| 1. |
- Chernoray, Valery, 1975, et al.
(författare)
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An efficient correction for the finite-size effects of multihole pressure probes in velocity gradients
- 2008
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Ingår i: Proc. of XXII International Congress of Theoretical and Applied Mechanics, Adelaide, Australia, Aug. 24–29. ; , s. 1-2
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This study describes an implementation and verification of an efficient and reliable correction for the finite-size effects of pressure probes. The performance of the correction in application to the highly three-dimensional flow downstream of the linear cascade is scrutinized through a detailed side-by-side comparison with corresponding cross hot-wire data. The influence of the correction on all three velocity components, flow streamlines and streamwise vorticity fields is thoroughly examined. The study demonstrates that the correction lead to a significant improvement of the velocity data. A very good performance of the correction for the finite-size effects of pressure probes presented in this study allow us to recommended it as a mandatory step in postprocessing procedures for multi-hole pressure probes.
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| 2. |
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| 3. |
- Chernoray, Valery, 1975, et al.
(författare)
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Improving the accuracy of multihole probe measurements in velocity gradients
- 2008
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Ingår i: 2008 ASME Turbo Expo; Berlin; Germany; 9 June 2008 through 13 June 2008. - 9780791843123 ; , s. 125-134
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Konferensbidrag (refereegranskat)abstract
- This study describes an implementation and verification of an effective and reliable correction for the finite-size effects of pressure probes. A modified version of correction by Ligrani et al. (Exp. Fluids, vol. 7, 1989, p. 424) was used. It is shown that the correction procedure can be implemented in two steps as in Ligrani et al. or in a single step, either for probe pressures, or for velocity components. The latter correction method is found to have the best performance and studied in very detail. The effect of the correction in application to the highly three-dimensional flow downstream of the outlet guide vanes is scrutinized through detailed side-by-side comparison with corresponding cross hot-wire data. The influence of the correction on all three velocity components, flow streamlines and streamwise vorticity fields is thoroughly examined. Two flow cases with different incoming turbulence intensities are considered. The study demonstrates a very good efficiency and reliability of the correction, which lead to a significant improvement of the corrected velocity data. The improvement in crossflow velocity components has allowed correct description of the flow streamlines, and as a result, the secondary flow field structures were resolved more accurately. The considered correction does not affect the streamwise vorticity component, which is clarified as well. A very important fact is that the correction is not found to over-correct and distort the data, thus can be used safely. A very good performance of the correction for the finite-size effects of pressure probes presented in this study allows us to recommend it as a mandatory step in postprocessing procedures for multihole pressure probes.
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| 4. |
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| 5. |
- Hjärne, Johan, 1975, et al.
(författare)
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An experimental investigation of secondary flows and loss development downstream of a highly loaded low pressure turbine outlet guide vane cascade
- 2006
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Ingår i: Proc. of ASME TURBO EXPO, 2006, Barcelona, Spain.
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Konferensbidrag (refereegranskat)abstract
- This paper presents a detailed experimental investigation of the evolution of secondary flow field characteristics and the losses at several measurement planes downstream of a highly loaded low pressure turbine/outlet guide vane (LPT/OGV). The experiments are conducted in a linear cascade equipped with a boundary-layer suction system designed at Chalmers in Sweden. The aerodynamic function of the LPT/OGV's is to turn the swirling flow out from the last low-pressure turbine rotor into an axial direction. This de-swirling gives a diffusive flow with growing boundary layers, strong secondary flows, and risk for separation both on vanes and end-walls. Important parameters that influence the secondary flow-field are the upstream boundary-layer height, the Re-number and the inlet incidence. All these parameters together with the turbulence intensity can be adjusted in the test-facility in order to encounter engine like conditions. In the final paper several upstream realistic incidences and turbulence intensities are investigated for one Reynolds number. Downstream characteristics have been measured by means of a 5-hole pneumatic probe. It allows for the determination of the mean vortical structures, their development and their interactions. The trailing edge vortices, the two branches of the passage vortex and the corner vortex are clearly visible close to the blade trailing edge. They merge and grow into a single large vortical structure further downstream. Their intensity is shown to be strongly dependent on the incidence. The turbulence level seems to play a role on the mixing inside and between the structures. The measurements also show the dependence of the losses and the mean outlet flow angles along the blade span on the vortices development.
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| 6. |
- Hjärne, Johan, 1975, et al.
(författare)
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Experimental analysis of the flow-field in a state-of-the-art linear cascade with boundary-layer suction
- 2005
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Ingår i: Proc. of ASME TURBO EXPO 2005, Reno, Nevada, USA.
