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A high temperature and no oxygen atmosphere fuel reforming has been proposed for the purpose of exergy saving by theoretical analyzing the detailed exergy loss events of combustion process, the correctness and feasibility of this fuel reforming have been verified through experiments. The exergy behaviors of high temperature and no oxygen atmosphere fuel reforming have been extensively studied, and many benefits had been observed including: (1) simplifying the reforming device where catalysts are not necessary; (2) improving the total chemical exergy while effectively converting large moleculae to small moleculae; (3) improving the mixture’s ratio of specific heat that can promote work-extraction; and (4) lengthening the ignition delay that buys time for better mixing process. All of these benefits are conducive to a better organized HCCI combustion that may improve the engine second law efficiency.

To explore the exergy loss of engine combustion process, entropy generations were numerically analyzed through detailed chemical kinetics. It revealed that the reformed fuel with simpler molecular tended to produce lower combustion irreversibility. Furthermore, a promising high efficiency RM- HCCI (Reformed molecule HCCI) combustion principle was proposed. In a RM-HCCI engine, hydrocarbon fuels were reformed into small molecule fuels under high temperature and low/no oxygen atmosphere before injection into the cylinder when the exhaust gas enthalpy to a certain extent was recovered, further improving the engine efficiency. The second law efficiency (η2nd) of a RM-HCCI combustion with a CR of 10 can be increased from 36.78% to 45.47% by coordination of multiple control parameters, and to 67.79% by raising CR from 10 to 100.