Design and numerical simulation of radial inflow turbine of the regenerative Brayton cycle using supercritical carbon dioxide

Carbon dioxide is abundant on earth and has a high density in the supercritical phase so that the turbomachinery size can be small. Thus the turbine, compressor, and alternator can be made compact. The advantage of the Brayton Cycle is using a regenerator on the exit side of the turbine for heat recovery. The S-CO2 radial inflow turbine is suitable for systems ranging from 0.1 MW to 25 MW. Turbomachinery can have high power densities for smaller-scale energy generation because to the low flow rates of the high-density working fluids. Small-modular heliostat fields, thermal storage, and radial inflow turbines with a power output of around 1 MW are appropriate for solar base-load energy systems in rural and isolated places, particularly in Indonesia. However, the experimental research is costly, time-consuming, and may pose security threats, whereas CFD modeling improves the design process and greatly saves time and money.This study aims to design a radial inflow turbine for the Regenerative Brayton Cycle. The turbine has designed to work at 70,000 RPM with a net power target of 40 kW. Regenerative Brayton Cycle with supercritical carbon dioxide working fluid (S-CO2) designed for turbine inlet temperature is 800 K, the compressor inlet temperature is 320 K, and the pressure ratio in turbine 1.63. Based on the cycle's design, the turbine and compressor powers are 113.84 kW and 60.53 kW, respectively. The geometric design has been carried out with an approach by some of the literature related to this research. Computational Fluid Dynamics (CFD) simulations are then performed on the results of the design of the turbine. The CFD simulation results of the radial inflow turbine show that can produced is 113.28 kW, and the total to total turbine efficiency is 81.63% at 70,000 RPM and 2.0 kg/s. However, in this study the turbine's design is targeted in around 40 kW. So, according to CFD simulation results, the net power and the efficiency of the Brayton cycle generated is 53.75 kW and 18.74%, respectively.