Abstract Alternative fuels will come from a variety of feed stocks and refinement processes. Understanding the fundamentals of combustion and pollutants formation processes of these fuels will be useful for their implementation in different combustion systems. In this work, optical diagnostics were performed to waste cooking oil (WCO) and canola oil (CAO) based biodiesel sprays to assess their combustion and soot formation processes. Conventional diesel was used as a reference fuel for comparison with the biodiesels. The experiments were conducted in an optically-accessible constant-volume combustion chamber (CVCC) with simulated compression-ignition engine conditions, with different degree of exhaust gas recirculation. The liquid length and lift-off length results indicate that there was no significant interaction between the liquid phases of the fuels and their combustion regions. The flame lift-off lengths were found to be affected by both the chemical and physical properties of the fuels. It was observed that a larger difference between the lift-off length and the first-luminosity distance was correlated with lesser downstream soot formation, although the molecular structure of the fuel was found to affect the process too. Assessing the sooting and combustion characteristics of the biodiesel and diesel flames across the varied ambient O2 atmospheres revealed that the estimated soot contents of the biodiesel and diesel flames peaked at 15 and 21 vol.% O2 concentration, respectively. The peak soot contents of the WCO and CAO biodiesel flames were found be comparable, but lower than that of diesel, across the various O2 environment. The results also demonstrated that the biodiesels have higher normalized peak pressure values than diesel at all O2 conditions. Two-color pyrometry data demonstrated that the measured soot temperature and soot KL factors of the flames were similar at 15 and 21 vol.% O2, but varied with further reduction of ambient O2 concentration. Variations in the combustion duration and flame area were found to be fuel dependent.

中文翻译：

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模拟发动机条件下废弃食用油和菜籽油基生物柴油的燃烧特性

摘要 替代燃料将来自各种原料和精炼过程。了解这些燃料的燃烧和污染物形成过程的基本原理将有助于它们在不同的燃烧系统中的实施。在这项工作中，对基于废弃食用油 (WCO) 和菜籽油 (CAO) 的生物柴油喷雾进行了光学诊断，以评估它们的燃烧和烟尘形成过程。使用常规柴油作为参考燃料与生物柴油进行比较。实验是在光学可接近的恒定容积燃烧室 (CVCC) 中进行的，该燃烧室具有模拟压燃发动机条件，具有不同程度的废气再循环。液体长度和升起长度结果表明燃料的液相与其燃烧区域之间没有显着的相互作用。发现火焰升起长度受燃料的化学和物理性质的影响。据观察，尽管发现燃料的分子结构也会影响该过程，但升空长度和第一光度距离之间的较大差异与下游烟灰形成较少有关。评估生物柴油和柴油火焰在不同环境 O2 气氛中的烟尘和燃烧特性表明，估计的生物柴油和柴油火焰的烟尘含量分别在 15 和 21 vol.% O2 浓度达到峰值。发现 WCO 和 CAO 生物柴油火焰的峰值烟尘含量在各种 O2 环境中相当，但低于柴油。结果还表明，在所有 O2 条件下，生物柴油具有比柴油更高的归一化峰值压力值。双色高温计数据表明，在 15 和 21 vol.% O2 时，测得的火焰烟尘温度和烟尘 KL 因子相似，但随着环境 O2 浓度的进一步降低而变化。发现燃烧持续时间和火焰面积的变化取决于燃料。双色高温计数据表明，在 15 和 21 vol.% O2 时，测得的火焰烟尘温度和烟尘 KL 因子相似，但随着环境 O2 浓度的进一步降低而变化。发现燃烧持续时间和火焰面积的变化取决于燃料。双色高温计数据表明，在 15 和 21 vol.% O2 时，测得的火焰烟尘温度和烟尘 KL 因子相似，但随着环境 O2 浓度的进一步降低而变化。发现燃烧持续时间和火焰面积的变化取决于燃料。