We present 3D numerical results on tri-fuel (TF) combustion using large-eddy simulation and finite rate chemistry. The TF concept was recently introduced by Karimkashi et al. (Int. J. Hydrogen Energy, 2020) in 0D. Here, the focus is on spray-assisted ignition of methane–hydrogen blends. The spray acts as a high-reactivity fuel (HRF) while the ambient premixed methane-hydrogen blend acts as a low-reactivity fuel (LRF) mixture. Better understanding on such a TF process could enable and motivate more extensive hydrogen usage in e.g. compression ignition marine engines where spray-assisted dual-fuel (DF) combustion is already utilised. The studied spray set-up is based on the modified ECN Spray A case, see Kahila et al. (Combustion and Flame, 2019) for DF combustion. The ambient pressure and temperature are $T_{\mathrm{a}\mathrm{m}\mathrm{b}}=$ 900 K and $p_{\mathrm{a}\mathrm{m}\mathrm{b}}=$ 60 bar. The hydrogen content of the LRF blend is varied systematically by changing the molar fraction $0\le x\le 1$, $x=\frac{\left[{\mathrm{H}}_2\right]}{\left[{\mathrm{H}}_2\right]+\left[\mathrm{C}{\mathrm{H}}_4\right]}$. The main added value of the study is that we extend the TF concept to 3D. The particular findings of the study are as follows: 1) Consistent with Karimkashi et al. 2020, hydrogen delays ignition also in 3D and the effect becomes significant for $x\ge 0.5$. 2) The ratio between the first- and second-stage ignition delay times $(\frac{{\tau }_2}{{\tau }_1}{)}^{0\mathrm{D}}\approx 2\pm 0.1$ and $(\frac{{\tau }_2}{{\tau }_1}{)}^{3\mathrm{D}}\approx 3\pm 0.3$. Furthermore, the ratio between 3D and 0D ignition delay times is given as $\frac{{\tau }_2^{3\mathrm{D}}}{{\tau }_2^{0\mathrm{D}}}\approx 2\pm 0.2$ for all TF cases. 3) Finally, consistent with Karimkashi et al. 2020, also in 3D the high-temperature combustion heat release mode is shown to appear stronger in TF than the low-temperature combustion mode compared to DF methane–diesel combustion.

我们使用大涡模拟和有限速率化学方法，对三燃料（TF）燃烧提供了3D数值结果。TF概念是Karimkashi等人最近提出的。（Int。J. Hydrogen Energy，2020）在0D中。在这里，重点是甲烷-氢气混合物的喷雾辅助点火。喷雾剂充当高反应性燃料（HRF），而周围环境预混合的甲烷-氢混合物充当低反应性燃料（LRF）混合物。对这种TF工艺的更好理解可以使并激发更广泛的氢气使用，例如在已经采用喷雾辅助双燃料（DF）燃烧的压燃式船用发动机中。所研究的喷雾设置基于改进的ECN喷雾A案例，请参见Kahila等。（Combustion and Flame，2019）用于DF燃烧。环境压力和温度为${Ť}_{\mathrm{一种}\mathrm{米}\mathrm{b}}=$ 900 K和 $p_{\mathrm{一种}\mathrm{米}\mathrm{b}}=$60巴 LRF共混物的氢含量可通过改变摩尔分数系统地改变$0\le X\le \mathrm{1个}$， $X=\frac{\left[{\mathrm{H}}_{\mathrm{2个}}\right]}{\left[{\mathrm{H}}_{\mathrm{2个}}\right]+\left[\mathrm{C}{\mathrm{H}}_4\right]}$。该研究的主要附加价值是我们将TF概念扩展到了3D。该研究的具体发现如下：1）与Karimkashi等人一致。2020年，氢气也将延迟3D点火，其效果对于$X\ge 0.5$。2）第一阶段点火延迟时间与第二阶段点火延迟时间之比$（\frac{{\tau }_{\mathrm{2个}}}{{\tau }_{\mathrm{1个}}}{）}^{0\mathrm{d}}\approx \mathrm{2个}\pm 0.1$ 和 $（\frac{{\tau }_{\mathrm{2个}}}{{\tau }_{\mathrm{1个}}}{）}^{3\mathrm{d}}\approx 3\pm 0.3$。此外，3D和0D点火延迟时间之间的比率为$\frac{{\tau }_{\mathrm{2个}}^{3\mathrm{d}}}{{\tau }_{\mathrm{2个}}^{0\mathrm{d}}}\approx \mathrm{2个}\pm 0.2$对于所有TF案件。3）最后，与Karimkashi等人一致。2020年，同样在3D模式下，与DF甲烷-柴油燃烧相比，TF中的高温燃烧放热模式表现出比低温燃烧模式更强的释放能力。