Explanipedia

The effect of unsteady vortex behavior on noise characteristics in a centrifugal compressor Open

K. Tajima, Hiroshi Miida, Nobumichi Fujisawa, Yutaka Ohta · 2021

The effect of diffuser width on the noise level of a centrifugal compressor equipped with vaneless diffusers was investigated through experiments and numerical techniques. In this regard, two diffusers with different widths were installed …

Unsteady behavior and mechanism of a rotating stall in a centrifugal compressor with vaneless diffuser Open

Nobumichi Fujisawa, Hiroshi Miida, K. Tajima, Yutaka Ohta · 2021

Unsteady diffuser stall behavior in a centrifugal compressor with a vaneless diffuser was investigated by experimental and computational analyses. The diffuser stall generated as the mass flow rate decreased. The diffuser stall cell rotate…

Numerical study on Estimation of Hydrodynamic Force acting on Open-frame Underwater Vehicle Open

Hiroyoshi Suzuki, Yosuke Okuda, Yoshiki Nagai, Toshio Iseki, Yoshitaka Watanabe , et al. · 2021

In this paper, the estimation accuracy of hydrodynamic force acting on the fuselage of an open frame type AUV by CFD analysis was investigated. The hydrodynamic force acting on the fuselage was examined in case that the fuselage is station…

Generation Mechanism of Diffuser Stall in a Centrifugal Compressor with Vaneless Diffuser Open

Nobumichi Fujisawa, K. Tajima, Hiroshi Miida, Yutaka Ohta · 2020

The generation mechanism of a diffuser stall in a centrifugal compressor with a vaneless diffuser was investigated by experimental and computational analyses. The diffuser stall generated as the mass flow rate decreased. The diffuser stall…

Generation Mechanism of Diffuser Stall in a Centrifugal Compressor with Vaneless Diffuser Open

Nobumichi Fujisawa, K. Tajima, Hiroshi Miida, Yutaka Ohta · 2020

The generation mechanism of a diffuser stall in a centrifugal compressor with a vaneless diffuser was experimentally and computationally investigated, and the main findings are presented in this paper.Diffuser stall is generated when the m…

Effect of Inflow Condition and Tip Clearance Size on Stall Inception in an Axial Compressor Open

Kotaro ARATA, Nobumichi Fujisawa, Yutaka Ohta, Dai Kato · 2020

The effect of inflow condition and rotor tip clearance size on the stall inception in an axial compressor is experimentally investigated. The rig in this research is a low-speed, single-stage flow compressor, which has two types of tip cle…

Measurement of Axial-flow Compressor Operation Using an AE Sensor Open

H. Takahashi, Nobumichi Fujisawa, Yutaka Ohta, Takeshi Suzuki, Shuichi UMEZAWA , et al. · 2020

In the gas turbine system, which is exposed to frequent variation of load, compressor operation needs to be monitored constantly. For the monitoring device, hot-wire probes or accelerometers are generally used, but those devices need measu…

Effect of Forward-Swept Rotor on Stall Margin in an Axial Flow Compressor at Distorted Inflow Condition Open

Kyonosuke Hamaguchi, Yuu Sakata, Nobumichi Fujisawa, Yutaka Ohta, Dai Kato · 2020

In this study, we aim to elucidate the effect of a forward-swept rotor on the stall margin and flow field at the distorted inflow conditions.The rig in this research is a low-speed, single-stage axial compressor, which has two types of rot…

Rotor Performance of an Axial Flow Compressor at Free and Highly Loaded Windmilling Conditions Open

Wenbo Zhang, Nobumichi Fujisawa, Yutaka Ohta, Takashi Goto, Dai Kato · 2020

The work characteristics and loss-generation mechanism of a single-stage axial flow compressor in windmilling operation were investigated via experiments and computational fluid dynamics analyses. The windmilling state occurs when air flow…

The Performance Test for the Autonomous Underwater Drone for Under-Ice Survey in the Arctic Ocean Open

Shojiro Ishibashi, Kiyoshi Tanaka, Yosaku Maeda, Yutaka Ohta, Hiroshi Yoshida · 2020

As well known, the Arctic Ocean are covered with vast and thick sea ice, it is difficult to grasp the state below sea ice from above sea ice. Analyzing the behavior of sea ice is directly related to the understanding of the Arctic region, …

