重型柴油机Urea-SCR系统尿素沉积物的试验研究

利用发动机台架试验研究了排气温度、排气流速以及尿素水溶液喷射量对尿素沉积物生成量的影响.测量对比了排气管内壁面与排气的温度差.通过热重与红外光谱分析研究了SCR系统耐久性试验和道路试验中产生的沉积物的加热分解过程及分解产物,通过电感耦合等离子体发射光谱仪和质谱仪对沉积物中杂质金属含量进行了分析.结果表明,排气温度、排气...

Experimental Study on Urea Deposits of Urea-SCR System for Heavy Duty Diesel Engines

The effects of exhaust gas temperature,flow velocity and urea solution injection rate on deposit formation were investigated through diesel engine bench test.The inner wall temperature of exhaust pipe was measured and compared with the exhaust gas temperature.The decomposition of deposits formed in durability test and road test was analyzed by using thermogravimetry(TG) and infrared spectroscopic analysis.The analysis of metallic impurities was carried out by using inductively coupled plasma emission spectrometer(ICP-OES) and mass spectrometer(ICP-MS).The results showed that the exhaust gas temperature,flow velocity and urea solution injection rate had the influence on deposit formation.The inner wall temperature in the position of 0.250 m and 0.885 m downstream the injector decreased separately from 155 ℃ and 126 ℃ to 137 ℃ and 116 ℃ after the injection of urea solution when the exhaust temperature was 227 ℃.The low inner wall temperature increased the possibility of deposit formation.At the temperature between 350 ℃ and 420 ℃,the deposits decomposed quickly.At the temperature of 420 ℃,ninety percent of deposits had decomposed.At the temperature of 700 ℃,the complete decomposition achieved.The main decomposition product of deposits was isocyanic acid.The mass content of metallic impurities in two deposit samples was separately 1 351.09×10-6 and 195.32×10-6.