The Research And Realization Of Electric Controlsystem Of Diesel Engine SCR

SCR technology is one of the most effective after-treatment techniques to meet Euro4emissions and above. In this paper, control strategies has been designed based on theSCR urea injection electronic control system on the basis of the diesel engine and SCRsystems.Aim to control the amount of urea injection precisely, hardware platform has beenbuilt and the related software code also been programmed. ESC bench test have been doneto verify whether the effect of SCR electronic control system meet the state Ⅳemissionstandards or higher.The main work includes:Develop control strategy in line with the test platform and calibration system base onin the full study of abroad urea-based SCR system.then get demand data of electric controlsystem on the basis of it, take89C52micro controller as the core to built SCR electriccontrol system hardware platform,Including the design of the smallest SCM system, theengine speed acquisition and conditioning circuit, acquisition and conditioning circuit ofaccelerator opening degree signal, the design of drive voltage value of the output demandurea pump converter circuit etc. Design filtering circuit to improve the system circuit’scapability of noise immunity for adapt to the engine’s harsh work environments.Puttingforward software design ideas and drawing program flowchart on the basis of the hardwaresystem which has been built. Including engine speed and throttle signal acquisition ideas,etc.Due to the speed signal is a sine wave output and it can not be directly identified bySCM,therefore, it should be converted to the square wave by conditioning circuit, theengine speed can be obtained by counting the number of signal.then give a detailedfunction description of chip which is used to date acquisition and conversion.at last,programming the code to micro controller by ISP online software.According to ESC thirteen condition method,do Emissions test of the original machineand load SCR electronically controlled system to verify the result of SCR diesel engineelectronic control system by comparing and analyzing the experimental results.Experimental results showed that Emissions of NOx,CO, HC, and other harmful ammonia gases are all met state Ⅳ emission standards and even Some of them havereached the state V emission standards.To sum up, the design of SCR electrical controlsystem applications on the engine can effectively reduce NOx emissions of nitrogen oxides,etc. It has satisfied the requirements of the state Ⅳ emission regulations completely.