This study explores the autoignition characteristics of three C5 isomers, namely n-pentane, 2-methylbutane (iso-pentane) and 2,2-dimethylpropane (neo-pentane). These measurements are intended to enhance understanding of C5 autoignition chemistry, and provide experimental data to guide improvements to a general hydrocarbon oxidation mechanism. To that end, the autoignition behavior of these three C5 isomers was investigated in a modified CFR engine at an intake temperature of 120 °C and a fixed engine speed of 600 rpm to determine the critical compression ratio (CCR) at which hot ignition occurs. To find the critical compression ratio, the engine compression ratio (CR) was gradually increased to the point where CO in the engine exhaust rapidly decreased and significant high temperature heat release was observed, while holding equivalence ratio constant. Fundamental ignition behaviors such as the CCR and the calculated percentage of low temperature heat release (%LTHR) demonstrate the impact of chain length and methyl substitutions on ignition reactivity. The %LTHR shows a stronger two stage heat release for n-pentane than for neo-pentane observed at critical ignition conditions. In contrast, single stage heat release is observed for iso-pentane, leading to the weakest overall oxidation reactivity of the three isomers. Key reaction paths forming conjugate alkenes and C₅ oxygenated species control the autoignition reactivity of n-pentane and iso-pentane within the low temperature and NTC regimes. However, neo-pentane forms no conjugate alkene due to its unique molecular structure, and instead produces iso-butene to retard its oxidation.

本研究探索了三种C5异构体的自燃特性，即正戊烷，2-甲基丁烷（异戊烷）和2,2-二甲基丙烷（新-戊烷）。这些测量旨在增强对C5自燃化学的理解，并提供实验数据以指导对一般烃氧化机理的改进。为此，在改进的CFR发动机中，在进气温度为120°C和固定发动机转速为600 rpm的情况下，研究了这三种C5异构体的自燃行为，以确定发生热着火的临界压缩比（CCR）。为了找到临界压缩比，将引擎压缩比（CR）逐渐增加到引擎排气中的CO迅速降低并观察到明显的高温放热的程度，同时保持当量比不变。基本的起燃行为（例如CCR）和计算的低温放热百分比（％LTHR）证明了链长和甲基取代对点燃反应性的影响。％LTHR显示出更强的两阶段热释放在临界点火条件下，正戊烷比新戊烷要高。相反，观察到异戊烷的单级放热，导致三种异构体的总氧化反应性最弱。形成共轭烯烃和C ₅氧化物种的关键反应路径控制着低温和NTC范围内正戊烷和异戊烷的自燃反应性。但是，新戊烷由于其独特的分子结构而不会形成共轭烯烃，而是会生成异丁烯以阻止其氧化。