In this work, the explosive combustion of NH3/CH3OH/air mixtures covering wide ranges of equivalence ratios (0.7–1.7) and CH3OH mole fractions (0.2–1.0) was investigated experimentally and theoretically at ambient temperature and pressure. Results showed that the addition of CH3OH increases the maximum explosion pressure and maximum pressure rise rate. The empirical correlations for the maximum explosion pressure and maximum pressure rise rate are proposed, respectively. Furthermore, the heat loss of the explosion decreases significantly with the increasing CH3OH mole fraction. According to the instability analysis, the tendency of flame instability is enhanced with the enrichment of CH3OH due to the promoted hydrodynamic instability. Besides, the maximum pressure rise rate is augmented by flame instability. Kinetic analysis indicates that the CH3OH addition enhances the net heat release rate and active radicals. The total heat release of the NH3/CH3OH/air explosion is mainly attributed to the reactions R3: OH + H2 ⇔ H + H2O, R11: HO2 + H ⇔ 2OH, R24: CO + OH ⇔ CO2 + H, and R284: NH3 + H = NH2 + H2, while the predominant endothermal reaction is R1: H + O2 ⇔ O + OH. With the addition of CH3OH, the chemical effect has the largest contributions to the accelerated flame propagation on the lean and stoichiometric side, while the contributions of thermal and transport effects are dominant on the rich side.

The blend of ammonia (NH3) and dimethyl ether (DME) is a promising renewable and clean fuel. This work studies the basic explosion characteristics of NH3/DME/air with varying equivalence ratios (from 0.6 to 1.8) and DME fractions (from 0.2 to 1). Three essential parameters, i.e., explosion pressure (P max), explosion time (t c), and maximum pressure rise rate ((dP/dt)max), were experimentally obtained, and the heat loss during the explosion was quantitatively analyzed. Besides, the heat release characteristics and critical flame radius of destabilization in the explosion process were analyzed using the detailed NH3/DME reaction mechanism. The results showed that adding DME to the mixture can significantly increase the P max, increase the (dP/dt)max, and shorten the t c. The heat loss during the NH3/DME/air explosion mainly presents a negative correlation with the explosion intensity, as reflected by (dP/dt)max and t c. In addition, at stoichiometric ratios, the elementary reaction R12: H + OH + M = H2O + M contributes most to the total heat release of the NH3/DME/air explosion, while the NH3- or DME-related reactions subdominate the total heat production. Adding DME reduces the critical flame radius, causing the flame to enter an unstable state earlier, which is mainly dominated by the hydrodynamic effect.

Recent investigations have indicated that co-firing CH3OH with H2 is a promising approach to develop a carbon-neutral energy system. However, accurate measurements of laminar burning velocities over a wide range of equivalence ratios, H2 mole fractions, pressures and temperatures are complicated and may not available. Hence, this research deeply investigates the application of several machine learning models in predicting the laminar burning velocities of CH3OH/H2 blended fuels. Results denoted that Random Forest Regressor is the most persuasive model based on a thorough comparison, as indicated by the correlation coefficient of 0.99707.