The transition between different combustion regimes is investigated experimentally for a stoichiometric argon-diluted n-decane/O₂ mixture. The focus is put on the influence of initial temperature (T = 420–470 K) and pressure (P = 1.5–3 bar) on the regime transitions. Fast schlieren visualization (≥ 120 kHz) and high-speed pressure and temperature measurements are used to monitor the evolution of the reactive processes inside a combustion chamber of square cross-section (40 mm × 40 mm × 172 mm). Results for P ≥ 2.5 bar and the entire temperature range and for P = 2 bar and T ≥ 440 K show three distinct stages following the adiabatic compression of fresh gases induced by the propagation of a flame into the chamber/test section, namely a cool flame, a main heat release stage, and detonation onset. For P = 1.5 bar, however, only the first two stages of the process are observed in the temperature range studied. A two-stage autoignition phenomenon, typical of large hydrocarbons, occurs systematically in the end gas and generates consecutive reactive fronts. The transition to detonation appears to result from the acceleration of the aforementioned fronts toward the speed of sound in fresh gases. Notably, the compression history plays a key role in setting conditions for detonation onset. Our results are in agreement with classical transition maps available in the literature.

中文翻译：

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正癸烷/ O 2 / Ar混合物的终气自燃-爆轰过渡的实验研究

实验研究了化学计量的氩气稀释的正癸烷/ O ₂混合物在不同燃烧方式之间的过渡。重点放在初始温度（T  = 420–470 K）和压力（P  = 1.5–3 bar）对状态转换的影响上。快速的schlieren可视化（≥120 kHz）以及高速压力和温度测量用于监视方形横截面（40 mm×40 mm×172 mm）燃烧室内部反应过程的演变。结果P  ≥2.5巴和在整个温度范围和P  = 2巴和Ť ≥440 K表示在绝热压缩之后，三个不同的阶段，绝热压缩是由火焰传播到燃烧室/测试部分而引起的，即冷火焰，主放热阶段和爆炸开始。 但是，对于P = 1.5 bar，在所研究的温度范围内仅观察到该过程的前两个阶段。两阶段自燃现象是大型烃类的典型现象，在末端气体中系统地发生并产生连续的反应前沿。爆炸的发生似乎是由于上述前沿向新鲜气体中的声速加速所致。值得注意的是，压缩历史在设定起爆条件方面起着关键作用。我们的结果与文献中的经典过渡图一致。