Most automobile manufacturers have developed hybrid vehicles that combine an internal combustion engine and an electric motor, fusing the advantages of these two power sources. For example Toyota in its Prius II uses a gasoline engine which achieves high efficiency by using a modified Atkinson cycle based on variable valve timing management. This implementation of the Atkinson cycle is not the optimal solution because e.g. some of the air is first sucked from the intake manifold into the cylinder and subsequently returned. This oscillating air stream considerably reduces the thermal conversion efficiency of this cycle. In this paper the losses in the thermal conversion efficiency of internal combustion engines, and especially of Atkinson cycles, are analyzed in detail and a proposal for an improvement cycle for such applications is made. The potential of the Atkinson cycle realized through extended opening of the intake valve - as implemented by Toyota in its Prius II - was investigated here in a number of different variants. Analysis of the simulation results shows that the benefits in the form of increased efficiency would be minimal in this kind of cycle. As an additional variant, the use of a new kind of crankshaft drive was presented which permits different size strokes for compression and expansion. In this case the improvements in the efficiency are clearly visible, even without supercharging of the engine.
Enhancement potential of the thermal conversion efficiency of ice cycles especially for use in hybrid vehicles
2007
6 Seiten, 14 Bilder, 7 Quellen
Aufsatz (Konferenz)
Datenträger
Englisch
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