This paper presents a numerical study on the aerodynamics loss reduction characteristics after the leading-edge(LE) optimization in a low-pressure turbine linear cascade. The LE was optimized with a simple and practic...This paper presents a numerical study on the aerodynamics loss reduction characteristics after the leading-edge(LE) optimization in a low-pressure turbine linear cascade. The LE was optimized with a simple and practical method of "Class Function/Shape Function Transformation Technique"(CST). The simulation conditions, covering the whole working range, were independently determined by incidence, Reynolds number and Mach number. Quantitative loss analyses were carried out with a loss breakdown method based on volumetric integration of entropy production rates. To understand the reason of loss reduction, the local sources at different operating points were identified with entropy production rates. The results showed that LE optimization with the CST method played a positive role in decreasing the total losses, and the working range with lower loss was extended. The profile loss and the endwall loss were significantly reduced by the LE optimization, which were also verified to be the major causes of the total loss reduction by loss breakdown. The decrease of profile loss can be attributed to the boundary layer near the LE region and the boundary layer of downstream at off-design incidence. The reduction mostly came from the pressure side at negative incidence, while came from the suction side at the positive incidence. The endwall loss was decreased markedly about 2.5%–5% by the LE optimization at the incidence of-12°, which was 1% at the incidence of 12°. The mechanism for the endwall loss reduction at different incidences was different from each other. At negative incidence, the LE optimization diminished the corner separation vortex on the pressure side. While at positive incidence, the benefits came from three aspects, i.e., reduced suction LE separation bubbles close to the endwall, reduced passage vortex strength, and weakened shear process between passage vortex and trailing shed vortex. The loss of the downstream zone was relatively lower than that of the profile losses and the endwall losses. The effect of LE optimization on the loss of the downstream zone at different conditions was complex and it depended both on the profile boundary layer behavior at the suction trailing edge and on the passage vortex strength.展开更多
In the present study, the trenched configurations, including traditional trench(TT), fillet trench(FT) and varying-radius trench(VRT), are numerically investigated at different conditions in terms of downstream coolin...In the present study, the trenched configurations, including traditional trench(TT), fillet trench(FT) and varying-radius trench(VRT), are numerically investigated at different conditions in terms of downstream cooling effectiveness and flow fields. Different trench width and fillet radii are discussed at different blowing ratios and density ratios. Results show that the downstream lips mainly change the downstream pressure distributions and then change the lateral coolant distribution. The downstream fillet can reduce the penetration of coolant and improve laterally averaged effectiveness in the configurations with the narrow trench at modest blowing ratios. The enhancement of cooling effectiveness near the centerline plane is the positive effect of downstream fillet. This enhancement becomes more obvious with the increase of fillet radius, except for high blowing ratio. The fillet lip, compared with TT cases, also leads to a decline of coolant lateral spread for configurations with the wide trench and large radius, and more decline in the lateral direction deteriorates downstream overall cooling performance. Besides, the increase of density ratio contributes to a higher cooling effectiveness for fillet trench configurations. VRT cases guarantee the streamwise extension and lateral spread of coolant, therefore improving downstream cooling effectiveness further at blowing ratio M=1.0 and 1.5.展开更多
Nonaxisymmetric endwall is an effective method to reduce secondary loss and improve aerodynamic performance.In this paper,a nonaxisymmetric endwall automated optimization process based on the nonuniform rational B-spl...Nonaxisymmetric endwall is an effective method to reduce secondary loss and improve aerodynamic performance.In this paper,a nonaxisymmetric endwall automated optimization process based on the nonuniform rational B-spline surface(NURBS)technique was proposed.This technique was applied for the aerodynamic optimization of the turbine stator shroud endwall to reduce total pressure loss and secondary kinetic energy.The flow fields of the datum endwall design(Datum)and optimization endwall design(Opt)were investigated and compared.Quantitative loss analysis was performed with a loss breakdown method.The entropy generation was classified as profile loss,secondary loss and trailing edge loss,all of which were reduced.The secondary loss was much smaller than the profile loss.In general,the blade row total entropy loss decreased by 11.7%.The results showed that the Opt design reduced total pressure loss and coefficient of secondary kinetic energy by 11.1%and 11.0%,respectively.The decrease in secondary kinetic energy could be attributed to the reduction in the horseshoe vortex and the reduced transverse pressure gradient.When the outlet Mach numbers and inlet incidence angles vary,the performance of the profiled endwall design was always better than the datum design.In the turbine stage simulation,the efficiency was increased by 0.28%with nonaxisymmetric endwall.展开更多
