EXPERIMENTAL STUDY ON EMISSION CHARACTERISTICS OF NON-ELECTRONIC CONTROL DIESEL ENGINE WITH DOC/POC/SCR COMBINED SYSTEM

An emission treatment study was conducted on a typical non-electronic control diesel engine using diesel oxidation catalyst (DOC)/particle oxidation catalyst (POC) / selective catalytic reduction catalyst (SCR) combined system to expect the engine would reach CN-V standard. The research was focused on the selection and the arrangement of the treatment units. The experiments results show that either particulate matters (PM) or NO. but not in the case of both can meet CN-V standard with only DOC+POC or SCR system, however, both PM and NOx, can reach CN-V standard by employing DOC/POC/SCR combined system. There is no obvious influence on the pollutants conversion efficiency with the different arrangement order of the SCR and DOC+POC system. The passive regeneration of POC can be fully achieved by placing the DOC+POC ahead of the SCR system due to the sufficient amount of NO2 in the exhaust which can be utilized for PM oxidation, and also in this case the hydrothermal aging effect on the SCR catalyst could be reduced owing to the lower of the inlet temperature. The backpressure of the combined system can be less than 25 kPa through the application of ceramic-based POC and optimal design of the packaging structure.