Matching Items (2)
Description
ABSTRACT The heat recovery steam generator (HRSG) is a key component of Combined Cycle Power Plants (CCPP). The exhaust (flue gas) from the CCPP gas turbine flows through the HRSG − this gas typically contains a high concentration of NO and cannot be discharged directly to the atmosphere because of environmental restrictions. In the HRSG, one method of reducing the flue gas NO concentration is to inject ammonia into the gas at a plane upstream of the Selective Catalytic Reduction (SCR) unit through an injection grid (AIG); the SCR is where the NO is reduced to N2 and H2O. The amount and spatial distribution of the injected ammonia are key considerations for NO reduction while using the minimum possible amount of ammonia. This work had three objectives. First, a flow network model of the Ammonia Flow Control Unit (AFCU) was to be developed to calculate the quantity of ammonia released into the flue gas from each AIG perforation. Second, CFD simulation of the flue gas flow was to be performed to obtain the velocity, temperature, and species concentration fields in the gas upstream and downstream of the SCR. Finally, performance characteristics of the ammonia injection system were to be evaluated. All three objectives were reached. The AFCU was modeled using JAVA - with a graphical user interface provided for the user. The commercial software Fluent was used for CFD simulation. To evaluate the efficacy of the ammonia injection system in reducing the flue gas NO concentration, the twelve butterfly valves in the AFCU ammonia delivery piping (risers) were throttled by various degrees in the model and the NO concentration distribution computed for each operational scenario. When the valves were kept fully open, it was found that it led to a more uniform reduction in NO concentration compared to throttling the valves such that the riser flows were equal. Additionally, the SCR catalyst was consumed somewhat more uniformly, and ammonia slip (ammonia not consumed in reaction) was found lower. The ammonia use could be decreased by 10 percent while maintaining the NO concentration limit in the flue gas exhausting into the atmosphere.
ContributorsAdulkar, Sajesh (Author) / Roy, Ramendra (Thesis advisor) / Lee, Taewoo (Thesis advisor) / Phelan, Patrick (Committee member) / Arizona State University (Publisher)
Created2011
Description
With the growth of the additive manufacturing (AM) industry for metal components, there is an
economic pressure for improved AM processes to overcome the shortcomings of current AM technologies (i.e., limited deposition rates, surface roughness, etc.). Unfortunately, the development of these processes can be time and capital-intensive due to the large number of input parameters and the sensitivity of the process’s outputs to said inputs. There consequently has been a strong push to develop computational design tools (such
as CFD models) which can decrease the time and cost of AM technology developments. However, many of the developments that have been made to simulate AM through CFD have done so on custom CFD packages (as opposed to commercially available packages), which increases the barrier to entry of employing computational design tools. For that reason, this paper has demonstrated a method for simulating fused deposition modeling using a commercially available CFD package (Fluent). The results from this implementation are qualitatively promising when compared to samples produced by existing metal AM
processes, however additional work is needed to validate the model more rigorously and to reduce the computational cost. Finally, the developed model was used to perform a parameter sweep, thereby demonstrating a use case of the tool to help in parameter optimization.
ContributorsWeissman, Eric (Author) / Huang, Huei-Ping (Thesis director) / Clarke, Amanda (Committee member) / Barrett, The Honors College (Contributor) / School for Engineering of Matter,Transport & Enrgy (Contributor) / School of International Letters and Cultures (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2024-05