|BMW’s Turbosteamer. Click to enlarge.|
BMW Group Research and Engineering is developing a steam-powered auxiliary drive—called the Turbosteamer—that uses the waste heat present in the exhaust gases and cooling system from a conventional gasoline engine as its source of power.
In tests with a 1.8-liter, four-cylinder engine, the new auxiliary power unit reduced fuel consumption by up to 15% while generating nearly 14 additional horsepower and 20 additional Nm of torque.
The Turbosteamer is based on the same principle as the steam engine: heated fluid forms steam in two circuits which is used to power the engine.
The primary energy supplier is the high-temperature circuit which uses exhaust heat from the internal combustion engine as an energy source via heat exchangers. More than 80% of the heat energy contained in the exhaust gases is recycled using this technology, according to BMW.
The steam is then conducted directly into an expansion unit linked to the crankshaft of the internal combustion engine. Most of the remaining residual heat is absorbed by the cooling circuit of the engine, which acts as the second energy supply for the Turbosteamer.
The Turbosteamer reinforces our confidence that the internal combustion engine is undoubtedly a technology fit for the future.—Professor Burkhard Göschel, BMW Board of Management
BMW designed the components of this drive system to fit in existing model series. Engineers carried out tests on a number of sample packages to ensure that a car such as the BMW 3 Series provides adequate space. Their conclusion is that the engine compartment of a four-cylinder model offers sufficient space to accommodate the auxiliary units.
Ongoing development of the concept is focusing initially on making the components simpler and smaller. The long-term development goal is to have a system capable of volume production within ten years.