中文摘要：

将傅里叶变换红外光谱仪与热重分析仪联用分析了柴油机尿素选择性催化还原（urea-SCR）系统中出现的沉积物的成分及沉积物形成原因。对尿素喷嘴附近和排气管壁两处沉积物分别取样分析。试验结果表明：喷嘴处沉积物热重曲线有两个失重阶段,第一阶段为150~250℃,分解出气体成分主要为异氰酸和氨,第二阶段为280~360℃,分解出的气体成分主要为异氰酸;排气管壁处沉积物的主要失重温度区间为320~400℃,分解出气体成分主要为异氰酸;喷嘴处沉积物的主要成分为尿素、缩二脲和三聚氰酸的混合物,排气管壁处沉积物主要成分为三聚氰酸。喷嘴处沉积物形成是因为低温、缺乏气流扰动导致喷嘴附近部分未反应尿素附着累积及尿素热解不完全而产生缩二脲和三聚氰酸;排气管壁处沉积物形成是由于排气温度和排气流量较低时部分尿素直接喷至管壁并逐渐形成三聚氰酸或者异氰酸在高温下直接聚合为三聚氰酸。

英文摘要：

Composition and formation cause of the deposits in diesel engine urea-SCR system were in- vestigated with the help of Fourier transform infrared （FTIR） spectrometer and thermal gravimetric （TG） analyzer. Deposits samples were respectively taken from places near the urea nozzle and on the exhaust pipe wall. Results indicate that the two samples of deposits decompose into gas when heated to above 430~C; There are two weight loss stages on the former TG curve in range of 150~C to 250~C the sample decomposes into isocyanic acid and ammonia; and in range of 280~C to 3600C it decomposes mainly into isocyanie acid. The latter loses its weight mostly in range of 320~C to 400~C and decomposes into isocyanic acid. The former is mainly blend of unreacted urea and biuret and cyanuric acid resulted from insufficient thermal decomposi- tion of urea in low temperature and lack of air flow disturbance conditions. The latter is mainly the cyanuric acid, formed by sprayed urea adhering on wall in low temperature and low exhaust flow conditions, or gener- ated directly by isocyanic acid high temperature polymerization.