Impacts of Vehicle Speed and Slope on Tailpipe Emissions Using Desirability Function Analysis

Abstract

Pollutant emissions from vehicles can significantly increase when driving on a road with a positive slope, according to previous studies. In internal combustion engines, minimizing tailpipe emissions like CO and HC by using different strategies increases CO2. Consequently, this causes global warming through the greenhouse effect. This study aimed to determine the effect of road slope and vehicle speeds on tailpipe emissions, such as CO, HC, and CO2. Full factorial analysis was employed for the design of the experiment. An experiment was conducted in Addis Ababa, Ethiopia, using a portable emissions analyser and GPS to collect emissions data from passenger vehicles at a speed of 10, 20, 30, 40, and 50 km/h and road slopes of -2, 0, 2, 4, and 6 degrees. The regression models developed for CO2, CO, and HC were accurate, with R-squares of 98%, 92.9%, and 84.88%, respectively. Finally, desirability function analysis was employed to simultaneously optimize the responses to identify optimum points that minimize CO, HC, and CO2 formation. The results show that the best speed to simultaneously reduce CO, HC, and CO2 emissions was found to be 40 km/h on a level road and 30 km/hr on a 2-degree road slope with composite desirability of 0.83 and 0.72, respectively. As a conclusion, it is shown that the use of desirability function analysis can effectively be used to identify the optimum driving speed at which CO, HC, and CO2 emissions are minimized simultaneously for the given roads.

Keywords

• Addis Ababa
• desirability function
• road slope
• tailpipe emissions
• vehicle speed