On Road Fuel Economy Impact by the Aerodynamic Specifications under the Natural Wind 2020-01-0678
According to some papers, the label fuel economy and the actual fuel economy experienced by the customers may exhibit a gap. One of the reasons may stem from the aerodynamic drag variations due to the natural wind.
The fuel consumption is measured through bench test under several driving modes by using the road load as input condition. The road load is measured through the coast down test under less wind ambient conditions as determined by each regulation.
The present paper aims to analyze the natural wind conditions encountered by the vehicle on public roads and to operate a comparison between the fuel consumptions and the driving energy. In this paper, the driving energy is calculated by the aerodynamic drag from the natural wind specifications and driving conditions. This driving energy and the fuel consumptions show good correlation.
The fuel consumption is obtained from the vehicle Engine control unit(ECU) data. The driving energy is calculated by the aerodynamic drag and the vehicle driving conditions through the time history data on the road. Aerodynamic drag is calculated using the yaw angle(ψ) and the air flow velocity relative to the vehicle from the natural wind and aerodynamic specifications, measured by the test vehicle on road under the several wind conditions. The 5-hole pressure probes and Cobra probe are used to measure the air flow velocity, yaw angle and other quantities as time history data. The vehicle aerodynamic specifications are measured at the full scale wind tunnel.
The vehicle driving conditions are measured by Global Positioning System (GPS) and obtained from the vehicle ECU data. The traction is measured by the torque meters mounted at the front axle.