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Due to strong motivation to reduce costs and increase performances of stationary diesel after-treatment systems, computational modeling has become a necessary step in system design and improvement. A unique mixing duct typified by significant changes in scale and strong flow curvature was evaluated for its potential to improve flow distribution across the SCR catalyst inlet face. The flow dynamics were investigated with a steady three-dimensional turbulence model and detailed chemistry was studied separately using a one-dimensional channel reactive flow model. Aqueous urea injection was modeled using Discrete Phase Modeling. The mixing duct performance relative to reactor dimensions and engine loads is discussed. The Impact of injector positions was studied using massless particle tracking. A total of three geometries were evaluated using a Uniformity Index of the ammonia-to-NOx feed ratio. It was found that a higher mixing duct height to inlet diameter ratio yielded better mixing.

Due to strong motivation to reduce costs and increase performances of stationary diesel after-treatment systems, computational modeling has become a necessary step in system design and improvement. A unique mixing duct typified by significant changes in scale and strong flow curvature was evaluated for its potential to improve flow distribution across the SCR catalyst inlet face. The flow dynamics were investigated with a steady three-dimensional turbulence model and detailed chemistry was studied separately using a one-dimensional channel reactive flow model. Aqueous urea injection was modeled using Discrete Phase Modeling. The mixing duct performance relative to reactor dimensions and engine loads is discussed. The Impact of injector positions was studied using massless particle tracking. A total of three geometries were evaluated using a Uniformity Index of the ammonia-to-NOx feed ratio. It was found that a higher mixing duct height to inlet diameter ratio yielded better mixing.

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The low pressure (LP) exhaust system presents a promising avenue for improving the performance of large steam turbines. For this reason, LP exhaust systems have attracted the attention of the research community for decades. Nevertheless, we still lack understanding of the flow physics and loss mechanisms in the exhaust system, especially at part-load conditions. It is also unclear how the exhaust system should be designed when its required operating range widens. This thesis provides solutions to these aerodynamic issues through experimental and numerical investigations, and provides tools that could contribute to better designs of LP exhaust systems. Firstly, the Computational Fluid Dynamics (CFD) solver ANSYS CFX was validated against experiments performed on a scaled test rig under representative part-load flow conditions. This validation exposed the weakness of Reynolds-averaged Navier-Stokes (RANS) CFD when there is a highly swirling flow and large separation regions in the exhaust diffuser. To facilitate the numerical studies, a series of tools were also developed. A design suite, ExhaustGen, was used to automate the pre- and post-processing of CFD calculations. The exhaust diffuser was parametrised using "Minimum Energy Curves", which reduce the dimension of parameter space. Further, a suitable stage-hood interface treatment (Multiple Mixing Planes) was chosen to predict the circumferentially non-uniform flow in the exhaust hood at low computational cost. Numerical investigation of the baseline geometry provided insights into the key flow features and loss mechanisms in the exhaust system, over a wide range of operating conditions. In particular, the bearing cone separation was identified as a key source of loss at part-load conditions. The effect of stage-hood interaction on the performance and design of the exhaust system was studied by varying the rotor blade design, which can positively influence system performance. Finally, a global sensitivity study was performed to identify the most influential design parameters of the exhaust hood. These findings allow, for the first time, LP exhaust hood performance maps to be constructed, so that the benefits of choosing a suitable hood geometry and blade design can be revealed. The thesis also offers contribution towards formulating LP exhaust system design guidance for a wide operating range.

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Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains x, 54 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 49-51).

In case of fire, the smoke plum will reach the roof creating a ceiling jet leading to the edge and starting to descend. The smoke descending rate depends heavily on the smoke production rate and the way it was produced. Recent research has been concentrated on the smoke produced in an axi-symmetric plume model, but rarely on wall or corner plume models. In addition, the smoke production rate was estimated based on different fire sizes, which neglected the effect introduced by the make-up air, and is the main theme of this study. During the earlier stage of this study, the calculation models to predict the smoke entrainment rate was analyzed to identify its effectiveness in calculating the smoke production rate under cornered fires. In addition, the effect of the make-up air on the mechanical and natural smoke exhaust system was analyzed to calculate the corresponding smoke descending rate. Finally, the optimal calculation model to be utilized for the performance-based fire engineering designs of smoke management systems will be proposed, so that the make-up air effect can also be coupled during the design process.