On the effects of leakages in Sliding Rotary Vane Expanders

Experimental Validation of a New Modeling for the Design Optimization of a Sliding Vane Rotary Expander Operating in an ORC-Based Power Unit

“…This class of models represents also the leakage paths between vanes and across the end-wall plates, as well as the friction losses inside the machine produced by the contact at tip blades and inside the rotor slots. The high accuracy of these models is witnessed by several contributions in the literature [40,41]. Of course, also the indicated diagram is well represented and the effects produced by some unconventional solutions, like for instance, a double port intake technology [43,44].…”

“…The reason for a new model of an SVRE stands on the need to have a good compromise between the existing models and a simpler representation that doesn't sacrifice the representation of the most relevant phenomena, which influence volumetric and mechanical efficiencies of the machine. Existing models have a high degree of reproducibility of real phenomena [40,41]. They are based on matching a 1D transient model, which represents the filling and emptying of the vanes facing intake and exhaust ports, with a lumped parameter approach, which describes the thermodynamic properties of the working fluid inside the chambers.…”

“…m WF being easily measurable upstream of the machine. The leakages taking place between adjacent chambers are driven by the angular phase shift of the pressure profiles [41]. The geometrical choices of the machine influence these volumetric losses through the leakage area too.…”

“…In order to assist a proper design of the SVRE, the development of a suitable mathematical model could allow to specifically design these machines through a model-based approach; the comprehension of the processes inside the machine certainly helps the behavior of the single machine, as well as that one when the machine operates in the recovery unit [39]. Comprehensive models of SVRE are available in the literature, published also by the authors [40,41], but their use is characterized by a certain complexity: difficulty to define the boundary conditions at the inlet and exhaust ports, matching of 1D transient phenomena (during filling and emptying of the vanes) with lumped parameters approaches (thermodynamic properties inside the closed vanes), long computational times due to the representation of transient phenomena. These models have a high capability of predicting real phenomena but are unsuitable to be used as a design tool and to approach the control needs with the help of a mathematical model (model-based control).…”

“…The effects produced by the fluid that passes between chambers on the pressure inside the chambers were represented as well, catching some important phenomena, which were experimentally observed and theoretically justified by the use of the aforementioned more complex models. In particular, the deviation of the pressure inside the chambers is from an adiabatic transformation [41,42]. Care was also used to represent friction losses in all their contributions (at tip blade, inside the rotor slots, etc.).…”