Simulation And Experimental Research On SCR System Control Strategy Of Marine Diesel Engine

With the development of the international shipping and ocean shipping, the emissionproduced by diesel engine has become a major source of pollution in coastal areas,particularly at the port. In order to limit the environmental pollution casued by NOxemissionsemitted from desiel engine, governments and international organizations have formulated thelegislation of limitations related to marine diesel engine NOxemissions. Selective catalyticreduction (SCR) aftertreatment is an effective technique to reduce NOxemissions. The controlsystem is one of the key techniques of SCR system, the performance of control strategy willdirectly affect the control behavior of NOxemissions control. This paper presents amodel-based SCR control algorithm which has been, conducted by simulation andexperimental studies. The results show that it can effectively reduce NOxemissions, and avoidexcessive NH3slip as well.The higher order chemical reaction kinetic model which can represent the chemicalreactions taking place in SCR catalyst is firstly established to relect the variety of each species.The higher order is subsequently simplified to3-states control model according to therequirement of control system. Altimately, a closed-loop control strategy for SCR system isset up based on the principle of model predictive control.The current onboard NOx sensors have been known to be cross-sensitive to ammonia, in thispaper, the NOx sensor ammonia cross-sensitivity correction model has been established throughtheoretical analysis combined with experiments. The correction model was added to thecontrol strategy in order to improve control accuracy. The programme of closed-loop modelpredictive control strategy is compiled in LabVIEW software and conducted withNI-USB6289board. According to the emissions regulations, the experiemts are conducted ona four stroke diesel engine at the operation points of10%，25%,50%,75%and100%loadconditions. The experimental results show that the NOxconversion rate achieves upwards of90%and the NH3slip can meet regulation requirements. The effectiveness and feasibility ofthe control strategy is thus validated by the control performance...