An Alternative Method for Generating Ultra-Clean Dilution Air for Engine Emissions Measurements

Many engine exhaust emissions measurements require exhaust dilution. With low-emission engines, there is the possibility for contaminants in the dilution air to contribute artifacts to the emissions measurement. The objectives of this work are to discuss common methods used to clean the dilution air, to present the detailed analysis of a pressure swing adsorption (PSA) system and to compare the performance of the PSA with 2 other systems commonly used to provide dilution air for engine exhaust nanoparticle measurements. The results of the comparison are discussed in context with some emissions measurements that require exhaust dilution.