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Rotating Choke and Choked Surge in an Axial Pump Impeller
Watanabe, Toshifumi,Sato, Hideyoshi,Henmi, Yasuhiko,Horiguchi, Hironori,Kawata, Yutaka,Tsujimoto, Yoshinobu Korean Society for Fluid machinery 2009 International journal of fluid machinery and syste Vol.2 No.3
Unlike usual turbopump inducers, the axial flow pump tested operates very stably at design flow rate without rotating cavitation nor cavitation surge. Flow visualization suggests that this is because the tip cavity smoothly extends into the flow passage without the interaction with the leading edge of the next blade. However, at low flow rate and low cavitation number, choked surge and rotating choke were observed. Their correlation with the performance curve under cavitation is discussed and their instantaneous flow fields are shown.
Cavitation Instabilities of Hydrofoils and Cascades
Tsujimoto, Yoshinobu,Watanabe, Satoshi,Horiguchi, Hironori Korean Society for Fluid machinery 2008 International journal of fluid machinery and syste Vol.1 No.1
Studies on cavitation instabilities of hydrofoils and cascades are reviewed to obtain fundamental understandings of the instabilities observed in turbopump inducers. Most of them are based on the stability analysis of two-dimensional inviscid cavitating flow. The most important finding of the analysis is that the cavitation instabilities depend only on the mean cavity length. For a hydrofoil, the characteristic length is the chord length and partial/transitional cavity oscillation occurs with shorter/longer cavity than 75% of the chord length. For cascades, the characteristic length is the blade spacing and various modes of instabilities are predicted when the mean cavity is longer than 65% of the spacing. In the last part, rotating choke is shown to occur when the cavity becomes longer than the spacing.
Unstructured Information Management Projects at IBM Tokyo Research Laboratory
Takeda, Koichi,Watanabe, Hideo,Uramoto, Naohiko,Nomiyama, Hiroshi,Matsuzawa, Hirofumi,Nasukawa, Tetsuya,Nagano, Tohru,Murakami, Akiko,Takeuchi, Hironori,Kanayama, Hiroshi,Kobayashi, Mei,Aono, Masaki,I 한국정보처리학회 2004 정보처리학회지 Vol.11 No.2
Cao, Linlin,Watanabe, Satoshi,Honda, Hironori,Yoshimura, Hiroaki,Furukawa, Akinori Korean Society for Fluid machinery 2014 International journal of fluid machinery and syste Vol.7 No.4
As a high specific speed pump, the contra-rotating axial flow pump with two rotors rotating reversely has been proved with higher hydraulic and cavitation performance, while in our previous researches, the potential interaction between two blade rows was distinctly observed for our prototype rotors designed with equal rotational speed for both front and rear rotors. Based on the theoretical and experimental evidences, a rotational speed optimization methodology was proposed and applied in the design of a new combination of contra-rotating rotors, primarily in expectation of the optimized blade pressure distributions as well as pertinently improved hydraulic performances including cavitation performance. In the present study, given one stationary and two rotating frames in the contra-rotating rotors case, a pressure measurement concept taking account of the revolutions of both front and rear rotors simultaneously was adopted. The casing wall pressure data sampled in time domain was successfully transferred into space domain, by which the ensemble averaged blade-to-blade pressure distributions at the blade tip of two contra-rotating rotors under different operation conditions were studied. It could be seen that the rotor pair with the optimized rotational speed combination as well as work division, shows more reasonable blade-to-blade pressure distribution and well weakened potential interaction. Moreover, combining the loading curves estimated by the measured casing wall pressure, the cavitation performance of the rotor pairs with new rotational speed combination were proved to be superior to those of the prototype pairs.
