Selective catalytic reduction (SCR) system has been proven to be an effective technology for the removal of NOx emitted from marine diesel engines. In order to comply with stringent International Maritime Organization (IMO) Tier III NOx emission regulations, a number of engine manufacturers have developed their own SCR systems. This paper focuses on modeling of an SCR reactor and developing model-based urea dosing control strategy. A mathematical model of SCR reactors has been established. Model-based control strategy relies on the three-state and one-state reactor models established to accomplish urea dosing algorithm and is promising in limiting excessive NH3 slip. The SCR reactor model is further used in a simulation for the purpose of developing model-based urea dosing control strategies. The simulation results show that the NO sliding mode control requires a massive prestudy of the NOx reduction capability of the catalyst in order to set an appropriate control objective for each operating condition. However, this calibration work can be omitted in the optimal control and NH3 sliding mode control, which mitigates the workload of the controller design. The optimal control strategy presents a satisfied control performance in limiting NH3 slip during transient state engine operating conditions.
The International Maritime Organization has set forth strict regulations about the NOx emission limit of ships to address the pollution problem in the transportation sector. Selective catalytic reduction (SCR) is the most effective post-engine means to reduce emission, and the control of urea spray critically affects the SCR performance. This paper developed a predictive control strategy of the SCR system based on the state space model. Specifically, the block model of the SCR reactor was established based on the reaction mechanism of the SCR system, and the unknown model parameters were identified. Rapid prototyping of the SCR system was carried out using the dSPACE real-time simulation platform to optimize the control under steady-state conditions. The catalyst ammonia coverage was set as the control target to maximize the NOx conversion rate while maintaining the NH3 escape at the outlet less than 10 ppm. The cyclic test results showed that the control strategy can quickly respond to external disturbance and modify the control target to keep the ammonia coverage rate within the target range, to thus achieve high NOx conversion rate while maintaining the required ammonia escape.
Data cleaning, also called data cleansing or scrubbing, deals with detecting and removing errors and inconsistencies from data in order to improve the quality. Currently the problem is that people hold large amounts of data but do not get any useful knowledge, being described as "data rich but information poor". This paper will introduce data cleaning and study how to clean the Chinese data in a system based on the character matching algorithm and SNM method.
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