柴油机SCR系统尿素结晶边界喷射量试验研究

杨永春^1,2，丰平^1,2，曹露露^1,2，李钊^1,2，毕晓东^1,2，谭治学^1,2

1.内燃机可靠性国家重点实验室,山东 潍坊  261061;

2.潍柴动力股份有限公司发动机研究院,山东 潍坊  261061

摘要：针对柴油机选择性催化还原后处理系统的尿素结晶现象，以某重型柴油机为研究对象，分析尿素结晶产生机理，提出利用混合器壁面温度变化幅度判断尿素结晶边界喷射量的方法，并进行稳态和瞬态工况试验验证。结果表明：180 s内壁面温度下降幅度达到3 ℃时，尿素实际喷射量达到结晶边界，可用于判断不同工况下的尿素结晶边界喷射量；拟合柴油机不同工况下尿素结晶边界喷射量，调节柴油机原排，可有效控制尿素喷射量在结晶边界以内，避免产生结晶。

关键词：后处理;壁面温度;尿素喷射量；尿素结晶

Experimental study on boundary injection quantity of urea crystallization in diesel SCR system

YANG Yongchun^1,2，FENG Ping^1,2，CAO Lulu^1,2，

LI Zhao^1,2，BI Xiaodong^1,2，TAN Zhixue^1,2

1.State Key Laboratory of Reliability of Internal Combustion Engine,Weifang 261061, China；

2.R&D Center,Weichai Power Co., Ltd., Weifang 261061, China

Abstract：In view of the urea crystallization phenomenon in the selective catalytic reduction (SCR) aftertreatment system of diesel engines, a heavy-duty diesel engine is taken as the research object. The mechanism of urea crystallization is analyzed, and a method to estimate the injection amount at the urea crystal boundary by using the temperature change amplitude of the mixer wall is proposed, and the steady state condition test and transient condition test are carried out for validation. The results show that when the temperature of the inner wall decreases by 3 ℃ within 180 s, the actual amount of urea injected reaches the crystal boundary, which can be used to determine the amount of urea injected at the crystal boundary under different working conditions. Fitting the injection amount of urea crystal boundary under different working conditions of the diesel engine, adjusting the original exhaust of the diesel engine, effectively control the urea injection quantity within the crystal boundary, and avoid crystallization.

Keywords:post-processing;wall temperature;urea; injection quantity; urea crystallization