Effect of periodic wakes and a contoured endwall on secondary flow in a high-lift low-pressure turbine cascade at low Reynolds numbers

2019 ◽  
Vol 190 ◽  
pp. 1-14
Author(s):  
Xiao Qu ◽  
Yanfeng Zhang ◽  
Xingen Lu ◽  
Zhijun Lei ◽  
Junqiang Zhu
Keyword(s):  
Secondary Flow ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
Turbine Cascade ◽  
High Lift ◽  
Low Reynolds Numbers ◽  
Low Pressure Turbine ◽  
Low Reynolds

Effects of periodic wakes on the endwall secondary flow in high-lift low-pressure turbine cascades at low Reynolds numbers

2017 ◽  
Vol 233 (1) ◽  
pp. 354-368 ◽  
Author(s):  
Xiao Qu ◽  
Yanfeng Zhang ◽  
Xingen Lu ◽  
Ge Han ◽  
Ziliang Li ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Secondary Flow ◽  
Low Reynolds Number ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
High Lift ◽  
Low Pressure Turbine ◽  
Low Reynolds ◽  
High Reynolds

Periodic wakes affect not only the surface boundary layer characteristics of low-pressure turbine blades and profile losses but also the vortex structures of the secondary flow and the corresponding losses. Thus, understanding the physical mechanisms of unsteady interactions and the potential to eliminate secondary losses is becoming increasingly important for improving the performance of high-lift low-pressure turbines. However, few studies have focused on the unsteady interaction mechanism between periodic wakes and endwall secondary flow in low-pressure turbines. This paper verified the accuracy of computational fluid dynamics by comparing experimental results and those of the numerical predictions by taking a high-lift low-pressure turbine cascade as the research object. Discussion was focused on the interaction mechanisms between the upstream wakes and secondary flow within the high-lift low-pressure turbine. The results indicated that upstream wakes have both positive and negative effects on the endwall flow, where the periodic wakes can decrease significantly the size of the separation bubble, prevent the formation of secondary vorticity structures at relatively high Reynolds numbers (100,000 and 150,000), and reduce the cross-passage pressure gradient of cascade. In addition, periodic wakes can improve the cascade incidence characteristic in terms of reducing the overturning and underturning of the secondary flow at downstream of the cascade all of which are beneficial for decreasing the endwall secondary losses, whereas more endwall boundary layer is involved in the main flow passage due to the wake transport, resulting in increased strength of the secondary flow at low Reynolds number of 25,000 and 50,000. Compared with the results without wakes, the total pressure loss for unsteady condition at the cascade exit decreases by 2.7% and 6.1% at high Reynolds number of 100,000 and 150,000, respectively. However, the secondary loss at unsteady flow conditions increases at low Reynolds number of 25,000 and 50,000.

A Low Reynolds Number Experimental Evaluation of Tubercles on a Low-Pressure Turbine Cascade

2019 ◽  
Author(s):  
Stephen A. Pym ◽  
Asad Asghar ◽  
William D. E. Allan ◽  
John P. Clark
Keyword(s):  
Boundary Layer ◽  
Turbine Blade ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
Blade Profile ◽  
Suction Surface ◽  
Low Reynolds Numbers ◽  
Low Pressure Turbine ◽  
Low Reynolds ◽  
Highly Loaded

Abstract Aircraft are operating at increasingly high-altitudes, where decreased air density and engine power settings have led to increasingly low Reynolds numbers in the low-pressure turbine portion of modern-day aeroengines. These operating conditions, in parallel with highly-loaded blade profiles, result in non-reattaching laminar boundary layer separation along the blade suction surface, increasing loss and decreasing engine performance. This work presents an experimental investigation into the potential for integrated leading-edge tubercles to improve blade performance in this operating regime. A turn-table cascade test-section was constructed and commissioned to test a purpose-designed, forward-loaded, low-pressure turbine blade profile at various incidences and Reynolds numbers. Baseline and tubercled blades were tested at axial chord Reynolds numbers at and between 15 000 and 60 000, and angles of incidence ranging from −5° to +10°. Experimental data collection included blade surface pressure measurements, total pressure loss in the blade wakes, hot-wire anemometry, surface hot-film measurements, and surface flow visualization using tufts. Test results showed that the implementation of tubercles did not lead to a performance enhancement. However, useful conclusions were drawn regarding the ability of tubercles to generate stream-wise vortices at ultra-low Reynolds numbers. Additional observations helped to characterize the suction surface boundary layer over the highly-loaded, low-pressure turbine blade profile when at off-design conditions. Recommendations were made for future work.

scholarly journals Unsteady wakes-secondary flow interactions in a high-lift low-pressure turbine cascade

2020 ◽  
Vol 33 (3) ◽  
pp. 879-892 ◽  
Author(s):  
Xiao QU ◽  
Yanfeng ZHANG ◽  
Xingen LU ◽  
Junqiang ZHU
Keyword(s):  
Secondary Flow ◽  
Low Pressure ◽  
Turbine Cascade ◽  
High Lift ◽  
Low Pressure Turbine ◽  
Flow Interactions
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