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4. Research Progress on Numerical Simulation of Temperature Field during Directional Solidification of Nickel-based Single Crystal Turbine Blades

Author

Sun Jiayi, Dong Longpei, ZHao Yunshon, Wang Enhui, Hou Xinmei

Subjects
nickel-based single crystal turbine blade； directional solidification； numerical simulation； temperature field； interfacial heat transfer coefficient, Materials of engineering and construction. Mechanics of materials, TA401-492, Technology
Abstract

As one of the indispensable core components of advanced aero-engine， nickel-based single crystal turbine blades （hereinafter referred to as single-crystal blades） have extremely demanding requirements in terms of dimensional accuracy of the hollow structure， uniformity of alloying element distribution， and metallurgical quality of the surface and inner cavity. It is found that the control of temperature gradient during directional solidification directly affects the performance and quality of single crystal blades， and whether the continuous acquisition of stable heat flow becomes the key of directional solidification .With the continuous progress of computer technology， numerical simulation has become one of the important methods of single crystal blade directional solidification research. Firstly， introduce the single crystal blade technology is introduced and the heat transfer method in the directional solidification process is then analyzed.Secondly， the optimization methods of boundary conditions of interfacial heat transfer coefficient for numerical simulation are summarized， focusing on the application of Beck's inverse method and finite difference method in the solution of interfacial heat transfer coefficient. The results proves that the two methods can be used to solve the interfacial heat transfer coefficient between castings/shells， where the accuracy of the simulation of the temperature field can be effectively improved.Finally， the research progress of numerical simulation of the temperature field during directional solidification is also traced， and the influence of process parameters on the temperature field is summarized. Based on the analysis of the research progress of numerical simulation of temperature field during directional solidification of nickel-based single crystal turbine blades， the optimization direction of the directional solidification process and the subsequent development trend of the related technology are proposed to promote the research and development process of single crystal turbine blades.

Published
2024
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25. Digestive Stability of Tannin-Enriched Fraction of Rubus chingii Hu Fruits and Its Regulatory Effect on the Intestinal Microflora

Author

JIA Xiaoyan, HU Pengpeng, WANG Peixin, DING Qiao, WANG Enhui, XIE Zuohua, TU Zongcai, ZHANG Lu

Subjects
rubus chingii hu, tannin, digestive characteristics, intestinal flora, biological activity, Food processing and manufacture, TP368-456
Abstract

Tannin is the major active ingredient of the dried unripe fruits of Chinese raspberry (Rubus chingii Hu), Fupenzi in Chinese, and has the functions of lowering blood sugar, reducing blood lipid, resisting inflammation, delaying aging and preventing cardiovascular and cerebrovascular diseases. In this study, a tannin-enriched fraction was prepared from Fupenzi, and the changes in its tannin content, antioxidant activity and α-glucosidase inhibitory activity before and after in vitro simulated digestion were investigated. Its regulatory effect on the intestinal microflora was analyzed by in vitro anaerobic fermentation. Finally, ultra-high performance liquid chromatography-quadrupole time of flight-tandem mass spectrometry (UPLC-ESI-QTOF-MS/MS) was used to compare the changes in the contents of tannin and its metabolite after in vitro digestion and fermentation. The results showed that the content of hydrolyzed tannin increased first and then decreased during both gastric and intestinal digestion. Gastrointestinal digestion increased 1,1-dipheny1-2-picryl-hydrazyl (DPPH) radical scavenging capacity of the tannin-enriched fraction, with half-maximal inhibitory concentration (IC50) values ranging from 29.15 to 39.65 µg/mL, but had no significant effect on 2,2’-azino-bis(3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS) cation radical scavenging capacity (P > 0.05). In addition, after simulated intestinal digestion, the α-glucosidase inhibitory activity increased by 7.16–7.86 times. In vitro colonic fermentation experiments showed that tannin-enriched fraction significantly increased the relative abundance of beneficial bacteria such as Coprococcus, Anaerostipes, Ruminococcus and Faecalibaterium. Simulated gastrointestinal digestion reduced its effect in improving beneficial bacteria such as bifidobacteria. UPLC-ESI-QTOF-MS/MS analysis showed that the content of tannin metabolites decreased first and then increased during gastrointestinal digestion; the contents of urolithin A and urolithin B decreased significantly after colon fermentation, and neither urolithin C nor urolithin D was detected. Therefore, this study provides a theoretical basis for the establishment of stable tannin delivery system to improve its bioavailability.

Published
2023
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