Generally speaking,main flow path of gas turbine is assumed to be perfect for standard 3D computation.But in real engine,the turbine annulus geometry is not completely smooth for the presence of the shroud and associa...Generally speaking,main flow path of gas turbine is assumed to be perfect for standard 3D computation.But in real engine,the turbine annulus geometry is not completely smooth for the presence of the shroud and associated cavity near the end wall.Besides,shroud leakage flow is one of the dominant sources of secondary flow in turbomachinery,which not only causes a deterioration of useful work but also a penalty on turbine efficiency.It has been found that neglect shroud leakage flow makes the computed velocity profiles and loss distribution significantly different to those measured.Even so,the influence of shroud leakage flow is seldom taken into consideration during the routine of turbine design due to insufficient understanding of its impact on end wall flows and turbine performance.In order to evaluate the impact of tip shroud geometry on turbine performance,a 3D computational investigation for 1.5-stage turbine with shrouded blades was performed in this paper.The following geometry parameters were varied respectively:-Inlet cavity length and exit cavity length,-Shroud overhang upstream of the rotor leading edge and downstream of the trailing edge,-Shroud radial tip clearance,The aim of this paper is to isolate the influence of shroud and cavity geometry modifications on turbine aerodynamic performance and to obtain clear trends of efficiency changes caused by different tip shroud geometry.Moreover,interaction between leakage flow and mainstream for different shroud configuration is also highlighted in order to penetrate into the physical mechanisms producing them.Due to the limitations of the model selected in this paper,the aim of research is not to put forward the design rules of turbine shroud.However,the results obtained from this work will be useful to the integrated design and optimization of turbine with shrouded blades.展开更多
The complex structure at trailing edge reduces the manufacturing precision, which results in an error in the size of the trailing edge structure. In this study, the performance of a stage high-pressure turbine(HP turb...The complex structure at trailing edge reduces the manufacturing precision, which results in an error in the size of the trailing edge structure. In this study, the performance of a stage high-pressure turbine(HP turbine) is calculated out in three dimensions. In the HP turbine guide vane, the trailing edge cutback configuration is adopted. Through three-dimensional simulation, the complex flow around the trailing edge with cutback cooling configuration is presented in this study, and the manufacturing precision reduction due to the complex structure at trailing edge is considered. Furthermore, the effect of trailing edge lip thickness and deflection of the stator on the turbine performance is discussed. Overall, as the press-side lip thickness increasing, the turbine efficiency and turbine inlet flow are reduced. However, the changes in the turbine work output are relatively complex. On the other hand, as the spacing between suction-side lip and press-side lip increases, turbine performance becomes worse. Both of the turbine efficiency and the turbine work output become smaller, while the turbine inlet flow becomes bigger. The effect of the spacing between suction-side lip and press-side lip is obviously greater than that of the press-side lip thickness. The change of the press-side lip thickness has little effect on the relation between the turbine performance and the spacing between suction-side lip and press-side lip. However, when the spacing between suction-side lip and press-side lip deviates from the baseline value, the effect law of the press-side lip thickness on the turbine performance will be affected. As the press-side lip thickness increases, it leads to an increase in the low-velocity zone at both of the pressure-side and suction-side trailing edge. And more main stream is affected or mixed into the wake flow. When the spacing between suction-side lip and press-side lip becomes smaller, the low-velocity zone at the trailing edge is smaller, and the change of vortex with the press-side lip thickness is affected. With a bigger spacing between suction-side lip and press-side lip, the variation is contrary.展开更多
基金Financial support from the Innovation Foundation of BUAA for PhD Graduates(YWF-13-A01-014)
文摘Generally speaking,main flow path of gas turbine is assumed to be perfect for standard 3D computation.But in real engine,the turbine annulus geometry is not completely smooth for the presence of the shroud and associated cavity near the end wall.Besides,shroud leakage flow is one of the dominant sources of secondary flow in turbomachinery,which not only causes a deterioration of useful work but also a penalty on turbine efficiency.It has been found that neglect shroud leakage flow makes the computed velocity profiles and loss distribution significantly different to those measured.Even so,the influence of shroud leakage flow is seldom taken into consideration during the routine of turbine design due to insufficient understanding of its impact on end wall flows and turbine performance.In order to evaluate the impact of tip shroud geometry on turbine performance,a 3D computational investigation for 1.5-stage turbine with shrouded blades was performed in this paper.The following geometry parameters were varied respectively:-Inlet cavity length and exit cavity length,-Shroud overhang upstream of the rotor leading edge and downstream of the trailing edge,-Shroud radial tip clearance,The aim of this paper is to isolate the influence of shroud and cavity geometry modifications on turbine aerodynamic performance and to obtain clear trends of efficiency changes caused by different tip shroud geometry.Moreover,interaction between leakage flow and mainstream for different shroud configuration is also highlighted in order to penetrate into the physical mechanisms producing them.Due to the limitations of the model selected in this paper,the aim of research is not to put forward the design rules of turbine shroud.However,the results obtained from this work will be useful to the integrated design and optimization of turbine with shrouded blades.
基金The National Natural Science Foundation of China (Grant No. 51575444)Aviation Power Foundation of China (Grant No. 6141B090319)the Natural Science Basic Research Plan in Shaanxi Province of China (Grant No. 2018JM5173) supported this work
文摘The complex structure at trailing edge reduces the manufacturing precision, which results in an error in the size of the trailing edge structure. In this study, the performance of a stage high-pressure turbine(HP turbine) is calculated out in three dimensions. In the HP turbine guide vane, the trailing edge cutback configuration is adopted. Through three-dimensional simulation, the complex flow around the trailing edge with cutback cooling configuration is presented in this study, and the manufacturing precision reduction due to the complex structure at trailing edge is considered. Furthermore, the effect of trailing edge lip thickness and deflection of the stator on the turbine performance is discussed. Overall, as the press-side lip thickness increasing, the turbine efficiency and turbine inlet flow are reduced. However, the changes in the turbine work output are relatively complex. On the other hand, as the spacing between suction-side lip and press-side lip increases, turbine performance becomes worse. Both of the turbine efficiency and the turbine work output become smaller, while the turbine inlet flow becomes bigger. The effect of the spacing between suction-side lip and press-side lip is obviously greater than that of the press-side lip thickness. The change of the press-side lip thickness has little effect on the relation between the turbine performance and the spacing between suction-side lip and press-side lip. However, when the spacing between suction-side lip and press-side lip deviates from the baseline value, the effect law of the press-side lip thickness on the turbine performance will be affected. As the press-side lip thickness increases, it leads to an increase in the low-velocity zone at both of the pressure-side and suction-side trailing edge. And more main stream is affected or mixed into the wake flow. When the spacing between suction-side lip and press-side lip becomes smaller, the low-velocity zone at the trailing edge is smaller, and the change of vortex with the press-side lip thickness is affected. With a bigger spacing between suction-side lip and press-side lip, the variation is contrary.
