This paper focuses on optimizing the aerodynamic performance of a high-pressure turbine under multiple operation conditions.Utilizing a self-adaptive updated Kriging model,we employ the Latin hypercube sampling method...This paper focuses on optimizing the aerodynamic performance of a high-pressure turbine under multiple operation conditions.Utilizing a self-adaptive updated Kriging model,we employ the Latin hypercube sampling method and NSGA-Ⅱ algorithm to find the optimum point with the maximum weighted average isentropic efficiency.The results show that compared with the original blade,the efficiency is increased by 2.35%for the optimized blade.Using the sensitivity analysis,it is indicated that the thicknesses near the leading edge and middle part in the mean section primarily influence the efficiency of turbine,in which the thickness near the leading edge is the most influential.It is also found that the proposed optimization method can greatly reduce the low-velocity regions caused by secondary flows,which thus significantly relieve the passage blockage.In addition,we notice a dramatical reduction of losses in the selected blade sections for the optimized blade.According to the entropy generation rate,the regions with high entropy generation,positioned near the pressure side,blade tip and corner regions in 50%axial blade section,and the tip regions in the section downstream the trailing edge,are also remarkably decreased.展开更多
Two-phase flow in two digital cores is simulated by the color-gradient lattice Boltzmann method.This model can be applied totwo-phase flow with high-density ratio(on order of 1000).The first digital core is an artific...Two-phase flow in two digital cores is simulated by the color-gradient lattice Boltzmann method.This model can be applied totwo-phase flow with high-density ratio(on order of 1000).The first digital core is an artificial sandstone core,and itsthree-dimensional gray model is obtained by Micro-CT scanning.The gray scale images are segmented into discrete phases(solid particles and pore space) by the Otsu algorithm.The second one is a digital core of shale,which is reconstructed usingMarkov Chain Monte Carlo method with segmented SEM scanning image as input.The wettability of solid wall and relativepermeability of a cylindrical tube are simulated to verify the model.In the simulations of liquid and gas two phase flow in digital cores,density ratios of 100,200,500 and 1000 between liquid and gas are chosen.Based on the gas distribution in the digital core at different times,it is found that the fingering phenomenon is more salient at high density ratio.With the density ratioincreasing,the displacement efficiency decreases.Besides,due to numerous small pores in the shale,the displacement efficiency is over 20% less than that in the artificial sandstone and the difference is even about 30% when density ratio is greaterthan 500.As the density ratio increases,the gas saturation decreases in big pores,and even reaches zero in some small pores orbig pores with small throats.Residual liquid mainly distributes in the small pores and the edge of big pores due to the wettability of liquid.Liquid recovery can be enhanced effectively by decreasing its viscosity.展开更多
基金supported by the National Natural Science Foundation of China(Nos.12072257 and 51876170)the Major Special Science and Technology Project of the Inner Mongolia Autonomous Region(No.2020ZD0022)the National Key Project(No.GJXM92579).
文摘This paper focuses on optimizing the aerodynamic performance of a high-pressure turbine under multiple operation conditions.Utilizing a self-adaptive updated Kriging model,we employ the Latin hypercube sampling method and NSGA-Ⅱ algorithm to find the optimum point with the maximum weighted average isentropic efficiency.The results show that compared with the original blade,the efficiency is increased by 2.35%for the optimized blade.Using the sensitivity analysis,it is indicated that the thicknesses near the leading edge and middle part in the mean section primarily influence the efficiency of turbine,in which the thickness near the leading edge is the most influential.It is also found that the proposed optimization method can greatly reduce the low-velocity regions caused by secondary flows,which thus significantly relieve the passage blockage.In addition,we notice a dramatical reduction of losses in the selected blade sections for the optimized blade.According to the entropy generation rate,the regions with high entropy generation,positioned near the pressure side,blade tip and corner regions in 50%axial blade section,and the tip regions in the section downstream the trailing edge,are also remarkably decreased.
基金supported by the National Natural Science Foundation of China(Grant No.51234007,51404291)Program for Changjiang Scholars and Innovative Research Team in University(Grant No.IRT1294)Introducing Talents of Discipline to Universities(Grant No.B08028)
文摘Two-phase flow in two digital cores is simulated by the color-gradient lattice Boltzmann method.This model can be applied totwo-phase flow with high-density ratio(on order of 1000).The first digital core is an artificial sandstone core,and itsthree-dimensional gray model is obtained by Micro-CT scanning.The gray scale images are segmented into discrete phases(solid particles and pore space) by the Otsu algorithm.The second one is a digital core of shale,which is reconstructed usingMarkov Chain Monte Carlo method with segmented SEM scanning image as input.The wettability of solid wall and relativepermeability of a cylindrical tube are simulated to verify the model.In the simulations of liquid and gas two phase flow in digital cores,density ratios of 100,200,500 and 1000 between liquid and gas are chosen.Based on the gas distribution in the digital core at different times,it is found that the fingering phenomenon is more salient at high density ratio.With the density ratioincreasing,the displacement efficiency decreases.Besides,due to numerous small pores in the shale,the displacement efficiency is over 20% less than that in the artificial sandstone and the difference is even about 30% when density ratio is greaterthan 500.As the density ratio increases,the gas saturation decreases in big pores,and even reaches zero in some small pores orbig pores with small throats.Residual liquid mainly distributes in the small pores and the edge of big pores due to the wettability of liquid.Liquid recovery can be enhanced effectively by decreasing its viscosity.
