EFFECT OF TURBULENCE AND FLOW DISTORTION ON THE PERFORMANCE OF CONICAL DIFFUSERS OPERATING ON SUPERCRITICAL CARBON DIOXIDE

摘要

A rapidly growing interest in the supercritical carbon dioxide power cycle has been observed in the last years due to the superb performance of this system in concentrated solar and nuclear applications; a sample of this interest is the number of technical publications submitted to Turbo Expo in the last couple of years. As active members of the supercritical carbon dioxide (SCO2) community, the authors of this work have lately studied the fundamentals of SCO2 flows. The approach followed has nevertheless been different to that of most researchers since it has concentrated on simple devices rather than on an entire turbomachinery. Thus, recent contributions by the authors have shown that major differences are to be expected when air and SCO2 diffuse through simple conical divergent ducts at subsonic speeds, most of which derive from the very different characteristics and performance of the boundary layer when adverse pressure gradients are faced. In particular, the effects of geometry (i.e. divergence angle) and aerodynamic blockage on the static pressure rise coefficient of such a conical diffuser have been reported by the authors in recent technical works. This work presents the effects of other aerodynamic features of the inlet flow to a conical diffuser on the capacity to convert kinetic energy into static pressure. Two flow features are studied: (ⅰ) the distortion of the inlet velocity distribution and (ⅱ) the turbulence intensity of the inlet flow. A parallel analysis is developed for air and SCO2 showing that the effects of both distortion and turbulence on diffuser performance are sensitive to the working fluid of choice.