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Chapter 3 Autoignition and Chemical-Kinetic Mechanisms of Homogeneous Charge Compression Ignition Combustion for the Fuels with Various Autoignition Reactivity Dongwon Jung Additional information is available at the end of the chapter http://dx.doi.org/10.5772/intechopen.70541 Provisional chapter © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. DOI: 10.5772/intechopen.70541 Autoignition and Chemical-Kinetic Mechanisms of Homogeneous Charge Compression Ignition Combustion for the Fuels with Various Autoignition Reactivity Dongwon Jung Additional information is available at the end of the chapter Abstract This work demonstrates the autoignition and chemical-kinetic mechanisms of homoge- neous charge compression ignition (HCCI) combustion for the fuels with various autoig- nition reactivity. This is done for four fuels: methane, dimethyl ether (DME), iso-octane and n-heptane. Methane and iso-octane are selected as the single-stage ignition fuel, and DME and n-heptane are selected as the two-stage ignition fuel. As a tool for under- standing the characteristics of autoignition and combustion process in HCCI engine, a zero-dimensional single-zone engine model of ‘CHEMKIN’ in Chemkin-Pro was used. The complete compression and expansion strokes were modeled using an engine with a connecting-rod length to crank-radius ratio of 3.5 and a compression ratio of 13. A detailed chemical-kinetic mechanism for methane and DME is Mech_56.54 (113 species and 710 reactions). For iso-octane and n-heptane, a detailed chemical-kinetic mechanism from Lawrence Livermore National Laboratory (1034 species and 4236 reactions) is used. The results show that methane and iso-octane exhibit only the main heat release, ‘high- temperature heat release (HTHR)’ by high-temperature reactions (HTR). In contrast, both DME and n-heptane exhibit the first heat release ‘low-temperature heat release (LTHR)’ associated with low-temperature reactions (LTR) before HTHR. Keywords: homogeneous charge compression ignition, autoignition, chemical-kinetic mechanisms, fuel autoignition reactivity, low-temperature reaction, intermediate-temperature reaction, high-temperature reaction © 2018 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.