Design, Analysis, and Simulation of a Turbine for Supercritical CO2 Brayton Cycle

• Main Authors: Wen, Meng-Yang, 溫孟揚
• Other Authors: Chiang, Hsiao-Wei
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/x4838c

碩士 === 國立清華大學 === 動力機械工程學系 === 105 === The research of Supercritical CO2 (sCO2) Brayton Cycle has been popular over the past decade, due to its higher efficiency and smaller component size compared with those of steam Rankine cycle and air Brayton Cycle. Studies showed that SCO2 Brayton Cycle can accommodate a wide range of temperature as the heat source, starting from 260°C to 1200 °C. Thus, various research had been investigated to apply sCO2 Brayton Cycle into fields such as concentrated solar power, nuclear power, geothermal power, and waste heat recovery, making it a viable option for renewable energy. This study is a subproject of SCO2 Brayton Cycle power generation system, a project under the National Energy Program-Phase II in Taiwan, with the objective of designing a power generation system using waste heat as heat source. The temperature of the waste heat is set to be 450°C, conforming to mid-range waste heat. The aim of this subproject is to design a turbine with the inlet total pressure of 14.1 MPa and total temperature of 573K, respectively, and outlet pressure of 8.5 MPa, corresponding to an expansion ratio of 1.658. Due to its small size and low mass flow rate, radial inflow turbine is selected instead of the axial flow turbine. Some efforts were made by previous member of this lab to modify the existing turbine model to avoid the complexity of designing a turbine model from scratch. The efficiency, however, turned out to be lower the expectation. Therefore, in this study, the previously modified turbine model would be discarded and the new turbine would be built from square one. This study tried to use Meanline Analysis from the literature as a preliminary design tool. Although most studies devoting to the design of radial inflow turbine were developed for turbine using air as working fluid, recent studies about the design of SCO2 turbine indicated that Meanline Analysis is qualified to be a preliminary design tool. The simulation result of the Meanline Analysis was shown to be deviate from the design point, as expected. Fortunately, with the aid of CFD, the problem predicted by the simulation could be corrected and the model could be adjusted accordingly. At the end, with some bold assumption, the turbine model close to the expected pressure ratio and power output was devised.