A novel fuel-substitution strategy was used to investigate the relationship between octane number and cetane number under representative low temperature combustion (LTC) thermodynamic conditions. The cetane number of the test fuels was known by using mixtures of the cetane number secondary reference fuels (SRFs) T-26 and U-19, which are full-blend certification fuels used in the place of 2,2,4,4,6,8,8-heptamethylnonane and n-hexadecane for engine cetane number testing. The octane number was derived from the fuel-substitution methodology in terms of the octane primary reference fuel (PRF, consisting of n-heptane and isooctane) mixture needed to maintain combustion phasing during homogeneous-charge compression-ignition (HCCI) engine operation as increasing amounts of the SRF mixture was substituted for the PRF mixture. A linear blending relationship was found to exist between the cetane and octane numbers. Results agree with other similar relationships from the literature acquired under substantially different operating conditions. The current study significantly expands the range of the cetane–octane correlation to a range of cetane numbers from 20 to 75 and validates the correlation at low equivalence ratios of interest to LTC operation.

在代表性的低温燃烧（LTC）热力学条件下，一种新颖的燃料替代策略被用于研究辛烷值和十六烷值之间的关系。通过使用十六烷值二级参考燃料（SRF）T-26和U-19的混合物来获知测试燃料的十六烷值，它们是代替2、2、4、4的全混合认证燃料， 6,8,8-七甲基壬烷和正十六烷，用于发动机十六烷值测试。辛烷值是根据辛烷主要参考燃料（PRF，由n需要在均质充量压燃（HCCI）发动机运行期间维持燃烧定相所需的正庚烷和异辛烷混合物），因为越来越多的SRF混合物代替了PRF混合物。发现十六烷值和辛烷值之间存在线性混合关系。结果与在实质上不同的操作条件下从文献中获得的其他类似关系相符。当前的研究将十六烷值与辛烷值的相关性范围扩大到十六烷值从20到75的范围，并验证了在低当量比的LTC操作时的相关性。