柴油机试验过程中影响NOx排放的因素分析

Analysis of Factors Affecting NOx Emission During Diesel Engine Experiment

随着重型车国六排放法规的实施,针对柴油机的污染物排放测试流程和要求进一步复杂化,柴油机在试验过程中容易出现NOx排放不稳定现象。针对此问题,通过分析EGR故障、尿素喷嘴精度及试验初始温度条件等因素对柴油机NOx排放结果的影响,并在一台国六轻型柴油上进行试验验证,试验结果表明EGR故障和发动机初始试验冷却液温度会引起明显的NOx原排增加,WHTC比排放增加6%-26%,同时尿素喷嘴结晶老化将会导致NOx尾排一致性偏差增大,而较低初始排气温度会延长SCR到达工作温度的时间,导致NOx尾排增加。为保证柴油机在不同试验室、不同环境条件下测试结果的一致性和准确性,在试验过程中监控这些影响因素是非常必要的。

With the implementation of National VI emission regulations for heavy vehicles, pollutant emission testing procedures and requirements for diesel engines are further complicated, and diesel engines are prone to NOx emission instability in the test process. To solve this problem, the influence of EGR fault, urea nozzle precision and initial test temperature conditions on the NOx emission results of diesel engine was analyzed, and the test was verified on a national six light diesel. The test results show that EGR fault and engine initial test coolant temperature can cause obvious increase of NOx primary discharge. WHTC increases by 6%-26% compared with emission. Meanwhile, crystallization aging of urea nozzle will lead to increased consistency deviation of NOx tail row, and lower initial exhaust temperature will prolong the time for SCR to reach working temperature, resulting in increased NOx tail row. In order to ensure the consistency and accuracy of the test results of diesel engine in different laboratory and different environmental conditions, it is very necessary to monitor these influencing factors during the test.