System Of Marine Diesel Engine SCR Control

With the rapid development of the world’s trade and marine transportation, thenumber of ships has been increased year by year. The pollution on atmosphere and theenvironment by ships becomes more and more serious, which has been caused muchmore concern worldwide. International Maritime Organization (IMO), as designatedby the United Nations of specialized agency which responsible for the prevention ofmarine pollution from ships, released relevant regulations in order to achieve effectivegovernance of the marine environment. IMO recently issued MARPOL73/78Convention Annex VI, which aims to reduce the pollution caused by ships to theatmosphere. In2016, IMO Tier Ⅲ,a more stringent standard for NOXemissioncontrol will be enforced into accomplice. For implementation of the Convention, theinternational marine research centers research on the technologies for reducing marinediesel engine exhaust emissions. Selective Catalytic Reduction technology is one ofeffective measures to control NOXemission from diesel engine. In this paper, thecontrol system for marine diesel engine SCR has been studied on a medium-speeddiesel engine. The main points of this study are as follows:（1） Based on the principles of the SCR system, the factors on influencing thereaction of selective catalytic reduction have been studied. Analyzing the chosencatalyst and reducing agents of SCR, the method of measuring urea solution isstudied.（2） Through the study of several factors that affect the control strategy of thesystem, and based on a typical control model and the complexity of ship operation,five control strategies have been studied on the bases of discrete time PID controlalgorithm. After a comprehensive analysis of the five control strategies, a closed-loopforward feed sensor control mode is proposed and applied to the experimentaldevelopment of the SCR control system.（3） On the basis of the working principle of the SCR system, the hardware andsoftware of control system have been designed and an own copyright SCR control system has been developed for SCR system using on the medium-speed diesel enginewith rated power1320kW.（4）Function tests and engine tests have been conducted to evaluate functions andemissions control effects of the control system. The test results show that the transientresponse and adaptive performance of the control system are well, and can beappliance with IMO Tier Ⅲ standard as applying on a set of own-developed SCRsystem for diesel engine exhaust after-treatment.The Study on SCR control system has laid a good technical foundation forown-developed SCR system for marine diesel engine.