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Konferensbidrag (refereegranskat)abstract
- This paper presents a detailed experimental evaluation of the flow field in a state of the art linear cascade with boundary-layer suction. The linear cascade was designed using a new design-process as described by Hjärne et al. [1]. From the measurements presented in this paper it can be concluded that all of the features of the test-rig work as expected. Hence the measurements validate the design process presented by Hjärne et al. in [1].The intention with the test facility is to provide high quality benchmark cases for the flow field around aggressive designs of Low Pressure Turbine/Outlet Guide Vanes (LPT/OGV's) to be used for validation of numerical codes. The flow quality is assessed by measuring inlet uniformity, boundary-layer heights, periodicity of the static pressure distribution around the OGV's and uniformity of the outlet flow.
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| 7. |
- Hjärne, Johan, 1975, et al.
(författare)
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Experimental investigations and numerical validation of an outlet guide vane with an engine mount recess
- 2008
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Ingår i: 2008 ASME Turbo Expo; Berlin; Germany; 9 June 2008 through 13 June 2008. ; 6:PART B
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Konferensbidrag (refereegranskat)abstract
- This paper presents experiments and CFD calculations of a Low Pressure Turbine/Outlet Guide Vane (LPT/OGV) equipped with an engine mount recess (a bump) tested in the Chalmers linear LPT/OGV cascade. The investigated characteristics include performance for the design point in terms of total pressure loss and turning as well as a detailed description of the downstream development of the secondary flow field.The numerical simulations are performed for the same inlet conditions as in the test-facility with engine-like properties in terms of Reynolds number, boundary-layer thickness and inlet flow angle. The objective is to validate how accurately and reliably the secondary flow field and losses can be predicted for an LPT/OGV equipped with a bump.Three different turbulent models as implemented in FLUENT, the k-epsilon realizable model, the komega-SST model and the RSM are validated against detailed measurements. From these results it can be concluded that the komega-SST model predicts both the secondary flow field and the losses most accurately.
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| 8. |
- Hjärne, Johan, 1975, et al.
(författare)
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Numerical validations of secondary flows and loss development downstream of a highly loaded low pressure turbine outlet guide vane cascade
- 2007
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Ingår i: Proc. of ASME TURBO EXPO 2007, Paper no GT2007-27712. - 0791837963
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Konferensbidrag (refereegranskat)abstract
- In this paper 3D numerical simulations of turbulent incompressible flows are validated against experimental data from the linear low pressure turbine/outlet guide vane (LPT/OGV) cascade at Chalmers in Sweden. The validation focuses on the secondary flow-fields and loss developments downstream of a highly loaded OGV.The numerical simulations are performed for the same inlet conditions as in the test-facility with engine-like properties in terms of Reynolds number, boundary-layer thickness and inlet flow angles with the goal to validate how accurately and reliably the secondary flow fields and losses for both on- and off-design conditions can be predicted for OGV’s.Results from three different turbulence models as implemented in FLUENT, k-epsilon Realizable, k-omega-SST and the RSM are validated against detailed measurements. From these results it can be concluded that the RSM model predicts both the secondary flow field and the losses most accurately.
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| 9. |
- Kennedy, S., et al.
(författare)
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Secondary flow measurement of an outlet guide vane cascade at low and high inlet turbulence intensities
- 2006
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Ingår i: Proc. of the 6th Euromech Fluid Mechanics Conference, 2006, Stockholm, Sweden. ; , s. 38-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this project is to investigate the secondary flow pattern downstream ofa low pressure turbine/outlet guide vane (LPT/OGV) cascade. These vanes are founddownstream of the low pressure turbine in turbojet engines, and are responsible forturning the inlet swirling flow from the low pressure turbine into an axial outflow,whilst minimising pressure losses. This is of prime importance with both cost andweight being reduced in modern turbojets resulting in a reduced amount of stages inthe LPT which in turn increases the loading on the OGV's.The experiments were carried out at Chalmers in Sweden, using a low speed linearcascade. This paper presents the experimental results carried out using a cross wireprobe at various downstream positions at 30 degrees inlet flow angle, which is the ondesignpoint. Both low and high turbulence intensity cases have been investigated atone Reynolds number. As shown in figures 1a and 1b, the main characteristics of theflow include the passage vortex, the trailing edge vortex sheet and the boundary layeron the sidewall. The results also show the interaction of these structures and how theyevolve as they move downstream. The effect of increased turbulence will be seen toplay an important role in the diffusion of the vortical structures as well as theirinteractions. These findings are then related to the main flow characteristics, includingvelocity, pitch angle, losses, turbulence intensity and Reynolds stresses. This will resultin an understanding of the significance of the secondary flows and how they affect theefficiency of turning the flow. The results from the cross wire probe will also becompared to those obtained from an earlier investigation using a five hole probe.
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| 10. |
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