THE IGNITION BEHAVIOR OF HIGH-TEMPERATURE AIR-SPRAY SYSTEMS AS A COMPLEX SYSTEM

喷雾的着火行为对高温空气的流场和温度场非常敏感，它们显著地改变着火延迟。这一事实似乎意味着高温空气喷雾系统显示出对初始条件高度敏感的复杂性。因此，在1998年，通过将液体燃料垂直喷射到流中，研究了高温气流的速度、湍流和温度对点火行为和延迟的影响。研究了喷雾撞击壁面对着火延迟期的影响。结果发现，点火行为显着变化，如果喷雾被阻止撞击在墙上。在1999年，详细的点火过程进行了研究，使用高速摄像机。结果发现，在高温条件下，点火开始附近的喷嘴，而在低温条件下，点火发生后，撞击壁面。当点火发生后，对壁的冲击，它开始在喷嘴的上游。此外，如果将OH自由基化学发光测定的点火延迟与发光火焰出现的时间进行比较，则前者仅为后者的一半或更少。这一事实意味着点火延迟数据受到点火标准的显著影响;蓝色火焰（小火焰）或发光火焰的外观。结果发现，总之，点火是强烈影响的速度和湍流的高温空气流，因为它发生在同向流动的低速区域周围的喷雾，对面对的壁的喷雾尖端的冲击显着改变的过程和点火延迟，点火的标准强烈影响点火延迟数据。

The ignition behavior of a spray is highly sensitive to the flow and temperature fields of high-temperature air, and they considerably alter the ignition delay. This fact seems to imply that a high-temperature air-spray system shows complexity that is highly sensitive to the initial condition. In 1998, therefore, the effects on the ignition behavior and delay of the velocity, turbulence and temperature of a high-temperature air stream were studied by perpendicularly injecting a liquid fuel into the stream. The effects of spray impingement against the confronting wall on the ignition delay were also examined. It was found that the ignition behavior markedly varied if the spray was prevented from impinging against the wall. In 1999, the detailed ignition processes were studied using a high-speed video camera. It was found that, in a high-temperature condition, ignition initiated near the injection nozzle, and that, in a low-temperature condition, ignition took place after impinging against the wall. When ignition took place after impingement against the wall, it initiated in the upstream of the injection nozzle. If, in addition, the ignition delay determined from the OH radical chemiluminescence was compared with the time of luminous flame appearance, the former was only a half or less than the latter. This fact implies that ignition delay data are significantly affected by the criterion of ignition ; either the appearance of a blue flame (a flamelet) or that of a luminous flame. It was found, in summary, that ignition was strongly affected by the velocity and turbulence of the high-temperature air stream since it took place in the co-flowing low-velocity region around the spray, that the impingement of the spray tip against the confronting wall significantly altered the process and delay of ignition, and that the criterion of ignition strongly affected the ignition delay data.