Vehicle Exhaust Emissions Simulator- A Quality Control Tool to evaluate the Performance of Low Level Emission Sampling and Analytical Systems

As the standards for exhaust emissions have become more stringent, the quality control tools used to evaluate the performance of low level samplers and analyzers has become more important. The Vehicle Exhaust Emissions Simulator (VEES) was developed to evaluate the performance of vehicle or engine exhaust emissions sampling and analytical systems. The simulator emulates emissions from low-emitting gasoline vehicles by producing a simulated exhaust stream containing emission constituents (HC, CO, CO₂, and NO_x) injected via Mass Flow Controllers (MFCs).

This paper discusses various applications of the VEES as a quality control tool for ULEV and SULEV testing. A comparison is made between the injected amount of exhaust species by the VEES and the amounts recovered by the different sampling systems. Different root cause scenarios are discussed as to the source of discrepancies between the results on the CVS and BMD for different driving cycles. The E-Flow calibration is shown to have a big influence on the phase to phase results. The comparison of the vehicle and VEES correlation results on the same test cell showed much lower variability with the VEES.

Time-alignment of the modal data with the VEES is studied. There is a one second time delay within the VEES, which needs to be taken into account for proper time alignment of the modal data. In addition, recommended future investigations and applications are discussed.