That is, the multiobjective optimization problem of choosing the proper riser and chill designs has been investigated using genetic algorithms while simultaneously considering their impact on centerline porosity, the macrosegregation pattern, and primarily on hot tear formation. Based on the initial casting process assessment, multiobjective optimization of the solidification pattern of the considered steel part followed.
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An original casting layout was simulated using a transient three-dimensional (3-D) thermal fluid model incorporated in a commercial simulation software package to determine potential flaws and inadequacies. The objective of this work is to show that by optimizing the solidification pattern, i.e., establishing directional and progressive solidification with the help of the Niyama criterion, macrosegregation and hot tearing issues can be both minimized or eliminated entirely. The physics behind macrosegregation and hot tears indicate that these two defects also are dependent heavily on thermal gradients and pressure drop in the mushy zone. The tendency of forming centerline porosity is governed by the temperature distribution close to the end of the solidification interval, specifically by thermal gradients and cooling rates.
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Kotas, Petr Tutum, Cem Celal Thorborg, Jesper Hattel, Jesper HenriĪ methodology of how to exploit the Niyama criterion for the elimination of various defects such as centerline porosity, macrosegregation, and hot tearing in steel castings is presented. In addition, we compare the search performance of NSGA-II enhanced by our method and NSGA-II enhanced by controlled elitism.Įlimination of Hot Tears in Steel Castings by Means of Solidification Pattern Optimization We investigate four eliminating methods analyzing their effects using NSGA-II. This method eliminates similar individuals in objective space to fairly distribute selection among the different regions of the instantaneous Pareto front. In this paper, we propose δ-similar elimination to improve the search performance of multiobjective evolutionary algorithms in combinatorial optimization problems. δ-Similar Elimination to Enhance Search Performance of Multiobjective Evolutionary AlgorithmsĪguirre, Hernán Sato, Masahiko Tanaka, Kiyoshi International Nuclear Information System (INIS)įu, Hui Ji, Ping Xia, Qingfu Guo, Xinlei This study provides a valuable reference for the future siphon well design of coastal power plants. The method mainly uses a diversion pier, diversion grid and multi-hole orifices to improve the hydraulic performance, thus reducing bubble entrainment at the hydraulic jump and shortening the bubble movement length in the siphon well. Compared to previous methods, the new method has a simple structure, is effective in eliminating bubbles and is well adapted to different tide levels. This study presents a new hydraulic performance optimization and bubble elimination method based on model experiments. Thus, bubble elimination in siphon wells has been a topic of considerable interest.
Abstract: In coastal nuclear power plants, bubble entrainment at the hydraulic jump in the siphon well causes foam pollution and salt fog erosion near the outfall of the siphon well. • The new method has a simpler construction and greater bubble elimination. • Double multi-hole orifices were arranged after the weir. • The diversion pier and diversion grid were used to stabilize the flow pattern. Highlights: • A new method was proposed to improve the hydraulic performance and bubble elimination. A siphon well model for hydraulic performance optimization and bubble eliminationĮnergy Technology Data Exchange (ETDEWEB)įu, Hui, E-mail: Ji, Ping Xia, Qingfu Guo, Xinlei
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