Evaluation of exhaust flowrate measurement techniques for a mobile emissions monitoring system

West Virginia University designed and developed Mobile Emissions Monitoring System (MEMS) for the six settling Heavy-Duty Diesel Engine (S-HDDE) manufacturers. The MEMS measures emissions concentrations while operating in a real world environment. The best method for measuring the emissions concentrations was found to be through raw exhaust sampling. In order to properly calculate the emissions concentrations the total exhaust flowrate through the engine must be determined. The devices evaluated were an Annubar, an Accutube, a hot film anemometer, a Pitot static tube, a venturi, and a vortex shedder.; The evaluation of the devices was broken down into two parts, the first part included cold bench testing and the second engine testing. The venturi was found to be the best flow device for a MEMS because of the increased flow range over the vortex shedder and was well suited for the environment of compression ignition exhaust streams.