Development Of Urea Injection Measurement And Control System For Performance Evaluation Of SCR Catalyst

For China ? Emission Standard,high-efficiency SCR is a basic requirement that must be met,so the evaluation experiment of catalytic converter is important in the application of SCR technology.In order to test if the selective catalytic reduction(SCR)catalytic converter matches the diesel engine and the monomer evaluation test of the SCR catalytic converter,a diesel engine aftertreatment device test evaluation system was constructed to develop a urea injection control system.The urea injection control system consists of a control unit and a background management system which is developed based on a 16-bit microcontroller.The control unit controls the injection pressure by means of double closed-loop control and the target pressure is given by host computer.The main research contents are as follows:Hardware design of measurement and control system.Analyzing the working principle and configuration requirements of the test object according to test requirements.The hardware system design is completed by using Freescale's 16-bit microcontroller,including the minimum system design of the control unit,power supply module design,actuator drive circuit design,communication module design and sensor signal conditioning circuit design.Software design for measurement and control system.Coding each hardware module driver and main program with CodeWarrior.The main program uses a front-end architecture that combines large loop scans,interrupt triggers,and beat triggers.The main program consists of the injection system state switching program,the urea pump pressure control program,the urea nozzle control program,and the electric heating control program.The background management software design of the measurement and control system.The background management software is developed based on the VB.NET compiler environment.The background management software communicates with the host computer to load and display the urea injection system status.The main functions include user login management,system parameter design,urea injection rate loading,data processing,and system status monitoring.The background software is used to test the characteristics of the urea nozzle and the urea pump,then the urea nozzle and urea pump control parameters were calibrated.verification of the test and control system bench function.The exhaust temperature and exhaust flow control subsystem of the post-treatment system performance evaluation test device guarantees the working conditions,and the test device detect NOx and ammonia leakage using emission measuring equipment and performs airspeed scanning,the put on temperature scanning and ammonia-nitrogen ratio scanning test.The function and usability of the urea injection control system was tested on the engine rig with the help of the control characteristics determined by the calibration test,and the performance of the catalyst is then evaluated.The results show that the urea injection control system can fully meet the requirements of post-treatment monomer test and catalyst efficiency evaluation test.