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Study of flow instability in off design operation of a multistage centrifugal pump
Akiha Shibata,Hideto Hiramatsu,Shutaro Komaki,Kazuyoshi Miyagawa,Manabu Maeda,Shun Kamei,Ryota Hazama,Takeshi Sano,Masamichi Iino 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.2
In recent years, attempts have been made to make multistage centrifugal pumps smaller in size and more efficient. However, such designs are known to cause positive-slope phenomena in the Q-H curve, especially under low-flow conditions. These phenomena, which have thus far been studied experimentally and numerically, stem from flow instability in the pump. However, their mechanisms have not yet been clarified because it depends on various parameters. In this study, we focused on diffuser rotating stall, observed in positive Q-H characteristics. This study elucidates the mechanism of positive-slope generation through experimental results and two-dimensional numerical analysis.
( Yoshiki Hirooka ),( Akihiro Itoh ),( Hiroki Kawashima ),( Eizaburo Ohno ),( Yuya Itoh ),( Yosuke Nakamura ),( Takeshi Hiramatsu ),( Hiroyuki Sugimoto ),( Hajime Sumi ),( Daijiro Hayashi ),( Naoki Oh 대한소화기학회 2013 Gut and Liver Vol.7 No.4
Background/Aims: To confirm the feasibility of using newly developed endoscopic ultrasound (EUS) with Zone sonographyTM technology (ZST; Fujifilm Corp.). Methods: Seventy-five patients with pancreatic disorders were enrolled: 45 with intraductal papillary mucinous neoplasm; 15 with ductal carcinoma; five with neuroendocrine tumors; three with serous cystic neoplasms; and seven with simple cysts. The endoscopes used were EG-530UR2 and EG-530UT2 (Fujifilm Corp.). Two items were evaluated: visualization depth among four frequencies and image quality after automatic adjustment of sound speed (AASS), assessed using a 5-scale Likert scale by two endosonographers blinded to disease status. Because sound speed could be manually controlled, besides AASS, image quality at sound speeds of 1,440 and 1,600 m/sec were also assessed. Results: In all cases, sufficient images were obtained in the range of 3 cm from the EUS probe. Judgments of image quality before AASS were 3.49 0.50, 3.65±0.48, respectively. After AASS, A and B scored 4.36±0.48 and 4.40±0.49 (p<0.0001). There were significant differences in the data before and after AASS and plus 60 m/sec, but no significant difference between the datasets were seen after AASS and at sound speeds manually set for minus 100 m/sec. Conclusions: EUS with ZST was shown to be feasible in this preliminary experiment. Further evaluation of this novel technology is necessary and awaited. (Gut Liver 2013; 7:486-491)