For marine diesel engines, the selective catalytic reduction (SCR) system can be tailored to ensure high nitrogen oxides (NO_x) reduction performance, low ammonia (NH₃) slip, and low urea consumption. A sufficient mixing zone of urea water solution (UWS) and exhaust gas are required because of the limited installation space. In this study, therefore, mixing units such as a swirl-type mixer and an additional mixing chamber were adopted to improve the flow mixing performance with a low-pressure drop in a marine urea-SCR system. The application of mixing units gave a positive influence on the flow turbulent characteristics and urea decomposition into NH₃. The mixer caused flow recirculation and increased turbulent intensity. Moreover, the additional mixing chamber was able to achieve an enhanced residence time for the UWS injections. When mixing units both were combined, it showed the highest conversion efficiency (urea to NH₃). In comparison to the SCR system without any mixing units, improvement in the efficiency of deNO_x was observed of 61.3 % by the application of the mixing chamber, 76.2 % by the application of the mixer, and 86.3 % by the application of the mixer and the mixing chamber combined.

对于船用柴油机，可以定制选择性催化还原（SCR）系统，以确保高氮氧化物（NO _x）还原性能，低氨（NH ₃）泄漏和低尿素消耗。由于安装空间有限，需要尿素水溶液（UWS）和废气的足够的混合区域。因此，在这项研究中，采用了诸如涡旋式混合器和附加混合室之类的混合装置，以提高船用尿素-SCR系统中的低压降下的流动混合性能。混合装置的应用对流动湍流特性和尿素分解为NH ₃有积极影响。混合器引起气流再循环并增加了湍流强度。而且，额外的混合室能够为UWS注射实现更长的停留时间。当将两个混合单元组合时，它显示出最高的转化效率（尿素到NH ₃）。相比于SCR系统而没有任何混合单元，改善DENO效率_X观察到61.3％通过混合室中的应用，76.2％由混合器的应用，和86.3％由混频器的应用和混合室合并。