Full steam ahead for BMW’S clean cars
EVEN the most efficient internal combustion engine can only convert about one-third of the energy derived from fossil fuels into the kinetic energy needed to power a motor vehicle. Engineers are working flat-out to find improvements, as the industry attempts to be all things to all men.
At BMW, for example, what it calls EfficientDynamics (ie Bluemotion, Greenline, ECOflex etc at other carmakers) has made great improvements in engine efficiency, with technologies such as direct fuel injection, variable valve timing, exhaustdriven turbochargers, brake energy regeneration and the Auto Start Stop function.
However, about 60 per cent of the generated energy is still lost as heat. Finding ways of recovering this lost heat energy is one of the major goals being pursued by engineers working on BMW EfficientDynamics.
Enter, the turbosteamer. “A heat exchanger recovers heat from the engine exhaust, and this energy is used to heat a fluid which is under high pressure – this heated fluid then turns into steam, which powers an expansion turbine that generates electrical energy from the recovered heat,” explains Jürgen Ringler, team leader for Thermal Energy Converters at BMW Group Research and Technology.
Intelligent heat management can also reduce consumption when the vehicle is being accelerated and driven. Before starting the car, insulation and encapsulation of the engine compartment will shorten the cold start phase.
An exhaust heat exchanger will keep gearbox oil warm to reduce friction and consumption. The turbosteamer will provide electrical systems with ample power, too.