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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.

The aircraft engine hot section is most vulnerable and failure prone to environmental particle ingestion, which, particularly for helicopters, can cause detrimental effects ranging from reduced performance to complete engine failure. The objective of this work is to develop an analytical tool to assess environmental particle impact on engine hot sections. The current state of the art in experimental and analytical research on environmental particle ingestion related to engine hot sections was reviewed, with emphasis on sand particles. From these efforts, the available experimental data for model calibration were identified, and an innovative particle rebound/deposition model has been developed. A semi-empirical approach is selected to model particles bouncing off metal surfaces, where the coefficients of restitution measured in a temperature range of 297–1323 K are used to calculate particle bounce-back velocity components. The developed deposition model is based on non-dimensional parameter analysis over more than seventy experiments related to particle deposition in engine hot sections. The metal surface temperature, one of two critical parameters in particle deposition, is also included in the model. The model was successfully implemented into commercial software and checked step by step. It was calibrated by two cases: sand [Arizona road dust (ARD)] particle impingement on a circular plate and Mt. St. Helens volcanic ash 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 deposition rate with flow/particle temperature. The latter case indicates that the particle deposition rate 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 the model can be only used under limited conditions. As additional relevant experimental data appears, the model will be continuously improved.

The beauty of numerical simulations is its ability to reveal the physics or nature of practical engineering problems in detail, and then, to identify adequate solutions. In this chapter, an excellent example is demonstrated. The rupture of a heavy-duty, high-pressure natural gas heat exchanger is numerically investigated, and the importance of gravity effect is identified, which is often considered as a trivial factor. For the original design, the natural convection in the flow field of the heat exchanger is comparable with the forced convection at the designed operating conditions. These two convections are perpendicular and compete with each other, the flow field is highly unsteady, and hightemperature natural gas is trapped in the upper portion of the vessel, which causes the damage of the exchanger. By vertically mounting the exchanger assembly and locating the outlet pipe on top of the exchanger, the flow parameters become rather uniform at each vertical cross section and the wall temperature of the heat exchanger remains more or less the same as the heated natural gas. The proposed design has been successfully used up to now.