Development Of Test Bench For China Ⅵ Diesel Engine Urea-SCR Control System

In recent years,environmental pollution caused by automobile exhaust has attracted more and more attention worldwide.As a result,various countries have successively introduced new phases of automobile emission standards to limit automobile pollutant emissions.my country issued the sixth set of emission standards for light vehicles and heavy diesel vehicles in 2016 and 2018.marking that my country’s vehicle exhaust emission standards have entered the China VI stage.Urea selective catalytic reduction technology,Urea-SCR technology,uses urea solution as a reducing agent to be injected into the exhaust pipe and mixed with engine exhaust to catalytically reduce nitrogen oxides(NOx)in exhaust gas.It is one of the most important means for diesel vehicles to reduce pollutant emissions.The high precision and high reliability of the Urea-SCR control system determines the emission reduction energy efficiency of diesel engines.In order to ensure the performance and quality of the Urea-SCR control system,it is of great practical significance to develop a set of Urea-SCR control system test equipment during the production process.The purpose of this thesis is to develop the Urea-SCR control system test bench,based on the study of the structure and working principle of the Urea-SCR control system,according to nozzle status test,two-dimensional code test,communication test,sensor and solenoid valve test,heating plate test,Negative pressure test,building pressure test,zero injection volume test,injection accuracy test,withdrawal test and motor test 11 test requirements analysis to obtain test methods,to develop test hardware and software solutions,The test hardware solutions include the design of test benches and electrical hardware solutions,and the test software solutions include the design of the upper computer program and the test card program.The hardware part uses CATIA to design the test bench and urea pump fixture in three dimensions according to the hardware design plan,and also uses Altium designer to design the circuit and PCB board of the test card,and according to the electrical design plan,the test bench host,code scanner,negative The pressure sensor and the negative pressure solenoid valve are select model and finally the construction is completed.The software part develops the data acquisition and processing program,the test system configuration program,the interface communication program,the data management program and the user management program of the test bench host computer based on LabVIEW according to the software design plan.Finally,the communication program and stability of the test card are developed based on the C language.Completed the software and hardware development of the Urea-SCR control system test bench.Use the built test bench to carry out system calibration and test verification.Use Lagrange interpolation and least squares method to calibrate the ratio of the injection volume of the test bench to the motor speed,And perform the test on the test bench calibrated by Lagrangian interpolation and least squares method,the obtained data is calculated by calculating the relative error value and the root mean square error value for screening,and the Lagrangian interpolation method is determined as the system calibration method.and obtain the calibration data between the injection volume and the motor speed.Test the test bench through the validity test and the failure simulation test,judge the consistency of the test bench test results in the validity test and the manual test results,and check the consistency of the test bench test results in the failure simulation test with the simulated failure After the performance is judged,the results show that both the effectiveness test and the fault simulation test of the Urea-SCR control system test bench have reached the test expectations and meet the test requirements of the Urea-SCR control system.