College of Power and Energy Engineering, Harbin Engineering University, Harbin, 150001, People's Republic of China.
Environ Sci Pollut Res Int. 2020 Apr;27(12):12851-12865. doi: 10.1007/s11356-019-04194-2. Epub 2019 Feb 7.
In order to avoid the production of sulfates and nitrates in marine diesel engines that burn sulfur-containing fuels, the operating temperature of their high-pressure selective catalytic reduction (HP-SCR) systems should be higher than 320 °C. For marine low-speed diesel engines, only the pre-turbine exhaust gas temperature can meet this requirement under specific conditions, with the main engine modulation method helping to increase the exhaust gas temperature. However, the main engine modulation method brings down the power output and fuel economy of the main engine and causes the matching problem of the turbine and the other devices with the main engine. The original engine model of the marine low-speed diesel engine and the high-pressure SCR system configuration model have been constructed using one-dimensional simulation software. In addition, the performance of the high-pressure SCR system under the conditions of low-sulfur and high-sulfur exhaust gas was thoroughly analyzed. Moreover, the two main engine modulation schemes of the scavenging bypass and the turbine exhaust bypass of the original engine matching with the high-pressure SCR system were studied. The study found that the weighted average value of the NOx under the condition of low-sulfur exhaust gas met with the requirement of the IMO Tier III regulations when the low-speed diesel engine was matched with the high-pressure SCR system. However, the weighted average value of the NOx under the condition of high-sulfur exhaust gas was slightly higher than that required by the IMO Tier III regulation. In addition, the optimal main engine modulation scheme for this low-speed diesel engine was clarified by comparing the effects of the scavenging bypass and the turbine exhaust bypass modulation on the exhaust performance, and the working performance of the original engine. With an opening of 0.4 of the CBV valve under 25% engine load, the weighted average NOx of the original exhaust gas was 3.38 g/(kW·h), the power had decreased by 0.7%, and the fuel consumption had increased by 1.0%. Furthermore, when the EGB valve opening was 0.3, the weighted average value of NOx was 3.31 g/(kW·h), the power had reduced by 2.4% and the fuel consumption had increased by 2.5%. Both modulation scheme methods made the exhaust performance of the original engine meet the requirements of the IMO Tier III emission regulations, but the scavenging bypass modulation scheme had less impact on the original engine's performance.
为避免燃烧含硫燃料的船用柴油机产生硫酸盐和硝酸盐，其高压选择性催化还原（HP-SCR）系统的运行温度应高于 320°C。对于船用低速柴油机，只有在特定条件下，前置涡轮废气温度才能满足这一要求，主机调节方法有助于提高废气温度。但是，主机调节方法会降低主机的功率输出和燃油经济性，并导致涡轮机与主机其他设备之间的匹配问题。使用一维模拟软件构建了船用低速柴油机的原动机模型和高压 SCR 系统配置模型。此外，还彻底分析了在低硫和高硫废气条件下高压 SCR 系统的性能。并且，研究了与高压 SCR 系统匹配的原机扫气旁通和涡轮排气旁通两种主要主机调节方案。研究发现，当低速柴油机与高压 SCR 系统匹配时，在低硫废气条件下，NOx 的加权平均值满足 IMO Tier III 法规的要求。但是，在高硫废气条件下，NOx 的加权平均值略高于 IMO Tier III 法规的要求。此外，通过比较扫气旁通和涡轮排气旁通调节对排气性能和原机工作性能的影响，明确了该低速柴油机的最佳主机调节方案。在 25%发动机负荷下，CBV 阀开度为 0.4 时，原废气的加权平均 NOx 为 3.38 g/（kW·h），功率下降 0.7%，燃油消耗增加 1.0%。此外，当 EGB 阀开度为 0.3 时，NOx 的加权平均值为 3.31 g/（kW·h），功率降低 2.4%，燃油消耗增加 2.5%。这两种调节方案都使原机的排气性能满足 IMO Tier III 排放法规的要求，但扫气旁通调节方案对原机性能的影响较小。
