In order to meet the requirement of the Special Beijing Phase V Standard on the number of particulate matter

hot world harmonized transient cycle (WHTC) tests were conducted on a China Ⅳ diesel engine fueled with China Ⅴ diesel fuel. Gaseous and particulate matter emissions from the engine with one single group of diesel oxidation catalyst(DOC) +particulate oxidation catalyst(POC) and with two groups of DOC+POC in series were compared with those from the engine without after-treatment. The results show that compared with the results without after-treatment

particulate matter and particulate number with one single group of POC+DOC are reduced by 63% and 23% respectively

while those with two groups of POC+DOC in series are reduced by 74% and 79% respectively. Two-groups of POC+DOC in series do not make the transient particulate number exceed the one without after-treatment as one single group of DOC+POC does. Equipped with two groups of DOC+POC in series

the emissions from the engine even fueled with China Ⅲ diesel fuel are equivalent to those fueled with China Ⅴ diesel fuel

which means that the usage of two groups of DOC+POC in series can overcome the adverse effects of fuel of worsened quality on pollution.