One-dimensional Optimization Design And Performance Analysis Of Supercritical Carbon Dioxide Radial Inflow Turbine Under Variable Working Conditions

The Brayton cycle using supercritical carbon dioxide as the working fluid has the advantages of high efficiency,compact cycle structure and environmental protection.The radial inflow turbine,as a key component of the power cycle,has an important impact on cycle efficiency.Therefore,the design mechanism of supercritical carbon dioxide radial inflow turbine and related research are of great significance.In this paper,a study on a radial inflow turbine using supercritical carbon dioxide as a working fluid is carried out.The main research contents include: aerodynamic analysis,one-dimensional optimization design,performance analysis under variable conditions,further design of the meridian flow channel and research on blade tip clearance.Perform aerodynamic analysis on the radial inflow turbine,and independently develop the one-dimensional optimization design program for the S-CO2 radial inflow turbine,and carry out one-dimensional optimization design for the radial inflow turbine.The program takes the maximum total static efficiency as the optimization goal,and takes seven important parameters as the optimization parameters to carry out the optimization design.Based on the one-dimensional optimization design results,further three-dimensional modeling is carried out,and NUMECA software is used to carry out three-dimensional flow field analysis and performance analysis of design conditions and variable conditions.The results show that the radial inflow turbine has good performance under the design expansion ratio,and has good performance under variable working conditions.Using the Bezier curve method and the linear arc method,the meridional flow path of the S-CO2 radial inflow turbine was designed,and numerical simulation was carried out to explore the influence of different design methods on the performance of the radial inflow turbine with carbon dioxide as the working fluid.The results show that the Bezier curve method is slightly better than the straight arc method,the meridian flow channel designed by it is smoother,the curvature change is more gentled,and the flow field is more unobstructed.In order to explore the effect of tip clearance on the performance of S-CO2 radial turbine,the radial turbine designed in this paper is taken as an example,and different clearance types and clearance sizes are set to conduct numerical simulations.The results show that when the gap size is in the range of 0.1-0.5 mm,the total-static efficiency decreases by about 1.07% for every 1% increase in the gap/exit leaf height.When the radial clearance is not equal to the axial clearance,the total-static efficiency is reduced by about 0.146% for every 1% increase in the axial clearance,and the total-static efficiency is reduced by about 0.362% for each 1% increase in the radial clearance.The influence of radial clearance on performance is much greater than that of axial clearance,and the influence of radial clearance on total static efficiency is about twice that of axial clearance.