Modeling, Analysis, and Experimental Testing of a Selective Catalytic Reduction Dosing System

In recent years, selective catalytic reduction (SCR) system has been used in modern ship or vehicle diesel engines to reduce emissions. SCR technique is a key enabler for NOx reduction, which is critical for the performance and fuel economy of both ship and vehicle diesel engines, since a more advanced timing of the diesel injection is used. The ammonia (NH3) is generated from reaction mechanism of SCR system by using the liquid urea as the reluctant. Therefore, a precise urea dosing system is crucial, and its flow control is very challenging as the traditional approach is still in the open-loop fashion or little urea requirement quantity. To address this challenge, a new urea dosing sub-system of SCR is proposed, which realizes flow feedback with a flow sensor and different control method. The proposed system is novel as it embeds all the control elements in the flow rate regulation, which successfully solves the precise control of the urea dosing system with nonlinear dynamics. In this paper, we first present the working principle of the new urea dosing system. Then, the mechanical system design is shown and the system dynamic model is built. To this end, the proposed system control mechanism is fabricated and validated in a testing fixture. The new urea dosing system performance is finally presented through a series of simulation and experimental results.