<p>The secondary air system and cooling passages of gas turbine components are prone to blockage&nbsp;from&nbsp;sand and dust.&nbsp;Modelling deposition&nbsp;requires accurate models of particle transport to the surface and thermo-mechanical&nbsp;interaction with the wall. Bounce-stick models predict whether a particle will bounce,&nbsp;stick,&nbsp;or shatter upon impact with a wall and&nbsp;calculate rebound trajectories if applicable. Existing bounce-stick models&nbsp;tend to&nbsp;use energy-based analyses of particle rebound and hence&nbsp;cannot&nbsp;capture the complex collision physics&nbsp;throughout the contact time.&nbsp;With&nbsp;close empirical&nbsp;fitting&nbsp;of mechanical properties, they are able to&nbsp;match experimental results, however this requirement makes them unreliable for&nbsp;industry-relevant analyses of particulate deposition&nbsp;using&nbsp;local dust compositions.&nbsp;&nbsp;</p><p>This paper&nbsp;proposes&nbsp;an analytically&nbsp;explicit&nbsp;bounce-stick model&nbsp;that&nbsp;uses&nbsp;analytical solutions of adhesion, plastic&nbsp;deformation&nbsp;and viscoelasticity&nbsp;to&nbsp;time-resolve&nbsp;all relevant aspects of collision physics.&nbsp;The&nbsp;Discrete-Element Methods (DEM)&nbsp;model&nbsp;is compared to experimental data of micron-scale particle collisions, showing good agreement. Required parametric fitting is&nbsp;minimal compared to existing approaches.&nbsp;In addition to&nbsp;coefficients of restitution,&nbsp;other&nbsp;variables&nbsp;crucial in modelling&nbsp;subsequent&nbsp;particle trajectories, for example angular velocity, are predicted. Analysis of particle collisions using the DEM approach&nbsp;allows full&nbsp;coupling between different internal processes during contact&nbsp;and&nbsp;through the&nbsp;use of&nbsp;a time-stepping explicit approach.&nbsp;The paper shows that&nbsp;particle deformation and hence viscoelastic properties&nbsp;play a significant&nbsp;role in&nbsp;adhesion.&nbsp;A number of&nbsp;non-physical&nbsp;artifices&nbsp;of&nbsp;the mechanical properties used in&nbsp;previous&nbsp;models are&nbsp;thus eliminated.&nbsp;Modelling time-dependent internal variables&nbsp;such as&nbsp;deformation and contact area&nbsp;create functionality for&nbsp;future&nbsp;modelling&nbsp;of arbitrarily shaped&nbsp;particles, the physics of which has been shown by previous work to differ significantly from that of spheres&nbsp;and&nbsp;is not&nbsp;easily&nbsp;captured&nbsp;by&nbsp;high-level energy-based models.&nbsp;</p>

A Discrete Element Methods-Based Model for Particulate Deposition and Rebound in Gas Turbines

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2021/volume/84898

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