A variant of the Fluidyne: the liquid piston ERICSSON engine

Abstract

A special configuration of Stirling liquid piston engine, known as Fluidyne, was invented fifty years ago and many works have been devoted to it since then. A variant of the Fluidyne is presented, in which the two ends of the U-tube containing the liquid piston are closed by valves, so that the system obtained belongs to the family of Ericsson engines rather than to the family of Stirling engines. This type of low-tech system is considered to be suitable for the production of low-power mechanical energy (up to ... 1... kW), for example for pumping or to drive an electric generator from renewable primary energy conversion (solar, biomass, hot gaseous effluents, ...). In the system considered, the working fluid of the Ericsson engine is air in open cycle. Different configurations are proposed for the extraction of mechanical energy. The preliminary design of a first demonstrator is presented. Results of a dynamic "intracycle"model of this liquid piston Ericsson engine are presented in the case of the coupling with a linear generator. The model allows to determine the frequency of operation of the engine, the instantaneous liquid piston position and the instantaneous working gas properties, so that the global performance of the engine can be predicted.