The oxidation of C2-C4 diols and diol/TPGME blends in a motored engine

[Display omitted] •The global oxidation reactivity of C2-C4 diols has been checked firstly by a modified CFR engine.•Both of ethanol and C2-C4 diols showed no phenomenon of low temperature heat release.•C2-C4 diols could be converted into TPGME with high selectivity, and diol/TPGME showed high global oxidation reactivity.•For diol combustion process, the chemical process played a more important role than physical process. Inspired by the announcement that liquid biofuel will be used nationally by 2020 in China, the autoignition of surrogates from hydrogenated biomass pyrolysis oil, namely, the C2-C4 diols, including ethanediol, 1,2-propanediol, and 1,2-butanediol has been studied using a modified CFR engine. From the oxidation process before critical compression ratio (CCR), it is observed that C2-C4 diols had similar oxidation reactivity as ethanol, indicating that C2-C4 diols had the potential for use as a supplement for ethanol. In addition, both of ethanol and C2-C4 diols did not display low temperature heat release. The ignition characteristics of C2-C4 diols suggest that diol/TPGME blends could be used, as TPGME has high ignition quality and could be generated from diols with a carbon selectivity as high as 75%. Based on this idea, diol/TPGME blends with volume ratio 20:80 were prepared and tested using the modified CFR engine. The blends showed strong low temperature oxidation behavior, even under a low intake temperature at 120 °C and a low compression ratio at 4, the low temperature heat release peak could still be found for the blends. Finally, the physical delay and chemical delay times were tested by a modified CID instrument between 540 and 640 °C, indicating that chemical process played a more important role on the combustion process than physical process, and the influence of temperature was more important for physical processes than chemical processes.