Autoignition delay times of ammonia/dimethyl ether (NH₃/DME) mixtures were measured in a rapid compression machine with DME fractions of 0, 2 and 5 and 100% in the fuel. The measurements were performed at equivalence ratios $\phi$=0.5, 1.0 and 2.0 and pressures in the range 10–70 bar; depending on the fuel composition, the temperatures after compression varied from 610 K to 1180 K. Admixture of DME is seen to have a dramatic effect on the ignition delay time, effectively shifting the curves of ignition delay vs. temperature to lower temperatures, up to ~250 K compared to pure ammonia. Two-stage ignition is observed at $\phi$=1.0 and 2.0 with 2% and 5% DME in the fuel, despite the pressure being higher than that at which pure DME shows two-stage ignition. At $\phi$=0.5, a reproducible pre-ignition pressure rise is observed for both DME fractions, which is not observed in the pure fuel components. A novel NH₃/DME mechanism was developed, including modifications in the NH₃ subset and addition of the NH₂+CH₃OCH₃ reaction, with rate coefficients calculated from ab initio theory. Simulations faithfully reproduce the observed pre-ignition pressure rise. While the mechanism also exhibits two-stage ignition for NH₃/DME mixtures, both qualitative and quantitative improvement is recommended. The overall ignition delay times for ammonia/DME mixtures are predicted well, generally being within 50% of the experimental values, although reduced performance is observed for pure ammonia at $\phi$=2.0. Simulating the ignition process, we observe that the DME is oxidized much more rapidly than ammonia. Analysis of the mechanism indicates that this ‘early DME oxidation’ generates reactive species that initiate the oxidation of ammonia, which in turn begins heat release that raises the temperature and accelerates the oxidation process towards ignition. The reaction path analysis shows that the low-temperature chain-branching reactions of DME are important in the early oxidation of the fuel, while the sensitivity analysis indicates that several reactions in the oxidation of DME, including cross reactions between DME and NH₃ species presented here, are critical to ignition, even at fractions of 2% DME in the fuel.

在快速压缩机中测量氨/二甲醚（NH ₃ / DME）混合物的自燃延迟时间，燃料中DME的分数为0、2、5和100％。以当量比进行测量$\phi$= 0.5、1.0和2.0，压力范围为10-70 bar；根据燃料成分的不同，压缩后的温度从610 K到1180 K不等。DME的混合物对点火延迟时间有显着影响，有效地将点火延迟与温度的关系曲线移至较低温度，直至与纯氨相比约250K。观察到两阶段点火$\phi$尽管压力高于纯DME表现出两阶段点火的压力，但在燃料中DME分别为2％和5％的情况下仍为= 1.0和2.0。在$\phi$＝ 0.5，对于两个DME馏分均观察到可再现的点火前压力升高，这在纯燃料组分中未观察到。开发了一种新颖的NH ₃ / DME机理，包括对NH ₃子集的修饰和NH ₂ + CH ₃ OCH ₃反应的添加，其速率系数从头计算。模拟忠实地再现了观察到的点火前压力上升。虽然该机制还表现出NH _3的两阶段点火/ DME混合物，无论是定性还是定量的改进都值得推荐。氨/ DME混合物的总着火延迟时间可以很好地预测，通常在实验值的50％以内，尽管在60°C时观察到纯氨的性能下降。$\phi$= 2.0。模拟点火过程，我们发现二甲醚的氧化速度比氨快得多。对该机理的分析表明，这种“早期DME氧化”会产生反应性物种，从而引发氨的氧化，继而开始释放热量，从而升高温度并加速氧化过程，直至着火。反应路径分析表明，DME的低温度的链支化反应是在燃料的早期氧化重要，而灵敏度分析表明，几个反应在DME的氧化，包括DME和NH之间交叉反应₃种呈现即使在燃料中DME的含量仅为2％的情况下，此处的点火也是至关重要的。