Optimization of automatic control system for $\text{NO}_{\mathrm{x}}$ emission reduction in smart marine diesel engine

Abstract

The International Maritime Organization (IMO) has formulated the MARPOL Convention, which imposes strict restrictions on the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{NO}_{\mathbf{x}}$</tex> emissions from ships, that is, the Tier III standard. China also stipulates that for Chinese domestic ships built on or after January 1, 2022, marine diesel engines with a single-cylinder displacement greater than or equal to 30 liters should meet the requirements of the Tier III standard. With the increasingly strict environmental protection requirements, the SCR system will definitely become the “standard” of the new generation of diesel engines in the future. At present, domestic marine diesel engines use a relatively wide range of fixed molar ratio control methods, and the injection and mixing of ammonia is not uniform enough, which leads to excessive nitrogen oxides at the exhaust gas outlet of the engine and a low automatic denitration input rate. Several SCR control methods widely used in the market through the research on the automatic control system of nitrogen oxides emission reduction for marine diesel engines were analyzed and compared, and several optimization methods for the automatic control system for nitrogen oxides emission reduction for marine diesel engines were proposed, and actual ship verification was carried out in this paper. The method provides a theoretical basis for the green development of smart marine diesel engine.