Development Of Metering Pump Driven By Electromagnetism And Its Test Research Of SCR System For Diesel Vehicles

At present,national V emission standard has been formally implemented in some cities in China.As one of the main exhaust aftertreatment technologies,SCR(Selective Catalytic Reduction)technology can effectively reduce NOx levels in the vehicle exhaust.This paper developed a metering pump driven by electromagnetism(electromagnetic metering pump)to meet the requirements of SCR system.It is simple,small and its measurement is accurate.It provides some new ideas for metering pumps by studying the key technologies.The main tasks are as follows:1.Mechanical design of the electromagnetic metering pump was completed.The principle of electromagnetic metering pump was studied on the basis of understanding the research achievements at home and abroad.After selecting the type of electromagnet,the general structure of the electromagnetic metering pump was designed by calculating the electromagnetic and electromagnetic field.According to the strong corrosion of urea solution,American 416 stainless steel,which belongs to soft magnetic materials,with corrosion resistance and high permeability,was chosen to make moving iron core.Straight-through cone valve structure and adding sealing ring at the other side of the reset spring were used to effectively reduce vibration and transverse displacement in the design of the one-way valve structure.2.The design of hardware circuit of controller has finished.The selection of electric control unit and power driven chip was completed.The whole system was modularly developed,including a series of functions such as power control,CAN bus communication and signal acquisition and processing module.Altium Designer software was used to design the layout of PCB for increasing the cooling efficiency.Organic silicon modified anti-corrosion paint was made to improve the performance of PCB.3.The software of controller was designed.To meet SCR system requirements,the program of metering pump driver was written based on CodeWarrior IDE.It includes main function module,timer interruption program,CAN bus communication program,state-control strategy of pump,metering correction and Adblue heating strategy.4.Simulation software was used to research the electromagnetic metering pump.The AMESim platform was built to study the dynamic characteristics of moving iron corn and the flow characteristic of electromagnetic metering pump.Batch processing function of the software simulated the dynamic response of the pump in the situation of different coil numbers of turns and spring stiffness.What's more,a 2D model for the pump was made to simulate the distribution of the lines of magnetic force and magnetic induction intensity during the process of energizing by using Ansoft Maxwell.And air gap and excitation current were parametrically solved to simulate the tendency of the electromagnetic force.Optimization scheme was put forward after comparing the results of simulation.5.Test verifications were made.The electromagnetic metering pump sample was tested in different conditions to measure the performance of the temperature variation and the rate of flow.The data was noted by comparing the atomization effect and flow test data of pumps equipped with different pore sizes.The result shows that the temperature of electromagnetic coils rises quickly.It can achieve more than 140 Celsius Degrees.It verifies that the selection of moving iron core material is correct.The rate of flow has a good linearity and its relative error is within 5%.It can control the flow accurately by changing the frequency when it works in 0~35Hz.The atomization effect of the nozzle with 0.6mm is good and can be equipped in the electromagnetic metering pump discharge.It is easy to calibrate the rate of flow in 0~35Hz.6.The ESC and ETC test target has been achieved smoothly by following the GB17691-2005 standard based on a specific model diesel engine.After the verification,the conclusion concludes that the SCR system is able to reduce the vehicle exhaust pollutant concentration.The NOx emission can fall to 1.109g·(kW·h)-1 and 1.160g·(kW·h)-1,which can meet the stringent requirements of the State V.It also verifies the stable performance and accurate measurement of the electromagnetic metering pump.