Investigation of the Effect of Stagnation Surface and Diffuser Angle on Aerodynamic Performance: A Case Study on Locally Built Isuzu Bus

The ISUZU midi bus is the primary mode of transportation for the majority of Ethiopians. Due to its blunt, rectangular appearance and high drag resistance forces, the bus has poor aerodynamic shapes and uses more fuel. Therefore, the study objective is to reduce the total aerodynamic drag force, which in turn reduces power demand, fuel consumption, and carbon dioxide emissions. As a result, the diffuser angle and bus stagnation surface shape are aerodynamically optimized. Solid Work CAD 2023 is utilized in the development of the model. Eight different car models were developed and analyzed. CFD and ANSYS Fluent 19.2 were used for the analyses. With a 15º diffuser angle in the rear weak zone and a taper in front and an arc segment on both sides in the stagnation surface, the model-6 had the lowest Cd and Fd values, measuring 0.2915 and 225.32N at 70 km/h and 0.3111 and 594.22N at 110 km/h, respectively. At 70 km/h and 110 km/h, respectively, the Cd reduction percentages attained with this model were 51.21% (48.8% due to the frontal effect and 2.41% due to the diffuser angle impact) and 50.79% (48.81% due to the frontal effect and 1.98% because of the diffuser angle impact). Compared to the baseline bus, the coefficient of drag was, on average, 51% lower. In comparison to the baseline model, model six uses 5026.6 W less power at 70 km/h and 18332.03 W less power at 110 km/h. Compared to the baseline model, the modified model six uses 1.45 L/h less gasoline at 70 km/h and 5.28 L/h less fuel at 110 km/h. At 70 km/h and 110 km/h, model six's CO2 decrease is 12.17 tons per year and 44.31 tons per year, respectively, compared to the baseline model.