中文摘要：

为了提高船用柴油机SCR的尿素蒸发分解速率以及与排气的混合均匀性,运用CFD手段对船机SCR系统的混合器进行优化设计,对比分析不同结构混合器对NH3分布均匀性、NOx转化效率、NH3泄漏及压力损失的影响。模拟结果表明：混合器有利于液滴的破碎,可促进尿素的蒸发及热解,同时能够提高喷雾与排气的混合均匀性;8叶片锥形混合器的混合效果最好,可使NOx转化率提高14.3%,氨泄漏降低25 ppm。对优化设计后的船机SCR系统进行柴油机D2循环排放试验,试验结果表明：在相同的催化剂体积和尿素喷射量下,安装8叶片锥形混合器后各工况点的NOx转化效率均上升约8%,NOx加权比排放从0.56 g/（k W·h）下降到0.37 g/（k W·h）。

英文摘要：

To improve the decomposition rate of urea and the mixing uniformity of NH3, a computational fluid dynamics （CFD） method was used to optimize the design of a static mixer in a marine selective catalytic reduction system （SCR）. The effect of different mixer structures on the ammonia concentration distribution, NOxconversion, NH3 slip, and pressure loss were analyzed. The simulation results showed that the mixer plays a role in the breakup of spray droplets, urea decomposition, and mixing of the spray with the exhaust, as well as the mixing uniformity of the spray and exhaust. It was established that a cone mixer with eight blades achieved better mixing than other mixers. An increase in NOx conversion of 14.3% and a decrease in ammonia slip of 25 ppm were achieved compared with the original SCR system. An emission test was conducted of the D2 driving cycle of the optimized SCR system. The results showed that when using the same volume of catalyst and urea dosing, the NOxconversion increased by approximately 8% after installing the cone mixer with ted, and the brake-specific emission of NOx in the eight blades under most of the operating conditions investiga- D2 driving cycle was decreased from 0.56 g/（ kW · h） to 0.37 g/（kW· h）.