Controlling secondary flows in very highly-loaded low-pressure turbine cascades

Knezevici, D. C.

doi:10.22215/etd/2012-09671

Cited by 2 publications

(31 citation statements)

References 86 publications

(240 reference statements)

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“…This consists on modifying the blade-passage endwall geometry to reduce the pressure gradients that drive the cross-flow at the endwall. This technology has been shown to alter the flow physics in a beneficial manner (Knezevici, 2011;Hartland et al, 2000;Harvey and Offord, 2008).…”

Section: List Of Figuresmentioning

confidence: 99%

“…The settling chamber contains four Plan View screens used to further improve the uniformity of the flow and to reduce the large scale turbulence. The flow leaving the settling chamber is nearly stagnant and is accelerated through a square to rectangular contraction (with an area ratio of 14:1) into the test section (Knezevici, 2011;Rodger, 1992).…”

Section: Figure 31: Wind-tunnel Schematic (Adapted From Knezevici (2mentioning

confidence: 99%

“…The test section was designed and commissioned by Goobie (1989) and is connected to the wind tunnel described in Section 3.2. The flow from the contraction entering the test section goes through a turbulence generating grid (item 7) which intent is to approximate engine representative levels of freestream turbulence intensity (FSTI) and length scale (Knezevici, 2011). The grid produces a FSTI of 4% and integral length scale of 0.4B x (Mahallati, 2003).…”

Section: Test Sectionmentioning

confidence: 99%

“…Prior to the beginning of this research, the data acquisition system was modified by Gordon MacIsaac (PhD candidate) from the existing system developed by Knezevici (2011) and Ellison (2005). A new data acquisition card was bought and new data acquisition software and a graphical user interface (GUI) were developed using the MATLAB programming language.…”

Section: Experimental Instrumentationmentioning

confidence: 99%

“…This chapter focus on the experimental methods and data reduction procedures that were used in the present experimental investigation conducted using an open-circuit wind tunnel and a modular test section in the Low-Speed Turbomachinery Laboratory (LSTL) at Carleton University. Recently, the facility has been used for investigations of compressor secondary flows by Ellison (2005) and for investigations of turbine secondary flows by Benner (2003), Zoric (2006), Knezevici (2011) andMacIsaac et al (2010). Thus, the operating procedures and experimental repeatability are well established.…”

Section: Introductionmentioning

confidence: 99%

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Controlling Secondary Flows in Highly-Loaded Compressor Cascades

Prevost¹

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This thesis documents the experimental results of a research program investigating the effect of non-axisymmetric endwall contouring on the secondary flows and loss generation in a highly-loaded compressor cascade. The results are compared with the losses for the baseline flat endwall in order to evaluate the potential benefits.The compressor blade was designed by Pratt & Whitney Aircraft and is representative of an exit guide vane row in an aircraft engine. The experimental study was conducted in Carleton University's low speed linear cascade wind tunnel. The measurements were made at a constant Reynolds number of 150,000 (based on the axial chord and the inlet velocity) for two values of incidence, 0° (design incidence) and +7°.Quantitative results were obtained from static pressure measurements on the suction and pressure surfaces of the blade to evaluate the blade loadings and from measurements made by a seven-hole pressure probe downstream of the cascade to assess the blade row losses. Qualitative results were obtained from oil surface flow visualisation on the endwall and on the blade surfaces and were used to assist in the interpretation of the flow physics.The current research showed that the application of non-axisymmetric endwall contouring at design incidence modified the secondary flows near the endwall, mitigating the formation of the corner stall. The benefits from contouring were observed in terms of reductions in the secondary losses and in the underturning of the secondary flows compared to the flat endwall test case.However, these benefits were not observed at the off-design incidence studied. The application of endwall contouring generated higher secondary kinetic energy near the endwall, which penetrated deeper along the span and occupied a larger area, resulting in higher secondary and total losses as it dissipated moving downstream of the cascade.iii

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Section: List Of Figuresmentioning

confidence: 99%

Section: Figure 31: Wind-tunnel Schematic (Adapted From Knezevici (2mentioning

confidence: 99%

Section: Test Sectionmentioning

confidence: 99%

Section: Experimental Instrumentationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Controlling Secondary Flows in Highly-Loaded Compressor Cascades

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Endwall Flows in Transonic Turbine Cascades

Taremi¹

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The results of an investigation of the midspan and endwall flows in transonic linear turbine cascades are documented here. A family of five turbine cascades with different levels of flow turning and aerodynamic loading were used for this study to quantify the effects of these parameters on loss generation in compressible flows. Experimental data on these flows are scarce in the open literature. In addition, the application of two different passive flow control techniques for reducing the endwall losses is examined here: these are referred to as endwall contouring, and airfoil pressure-side modification. The experimental investigations were conducted in the Pratt and Whitney Canada (PWC) High-Speed Wind Tunnel Laboratory at Carleton University. The measurements were made using a seven-hole pressure probe downstream of the cascades at both design and off-design Mach numbers. In addition to the measurements, surface flow visualization was conducted to assist in the interpretation of the flow physics. The results from complementary numerical investigations are also presented, and compared with the experimental data. Overall, the examined secondary flow structures are in agreement with previous lowspeed findings. However, in contrast to low-speed results, the downstream mixing losses are mainly attributed to the dissipation of primary kinetic energy in the present study. Raising the exit Mach number results in weaker secondary flow structures and smaller secondary losses.The experimental results demonstrate that endwall contouring is a viable option for mitigating the secondary flows, particularly for the more highly-loaded cascade. The modification of the airfoil pressure surface is also found to provide a significant benefit in terms of endwall loss reduction. The differences between the measurements and the computational results highlight the need for detailed experimental investigations.ii Acknowledgments I would like to express my gratitude to my thesis supervisor, Professor Steen Sjolander, for giving me the opportunity to work on this research project. I would also like to thank him for his invaluable advice regarding the interpretation of the results, and for reviewing the text.

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Controlling secondary flows in very highly-loaded low-pressure turbine cascades

Cited by 2 publications

References 86 publications

Controlling Secondary Flows in Highly-Loaded Compressor Cascades

Controlling Secondary Flows in Highly-Loaded Compressor Cascades

Endwall Flows in Transonic Turbine Cascades

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