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This work proposes a focus on the simulation of a rotative volumetric expander via a CFD code. A customized application of OpenFOAM® has been developed to handle the particular motion of the calculation grid. The model uses a mesh to mesh interpolation technique, switching from a calculation grid to the new one on the basis of mesh quality considerations performed on the fly. This particular approach allows to account for the presence of leakages occurring between the stator and blade tips and also occurring at the top and bottom of the vanes. The fluid considered is the refrigerant R245fa, whose particular properties have been determined resorting to the NIST database. Experimental data, measured at different conditions of mass flow and fluid temperature, are compared to calculation results. Moreover, the CFD analysis has allowed the estimation of the influence of the leakage mass flow occurring at the tip of the vanes on the overall machine performances.

The paper contains the design and simulation of a purely mechanical system for storing energy during vehicle deceleration, which can be utilized during subsequent acceleration (regenerative braking). A continuously variable transmission (CVT) regulates the energy transfer, energy storage is accomplished by means of a spiral spring and additional use of a planetary transmission. The transmission ratio of the CVT is adapted by a combined feed-forward and feed-back control. A computer simulation for a vehicle with an overall mass of 1500kg, and an energy storage capacity of 30kJ was performed for different driving cycles. In a typical urban stop and go situation the proposed device will save up to 0.72kg fuel per 100km and the overall efficiency analysis together with simple design, easy recycling, and long life expectance, showed a clear advantage over other hybrid concepts for frequent stops and accelerations.