AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Analyses of Emission Measurements for a Heavy-duty Diesel Bus through Experiments and Simulations: The Comparison between On-road and In-lab Methods
ZHEMING TONG, Yan Wang, Bo Yang, Topi Ronkko, Jorma Keskinen, Liisa Pirjola, K. Max Zhang, Cornell University
Abstract Number: 538 Working Group: Urban Aerosols
Abstract The development of emission inventories relies on the emission testing. On-road chasing method can capture the real world vehicle emissions and establish a link between the atmospheric dilution and the undiluted exhaust; while the in-lab chassis dynamometer measurements are widely used for regulatory purposes because tests are made under well-controlled conditions. However, the differences between the on-road and in-lab methods have not been well studied; meanwhile, experimental and modeling results have indicated that particle emission measurements are sensitive to how dilution is conducted. The objective of this study is to investigate the impact of on-road and in-lab transport and transformation of aerosol particles on particulate emissions through experimental and modeling analyses.
For the on-road method, the turbulent flow field in the wake of a scaled diesel bus is studied in a wind tunnel using Particle image velocimetry (PIV) method and the numerical Large-eddy Simulation model. Aerosol dynamics in this diluting exhaust plume is simulated by a turbulent reacting flow model (CTAG) and evaluated by the corresponding on-road experiments. For the in-lab method, the turbulent flow field and aerosol dynamics inside a two-stage dilution system (a porous diluter followed by an ageing chamber and a Dekati ejector diluter) are modeled by CTAG and evaluated by in-lab experiments. The approach of in-lab experiments is based on exhaust sampling and dilution method developed in “Particulates” program of EU. In that method, the exhaust is mixing rapidly with the dilution air inside the porous diluter and near the entrance of the ageing chamber. A thorough understanding of these two methods is important for the ongoing effort to define a standardized sampling methodology for characterizing emissions from vehicles, especially with diesel engines.