Analysis Of Exergy Loss Of Gasoline Surrogate Combustion Process Based On Detailed Chemical Kinetics

Numerical analysis based on non-equilibrium thermodynamics combined with detailed chemical kinetics is conducted to explore the exergy loss mechanism of gasoline engine combustion process. The gasoline surrogates consist of four components: iso-octane(57%), n-heptane(16%), toluene(23%), and 2-pentene(4%). The overall exergy loss rate of gasoline surrogates is composed of three peaks, mainly resulting from the conversion reactions of large molecules into small molecules(classified as Stage 1), the H2O2 loop-related reactions(classified as Stage 2), and the oxidation reactions of CO, H, and O(classified as Stage 3). With an increase in initial temperature, equivalence ratio, and oxygen concentration, the exergy loss rates for all three stages increase, whereas the corresponding durations of each stage decrease. With an increase in initial temperatures, the exergy loss decrease is mainly due to the exergy loss reduction in Stages 1 and 2, while with an increase in equivalence ratios and oxygen concentration, the exergy loss decrease is mainly due to the exergy loss reduction in all three stages. Increasing initial pressure benefits the inhibition of incomplete exergy loss but has little effect on overall exergy loss. As the initial combustion condition varies, the key exergy loss reduction sources for Stage 1 are toluene and iso-octane related reactions. In this study, the combined effects of combustion boundaries on the total loss of gasoline surrogates are investigated. For a gasoline engine with a compression ratio of 10, the total loss can be reduced from 31.3% to 24.3% using lean combustion. The total loss can be further reduced to 22.4% by introducing exhaust gas recirculation and boosting the inlet charge. If the compression ratio is increased to 17, the total loss can be decreased to 20.4%, and finally to 16.8%, if the compression ratio is further increased to 100.It revealed that the reformed fuel with simpler molecular tended to produce lower combustion irreversibility. Furthermore, a promising low exergy loss combustion principle was proposed. By reforming gasoline fuel to simpler molecular, the overall exergy loss rate of gasoline surrogates is composed of two peaks, mainly resulting from the reactions of the H2O2 loop-related reactions(classified as Stage 2), and the oxidation reactions of CO, H, and O(classified as Stage 3). The conversion reactions of reformed large molecules into small molecules are classified as Stage 1. The processes of large hydrocarbon fuels to small molecule fuels through ?-scission provide an optimal approach to reduce the exergy losses of Stage 1. With an increase in reforming temperatures, the exergy loss decrease is mainly due to the exergy loss reduction in Stages 1, while with an increase in reforming times, the exergy loss decrease is mainly due to the exergy loss reduction in Stage 2. As the initial combustion condition varies, the key exergy loss reduction sources for Stage 1 is still toluene related reactions.