Combustion and emissions of a Euro VI heavy-duty natural gas engine using EGR and TWC

The application of cooled exhaust gas recycle (EGR) and three-way catalyst (TWC) on natural gas engines has been considered to be a cost effective solution for meeting Euro VI emission standards. In the present work, systematic experiments have been performed on a six-cylinder commercial heavy truck spark ignition (SI) natural gas engine with a cooled EGR and TWC after-treatment system. The combustion and emission characteristics of the engine were fully analyzed. The results show that by combining stoichiometric combustion with EGR and TWC, EURO VI emission standards for NOx, CO and NMHC, as well as smoke emission standards, could be comfortably met. Although with the current configuration, the EURO VI limits for CH4 and NH3 emissions could not be satisfied, this could possibly be settled by the recalibration of the excess air ratio and the addition of an ammonia slip catalyst (ASC) device. (C) 2015 Elsevier B.V. All rights reserved.