基金sponsored by the Project NO.51576037 supported by National Natural Science Foundation of China (NSFC)
文摘This paper presents a numerical study on the aerodynamics loss reduction characteristics after the leading-edge(LE) optimization in a low-pressure turbine linear cascade. The LE was optimized with a simple and practical method of "Class Function/Shape Function Transformation Technique"(CST). The simulation conditions, covering the whole working range, were independently determined by incidence, Reynolds number and Mach number. Quantitative loss analyses were carried out with a loss breakdown method based on volumetric integration of entropy production rates. To understand the reason of loss reduction, the local sources at different operating points were identified with entropy production rates. The results showed that LE optimization with the CST method played a positive role in decreasing the total losses, and the working range with lower loss was extended. The profile loss and the endwall loss were significantly reduced by the LE optimization, which were also verified to be the major causes of the total loss reduction by loss breakdown. The decrease of profile loss can be attributed to the boundary layer near the LE region and the boundary layer of downstream at off-design incidence. The reduction mostly came from the pressure side at negative incidence, while came from the suction side at the positive incidence. The endwall loss was decreased markedly about 2.5%–5% by the LE optimization at the incidence of-12°, which was 1% at the incidence of 12°. The mechanism for the endwall loss reduction at different incidences was different from each other. At negative incidence, the LE optimization diminished the corner separation vortex on the pressure side. While at positive incidence, the benefits came from three aspects, i.e., reduced suction LE separation bubbles close to the endwall, reduced passage vortex strength, and weakened shear process between passage vortex and trailing shed vortex. The loss of the downstream zone was relatively lower than that of the profile losses and the endwall losses. The effect of LE optimization on the loss of the downstream zone at different conditions was complex and it depended both on the profile boundary layer behavior at the suction trailing edge and on the passage vortex strength.
基金financial support from the Natural National Science Foundation of China (No. 51206034 and 51436002)the Research Fund for the Doctoral Program of Higher Education of China (No. 20122302120066)
文摘In the present study, the trenched configurations, including traditional trench(TT), fillet trench(FT) and varying-radius trench(VRT), are numerically investigated at different conditions in terms of downstream cooling effectiveness and flow fields. Different trench width and fillet radii are discussed at different blowing ratios and density ratios. Results show that the downstream lips mainly change the downstream pressure distributions and then change the lateral coolant distribution. The downstream fillet can reduce the penetration of coolant and improve laterally averaged effectiveness in the configurations with the narrow trench at modest blowing ratios. The enhancement of cooling effectiveness near the centerline plane is the positive effect of downstream fillet. This enhancement becomes more obvious with the increase of fillet radius, except for high blowing ratio. The fillet lip, compared with TT cases, also leads to a decline of coolant lateral spread for configurations with the wide trench and large radius, and more decline in the lateral direction deteriorates downstream overall cooling performance. Besides, the increase of density ratio contributes to a higher cooling effectiveness for fillet trench configurations. VRT cases guarantee the streamwise extension and lateral spread of coolant, therefore improving downstream cooling effectiveness further at blowing ratio M=1.0 and 1.5.
基金the support of the National Science and Technology Major Project of China(No.2017-I-0005-0006)the Outstanding Youth Science Foundation of Heilongjiang Province of China(No.YQ2020E016)。
文摘Nonaxisymmetric endwall is an effective method to reduce secondary loss and improve aerodynamic performance.In this paper,a nonaxisymmetric endwall automated optimization process based on the nonuniform rational B-spline surface(NURBS)technique was proposed.This technique was applied for the aerodynamic optimization of the turbine stator shroud endwall to reduce total pressure loss and secondary kinetic energy.The flow fields of the datum endwall design(Datum)and optimization endwall design(Opt)were investigated and compared.Quantitative loss analysis was performed with a loss breakdown method.The entropy generation was classified as profile loss,secondary loss and trailing edge loss,all of which were reduced.The secondary loss was much smaller than the profile loss.In general,the blade row total entropy loss decreased by 11.7%.The results showed that the Opt design reduced total pressure loss and coefficient of secondary kinetic energy by 11.1%and 11.0%,respectively.The decrease in secondary kinetic energy could be attributed to the reduction in the horseshoe vortex and the reduced transverse pressure gradient.When the outlet Mach numbers and inlet incidence angles vary,the performance of the profiled endwall design was always better than the datum design.In the turbine stage simulation,the efficiency was increased by 0.28%with nonaxisymmetric endwall.
