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BMW's
Turbosteamer - Reinventing steam power The long story. (From BMW press release) Researchers at the BMW Group are putting their cars under pressure: With an old idea and new technology the company is for the first time making use of engine heat 
Based on the principle of the steam engine, BMW's research and technology division has, under the project name "Turbosteamer", developed a way of using combined heat and power in cars. In conjunction with the new secondary drive, the four-cylinder engine consumes up to 15 percent less energy, while producing 10 kilowatts more power. At the same time the additional energy is gained exclusively from the heat in exhaust emissions and cooling water. The advantages: less emissions and consumption with increased dynamism and performance. The northern region of South Africa seems to be a good place for innovative ideas - especially when it comes to eliminating heat. Prof. Dr. Raymond Freymann, head of BMW's research and technology division, once tested the heat resistance of trial engines in the Kalahari Desert, where temperatures in the shade exceeded 50 degrees. Engineers have been brooding over the unresolved problem of motor heat for some time. This is because "two thirds of the energy contained in petrol is lost via exhaust emissions and cooling water, and the heat drop in cooling water has to be disposed of via the radiator", explains Freymann. In the heat of the African desert, however, the engineers of BMW's research and technology division came upon the brilliant idea of tapping into this unused energy. The system is astoundingly logical and essentially centuries-old. Now for the first time the BMW Group is allowing outsiders to see how there could soon be a renaissance in modern car construction - thanks to the steam engine. No wrought-iron contraption is to set to take the place of the engine, however. Instead it is merely to be supplemented with a compact additional component. Closed circuit BMW's engineers have christened their innovation the "Turbosteamer". Its purpose is to convert by far the largest unused energy reserve in conventional vehicle technology into driving power, i.e. the heat emitted by the exhaust system and cooling water. The Turbosteamer is based on two circuits: "The first and most important is the 'high temperature circuit' which uses the exhaust heat of petrol-driven cars as an energy source", explains Dr. Andreas Obieglo, project leader for the Turbosteamer. In addition there are two heat exchangers in the exhaust line, through which water is pumped at a pressure of up to 40 bar. Even if a car engine is only placed under moderate pressure, the water in this circuit is heated up to a maximum of 550 degrees Celsius. The hot steam flows into an expander machine, which is coupled to the crankshaft. There the highly-pressurized steam is converted into a rotation and the additional energy guided to the power train. The pressure drives forward one of the steam engines, and at the same time the water cools and becomes liquid once again - a closed circuit. The typical huffing and puffing of olden-days steam locomotives is not something the driver will hear, however! The second circuit of the Turbosteamer system works with lower temperatures. In this so-called pipe system, however, it is not water that circulates around it but ethanol i.e. alcohol. This is heated up to 150 degrees Celsius, both by the cooling water heat of the engine and by the heat of the high-temperature circuit. "In this way we ensure sufficient energy for heating up the ethanol to approx. 100 degrees in order to drive a second expander machine that also contributes to a performance increase or consumption decrease", says Obieglo, describing the technology. While the temperature was sufficient to drive forward the second expander machine, the degree of efficiency was still not satisfactory, however. "For this reason we installed a second loop at the end of the exhaust heat exchanger, a point at which enough heat is also released to heat up the ethanol to approx. 150 degrees", says Obieglo. The second expander machine converts this heat into an additional rotation, and the low temperature circuit is closed by a conventional radiator that releases the remaining warmth from the ethanol's condensation into the surrounding atmosphere. The amount of added power provided by the Turbosteamer can be up to 10 kilowatts, and the concept has the greatest impact when used with an internal combustion engine. Nevertheless it remains suited for use with diesel engines, with no alteration work necessary. "In the case of diesel engines, however, the exhaust emissions are lower, and consequently so is the amount of energy that can be regained", explains Obieglo. Ready for mass productions in ten years At the moment the Turbosteamer is still in its test phase. However "the parts and components are designed in such a way that they can easily be integrated into a BMW 3 series vehicle, for example." The team around Andreas Obieglo has already been working for more than five years on the technology. "In around ten years' time the Turbosteamer could be ready for mass production", forecasts Obieglo. Until then the engineers are working on concepts that will significantly reduce the weight of the system from the current 50 kilograms per circuit. Furthermore the components are set to be made smaller and the efficiency of the expander machine improved. In order to realise these aims, the company is striving for additional co-operative partnerships with other car component suppliers. The larger framework: BMW Efficient Dynamics According to Obieglo, if the Turbosteamer is used, the efficiency of the combined drive system increases by 15 percent. In an optimal scenario, travelling on a highway at a constant speed of 120 km/h, a car with an average consumption of 7 litres per 100 kilometres could save 1.5 litres per 100 kilometres. The system however can also be optimized for use in urban traffic. "The special attraction of this innovation is that it provides additional power and increased efficiency, at least as far as energy input is concerned, at no additional cost", explains Obieglo. Because the additional kilowatts are derived exclusively from the heat from exhaust emissions and cooling water, no additional fuel is required. "As a result, the apparent contradiction between consumption and emissions reduction on the one hand, and performance and agility on the other is resolved", says Prof. Burkhard Göschel, development and purchasing director at BMW. True to the motto that a few percentage points less consumption across an entire model range can have a higher general impact than many percentage points for a single niche model, BMW is keen to ensure that the latest technology for lower consumption is made available to a large number of customers. The Turbosteamer is evidence of the company's medium-term aims with its BMW Efficient Dynamics project. And who would have thought that combined heat and power, in addition to being used in large-scale power stations, would also one day be used in vehicles, and accordingly become mobile? |