Coolant migration in double-wall effusion cooling systems
<p>Over recent decades, aeroengines have seen continuous rises in Turbine Entry Temperature (TET) as engineers seek to achieve greater values of turbine thermal efficiency. As TETs continue to climb, increasingly sophisticated cooling systems are required to keep component temperatures below t...
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| Other Authors: | |
| Format: | Thesis |
| Language: | English |
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2023
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| _version_ | 1826312394185375744 |
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| author | van de Noort, M |
| author2 | Ireland, P |
| author_facet | Ireland, P van de Noort, M |
| author_sort | van de Noort, M |
| collection | OXFORD |
| description | <p>Over recent decades, aeroengines have seen continuous rises in Turbine Entry Temperature (TET) as engineers seek to achieve greater values of turbine thermal efficiency. As TETs continue to climb, increasingly sophisticated cooling systems are required to keep component temperatures below their softening levels. This thesis examines the application of one such high performance cooling system: double-wall effusion cooling, which combines impingement, pedestal, and effusion cooling. A particular focus is placed on the effects of coolant migration, where coolant in the pedestal cavity moves under the influence of an external pressure gradient, potentially producing a dangerous maldistribution of outlet coolant flow which could lead to hot gas ingestion.</p>
<p>A Low Order Flow Network Model (LOM) is built up to allow rapid analysis of mass flow distributions in a double-wall set-up. This is done by approximating flow through the cooling system as a one-dimensional pipe network, for which literature-based empirical correlations can be used for flow rates and mass flow continuity can be resolved at junctions. The LOM is validated experimentally and used to demonstrate the effects of select geometric features on the outlet flow distribution, such as restrictive fences, chamfered impingement holes, and extended pedestals. Computational Fluid Dynamics (CFD) based methods are then utilised to explore more complex geometric features which could be used to reduce coolant migration.</p>
<p>The LOM is then expanded to incorporate thermal effects, allowing the assessment of cooling performance. Literature-based empirical correlations are used to find heat transfer rates, allowing a network based on the conservation of energy to be solved alongside the original Continuity LOM. Comparisons with experiments show that the Thermal LOM predicted coolant consumption and cooling effectiveness to within 15% and 10% respectively. The Thermal LOM is then used to demonstrate the effect of Coolant Migration on the external cooling performance.</p>
<p>Analysis of a double-wall effusion cooling system in a full Nozzle Guide Vane is carried out using the Thermal LOM. It’s high solving speed is exploited to produce a full vane cooling system using a Genetic Algorithm optimisation method, producing a design which minimises coolant consumption whilst maintaining adequate cooling. Potential performance changes due to manufacturing variations are then examined using high-sample Monte Carlo analysis. Within standard manufacturing tolerances, maximum metal temperatures are shown to vary by ±30 K for a baseline double-wall effusion cooling system, which would have a major effect on component life variation.</p> |
| first_indexed | 2024-03-07T08:28:16Z |
| format | Thesis |
| id | oxford-uuid:d64c273d-def5-4177-b4f0-b41f7472a5f3 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T08:28:16Z |
| publishDate | 2023 |
| record_format | dspace |
| spelling | oxford-uuid:d64c273d-def5-4177-b4f0-b41f7472a5f32024-02-28T09:38:54ZCoolant migration in double-wall effusion cooling systemsThesishttp://purl.org/coar/resource_type/c_db06uuid:d64c273d-def5-4177-b4f0-b41f7472a5f3TurbomachineryGas-turbines--CoolingEnglishHyrax Deposit2023van de Noort, MIreland, PGillespie, DPountney, O<p>Over recent decades, aeroengines have seen continuous rises in Turbine Entry Temperature (TET) as engineers seek to achieve greater values of turbine thermal efficiency. As TETs continue to climb, increasingly sophisticated cooling systems are required to keep component temperatures below their softening levels. This thesis examines the application of one such high performance cooling system: double-wall effusion cooling, which combines impingement, pedestal, and effusion cooling. A particular focus is placed on the effects of coolant migration, where coolant in the pedestal cavity moves under the influence of an external pressure gradient, potentially producing a dangerous maldistribution of outlet coolant flow which could lead to hot gas ingestion.</p> <p>A Low Order Flow Network Model (LOM) is built up to allow rapid analysis of mass flow distributions in a double-wall set-up. This is done by approximating flow through the cooling system as a one-dimensional pipe network, for which literature-based empirical correlations can be used for flow rates and mass flow continuity can be resolved at junctions. The LOM is validated experimentally and used to demonstrate the effects of select geometric features on the outlet flow distribution, such as restrictive fences, chamfered impingement holes, and extended pedestals. Computational Fluid Dynamics (CFD) based methods are then utilised to explore more complex geometric features which could be used to reduce coolant migration.</p> <p>The LOM is then expanded to incorporate thermal effects, allowing the assessment of cooling performance. Literature-based empirical correlations are used to find heat transfer rates, allowing a network based on the conservation of energy to be solved alongside the original Continuity LOM. Comparisons with experiments show that the Thermal LOM predicted coolant consumption and cooling effectiveness to within 15% and 10% respectively. The Thermal LOM is then used to demonstrate the effect of Coolant Migration on the external cooling performance.</p> <p>Analysis of a double-wall effusion cooling system in a full Nozzle Guide Vane is carried out using the Thermal LOM. It’s high solving speed is exploited to produce a full vane cooling system using a Genetic Algorithm optimisation method, producing a design which minimises coolant consumption whilst maintaining adequate cooling. Potential performance changes due to manufacturing variations are then examined using high-sample Monte Carlo analysis. Within standard manufacturing tolerances, maximum metal temperatures are shown to vary by ±30 K for a baseline double-wall effusion cooling system, which would have a major effect on component life variation.</p> |
| spellingShingle | Turbomachinery Gas-turbines--Cooling van de Noort, M Coolant migration in double-wall effusion cooling systems |
| title | Coolant migration in double-wall effusion cooling systems |
| title_full | Coolant migration in double-wall effusion cooling systems |
| title_fullStr | Coolant migration in double-wall effusion cooling systems |
| title_full_unstemmed | Coolant migration in double-wall effusion cooling systems |
| title_short | Coolant migration in double-wall effusion cooling systems |
| title_sort | coolant migration in double wall effusion cooling systems |
| topic | Turbomachinery Gas-turbines--Cooling |
| work_keys_str_mv | AT vandenoortm coolantmigrationindoublewalleffusioncoolingsystems |