Methodology Development for External Aerodynamic Evaluation of a Bus and Its Impact on Fuel Economy along with Experimental Validation

The objective of this study is to develop, demonstrate and validate the methodology of external aerodynamic analysis of a State Road Transport bus for prediction of drag coefficient and its impact on fuel consumption with experimental validation. It has been verified that vehicle consumes around 40% of the available engine power to overcome the air drag. This gives us a huge scope to study the effect of aerodynamic drag.

Baseline model of State Road Transport Bus was evaluated for estimating fuel consumption using Computational Fluid dynamics (CFD) methodology. The CFD results were validated with the experimental data with less than 10% deviation. Bus design was optimized with an objective of reducing the fuel consumption with parameters like angle of windshield, rounding and tapering corners and rear draft angle. Optimized bus design is also ensured to meet functional specifications as per AIS052. The prototype of the optimized bus design has been tested experimentally as per IS 11921: 1993 standard to estimate fuel consumption. The results obtained from CFD and experimental tests were analyzed and they were found to be in good agreement. With the optimized design of the bus, it is found that the fuel efficiency remains almost same though weight of the bus has been increased by around 1.5 ton.