MOBILE EMISSION MEASUREMENTS FOR ASSESSING LOW EMITTING VEHICLES EXEMPLIFIED ON A CRT-EQUIPPED BUS

An on-board system capable of determining ppm level emissions of carbon monoxide (CO), total hydrocarbons (THC), and nitrogen oxides (NOx) is developed. The data acquisition allows for the simultaneous retrieval of engine and vehicle parameters to calculate on-line mass based time resolved emissions that can be quickly linked to relevant parameters of the emission control system. The on-board system is validated by 160 comparative measurements on three Constant Volume Sampling (CVS) chassis dynamometers. The tests are executed on a Heavy Duty diesel truck and on three modern Light Duty vehicles. The differences in emissions are generally below 10% until 0.02 g/km. A real life performance evaluation is executed on a Eminox/Johnson Matthey Continuous Regenerating Trap (CRT) equipped VanHool A308 city bus. All tests are performed with, and without, CRT. The CRT reduces, almost eliminating, PM emissions to over 90% CO and THC to over 85%. It is found that the resulting THC ppm concentrations yield mass emissions as low as 0.03 g/km. No significant effect of fuel sulphur content was found in the tests without CRT.