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Nagel, Alexander ; Thäter, Stefan ; Steinhilper, Rolf:
Range-extender in electric vehicles : a revival of (highly optimized) two-stroke engines on a small scale.
2013
Veranstaltung: 12th International Conference on Management of Innovative Technologies & 4th International Conference on Sustainable Life in Manufacturing
, 22.-24.09.2013
, Fiesa, Slovenia.
(Veranstaltungsbeitrag: Kongress/Konferenz/Symposium/Tagung
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Paper
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Abstract
The limited accumulator capacity of modern electric vehicles, which are driven by accumulator powered electric motors, is one reason why these systems do not prevail. To increase the range and the attractiveness of electric powered vehicles, the research project "MIHY - Miniatur Hybrid" is handling the development of a modern range extender by using two-stroke engines (mechanical power: ~ 3 kW) on a small scale. To increase the over-all efficiency, thermal energy in the exhaust system has to be converted into kinetic energy. Therefore a laval nozzle accelerates the exhaust gas to supersonic speed, which is driving a subsequent, for the exhaust conditions specialized, turbine generator. Furthermore the whole exhaust system, including the turbine and the laval nozzle, is optimized for the resonance of sound waves in order to minimize the loss of fresh gas during the gas exchange in the two-stroke engine. So the sound waves, which are caused by the combustion, must reflect at the nozzle to a certain time to assure an optimal charge of the combustion chamber. Therefore the length of the exhaust system and the propagation delay are synchronized. At the piston outlet they provoke a local pressure increase, which forces unburned gases back to the piston. All relevant conditions like pressures and temperatures at different points, the crankshaft speed and angle, the flow speed, the generated electrical power are recorded by using high speed analyzing equipment and simulated by using CFD (Computational Fluid Dynamics). In this paper relevant calculations and the dimensioning of a revolutionary exhaust system for increasing the efficiency of a light weight two-stroke range extender are presented for the first time.