Higher efficiencies and more compact designs in spite of larger built-in volume ratios are associated with variable wall thickness scroll expander geometries. In this research paper, transient 3D CFD simulations of this scroll-type design were presented to examine the influence of radial clearances on the aerodynamic performance in small scale Organic Rankine cycle systems. The decrease of radial clearances resulted in high speed flank leakages. There was a sharp increase in the Mach number in conjunction with a decrease in the static pressure. Supersonic flows were generated through those gaps between the fixed and orbiting scroll. Thus, the radial clearances need to be sealed.
Keywords Scroll expander, Variable wall thickness geometry, ORC system, Aerodynamic performance, Radial clearance, Flank leakage