当量比对斜爆轰波诱导区特性影响的数值模拟研究

Numerical Study on Effects of Equivalence Ratio on Initiation Characteristics of Oblique Detonation Waves

关键词:  斜爆轰波  诱导区特性  压缩波

Key words:  Oblique detonation wave  Initiation characteristics  Compression waves

摘要:

为探索斜爆轰波诱导区特性变化的内在机制，利用带H2/O₂详细化学反应模型的二维欧拉方程进行数值模拟，研究了当量比对诱导区特性的影响。结果表明，随着当量比增大，诱导区长度呈U型曲线变化，在此过程中温度起到了关键作用。通过研究诱导区末端的压力分布发现，诱导区末端的压缩波强度是影响诱导区过渡形式的决定性因素。当量比在0.6～2.5时，压缩波强度较强，过渡形式为突变型，超出该范围，压缩波强度较弱，过渡形式为平滑型。此外，结合定容燃烧(CVC)理论分析了不同来流压力下的诱导区长度随当量比的变化情况，得出诱导区内的化学动力学效应影响了诱导区长度，使其沿理论所预测的U型曲线变化；气动力学效应影响了诱导区长度的变化幅度和速率，避免其过度增大或减小。

Abstract:

The initiation characteristics of oblique detonation waves in hydrogen-air mixture were investigated via numerical simulations using the two-dimensional reactive Euler equations with detailed chemistry. A parametric study was conducted to analyze the effects of equivalence ratio on the initiation characteristics. Numerical results show that the dependence of initiation length on equivalence ratio is a U-shape curve and temperature is the key factor influencing initiation length. The strength of compression waves near the end of initiation zone was found to dominate the transition type of initiation zone. The critical range for equivalence ratio is 0.6 to 2.5， in which compression waves are strong enough to lead to abrupt transition. When equivalence ratio is out of this range， compression waves get weak and transition type turns to be smooth. Furthermore， theoretical analysis based on the constant volume combustion (CVC) theory was also performed. Comparison between numerical and theoretical results demonstrate that initiation length is controlled by chemical kinetic effects in initiation zone which leads the initiation length to move in a U-shape curve like the CVC theory predicts. Nevertheless gasdynamic effects dominate the range and varying rate of initiation length， preventing the initiation length to change extensively like the theoretical results.