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中文核心期刊

高速弹丸诱导斜爆轰激波结构实验研究

EXPERIMENT INVESTIGATION OF OBLIQUE DETONATION WAVE STRUCTURE INDUCED BY HYPERSONIC PROJECTILES

  • 摘要: 斜爆轰推进系统在高超声速推进领域具有广阔的应用前景, 其释热迅速、比冲高、燃烧室结构简单的优点吸引研究人员的持续关注. 然而, 斜爆轰的地面试验同时涉及到高速试验环境模拟、燃料与氧化剂混合、高温燃烧流场结构测量等技术难点, 当前国内外系统的试验研究仍然十分有限, 难以支撑斜爆轰发动机的研制. 为了研究自持传播的斜爆轰激波结构与波面流动特性, 基于爆轰驱动二级轻气炮开展了高速弹丸诱导斜爆轰实验研究, 使用直径30 mm球头圆柱形弹丸发射进入充满氢/氧可燃混合气体的实验舱中以起爆斜爆轰波, 并采用两种阴影技术对实验流动结构进行测量. 实验中在不同速度、不同充气压力下观察到三种弹丸诱导激波结构, 即激波诱导燃烧、弹丸起爆爆轰波和相对弹丸驻定的斜爆轰波, 实验舱充气压力下降则会造成爆轰横波尺度增加与波面流动失稳. 实验中, 斜爆轰激波角与理论分析结果吻合较好, 弹丸气动不稳定带来较大的弹丸攻角会对激波角测量带来一定偏差. 通过对斜爆轰波波面法向传播速度的测量发现, 随着远离弹丸, 斜爆轰传播速度由弹丸飞行速度衰减至接近实验气体CJ速度, 弹丸速度的降低会加速斜爆轰波传播速度的衰减.

     

    Abstract: By taking advantages of rapid heat release, high specific impulse and simple combustion chamber structure, oblique detonation plays an important role in hypersonic air-breathing propulsion systems, which has been attracted more attentions in recent decades. However, due to the existence of technical difficulties, such as high-speed test environment generating, fuel and oxidant mixing, and high-temperature combustion flow-field structure measurement, the ground experimental research about oblique detonation wave at home and abroad is still limited at present. Thus, it’s difficult to support the development of oblique detonation engines. To study the wave structures and dynamic characteristics of the self-sustained propagating oblique detonation wave, investigation on oblique detonation induced by a hypersonic projectile launching has been conducted based on a two-stage light-gas gun device. The spherical projectile with a diameter of 30 mm is launched into a test chamber, in which fills with stoichiometric hydrogen/oxygen combustible mixture to induce the initiation of the detonation wave. In this work, two different shadowgraph techniques have been employed to record the structures of shock induced by the projectile. Three kinds of shock structures have been observed with different projectile velocities and filling pressure: shock induced combustion, detonation wave initiated by the projectile and steady oblique detonation wave around the projectile. A decrease in the filling pressure results in increasing length of transverse wave and unsteady flow structure of detonation wave. The measured oblique detonation wave angle agrees well with the theoretical result. The discrepancy of the shock wave angle between experiment and theory exists due to large angle of attack of the projectile, which is caused by aerodynamic instability. The propagation velocity of the oblique detonation wave is determined by oblique detonation wave angle at various points of detonation wave. Moreover, it shows that the detonation propagation velocity decays to the CJ detonation velocity as moving away from the projectile, and thus accelerate the attenuation of propagation velocity of the oblique detonation wave.

     

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