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To accurately predict the combustion and emissions characteristics of a diesel engine fueled with n-butanol/diesel blends, a more realistic compact-sized skeletal mechanism with (149 species and 497 reactions) was developed in this study based on the decoupling method. It was generated by integrating the simplified fuel-related sub-mechanisms of n-butanol and diesel surrogates including n-dodecane, iso-cetane, iso-octane, toluene, and decalin. The same detailed core sub-mechanisms of C2-C3 and H2/CO/C1, in which the formation and oxidation of benzene (A1) and larger polycyclic aromatic hydrocarbon (PAH) up to coronene (A7) of alkanes, aromatics, cycloalkanes and alcohols were used. The PAH formation behavior of individual fuel components in the mechanism were analyzed in detail based on the methods of pathway analysis, rate of production and sensitivity analysis. The mechanism was extensively validated against ignition delay time, laminar flame speed, species profile and three-dimensional engine simulation. The results show that the effects of fuel types on the PAH formation are satisfactorily captured, and the combustion characteristics of n-butanol/diesel blends and each component are reliably reproduced by the current mechanism.

Micro-combustor can provide the required thermal energy of micro-thermal photovoltaic (MTPV) systems. The performance of MTPV is greatly affected by the effectiveness of a micro-combustor. In this study, a numerical simulation was conducted to explore the benefits of annular rectangular rib for enhancing the thermal performance of a nonpremixed micro-combustor. Based on the investigations under various rib heights, rib positions, and inlet mass flow rates, it is found that the addition of annular rectangular ribs in the micro-combustor creates a turbulent zone in the combustion chamber, thereby enhancing the heat transfer efficiency between the inner wall of the combustion chamber and the burned gas. The micro-combustor with annular rectangular rib shows a higher and more uniform wall temperature. When the H2 mass flow is 7.438 × 10−8 kg/s and the air mass flow is 2.576 × 10−6 kg/s, the optimum dimensionless rib position is at l = 6/9 and r = 0.4. At this condition, the micro-combustor has the most effective and uniform heat transfer performance and shows significant decreases in entropy generation and exergy destruction. However, the optimum l and r significantly depend on the inlet mass flow of H2/air mixture.