摘要
以一台排量11.12L的柴油机为平台,研究了排气管中沉积物的生成过程,并对沉积物进行了热重试验。定量分析了排气温度、空速及尿素喷射速率对沉积物生成量的影响,应用正交设计方法确定各影响因素的权重系数。研究结果表明:在排气温度为330℃、空速为3×10 4h-1的情况下,以2600mL/h的速率持续喷射尿素水溶液5h后,柴油机排气管中形成的沉积物导致排气背压升高了1.4kPa,NOx转化效率降低了3%,且沉积物在700℃高温下才能完全分解。排气温度越低,空速越小,尿素喷射速率越高,越易生成沉积物。各影响因素的权重从大到小依次为:尿素喷射速率(0.39)>空速(0.37)>排气温度(0.24)。针对实车沉积物问题,在满足国-Ⅳ排放法规的前提下,通过二次标定降低经济运行工况的尿素喷射速率,将喷嘴前移2600mm,并用保温材料包裹排气管,运行车辆排气管中再未发现沉积物。
The deposit formation process in exhaust pipes was studied on a diesel engine with displacement of 11.2 L, which was verified by a thermogravimetric experiment. The influence of the exhaust temperature, space velocity and urea injection rate on the deposits yield was analyzed quantitatively and the orthogonal design method was used to determine the weight coefficient of each influence factor. The results demonstrate that, when the exhaust temperature was 330 ℃, the space velocity was 3;〈 104h J and the injection rate was 2600 mL/h, a large amount of deposits generated in diesel engine exhaust pipes after continuous injection of urea aqueous solution for 5 h, which caused exhaust back pressure to increase by 1.4 kPa, NO, conversion efficiency to reduce by 3% and could be completely decomposed at a high temperature of 700 ℃. The lower the exhaust temperature, the smaller the space velocity and the larger the urea injection rate, the more prone to deposits. The weight coefficients of each influence factor in ascending order were as follows：urea injection rate （0. 39）〉 space velocity （0. 37）〉 exhaust temperature （0. 24）. Finally, under the premise of meeting China stage Ⅳ emission regulation, the deposit problem of real vehicles has been solved through reducing the urea injection rate in economic operation area by secondary calibration, moving the injector position forward 2600 mm and wrapping the exhaust pipes with heat insulating material.
出处
《内燃机工程》
EI
CAS
CSCD
北大核心
2015年第6期8-13,共6页
Chinese Internal Combustion Engine Engineering
基金
国家自然科学基金项目(51379165)
国家基金委专项基金项目(L1422029)
关键词
内燃机
柴油机
选择性催化还原
沉积物
正交设计
IC engine
diesel engine
selective catalytic reduction（SCR）
deposit
orthogonal design
