农用柴油机SCR催化箱外置保温层对其温度场影响的试验研究

在发动机台架上,通过转动SCR催化箱内呈一字形布置热电偶的测量段,在稳态工况下对沿轴向多个截面内的温度场进行测量,研究催化箱外保温层对SCR催化箱内温度场分布规律及其对NOX转化效率的影响。结果表明:催化箱外设置保温层能使催化箱内温度沿轴向下降幅度减小,并改善其温度分布的均匀性。试验条件为:空速21 000 h^-1,排气温度475℃,尿素喷射量氨氮比为1。催化箱外无保温层时,因散热损失大于SCR反应放热,SCR催化剂载体后的平均排气温度低于催化剂前3℃;设置保温层后,散热损失减少,SCR催化剂载体后的平均排气温度高于催化剂前4℃。排气温度265℃时,外置保温层使NOX转化效率提高2%;排气温度475℃时,外置保温层反而使NOX转化效率降低3%。

Experimental investigation the influence of exterior insulation layer of agricultural diesel SCR catalyst container on its temperature field

In order to study the influence of wall heat dissipation and SCR reaction on the temperature field and NOx conversion efficiency in the catalytic container, the temperature in different positions in SCR catalytic container is measured. A group of thermocouples arranged in the SCR catalytic container is used to measure temperature field in several cross sections along the axial direction. The results show that, the thermal insulation can reduce the heat loss on the wall, so the temperature drop in the catalyst container decreases along the axial direction and the uniformity of the temperature distribution in the catalyst container is improved. At the space velocity of 21 000 h^-1,the exhaust temperature is 475 ℃ and the ammonia-nitrogen ratio is 1. Without thermal insulation, the exhaust temperature after the catalyst is 3 ℃ lower than the exhaust temperature before the catalyst;the exhaust temperature after the catalyst is 4 ℃ higher than the exhaust temperature before the catalyst due to insulation can reduce heat loss. When the exhaust temperature is 265 ℃, the insulation layer improves NOx conversion efficiency by 2%, on the contrary, the conversion efficiency of NOx is reduced by 3%, When the exhaust temperature is 475 ℃.