Abstract: The effects of intake temperature and humidity on NOx emission were studied in different cycle conditions, such as ESC, WHSC and WHTC, on the engine bench. The results show that the NOx emission before the catalyst decreases slightly with the increase of inlet humidity in both WHSC and hot WHTC cycles. Adjusting by the NOx correction coefficient, the NOx emission before the catalyst basically remains unchanged after the correction. With the increase of inlet humidity and inlet temperature, NOx emissions after the catalyst of China Ⅵ diesel engine has a tendency to gradually reduce, but the amplitude is small. The aftertreatment system of China Ⅵ diesel engine form a closed loop control, while the SCR system has a high efficiency conversion on NOx emission. Thus, the inlet humidity has a less effect on the NOx emission after the catalyst.

Key words: China Ⅵ diesel engine; NOx emissions; Correction factor; Intake air temperature; Inlet air humidity

摘要： 在发动机台架上，使用不同后处理系统的发动机进行了 ESC、WHSC 和 WHTC 等不同 循环工况的排放试验，研究了进气温度和进气湿度等因素对发动机 NOx 排放的影响规律。研 究结果表明，无论是 WHSC 还是热态 WHTC 循环工况，随着进气湿度的增加，催化剂前 NOx 排放略有降低，经过 NOx 修正系数的调整后，修正后的催化剂前 NOx 排放基本保持不变。 国六柴油机催化剂后的 NOx 排放随着进气湿度和进气温度的增加而有逐渐降低的趋势，但是 幅度很小。国六柴油机的后处理系统形成闭环控制，SCR 对 NOx 的转化效率高，进气湿度对 催化剂后 NOx 排放的影响较小。

关键词: 国六柴油机；NOx 排放；修正系数；进气温度；进气湿度