Inducer Design to Avoid Cavitation Instabilities
Kang, Dong-Hyuk,Watanabe, Toshifumi,Yonezawa, Koichi,Horiguchi, Hironori,Kawata, Yutaka,Tsujimoto, Yoshinobu Korean Society for Fluid machinery 2009 International journal of fluid machinery and syste Vol.2 No.4
Three inducers were designed to avoid cavitation instabilities. This was accomplished by avoiding the interaction of tip cavity with the leading edge of the next blade. The first one was designed with extremely larger leading edge sweep, the second and third ones were designed with smaller incidence angle by reducing the inlet blade angle or increasing the design flow rate, respectively. The inducer with larger design flow rate has larger outlet blade angle to obtain sufficient pressure rise. The inducer with larger sweep could suppress the cavitation instabilities in higher flow rates more than 95% of design flow coefficient, owing to weaker tip leakage vortex cavity with stronger disturbance by backflow vortices. The inducer with larger outlet blade angle could avoid the cavitation instabilities at higher flow rates, owing to the extension of the tip cavity along the suction surface of the blade. The inducer with smaller inlet blade angle could avoid the cavitation instabilities at higher flow rates, owing to the occurrence of the cavity first in the blade passage and its extension upstream. The cavity shape and suction performance were reasonably simulated by three dimensional CFD computations under the steady cavitating condition, except for the backflow vortex cavity. The difference in the growth of cavity for each inducer is explained from the difference of the pressure distribution on the suction side of the blades.
Linlin Cao,Satoshi Watanabe,Hironori Honda,Hiroaki Yoshimura,Akinori Furukawa 한국유체기계학회 2014 International journal of fluid machinery and syste Vol.7 No.4
As a high specific speed pump, the contra-rotating axial flow pump with two rotors rotating reversely has been proved with higher hydraulic and cavitation performance, while in our previous researches, the potential interaction between two blade rows was distinctly observed for our prototype rotors designed with equal rotational speed for both front and rear rotors. Based on the theoretical and experimental evidences, a rotational speed optimization methodology was proposed and applied in the design of a new combination of contra-rotating rotors, primarily in expectation of the optimized blade pressure distributions as well as pertinently improved hydraulic performances including cavitation performance. In the present study, given one stationary and two rotating frames in the contra-rotating rotors case, a pressure measurement concept taking account of the revolutions of both front and rear rotors simultaneously was adopted. The casing wall pressure data sampled in time domain was successfully transferred into space domain, by which the ensemble averaged blade-to-blade pressure distributions at the blade tip of two contra-rotating rotors under different operation conditions were studied. It could be seen that the rotor pair with the optimized rotational speed combination as well as work division, shows more reasonable blade-to-blade pressure distribution and well weakened potential interaction. Moreover, combining the loading curves estimated by the measured casing wall pressure, the cavitation performance of the rotor pairs with new rotational speed combination were proved to be superior to those of the prototype pairs.
Seigo Nakatani,Kosuke Okuwaki,Masafumi Watanabe,Hiroshi Imaizumi,Tomohisa Iwai,Takaaki Matsumoto,Rikiya Hasegawa,Hironori Masutani,Takahiro Kurosu,Akihiro Tamaki,Junro Ishizaki,Ayana Ishizaki,Mitsuhir 대한소화기내시경학회 2024 Clinical Endoscopy Vol.57 No.1
Background/Aims: In stereomicroscopic sample isolation processing, the cutoff value (≥4 mm) of stereomicroscopically visible white cores indicates high diagnostic sensitivity. We aimed to evaluate endoscopic ultrasound-guided tissue acquisition (EUS-TA) using a simplified stereomicroscopic on-site evaluation of upper gastrointestinal subepithelial lesions (SELs). Methods: In this multicenter prospective trial, we performed EUS-TA using a 22-gauge Franseen needle in 34 participants with SELs derived from the upper gastrointestinal muscularis propria, requiring pathological diagnosis. The presence of stereomicroscopically visible white core (SVWC) in each specimen was assessed using stereomicroscopic on-site evaluation. The primary outcome was EUS-TA’s diagnostic sensitivity with stereomicroscopic on-site evaluation based on the SVWC cutoff value (≥4 mm) for malignant upper gastrointestinal SELs. Results: The total number of punctures was 68; 61 specimens (89.7%) contained stereomicroscopically visible white cores ≥4 mm in size. The final diagnoses were gastrointestinal stromal tumor, leiomyoma, and schwannoma in 76.5%, 14.7%, and 8.8% of the cases, respectively. The sensitivity of EUS-TA with stereomicroscopic on-site evaluation based on the SVWC cutoff value for malignant SELs was 100%. The per-lesion accuracy of histological diagnosis reached the highest level (100%) at the second puncture. Conclusions: Stereomicroscopic on-site evaluation showed high diagnostic sensitivity and could be a new method for diagnosing upper gastrointestinal SELs using EUS-TA.