Design And Optimization Of Small Radial Turbines For On-board ORC Systems

In this paper,the organic Rankine Cycle(ORC)is used to recover exhaust heat from vehicle exhaust gases with the purpose of improving the fuel utilization efficiency of vehicle engines.The influence of the thermal cycle parameters on the ORC system is analyzed.Based on this analysis,a miniaturized centripetal turbo expander is designed for the ORC system,and its performance,internal flow field and structural parameters are analyzed by numerical simulation.The main research contents are as follows:1.The mathematical modeling of the exhaust gas waste heat utilization ORC system is based on the laws of thermodynamics to analyze the effects of expansion ratio and superheat on the circulating thermal performance of the system.The results show that the influence of superheat on the circulating thermal performance of the system is small;the increase of the expansion ratio can effectively improve the system performance and increase the net output work,thermal efficiency,and operational efficiency of the system.2.Based on the analysis of the thermal cycle parameters of the exhaust gas waste heat utilization ORC system,the design parameters of the centripetal turbine are determined,the structural parameters of the centripetal turbine are determined by establishing the mathematical model of the centripetal turbine,and the numerical simulation analysis is carried out.The results show that the internal pressure,temperature and velocity flow lines of the centripetal turbine change uniformly,and the aerodynamic performance of the centripetal turbine is good,and the isentropic efficiency of the centripetal turbine under the design condition can reach 84.65%.3.The effects of impeller blade to blade ratio,annular radial clearance,impeller inlet coverage,impeller inlet blade angle,and impeller blade thickness on the centripetal turbine performance and internal flow are investigated to improve centripetal turbine efficiency and aerodynamic performance,and provide useful references for the design of centripetal turbine structural parameters.4.The effects of inlet temperature and mass flow rate on the performance of centripetal turbines are investigated by constructing an experimental platform for a centripetal turbine expander.The results show that increasing the mass flow rate can effectively improve the overall performance of the centrifugal turbine.The increase of the inlet temperature from 300 K to 330 K increases the power generation by 24.07%,but it causes the increase of the after-velocity loss and the decrease of the isentropic efficiency of the centripetal turbine.