Reduction in flow parameter resulting From volcanic ash deposition in engine representative cooling passages

• Published in: Volume 5B: Heat Transfer
• Main Authors: Gillespie, D, Mcgilvray, M, Bucknell, A, Wylie, S, Forsyth, P
• Format: Conference Object
• Language: unknown
• Published: American Society of Mechanical Engineers 2016
• Subjects: Eyjafjallajökull
• Online Access: https://doi.org/10.1115/GT2016-57296; https://ora.ox.ac.uk/objects/uuid:52741a7c-3aad-4012-8b88-f5f2b66b3939

Internal cooling passages of turbine blades have long been subject to blockage through the deposition of sand and dust during fleet service life. The ingestion of high volumes of volcanic ash therefore poses a real risk to engine operability with the additional difficulty that the cooling system is frequently impossible to inspect to assess the level of deposition. This paper reports results from experiments carried out at typical HP turbine blade metal temperatures (1163K to 1293K) and coolant delivery temperatures (800K to 900K) in engine scale models of a turbine cooling passage with film-cooling offtakes. Volcanic ash samples from the Eyjafjallajökull eruption were used for the majority of the experiments conducted. Ash particle size distributions typical of those reaching internal cooling systems were generated through the sieving of the ash, with subsequent measurement of the distribution and characterization of the particle shape through SEM analysis. A further ash sample from the Chaiten eruption allowed the effect of changing ash chemical composition to be investigated. The experimental rig allows the metered delivery of volcanic ash through the coolant system at the start of a test. The geometry, rate of injection, metal and coolant temperatures can be independently varied, allowing the sensitivity of passage blockage to each parameter to be determined. The key metric indicating blockage is the flow parameter which can be determined over a range of pressure ratios (1.01 – 1.06) before and after each experiment. The data are reported at hot and cold conditions. Visual inspection of the test pieces is useful in determining where deposition has occurred. Results from the experiments have determined the threshold metal temperature at which blockage occurs for the ash samples available, and characterise the reduction of flow parameter with changing particle size distribution, blade metal temperature, ash sample composition, film-cooling hole configuration and pressure ratio across the holes. There is ...