Analysis of entropy generation and exergy efficiency of the methane/dimethyl ether/air premixed combustion in a micro-channel

Abstract

This work presents a numerical investigation on the entropy generation and exergy efficiency in a methane/dimethyl ether/air-fueled micro combustor. To this end, a three-dimensional numerical model established is first validated by comparing its predictions with experimental data in the literature. It is, then, applied to assess the effects of the inlet velocity and blending ratio on the entropy and exergy generation. As far as the entropy generation caused by chemical reactions is concerned, there exists a reaction step that contributes most to the overall entropy. The contributing rate of such a reaction is inhibited by increasing the blending ratio. Meanwhile, for a given fuel composition, the entropy generation due to chemical reactions and heat conduction is found to exhibit a monotonic trend with the inlet velocity, whereas the entropy induced by mass diffusion shows a non-monotonic dependence. Furthermore, the exergy destruction ratio induced by the chemical reaction plays a dominant role in the total exergy generation, irrespective of inlet velocity and blending ratio. Both the exergy loss and efficiency are shown to be increasing as the inlet velocity is elevated, along with the increase in the combustor wall temperature. In general, this work identifies how blended combustion affects the entropy and exergy generation in methane/dimethyl ether combustion systems and sheds light upon the underlying mechanism.