The study of auto-ignition under temperature stratification is of great interest. Indeed, further understanding of the thermo-kinetic interactions and its influence on the combustion propagation regime is needed. In a previous work [1], experiments in a flat piston Rapid Compression Machine (RCM) demonstrated that the apparent propagation of reaction fronts is highly influenced by the typical temperature stratification observed at inert conditions. Nevertheless, the influence of low temperature heat release (LTHR) on the internal aerodynamics and temperature of the RCM is not well understood. In the present study, we first address the LTHR-flow interaction then address the LTHR-temperature interaction. We performed 2D-PIV experiments at 10 kHz for inert and reactive lean isooctane mixtures. We averaged spatially the acceleration to present the time evolution during the cool flame period. We found that the normalized acceleration has a decreasing trend in both inert and reactive tests. No significant effect of the cool flame was observed on the trend. We performed temperature measurements using thin wire (7.6 µm) type K thermocouples at inert and reactive n-hexane mixtures (same test conditions of Fig. 7 in [1]). The temperature evolution of the hot (adiabatically compressed) and the colder gases were recorded when cool flame occurs. The corrected gas temperature showed good agreement with the theoretical adiabatic core temperature as well as previous measurements with toluene LIF. In the tested case, we found that the cool flame induces an equal temperature rise of approximately 110 K in both the adiabatically compressed and the colder vortex gases. These results confirm quantitatively that LTHR does not significantly affect the mixing of the temperature stratification of our flat piston RCM. In the studied test conditions, the temperature stratification is conserved globally despite the LTHR.

在温度分层下自燃的研究引起了极大的兴趣。实际上，需要进一步了解热动力学相互作用及其对燃烧传播方式的影响。在以前的工作[1]中，在扁平活塞快速压缩机（RCM）中进行的实验表明，在惰性条件下观察到的典型温度分层对反应前沿的表观传播有很大的影响。然而，人们对低温放热（LTHR）对RCM内部空气动力学和温度的影响还知之甚少。在本研究中，我们首先解决了LTHR与流的相互作用，然后解决了LTHR与温度的相互作用。我们在10 kHz下对惰性和反应性稀异辛烷混合物进行了2D-PIV实验。我们在空间上对加速度进行平均，以显示在凉爽的火焰时期内的时间演变。我们发现归一化的加速度在惰性和反应性测试中都有下降的趋势。没有观察到冷火焰对该趋势的显着影响。我们在惰性和反应性正己烷混合物中使用细线（7.6 µm）K型热电偶进行温度测量（与[1]中的图7相同的测试条件）。当出现冷火焰时，记录了高温（绝热压缩）和低温气体的温度变化。校正后的气体温度与理论绝热核心温度以及之前使用甲苯LIF进行的测量显示出良好的一致性。在经过测试的情况下，我们发现，在绝热压缩和较冷的涡流气体中，冷火焰均会引起大约110 K的相等温度上升。这些结果定量地证实了LTHR不会显着影响我们扁平活塞RCM的温度分层的混合。在研究的测试条件下，尽管进行了LTHR，但温度分层在全球范围内得以保留。