The Aerodynamics of Future Electric and Hydrogen Fuel-Cell Cars

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The Aerodynamics of Future Electric and Hydrogen Fuel-Cell Cars

Wilson Tong

School of Aerospace, Mechanical and Manufacturing Engineering

RMIT University, Melbourne, Australia

ABSTRACT

This document will investigates the influence of global warming and peak oil including the consequences that affect the vehicle industry. Much research and development have been done in recent years to either "electrified" or to implement fuel cell onto normal road vehicles. The use of fuel cell on a road vehicle might be the solution but it is considered too implausible to mass-produced in today's technology (Suplee, 2009). Electric vehicle, on the other hand, are more practical and easy to develop. This paper will focus on the technical review of a purely electric car.

The performance, styling, comfort and cooling of an Electric Vehicle (EV) is different from most Internal Combustion Engine (ICE) vehicles as they are more energy efficient and the way electric vehicle gets its energy are dissimilar to ICE vehicle. In addition, the mass use of such vehicle is relatively new and is not as matured as ICE vehicle. The study of aerodynamics and aero-acoustic of an electric car is important as both factors can improve the car's range and usability.

Various methods of reducing the overall drag of the car and the potential wind noise that would affect the occupants inside the vehicle are analysed in this paper, as well as ways to optimise the usage of the battery will be examined.

INTRODUCTION

The effect of global warming and peak oil has prompted car manufacturers to look for an alternative for vehicle propulsion. Alternative propulsion such as bio-fuel, petrol-electric hybrids and turbo-charged diesel have been proposed and manufactured in recent years. All these substitutes can reduce carbon emission to a certain extent but these are not long term solutions for solving global warming.

A new concept of vehicle propulsion is therefore required to solve the carbon build up in the atmosphere. Electric vehicle is the only answer to this problem for the majority.

Better engine design can improve the overall efficiency of the vehicle, however, other aspect such as aerodynamics cannot be ignore as reduction of drag can dramatically reduce the power required to propel the vehicle. Much effort has been done in streamlining the front of electric vehicle but majority of the drag induced on cars are pressure drag. A good rear vehicle design is needed to reduce the overall drag of the vehicle as well as to prevent unwanted lift produced by downwash effect. According to Ahmed (1984), the drag coefficient of a vehicle reaches a maximum with a 30o rear slant angle. Steps have to be taken to ensure a gentle real slant angle is achieved or an implementation of a device to recover the pressure on the roof surface. Besides refining the back of the vehicle, the aerodynamic of an electric car can further improve by optimising the underfloor.

In order to convince the majority of the society that electric vehicle should be the correct step towards clean energy, creative measures has to be done in order to optimise the usage of electricity, such as battery swap by Better Place and integrating car body with battery by Volvo.

EVs run quieter than ICE counterpart due to the fact that they do not have pistons, crankshaft and combustion happening within the vehicle. This however, has its drawback as the lack of noise covering from the vibration of the engine has place more emphasis in sealing doors and windows to prevent disturbing wind noise from entering the cabin. Special design has to be placed on EVs to ensure it produces sufficient noise to warn nearby pedestrians and yet the sound will not enter the cabin.

EFFECT OF GLOBAL WARMING

Much of Earth's average temperature rose in the last century due to the fact that more carbon dioxide (CO2) has been produced by various human activities. The burning of fossil fuel...
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