Small-scale Organic Medium Radial-inflow Turbine Aerodynamic Optimization Design And Strength Analysis

Based on the increasingly severe energy and environment condition,it is quite essential to exploit green and renewable energy deeply.Using new energy like solar power,geothermal and tidal energy or employing waste heat recovery can effectively alleviate energy shortage while improve the environment.Being an effective method to utilize these low temperature and low-grade energy Organic Rankine Cycle(ORC)has gradually drawn people's attention.In this paper,the design and research of 10 k W small-scale ORC radial-inflow turbine based on low temperature ORC system are studied.The main content is as follows:Firstly,using MATLAB as software,aerodynamic design optimization is made for the radial-inflow turbine by combining the screening method and the genetic optimization algorithm(GA)to encode the 1-D design program.The optimized turbine efficiency could reach 80.96%.Based on the one-dimensional aerodynamic design,components of radial inflow turbine are modeled and meshed and the flow path of the turbine is calculated by CFD.It can be seen from the result of CFD that the turbine shows good overall performance while shock waves are generated at the entrance of the rotor blades,which will cause boundary layer separation and raise rotor loss.The match between stator and rotor can still improve.By comparing simulation parameters and design parameters,these parameters match well and all parameter errors are in acceptable limits.To judge the performance differences among shroud-impeller,unshroud-impeller and open-impeller,studies are made in the influences on the turbine flow field caused by the tip clearance and Hub-leakage of impeller.The results shows that: The existence of the clearance will degrade the impeller performance while the influence of the tip clearance is higher,and it shows certain necessity for small-scale radial-inflow turbines to use shroud-impeller.Considering the possible blockage effect at the outlet of the small-scale radial inflow turbine,analysis are made on the modelling of splitter blade and the influences on impeller performance caused by circumferential offset and the length of splitter blade are studied.The results show that the offset and the length of splitter blade will both influence impeller performance greatly,the best offset stands within the limits of 0.5 ~0.6 while the optimized blade length is 80% of the main blade.Comparison of the static strength analysis of the shroud-impeller and unshroudimpeller with or without aerodynamic loading are made.The results show that the overall deformation of the shroud-impeller is smaller than that of the unshroud-impeller under the same working conditions,but the maximum stress value is much larger than that of the unshroud–impeller.In addition,in high-speed small-scale turbines,aerodynamic forces have little effect on the deformation and stress distribution of the impeller.And then,the static strength analysis of splitter-impeller with different splitter circumferential positions and length is made to study the effect of splitter-blade on the deformation and stress distribution.The results show that compared with the circumferential position,the influence of the split-length on the structure of the impeller is more pronounced.