Adhesion of Ash Particles on Heat Transfer Surfaces in Coal Combustion Applications: Mechanisms and Implications
The useful lifetime of rotor blades and stator vanes in gas turbines burning pulverized coal may be limited by the build-up of thick, strongly-adherent, insulating multiphase deposits composed of captured ash particles and condensed liquid ‘glue’. The rate of growth of the deposit layer is governed by the competing dynamics of ash particle deposition and deposit erosion due to oncoming particles. A model for ash deposition developed previously has been extended here to account for deposit erosion due to particle impact. Sticking coefficient (ratio of captured to incident particle mass) predictions made using the present theory are compared against corresponding measurements in the DOE-METC combustion/deposition entrained reactor (CDER), a test facility designed to simulate the deposition characteristics of a cooled turbine blade surface. Inferences are drawn regarding the deposition mechanisms predominating at different gas and surface temperatures, and the role deposit erosion plays in determining the rate of deposit build-up.
KeywordsBituminous Coal Sticking Coefficient Coolant Flow Rate Deposition Regime Deposit Growth
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