A study on the rotary steam engine for distributed generation in small size power plants

The widespread use of the renewable energies requires compulsorily the development of new technological solutions for the efficient employment of these resources, such as small size, cogenerative power plants.A small volumetric steam engine may be considered an interesting device for an efficient and flexible use the heat generated by biomasses combustion or solar thermal collectors. In effects, this kind of engine may be operated with different kind of fluids, is quite insensitive to high degrees of humidity at the end of the expansion and is able to manage small volumetric flow rates with no losses in conversion efficiency.This paper shows the development of a rotary steam engine derived from a Wankel internal combustion engine. This engine was taken into account for this use due to its low bulk, vibration and noise running. Moreover, its use as an external combustion engine overrides its typical disadvantages that mainly belong to the combustion phase.The numerical modeling and the experimental tests using compressed air in a first prototype are shown in this paper. The results of the experiments allowed the validation of the model developed and this was employed to carry out a first optimization of the engine by means of the increase of the discharge coefficient of the exhaust valves.

► We studied a volumetric rotary engine for small size biomass power plants.
► We built a prototype running with compressed air and its numerical model with AMESim.
► We compared the results and we found quite a good agreement.
► Volumetric efficiency decreased with the rotating speed.
► Accurate fluid dynamic study to improve performances and efficiency.