Model-based urea injection control strategy and ammonia storage estimation for diesel engine SCR system

The selective catalytic reduction (SCR) technology is one of the most effective approaches of reducing the diesel engine exhaust emissions. A brief introduction to the features of the diesel exhaust aftertreatment system is given, then the ammonia storage characteristics of SCR catalyst is studied based on the nonlinear continuous-time model for SCR system. A closed-loop control system of urea measurement and injection is proposed. The state observer based on the extended Kalman filter (EKF) and closed-loop controller is designed. SCR test bench is set up for the experimental validation of the control strategy. The experimental results show that the closed-loop control system is satisfying for the diesel engine exhaust aftertreatment SCR system. It also can effectively reduce the diesel nitrogen oxide emissions and avoid the secondary pollution caused by the ammonia leakage.