Performance, combustion timing and emissions from a light duty vehicle at different altitudes fueled with animal fat biodiesel, GTL and diesel fuels

The altitude effect on performance, emissions and thermodynamic diagnosis under real world driving conditions has been evaluated using two alternative fuels and a diesel fuel. Three places, at different altitudes, were selected for the tests, from 0 to 2500m above the sea level. Besides, two type of circuits (Urban and Extra-urban) have been selected in order to evaluate these two driving pattern conditions. A light duty diesel vehicle equipped with the same after-treatment system as Euro 5 engines was used as test vehicle. Thermodynamic diagnosis shows that, when the engine works with two pre-injection events (mainly at high altitude and without EGR) the ignition delay agrees of the cetane number of fuels. At urban conditions, altitude increases the combustion duration of all fuels and particularly with paraffinic fuels. The effect of altitude on THC and CO emissions is not noticeable, but at high altitude, NOx emissions during extra-urban tests were around three times higher than those from testing along the urban circuit. Besides, compared to circuits next to the sea level, these emissions at both circuits (urban and extra-urban) were around ten times higher, respectively, than the limits established by the Euro standards. The effect of fuels on pollutant emissions was masked by the variability associated to real driving conditions.