Testing emissions and other parameters from vehicles driven on the chassis dynamometer

Abstract

The driving conditions in the Maltese islands are characterised by frequent stopping due to traffic and traffic lights, and also by inclined roads. These conditions have an impact on both fuel consumption and emissions, providing differing results when compared to highway conditions. The New European Drive Cycle (NEDC), which has been used by regulatory bodies to certify vehicles’ compliance to regulations regarding emissions, fails to replicate the usual driving conditions within Malta, especially the inclines. The aim of this dissertation was to investigate the effect of positive road grades and frequent stopping on the fuel consumption and emissions of two vehicles, both Dacia Sandero Stepways, one being Euro 6 certified and the other Euro 5 certified. The Diesel Particulate filter (DPF) regeneration process for these vehicles was also tested and discussed. Testing was carried out through use of the chassis dynamometer within the Thermodynamics laboratory. Initially, LabVIEW was used in order to extract real time data through the vehicles’ OBD-II port through an ELM327. A heated line was also designed and installed in order to be able to also make use of the Fourier Transform Infrared spectroscopy (FTIR) emissions bench. The FTIR emissions bench was then used in order to obtain more detailed data regarding the tailpipe emissions from both vehicles. The drive cycles used were taken from trips carried out in Malta, and were chosen in order to replicate a variety of driving conditions. The driving conditions during these drive cycles varied from completely flat with no stops to inclined with stops. It was found that the inclines and stops resulted in increases in both emissions and fuel consumption. The latter’s increase was more significant, with NOx emissions reaching up to 17 times higher (0.51g/km compared to 0.03g/km) during an inclined drive cycle with stops. The fuel consumption was 123% higher, when comparing the same two drive cycles. Furthermore, the stop start feature, present in most modern cars, was found to be most useful when it comes to decreasing CO2 and fuel consumption but was found to have minimal effect in Nitrogen Oxides (NOx) reduction when AdBlue is used. The DPF regeneration process was found to be dependant mostly upon the pre DPF and coolant temperatures, reaching levels of 500-700°C and 80-100°C respectively. Furthermore, post injection was confirmed to be one of the primary methods of increasing pre DPF temperature on the tested vehicles. The Euro 6 certified vehicle was found to be compliant with regulations regarding NOx and CO2 emissions when tested on flat conditions. However, the emissions exceeded the limit substantially when an incline and stops are introduced into the drive cycle, exceeding by 537% and 103% for NOx and CO2 emissions respectively. AdBlue injection was found to be an effective NOx aftertreatment method. The Euro 5 compliant vehicle, which does not use AdBlue, emitted up to 27 times more NOx than the Euro 6 compliant vehicle (0.03g/km compared to 1.10g/km during a flat drive cycle test).