Due to the advantages - like high power density, low weight, and compact design - the two-stroke engines are an interesting technology for electric vehicles with range extender application. Therefore, an intensive concept evaluation process, focussing only on two-stroke technologies, was conducted in order to identify the best possible solution. The assessment showed that for the high emission standard of automotive applications the uniflow scavenged two-stroke engine has fundamental advantages compared to a conventional loop scavenged engine. Only with very high trapping efficiency for both, fuel and air, a 3-way after treatment system can be applied. Due to the compact design and the knowledge that the uniflow scavenged twin-piston engine was very successful in the past, this technology was evaluated best. The engine test bench values of the tested twinpiston engine demonstrate the high potential of this engine type. The measured high trapping efficiency of the twin piston engine confirms the possibility to apply a 3-way after treatment system. Knowing that conventional loop-scavenged two-stroke engines with direct injection achieve a BSFC (brake specific fuel consumption) of 270 g/kWh at WOT (wide open throttle) and about 250 g/kWh in the optimum operational point, it is realistic that a twin-piston engine, with higher trapping efficiency, can be developed with a target of BSFC < 250 g/kWh in the relevant operational range of a range extender. Of course the newly developed twin-piston engine will be applied with state of the art technology and thus show different design details than older generations of this technology. Both developed concepts use an external scavenge pump instead of the crankcase. With this solution it is possible to work with a closed oil circuit and avoid emissions. The external pump (turbine) allows a higher average scavenging pressure and provides the possibility of an adjustable pressure and therewith an additional parameter to control the scavenging process. The possibility to influence port timing by piston phasing is a further key to optimize the twin-piston scavenging process by the new split-pin concept and the two-crankshaft solution. The counter rotating crankshafts are excellent regarding the NVH characteristic of the twin piston engine. The high ignition frequency at low engine speed - NVH characteristic similar to a four-cylinder four-stroke engine - is a further advantage of the twin-piston two-stroke engine. The concepts showed a total weight, including 11 kg generator weight, between 28 kg and 35 kg for the complete (dry) system without cooler and fuel tank. The introduced concepts serve as a discussion basis and can be used to start a development project with interested partners.


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    Titel :

    Twin-piston 2-stroke range extender concept


    Beteiligte:
    Winkler, F. (Autor:in) / Kirchberger, R. (Autor:in) / Eichlseder, H. (Autor:in)


    Erscheinungsdatum :

    2011


    Format / Umfang :

    9 Seiten, 19 Bilder, 1 Tabelle, 4 Quellen


    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Datenträger


    Sprache :

    Englisch




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