Rolls-Royce Fuel Cell Systems Ltd in the last few years has been developing a low cost hybrid system for electricity production based on SOFC (Solide Oxide Fuel Cells). The novel cycle is based on the recycle of cathodic off-gas to pre-heat the oxidant flow, using ejectors. On the anode side, ejectors are used to recycle steam-rich off-gas to the reforming reactor.This paper describes the analysis process carried out to optimize the ejector geometry, from the preliminary sizing of lengths and sections, to the flow path optimisation. Further study has been carried out in order to evaluate the influence of altered geometries on the ejector performance varying the nozzle position relative to the ejector body.An extensive use of CFD (Computational Fluid Dynamics) combined with experimental results allowed the validation of the basic design tools and the optimisation of the ejector performance.
