Methodology to Estimate Road Grade Effects on Consumption and Emissions from a Light Commercial Vehicle Running on the WLTC Cycle

Abstract

A novel methodology is suggested in this study, with the aim of assessing the impact of the road grade on a vehicle’s performance and emissions. This methodology consists of creating multiple sinusoidal elevation profiles that simulate a vehicle trip between consecutive peaks and valleys with the total net elevation being zero. A light commercial vehicle is considered, powered by a turbocharged diesel engine, and the baseline trip is the worldwide harmonized light-duty vehicles test cycle (WLTC). A detailed engine-mapping approach is used as the basis for the results, with experimentally derived correction coefficients applied to account for engine transient operation. Engine-out NO and soot are the examined pollutants, as well as fuel, energy consumption, and CO2 emissions. Results from this study show that there is a noteworthy increase in emissions, even for a zero net elevation trip, with the magnitude of this increase being proportional to the trip root mean square (RMS) grade. For the engine/vehicle studied, higher RMS grade values (approximately 5%) result in a 3.5% increase in fueling/CO2 emissions, 5.6% increase in NO emissions, and 7.9% increase in soot emissions; on the other hand, lower RMS grade values (approximately 2%) have fueling/CO2 emissions remaining practically unchanged but still showcase a slight increase in NO and soot emissions (1.8% and 2.6%, respectively).