基于NO_(x)传感器偏差的SCR自适应功能研究

Research of SCR Self-Adaption Based on NO_(x) Sensor Deviation

选择性催化还原(SCR)尿素喷射控制和SCR自适应修正都依赖于氮氧化物(NO_(x))传感器的测量精度,如果NO_(x)传感器测量发生偏差,就会导致尿素喷射量出现偏差,进而影响NO_(x)排放。将5组不同偏差的NO_(x)传感器进行组合,测量并分析NO_(x)传感器偏差对NO_(x)排放及SCR自适应后尿素喷射的影响。结果表明,当后处理器上下游NO_(x)传感器都是高精度传感器时,SCR自适应不修正尿素喷射;当后处理器上下游NO_(x)传感器均为上偏差或者下偏差的NO_(x)传感器时,SCR自适应可以将尿素喷射偏差减小;当后处理器上下游NO_(x)传感器分别为上偏差和下偏差传感器或者下偏差和上偏差传感器时,SCR自适应将尿素喷射量偏差往上游NO_(x)传感器偏差的相反方向进行修正,从而减小尿素喷射偏差。

NO_(x)sensor of high accuracy is very important for the selective catalytic reduction(SCR)system.Poor measurement accuracy of NO_(x)caused by NO_(x)sensor would lead to unreasonable urea injection,poor SCR efficiency,and undesired NO_(x)tailpipe emission.NO_(x)sensors with five different degrees of deviations were tested,the experiments demonstrated how NO_(x)sensor deviation effects urea injection and self-adaptive control of SCR system.No self-adaption correction for urea injection was observed when sensors with high accuracy were used for both engine out NO_(x)and tailpipe NO_(x).As comparison,sensors with lower deviation and upper deviation were used respectively,self-adaption correction for urea injection was activated under both conditions,and thus a low deviation of urea injection can be achieved.For the other conditions,upper deviation sensor for engine out NO_(x),lower deviation for NO_(x)tailpipe emission,and vice versa,a reverse direction correction was performed under self-adaption strategy,and still a low deviation of urea injection can be achieved.