Autoignition delay time data are one important means to develop, quantify, and validate fundamental understanding of combustion chemistry at low temperatures (T<1200 K). However, low-temperature chemistry often has higher uncertainties and scatter in the experimental data compared with high-temperature ignition data (T>1200 K). In this study, autoignition properties of propane and oxygen mixtures were investigated using the University of Michigan rapid compression facility in order to understand the effects of ignition regimes on low-temperature ignition data. For the first time for propane, autoignition delay times were determined from pressure histories, and autoignition characteristics were simultaneously recorded using high-speed imaging of the test section through a transparent end-wall. Propane mixtures with fuel-to-O₂ equivalence ratios of ϕ = 0.25 and ϕ = 0.5 and O₂-to-inert gas molar ratios of 1:3.76 were studied over the pressure range of 8.9 to 11.3 atm and the temperature range of 930 – 1070 K. The results showed homogeneous or strong autoignition occurred for all ϕ = 0.25 experiments, and inhomogeneous or mixed autoignition occurred for all ϕ = 0.5 experiments. While a limited temperature range is covered in the study, importantly the data span predicted transitions in autoignition behavior, allowing validation of autoignition regime hypotheses. Specifically, the results agree well with strong-autoignition limits proposed based on the Sankaran Criterion. The autoignition delay time data at the strong-ignition conditions are in excellent agreement with predictions using a well-validated detailed reaction mechanism from the literature and a zero-dimensional modeling assumption. However, the experimental data at the mixed autoignition conditions were systematically faster than the model predictions, particularly at lower temperatures (T< ~970 K). The results are an important addition to the growing body of data in the literature that show mixed autoignition phenomena are important sources of the higher scatter observed in the low-temperature autoignition data for propane and other fuels. The results are discussed in terms of different methods to capture the effects of pre-autoignition heat release associated with mixed autoignition conditions and thereby address some of the discrepancies between kinetic modeling and experimental measurements.

自燃延迟时间数据是开发，量化和验证低温（T <1200 K）下燃烧化学基础知识的重要手段之一。然而，与高温点火数据相比，低温化学通常在实验数据中具有更高的不确定性和分散性（T> 1200 K）。在这项研究中，使用密歇根大学的快速压缩设备对丙烷和氧气混合物的自燃特性进行了研究，以了解点火方式对低温点火数据的影响。对于丙烷，这是第一次根据压力历史记录确定自燃延迟时间，并使用测试部分通过透明端壁进行高速成像，同时记录自燃特性。燃料与O _2的当量比为ϕ = 0.25和ϕ = 0.5和O _2的丙烷混合物在8.9至11.3 atm的压力范围和930 – 1070 K的温度范围内，研究了惰性气体与惰性气体的摩尔比为1：3.76。结果表明，在所有= 0.25实验中均发生了均匀或强烈的自燃，并且ϕ = 0.5的所有实验均发生混合自燃。尽管研究涵盖了有限的温度范围，但重要的是，数据跨度可预测自燃行为的转变，从而可以验证自燃机制假设。具体而言，结果与基于Sankaran标准提出的强自燃极限非常吻合。强点火条件下的自燃延迟时间数据与使用文献中充分验证的详细反应机制和零维建模假设进行的预测非常吻合。然而，T <〜970 K）。该结果是对文献中不断增长的数据的重要补充，这些数据表明混合自燃现象是丙烷和其他燃料在低温自燃数据中观察到的较高散度的重要来源。将根据不同的方法来讨论结果，以捕获与混合自​​燃条件相关的自燃前放热的影响，从而解决动力学建模与实验测量之间的某些差异。