| Popis: |
The current state of the art in experimental and analytical research on environmental particle ingestion related to engine hot sections was reviewed, with greater emphasis focussed on sand particles. From these efforts, the available experimental data for model calibration were identified, and a particle rebound/deposition model has been developed. A semi-empirical approach is selected to model sand particles bouncing off metal surfaces, where the coefficients of restitution measured in a temperature range of 297–1323 K from Delimont et al are used to calculate particle bounce-back velocity components. The developed deposition model is based on non-dimensional parameters and the analysis over more than seventy experimental datasets related to particle deposition in engine hot sections carried out by Suman et al. Moreover, the metal surface temperature, one of two critical parameters in particle deposition, is also included in the model. The developed rebound/deposition model was successfully implemented into the ANSYS CFD Premium solver and checked step by step. The model is calibrated by two cases: sand [or Arizona road dust (ARD)] particle impingement on a circular plate and Mt. St. Helens volcanic ash (comparable with ARD particles in terms of chemical composition) impinging on a first-stage air-cooled nozzle guide vane (NGV). For the former case, the calibrated model predicts fairly well the variation of particle capture efficiencies with flow/particle temperatures. The latter case indicates that the particle capture efficiency at engine operating conditions can be assessed by the developed model. Due to the lack of experimental data that would permit a full calibration/validation, for the time being it could be only used under limited conditions. Certainly, the model will be continuously improved as the relevant experimental data appears. |
