Optimal design of a dual-pressure radial-inflow turbine for S-CO2 cycle based on constructal theory

Based on constructal theory, a dual -pressure turbine (DPT) model for supercritical CO2 cycle is established. Seven kinds of losses, such as the nozzle, incidence, passage, windage, tip clearance, trailing and exit velocity losses, are considered in the radial-inflow turbine. The volume fraction, wheel diameter ratio and inlet pressure of the DPT are optimized, and its power output (PO) is maximized. The parameter influences on constructal results are analyzed. It reveals that the total POs after primary and twice optimizations are 1.041 MW and 1.058 MW, and are augmented by 3.89 % and 5.62 %, respectively. The total PO after triple optimization is 1.148 MW, and the corresponding optimal volume fraction, wheel diameter ratio and inlet pressure are 0.194, 0.350 and 10600.2 kPa, respectively. The PO of DPT after optimization is improved by 14.57 %, and its performance is obviously improved by optimizing three variables. Among the discussed parameters, the total mass flow rate has a more significant effect on the triple maximum PO. The results supply valuable guidelines for the turbine designs of supercritical CO2 cycles.