Effects of a Diesel Particulate Filter on Emission Characteristics of a China II Non-road Diesel Engine

The emission standard of China's non-road diesel engines is experiencing the transition period from China II to China III, and the relative non-road diesel engine emission issues need to be urgently solved. As a kind of effective after treatment technology, a diesel particulate filter (DPF) has become increasingly important in non-road diesel engine emission research. To evaluate the emission characteristics of a non-road diesel engine retrofitted with a DPF, particulate matter (PM) and gaseous emissions emitted from a China II non-road diesel engine loaded with a DPF were investigated on the engine bench. The mass (specific emissions) and number concentrations of PM emissions were obtained by a DLS7200 mass collection system and matter CU-2 number instrument with and without a DPF, respectively. Additionally, gaseous emissions [NOx, CO, and hydrocarbon (HC)] were quantitatively analyzed with and without a DPF by a MEXA-7100EGR emission analysis chamber. Results showed that a DPF could lower the mass and number concentrations of PM emissions effectively. The mass trapping efficiency of PM was more than 90%, and the number trapping efficiency of PM was over 99%. NOx total specific emissions were not obviously influenced by a DPF. However, the emission ratio of NO2/NOx significantly increased by 10-30% compared to the situation without a DPF. Because of the oxidation catalyst of the diesel oxidation catalyst (DOC), the specific emissions of CO and HC decreased by more than 90%. Additionally, there was a substantial reduction of the free acceleration smoke value above 95% after installing a DPF. The DPF is one of the great technological routes that can readily make PM emissions of China II non-road diesel engines meet the emission demands of China IV.