axle tube, coupled with thermomechanical and microstructural aspects of workpieces. Using the developed model, we investigated the microstructural evolution of the CWR process. Also, the influence of numerous parameters, including the initial temperature of workpieces, the roll speed, the forming angle, and the spreading angle, on the grain size and the grain-size uniformity of the rolled workpieces was analyzed. The numerical simulation was verified through rolling and metallographic experiments. Good agreement was obtained between the calculated and experimental results, which demonstrated the reliability of the model constructed in this work.

乙炔-空气混合物中有限长楔面诱导斜爆轰波的起爆特性

斜爆轰波在高超声速推进具有重要的应用潜力,受到了研究者们的广泛研究。以往的研究,大多基于氢气燃料,且楔面总是无限长的.本文基于详细的化学反应模型,通过求解二维考虑基元反应的多组分欧拉方程,对乙炔-空气混合物在有限长楔形面诱导的斜爆轰进行了数值和理论研究.根据受限空间内的起爆判据,研究了膨胀波、来流马赫数和当量比对斜爆轰波起爆特性的影响.结果表明,乙炔诱导的斜爆轰波的起爆距离相对大于氢燃料诱导的。爆燃波的会聚位置和膨胀波的产生位置决定了斜爆轰波的起爆特性.当膨胀波的产生位置在爆燃波会聚位置的下游,斜爆轰波被点燃;否则,斜爆轰波不会起爆.诱导区特征长度在不同当量比下呈U型曲线分布,无论是富燃还是贫燃都会导致斜爆轰波不起爆.