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Numerical Investigation of Powder Aerosolization in Dustiness TestingChen, Hongyu 23 August 2022 (has links)
No description available.
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Oil Cooling of Electric Motor using CFDAl Shadidi, Kamilla January 2014 (has links)
This thesis investigated the heat transfer of internally oil cooled rotors in permanent magnet electric machines which are, among other things, used in hybrid vehicles or zero emission vehicles. The magnets become sensitive and can be demagnetized at high working temperatures, hence the need of cooling. The scope of this work included CFD simulations in STAR-CCM+. Three different 3D multiphase models simulating the oil propagation in the rotor were performed. A Lagrangian multiphase model combined with a fluid film model was the most suitable model for simulating the spray of the oil and the film thickness along the inner rotor wall. It was noticed that periodic boundaries caused problems for the fluid film model, therefore a complete geometry was preferred over a truncated model. The 3D solutions provided thicker film thicknesses than the analytical solutions from the fluid film thickness theory. The maximum analytical thickness was of the same order of magnitude as the surface average film thickness provided by the multiphase models. This thickness was assumed to be constant when used as the base for the fluid region in the 2D one-phase models.The study showed that aluminum was the most suitable rotor material due to its high conductive capacity, which provided a more even distribution of the temperature in the solid and hence resulted in lower overall temperatures. The cooling power increased linearly with the volumetric flow rate, however the heat transfer coefficient decreased for the higher flow rates. A volumetric flow rate of 10dl/min was recommended. A 2D model was compared to a preliminary experiment and showed that these were not correlated. The conclusion was that more experiments and simulations are needed in order to confirm the validity of the 2D model.
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A Near Field Lagrangian Particle Modeling for the Multiphase Flow of Reaction Control System Thrusters in Space EnvironmentsZou, Janice 01 January 2024 (has links) (PDF)
In the current age of space exploration, the push to reach further to deep space presents a greater need for analysis and verification and validation of rocketry components in the space environment. Due to the nature of space, firings of rocket thrusters in space is a multi-regime problem. With the low density, pressure, and temperature of the environment, the resultant plume structure, seeded with unburnt fuel droplets, extends up to multiple orders of magnitude in distance as compared to a plume structure in the Earth’s atmosphere. The frozen droplets, or particles, create concerns including surface contamination and erosion, calling a cause for study and model development to understand particle behavior in this multi-regime environment. This work intends to develop a model to analyze and understand multiphase flow and particle behavior in this environment utilizing the lower fidelity, but more computationally efficient, RANS turbulence modeling. Particle properties are compared against a regime-defining parameter to understand the trends in behavior. Finally, the work closes out on a preliminary look into implementing fully reacting flow chemistry for the multiphase flow. These results and progress are promising in developing an efficient model that may be integrated into a hybrid model to better predict particle behavior and dispersion in this multi-regime environment.
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Investigation of fuel and water injection in gas turbine combustion : Evaluate the methodologies available in Star CCM+ for modeling of water injection in simplified combustor using liquid and gas fuelsShinwari, Sanger January 2023 (has links)
The negative impact of gas turbine emissions on the environment and human health is a growing concern. Recent studies suggest injecting water into the combustion process effectively reduces emissions and increases power output. However, this approach presents new challenges that need to be thoroughly investigated. Siemens Energy (SE) has recently conducted a study on water injection and its effects on gaseous combustion mixtures but encountere challenges the simulation results when adding water. Therefore, the primary objective of this thesis is to evaluate the methodologies available in Star CCM+ for modeling water injection in a simplified combustor model (SCM) using both liquid (diesel) and gas (methane) fuels. In addition, the behavior of the flame, temperature field inside the combustor, and burner outlet temperature, are investigated.The study has compared physical phenomena such as, the flame shape, velocity, and vorticity field of SCMs with the complete combustor model of the SGT-800 gas turbine for gas fuel. Additionally, the thesis has examined the capability of STAR CCM+ for predicting flame temperature at the outlet against in-house calculation data and Cantera software for parametric cases. The methodology involves a parametric study using the Realizable k-ε TwoLayer turbulence model for steady-state RANS simulations. Combustion is modeled using the FGM method, while Lagrangian multiphase approach is used for liquid injection.The employed FGM combustion model, Lagrangian multiphase model, and RANS simulations yielded realistic results. In addition, the convergence of gas fuel cases was smoother compared to liquid fuel cases, which involved multiphase modelling and evaporation, makes it more complex. The physical phenomena were captured by CFD simulations for the SCM. Flame shape, velocity and vorticity field have good agreement with the theory in the field of gas turbine combustion and other literature sources. Disagreements between CFD and in-house calculations were observed, with the greatest differences being 24 ℃ for premixed methane (at WFR (Water Fuel Ratio) of 0) and 28 ℃ for non-premixed diesel (at WFR of 1). On the other hand, Cantera results for Vapor and for methane cases with water addition were in limit of 10 ℃ with CFD results for WFR between 0-0.5. Nevertheless, achieving a simulation accuracy within a 10 ℃ limit proved challenging due to limitations and potential sources of error in the in-house calculation sheet, combustion modelling, RANS simulations, and reaction mechanism.
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