SCR催化器失效故障诊断和容错控制方法研究

Research on Fault Diagnosis and Fault Tolerance Control of SCR Catalytic Converter

针对SCR催化器由于老化、硫中毒等因素出现的失效故障,基于转化效率对其进行故障评估,并引入了一种失效因子,用来表征SCR催化器的失效程度。在此基础上,对不同工况下的尿素喷射量进行修正,以保证尾气排放符合OBD限值要求。最后,以某型号6缸高压共轨柴油机为对象,加装已经部分老化失效的后处理系统进行台架验证。试验结果表明:通过失效因子修正后,稳态循环工况下,发动机尾气排放为1.4 g/(kW·h),瞬态循环工况下,排放为1.77 g/(kW·h),与催化器失效前的值基本相当,均低于非道路国四阶段法规要求,有效地降低了催化器失效对SCR系统造成的负面影响。

Aiming at the failure of SCR catalyst due to aging,sulfur poisoning and other factors,this paper evaluates its failure based on conversion efficiency,and introduces a failure factor to characterize the failure degree of SCR catalyst.On this basis,the urea injection amount under different working conditions is modified to ensure that the exhaust emissions meet the OBD limit.Finally,taking a type of 6-cylinder high pressure common rail diesel engine as an object,a post-processing system which has been partially aged and failed is installed to carry out bench verification.The test results show that:After the failure factor is corrected,emission of engine exhaust is 1.4 g/(kW·h)under steady cycle condition and 1.77 g/(kW·h)under transient cycle condition,which is basically equivalent to the value before the catalyst failure,and both are lower than the four-stage regulations of non-road countries,effectively reducing the negative impact of catalyst failure on SCR system.