Control Research Of SCR System Based On Model For Marine Diesel Engine

IMO has issued MARPOL annex VI to control emission pollution from marine diesel engine.SCR technology is one of the promising ways to mee the standards according to MARPOL annex VI Tier III.In this paper,SCR chemical reaction model and engine exhaust characteristic model were established,combined with engine and SCR system test data,the control research of urea was studied.Firstly,SCR chemical reaction was analyzed,then the SCR reaction of chemical kinetics model was established,and the model of NO_x,NH₃,ammonia storage and temperature were established based on the Matlab/Simulink.Secondly,test of emission characteristic for diesel engine was conducted,by analyzing the influencing factors on emission characteristic of diesel engine,the exhaust characteristic model of diesel engine was established and verified by BP neural network,the model validation relative error is 6% and exhasut characteristic was predicted in the operating range.Thirdly,the parameter of SCR model was modified through SCR test,then the results of parameter modification were as follows: probcS ×a was 15.0432,kSCR was 2.5852 m2 / s,Ea,SCR was 31283 J/mol.The revised SCR model prediction value and SCR test bench data relative error is 12%.Finally,taking diesel engine E3 test cycle model as an example,according to the engine exhasut characteristic model and SCR model determined the urea injection amount,combined with transient correction and corrective deedback,initial urea injection control strategy is proposed.