SCR系统高精度隔膜计量泵设计与试验

Design and Experiment on High Precision Diaphragm Metering Pump for SCR System

针对往复泵因配流单向阀运动不稳定和关闭不及时导致的计量精度不高等问题,设计了一种采用泵控式计量的轻型商用车用高精度隔膜计量泵。阐述了隔膜计量泵的结构及其工作原理,并借助AMESim仿真平台对隔膜计量泵进行了动态模拟,分析了进口单向阀阀芯的响应特性。对进口单向阀的结构进行了优化,在满足阀口最小开度的前提下,通过机械限位限制阀芯的最大开启量x_(max),降低了阀芯关闭时间和尿素液回流对输出流量的影响。最后,搭建了隔膜计量泵性能试验系统。在额定喷射压力2 MPa时,测得隔膜计量泵单次排量为0.09 mL;经结构优化后的隔膜计量泵计量精度由±5%提高至±3%;在150~420 r/min时,喷射尿素液流量可在13.5~40 mL/min范围内调节,且最大流量为2.26 L/h,能够满足轻型商用车SCR系统在不同工况下的尿素液需求。

Aiming at the problem of low measuring accuracy of the reciprocating pump due to unstable movement and untimely closure of the distribution one-way valve, a high precision diaphragm metering pump （DMP） with pump control metering, which is used for light commercial vehicle, was designed and developed. The DMP realized the integration of urea solution transportation and metering, simplified the structure of SCR system and reduced the cost. The structure and working principle of the DMP were introduced. The DMP was driven by a stepping motor. By setting the speed n of the stepper motor, the flow rate q can be adjusted accurately. Dynamic simulation of the DMP was carried out by using AMESim, and the response characteristics of the inlet one-way valve core were analyzed. The structure of the inlet one-way valve was optimized. Under the premise of meeting the minimum opening of the valve port, the maximum opening x of the valve core was limited by mechanical limit, which reduced the closing time of the valve core and the influence of urea solution reflux on the flow rate. Finally, the test system was built to test the performance of the DMP. When the rated injection pressure was 2 MPa, the single displacement of the DMP was measured to be 0.09 mL. The measuring accuracy of 4 - 6 DMP without structural optimization were reduced as the speed increase. The measuring accuracy were within ＋5%. However, the measuring accuracy of 1 -3 DMP were within the range of ＋3% after structural optimization. At 150 -420 r/min, the flow rate of urea solution can be adjusted in the range of 13.5 40 mL/min, and the maximum flow rate was 2.26 L/h, which can meet the requirement for urea solution of the light commercial vehicle SCR system under different working conditions.