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Session: Session 4A: Volumetric Expanders (1)
Session starts: Tuesday 10 September, 14:00
Presentation starts: 15:00
Room: Olympia

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Vaclav Vodicka (University Centre for Energy Efficient Buildings, Czech Technical University in Prague, Třinecká 1024, 273 43 Buštěhrad Czech Republic)
Vaclav Novotny (University Centre for Energy Efficient Buildings, Czech Technical University in Prague, Třinecká 1024, 273 43 Buštěhrad Czech Republic)
Zbynek Zeleny (University Centre for Energy Efficient Buildings, Czech Technical University in Prague, Třinecká 1024, 273 43 Buštěhrad Czech Republic)
Jakub Mascuch (University Centre for Energy Efficient Buildings, Czech Technical University in Prague, Třinecká 1024, 273 43 Buštěhrad Czech Republic)

Abstract:
Rotary vane expander (RVE) is a perspective solution in the case of requirement for expanders with low power output in range of single kW as they can provide attractive cost to performance ratio, especially in case of small series or single units manufacturing. Specific feature of the RVE are the vanes sliding on the surface of a stator cylinder, thus creating chambers. Permanent contact between the vanes and the stator is essential from the perspective of expander efficiency and lifetime of the vanes. If the vane does not maintain contact with the stator, a phenomenon called vane chatter occurs. In this case, the working chamber is not properly formed, which is associated with excessive leaks of the working fluid from the working chamber. If this occurs during the filling phase, the mass flow of the working fluid through the machine will be greatly increased, while at the same time the overall efficiency of the expander will be significantly reduced. This work provides a mathematical model, which extends previous models describing internal leakage pathways by prediction of the occurrence and extent of the delayed closure of the working chamber in the filling phase. The model is based on combination of 1D quasi-steady flow of working fluid through a set of described leakage pathways combined with a dynamic model of vanes, describing their radial position. The model results are after preliminary assessment in agreement with experimental measurements on an in house developed RVE with MM as working fluid. Vanes of various mass were tested for a given range of rotational speed as the difference in the centrifugal force acting on the vanes has major influence on the proper closure of the working chamber (but also on friction losses). This combined model can serve for future throughout optimization or check of occurrence of delayed chamber closure in RVE design works.