Exergy Loss Characteristics of Laminar Premixed Flames for Hydrogen/Methane and Dimethyl Ether/Methane Fuel Blends

To reduce fossil energy consumption and achieve global carbon neutrality, it is essential to develop alternative fuels such as hydrogen (H-2) and dimethyl ether (DME). In order to analyze the energy-mass conversion behavior of alternative fuels for power units (including gas turbines) and to explore the principles of efficiency enhancement, the exergy loss characteristics of methane (CH4)/air laminar premixed flames blended with H-2/DME were investigated. The effects of blending ratio, unburned gas temperature, operating pressure, and equivalence ratio on the exergy loss fraction were considered. The results indicated that DME and H-2 had opposite effects on the total exergy loss fraction of the premixed flame. Elevating the operating pressure was beneficial to reducing the exergy loss caused by chemical reactions and exhaust gas, which more significantly enhanced the exergy efficiency of each fuel mixture compared to increasing the unburned gas temperature. The exergy loss fraction due to the exhaust gas was also lower in the lean flame, suggesting that DME could be a promising alternative to CH4 in this scenario. As the exergy loss fraction due to chemical reaction was minimized at an equivalence ratio of 1.2, a variable equivalence ratio operating strategy was expected to further optimize the exergy efficiency of each fuel mixture. Furthermore, response functions of the total exergy loss fraction, which considered the combined effects of multiple operating parameters, were constructed. These response functions allow the total exergy loss fractions of CH4 premixed flames with high DME blending ratios and moderate H-2 blending ratios to be quantified. The results from this study enable a deeper understanding of the energy-mass conversion behavior of systems with added H-2/DME during combustion and provide theoretical support for the application of alternative fuels to more complex configurations of industrial burners.