Study And Assessment On Self-learning Control Of Universal SCR System

In the traditional internal combustion engine,compares to the gasoline engine,diesel engine has larger compression ratio,so it has obvious advantage in fuel economy,power performance and reducing greenhouse gas emission.therefore,diesel engine is not only take over the mainstream of the commercial vehicles market,but in the passenger car market share is increasing. However,diesel engine NOX and PM emission is higher than gasoline engine,and which is a relation of trade-off,so the selective catalytic reduction post-processing system has great advantages in reducing NOX emission.So it has become the preferred technology when many merchants in the face of increasingly stringent emission regulations.However,due to historical reasons,we draw heavily on the introduction of foreign product on the diesel engine electronic control systems and high-pressure injection systems,lacking of self-developed in the machine control algorithm, signaling protocols,core hardware,resulting in following the abroad models in product architecture,control stratege,Signal pattern,and each diesel engine requires calibration,lacking of versatility.But the principle is based on Universal SCR system self-learning control strategy and algorithm of Han Xunfeng, Jilin University, Optimizing and improving its control strategies and algorithms on using of the laboratory resources,and also do some developed research and achieve functions about the control strategy, the introduction of closed-loop control PID regulator, provides research ideas and basis for further study and Productized.This paper firstly introduces the chemical reaction mechanism of the SCR after treatment system and quantifies all the possible reaction of the nitrogen oxides in the exhaust with chemical formula, provides universal SCR system design with an important reference. Based on the quantification analysis of the chemical equations of nitrogen oxides, we redesign the liquid storage tank, tank replenishing and constant pressure tank of the universal SCR system, ensure the feasibility and practicality of universal SCR system.This paper introduces the structure and working principle of the new hardware in detail, according to the working principle of a new hardware device,we develope corresponding software control procedures, realizing the control of electromagnetic valve and urea nozzle in urea supply automatic systemand real-time signal feedback and display, to enable the control to get quantitative, to ensure the stability and accuracy control. Using MC9S12XS128 freescale MCU development board and the corresponding software Codewarrior, we realize the liquid level, temperature,nitrogen oxides signal data acquisition and control, formulate control strategy of the rehydration and constant pressure injection solenoid valve and nozzle.The injection process of urea nozzle was compiled, and the injection characteristics of a new generation of BOSCH nozzle under different injection pressure and injection frequency were studied in this program, which laid the foundation for further research.According to test data to determine the total nox generation pulse spectrum and catalytic conversion efficiency pulse spectrum, to map the ammonia-nitrogen pulse spectrum of SCR system and the Reducing injection quantity pulse spectrum, laid a basis for determining the nozzle control strategy. According to the PID algorithm to make the exhaust of nitrogen oxides self tuning control strategy and B50 conditions tested, selected for the PID parameters of the system. Using the LabVIEW software to achieve computer software development of the universal SCR system, and realize LabVIEW and electric control unit communications test and verify the feasibility of the software communication function, achieve the more intuitive monitoring data.