Research On Control Strategy Based On SCR Aging Characteristics

Due to the increase of engine exhaust emission standards,the traditional SCR control strategy can no longer meet the national V emission regulations,and the proposed new SCR(Selective Catalytic Reduction)control strategy has become the focus of research in various countries.Based on the existing control strategy,this paper proposes a new control strategy based on the SCR aging characteristics and develops the associated software to achieve more efficient NOx conversion,The main research content is as follows:(1)Aging mechanism analysis: 1)The catalytic mechanism of the copper-based molecular sieve catalyst SAPO-34 was analyzed and an aging three-state model of the molecular sieve catalytic converter was established.The SCR catalyst model based on the SCR chemical reaction rate model was established to solve the SCR model;2)Analyze and study the aging mechanism Based on the aging mechanism of copper-based molecular sieve catalyst SAPO-34,the effects of four major inactivation factors(high temperature deactivation,chemical element poisoning,coking agglomeration,and mechanical damage)on copper-based zeolite catalysts were analyzed and studied.Inactivation is the main method of inactivation of molecular sieve catalysts,and an aging kinetic model based on cluster velocity and reaction rate is proposed.(2)Establish an aging control strategy model: 1)Present a temperature calculation model based on the pre-temperature sensor,obtain the carrier temperature and gas temperature,and calibrate the pre-temperature sensor,and finally compare the model simulation with the experiment;2 A NOx generation mechanism calculation model based on the instantaneous reaction equilibrium state is proposed.Based on the NOx value obtained by the sensor,the NOx temperature correction coefficient of the intercooled water temperature and the intake air temperature is added,and the NOx original emission is corrected in combination with the aging coefficient,and the NOx is corrected.The sensor is calibrated.Finally,the model simulation is compared with the experimental verification.3)The aging coefficient calculation model based on the temperature calculation model is proposed to analyze the SCR aging characteristics,and the parameters of the aging model are experimentally solved,and the aging is established using GT-POWER software.The system model obtains the optimal value of each parameter;4)Proposes a urea injection correction strategy based on the aging coefficient,ensures the conversion efficiency of NOx and low leakage of NH3 according to the optimal adsorption ratio of NH3,and proposes a model self-calibration method for the urea nozzle Calibration;5)Using GT-POWER's own engine module combined with S IMULINK performs the joint simulation.The accuracy of the aging control strategy model established by SIMULINK is verified by comparing the experimental and simulation results.(3)The software development is to transform the aging control strategy model into the code through the RTW modules that are provided by SIMULINK.There are three types of parameters that need to be configured in the automatic conversion code.Configure the SOLVER,hardware specification configuration and output target files;and design the signal acquisition and preprocessing program.With the aging control program,and the aging control program to verify;develop PC software for human-computer interaction,PC software is based on LABVIEW development environment for design,including data exchange design and host computer interface;PC interface contains real-time data acquisition,Condition monitoring and historical data acquisition in three parts;hardware selection,the selectedmicroprocessor is a 16-bit high-performance chip S12XEQ64,and design selected power supply module,signal acquisition module and communication module,as a basis for the combination of hardware The follow-up experiment was conducted on the platform of the company.(4)The experiment verified that the rig verification laboratory compared the results of the traditional control strategy with the aging control strategy according to the ESC steady state operating conditions for the catalysts with different degrees of aging,indicating that the aging control strategy can be applied to SCRs with a relatively deep aging degree.The controller achieves good control objectives;there are three ways to extend the life of an SCR catalyst: 1)ensure fuel quality;2)use aging control strategies;3)regenerate measures.