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Dissertation
Autoignition chemistry studies of primary reference fuels and their mixtures with oxygenates in a research engine
Doctor of Philosophy (Ph.D.), Drexel University
Aug 1995
DOI:
https://doi.org/10.17918/00008012
Abstract
Autoignition chemistry plays an important role in engine knock which limits the thermal efficiency of spark ignition engines. To develop a better understanding of autoignition chemistry, this study investigated the primary reference fuels (PRF's), i.e., n-heptane and iso-octane (2,2,4-trimethyl pentane), their blends, and their mixtures with oxygenates which have been proposed as gasoline additives. The approach used was to conduct experiments in a motored research engine fueled with neat PRF's, an 87 octane blend of PRF's (87 PRF), and 87 PRF blended with methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), methyl tert-amyl ether (TAME), diisopropyl ether (DIPE), methanol and ethanol. Detailed evolution profiles of reactants, molecular intermediates, and products were measured prior to autoignition via in-cylinder sampling combined with gas chromatographic analysis. The experiments provided kinetic and mechanistic information on oxidation reactions leading to autoignition. An oxidation mechanism was assembled to describe the chemical processes responsible for the measured species and ignition behavior. Some key reactions were examined and discussed in detail based on the species data. In addition, the interaction between n-heptane and iso-octane oxidation was addressed using the results of 87 PRF. The effects of adding the oxygenates on the oxidation and autoignition of 87 PRF were identified. The results showed that all of the ethers and alcohols were effective in reducing preignition reactivity and retarding autoignition, and mechanistic explanations for the behavior were proposed. In addition to the experimental approach, this study also included a modeling effort. Based on an existing ignition model, a reduced chemical kinetic model was developed for prediction of major oxidation behavior of PRF's, using the experimental results primarily from this study. The model was tuned to be applicable for the neat PRF's, 87 PRF and 63 PRF, and at various engine conditions. At a constant inlet condition, the model predicted oxidation behavior is in fairly good agreement with experiments, including ignition delay(s), preignition heat release, fuel consumption, CO formation, and production of other species classes. In addition, the model reproduced the experimentally observed dependence of overall reactivity on temperature and pressure.
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Details
- Title
- Autoignition chemistry studies of primary reference fuels and their mixtures with oxygenates in a research engine
- Creators
- Houliang Li
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xvii, 215 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Engineering (1970-2026); Drexel University
- Other Identifier
- 991021888825004721