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- Alameldin, A., et al.
(författare)
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CFD analysis of suction and pressure side film cooling influence on vane aero performance in a transonic annular cascade
- 2014
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Ingår i: Proceedings of the ASME Turbo Expo. - 9780791845622
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Konferensbidrag (refereegranskat)abstract
- Operating at temperatures well above their melting point, gas turbines' components are subject to terribly high thermal stresses. In order to keep them intact and performing, different cooling techniques are implemented. One of these methods is film cooling. Film cooling implementation in vane cascades has a potential loss expense. Proper assessment of its impact on the vane performance has to be conducted. The CFD approach of modeling each hole and cooling tube autonomously is very computationally expensive. In the current work an assessment of a new, more computationally efficient CFD approach for modelling film cooling was conducted on a vane cascade operating in the transonic regime (M =0.89). The film cooling holes were represented by orifice boundary condition at the vane surface, omitting the need to model internal coolant plenum and cooling tubes mesh, resulting in 180% reduction in grid size and attributed computational cost interpreted in 300% saving in computation time. Uncooled, and film cooled with different configurations and at different blowing ratios (BR) simulations were performed and compared to experimental measurements. A good agreement was obtained for the exit flow angles, vorticity and aerodynamic loss for all the cases (uncooled and cooled). Pitch-averaged exit flow angle outside endwalls regions remains unchanged for all cooling configurations and blowing ratios. The aerodynamic loss was found to be more sensitive to increasing the blowing ratio on the suction side than on the pressure side. The proposed approach of coolant injection modeling is shown to yield reliable results, within the uncertainty of the measurements in most cases. Along with lower computational cost compared to conventional film cooling modeling approach, the new approach is recommended for further analysis for aero and thermal vane cascade flows.
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- El-Gabry, Lamyaa, et al.
(författare)
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Measurements of Hub Flow Interaction on Film Cooled Nozzle Guide Vane in Transonic Annular Cascade
- 2015
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Ingår i: Journal of turbomachinery. - : ASME International. - 0889-504X .- 1528-8900. ; 137:8
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Tidskriftsartikel (refereegranskat)abstract
- An experimental study has been performed in a transonic annular sector cascade of nozzle guide vanes (NGVs) to investigate the aerodynamic performance and the interaction between hub film cooling and mainstream flow. The focus of the study is on the endwalls, specifically the interaction between the hub film cooling and the mainstream. Carbon dioxide (CO2) has been supplied to the coolant holes to serve as tracer gas. Measurements of CO2 concentration downstream of the vane trailing edge (TE) can be used to visualize the mixing of the coolant flow with the mainstream. Flow field measurements are performed in the downstream plane with a five-hole probe to characterize the aerodynamics in the vane. Results are presented for the fully cooled and partially cooled vane (only hub cooling) configurations. Data presented at the downstream plane include concentration contour, axial vorticity, velocity vectors, and yaw and pitch angles. From these investigations, secondary flow structures such as the horseshoe vortex, passage vortex, can be identified and show the cooling flow significantly impacts the secondary flow and downstream flow field. The results suggest that there is a region on the pressure side (PS) of the vane TE where the coolant concentrations are very low suggesting that the cooling air introduced at the platform upstream of the leading edge (LE) does not reach the PS endwall, potentially creating a local hotspot.
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| 6. |
- El-Gabry, Lamyaa, et al.
(författare)
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Measurements of Hub Flow Interaction on Film Cooled Nozzle Guide Vane in Transonic Annular Cascade
- 2012
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Ingår i: Proceedings of the ASME Turbo Expo. - : ASME Press. - 9780791844748
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Konferensbidrag (refereegranskat)abstract
- An experimental study has been performed in a transonic annular sector cascade of nozzle guide vanes to investigate the aerodynamic performance and the interaction between hub film cooling and mainstream flow. The focus of the study is on the endwalls, specifically the interaction between the hub film cooling and the mainstream. Carbon dioxide (CO2) has been supplied to the coolant holes to serve as tracer gas. Measurements of CO2 concentration downstream of the vane trailing edge can be used to visualize the mixing of the coolant flow with the mainstream.Flow field measurements are performed in the downstream plane with a 5-hole probe to characterize the aerodynamics in the vane. Results are presented for the fully cooled and partially cooled vane (only hub cooling) configurations. Data presented at the downstream plane include concentration contour, axial vorticity, velocity vectors, and yaw and pitch angles. From these investigations, secondary flow structures such as the horseshoe vortex, passage vortex, can be identified and show the cooling flow significantly impacts the secondary flow and downstream flow field. The results suggest that there is a region on the pressure side of the vane trailing edge where the coolant concentrations are very low suggesting that the cooling air introduced at the platform upstream of the leading edge does not reach the pressure side endwall, potentially creating a local hotspot.
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- Mamaev, Boris, et al.
(författare)
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Aerodynamic investigation of turbine cooled vane block
- 2015
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Ingår i: Thermal Engineering. - 0040-6015. ; 62:2, s. 97-102
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Tidskriftsartikel (refereegranskat)abstract
- The vane block (VB) has been investigated and it gives several important results related to test methods and calculation procedures. The vane block is characterized by a developed film and convective cooling system. Blowing tests demonstrate that there is a weak correlation between cooling type and energy loss. Superposition of these effects is true for the central part over VB height without secondary flows. Coolant discharge increases profile loss and it rises if coolant flow rate is increased. Discharge onto profile convex side through the trailing edge slot influences the most considerably. The discharge through perforation decreases the vane flow capacity and insufficiently influences onto the flow outlet angle, but the trailing edge discharge increases this angle according to loss and mixture flow rate growth. The secondary flows reduce the effect of coolant discharge, which insufficiently changes losses distribution at turbine blades tips and even decreases the secondary losses. The flow outlet angle rises significantly and we are able to calculate it only if we correct the ordinary flow model. In the area of secondary flows, the outlet angle varies insufficiently under any type of cooling. This area should be investigated additionally.
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- Ranjan, Rajiv, et al.
(författare)
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Do-it-yourself content delivery network orchestrator
- 2012
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Ingår i: Web Information Systems Engineering - WISE 2012. - Piscataway, NJ : Encyclopedia of Global Archaeology/Springer Verlag. - 9783642350627 - 9783642350634 ; , s. 789-791
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Konferensbidrag (refereegranskat)abstract
- Content delivery networks (CDNs) [1] provide fast and reliable content access to the end-users. CDN providers (e.g., Akamai [2]), either own the entire infrastructure or it is outsourced to a single Cloud provider. Content owners (e.g., clients and end-users) need to establish expensive contracts with third party ISPs or CDN providers. Hence, existing CDN services are out of reach for all but large enterprises. Current CDNs do not provide services that allow an end-user to create dynamic content such as combining music videos from an existing content source on the Internet. Finally, the content owners do not have low-level control over the orchestration operations such as, multiple Cloud provider selection and resource management for hosting content. Hence, the content owners are dependent on their CDN providers to perform these operations behind the scene.
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