Experimental and numerical analysis of the thermodynamic characteristics of a hydrocarbon flame with an improved second-law thermodynamic model

This paper presents an improved analysis model for the combustion process, based on the second law of thermodynamics, that includes an exergy balance equation that reflects the influence of thermal radiation in the flame. In the experimental analysis, the model is combined with the infrared spectrum measurement technique, and the exergy efficiency of the flame is determined using the measured radiative intensities. In the numerical analysis, we calculate the entropy generation rates (EGRs) associated with the irreversibilities of various processes, including thermal radiation, heat conduction, mass diffusion and chemical reactions. The second law of thermodynamics is used for the first time to analyse the chemical mechanism and the combustion characteristics of the flame, and the relationship between the flame structure and energy conversion in the flame is established. Both the experimental and numerical results indicate that the exergy efficiency first decreases and then increases as the equivalence ratio is reduced. The results of an entropy analysis indicate that CH2O and HCO are two important substances in the generation process of CO2. An exergy analysis shows that the energy conversion processes in the different zones have different characteristics and that the strongest energy conversion takes place near the inner combustion surface.