Abstract: Selective catalytic reduction (SCR) is a widely adopted technology for reprocessing diesel emissions to comply with regulations. In SCR systems, an aqueous urea solution acts as a reducing agent to convert NOX into N2, ensuring that engine emissions meet regulatory standards. To achieve real-time monitoring of engine emissions and ensure the quality of urea meets requirements, this paper presents a method for detecting the quality of urea solution in diesel vehicles based on on-board diagnostic (OBD) system data. By thoroughly analyzing the working principle of SCR systems and the calculation method for urea injection quantity, a detection method for urea quality based on NH3 influence deviation factor is established. The feasibility of this approach is verified through actual road tests involving three different concentrations of urea solution added to a diesel vehicle. The results demonstrates that proposed method can effectively detect urea quality and provide reliable data support for real-time control of engine emissions.

Key words: On-board diagnostic system; SCR; Urea solution quality; Detection method

摘要： 选择性催化还原（SCR）是目前满足柴油机排放法规的主流后处理技术。在 SCR 系统 中，尿素水溶液被用作将 NOX 转化为 N2 的还原剂，以确保发动机排放达到法规标准。为了 实现发动机排放的实时监测，保证尿素品质满足要求，提出了一种基于车载诊断（OBD）系 统数据的柴油车尿素溶液品质检测方法。通过对国六柴油车 SCR 系统工作原理和尿素喷射量 计算方法的深入分析，提出了基于 NH3 影响偏差因子的尿素品质检测方法。通过对一辆柴油 车添加三种不同浓度尿素溶液进行实际道路行驶测试，验证了该方法的可行性。结果表明， 所提方法能够有效检测尿素品质，并为发动机排放的实时控制提供了可靠的数据支持。

关键词: 车载诊断系统；SCR；尿素溶液品质；检测方法