Motion simulation of sensor cable towed by X rudder AUV “YUMEIRUKA" Open

Masahiko Nakamura, Tadahiro Hyakudome, Takafumi Kasaya, Hisanori Iwamoto, Yutaka Ohta · 2019

“YUMEIRUKA" is an AUV that Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has developed and is operating. A seabed resource exploration is carried out by two-set simultaneous operation with AUV “JINBEI" developed by JAMSTEC…

Rotor work characteristics and loss generation mechanism of an axial flow compressor at windmill operation Open

Nobumichi Fujisawa, Naomichi NISHIYAMA, Yutaka Ohta, Takashi Goto, Dai Kato · 2019

Work characteristics and loss generation mechanism of a single-stage axial flow compressor at windmill operation were investigated by experiment and CFD analyses. When the inlet flow coefficient is gradually increased from the design point…

Real-time Analysis of Non-linear Hydrodynamic Derivatives Open

Saki Sekine, Yutaka Ohta, Toshio Iseki · 2018

Pressure Propagation of Impinging Jet with Cavitation by Numerical Analysis Open

Daisei Kanamori, Fumihiro Inoue, Yutaka Ohta · 2017

In recent years, cavitating jet has attracted attention as an application of water jet technology. In its application, it is important to clarify the jet flow structure and the behavior of bubble cloud collapse. Therefore, in order to visu…

Transition Process from Diffuser Stall to Stage Stall in a Centrifugal Compressor with a Vaned Diffuser Open

Nobumichi Fujisawa, Yutaka Ohta · 2017

The transition process from a diffuser rotating stall to a stage stall in a centrifugal compressor with a vaned diffuser was investigated by experimental and numerical analyses. From the velocity measurements, it was found that the rotatin…

Heat Pump Technology : Development of an Industrial High Performance and High Temperature Heat Pump Open

Kosaku NISHIDA, Mizuo Kudo, Keizo Kobayashi, Akito Machida, Kiyoshi Saito , et al. · 2016

In industrial applications, large amounts of steam are used after which unused low temperature waste heat is released into the environment. It is important to develop a high performance and a high temperature heat pump using a waste heat r…

The observation performance of “Yumeiruka”, an AUV with X canard and rear X rudder Open

Yutaka Ohta, Hiroshi Yoshida, Shojiro Ishibashi, Makoto Sugesawa, Frank Fan , et al. · 2016

JAMSTEC has developed several underwater vehicles. These vehicles are currently being used for tasks ranging from seabed topography mapping to deep-sea biological survey. In particular, the AUV "Yumeiruka" was developed to perform seabed r…

Transition Process of Rotating Stall in a Centrifugal Compressor with Vaned Diffuser Open

Daiki Ema, Sota Ikezu, Nobumichi Fujisawa, Yutaka Ohta · 2016

The characteristics and the transition process of rotating stall behavior, which were followed by the decline of flow rate, in centrifugal compressor with vaned diffuser were investigated through experimental analysis. Measurements showed …

World's First Private Security For the Drone Open

Ryōsuke Takahashi, Toshihiro FUJINOKI, Kousuke INAKAZU, Daishi KOBUSE, Yutaka Ohta · 2016

1.はじめに近年,頻発するテロや多様化する犯罪に対応すべく世界的に防犯に対する意識が高まっている。日本でも防犯グッズや防犯カメラ,ホームセキュリティシステムを導入する家庭が増えている。そんな中,2015年12月にセコム(株)が世界初の民間防犯用ドローンと称して,ドローンを利用

SEVERITY OF MORTALITY IN THE 2011 GREAT EAST JAPAN EARTHQUAKE: AGE DEPENDENCY IN COMPARISON WITH PAST MAJOR EARTHQUAKES Open

Yutaka Ohta, Maki Koyama · 2016

This paper aims at determining who is most vulnerable in disasters such as an attack by an inland or oceanic earthquake. We found two major patterns (types U and J, represented by English capital letters) when we introduced two-dimensional…

Development of Autonomous Underwater Vehicle “Otohime” and Underwater Recharging System Open

Kiyotaka Tanaka, Hiroshi Yoshida, Shojiro Ishibashi, Yutaka Ohta, Fan Frank , et al. · 2016

Underwater Recharging System (URS) was devised to perform seabed exploration efficiently. URS has the ability to charge the battery of autonomous underwater vehicle (AUV) by a non-contact method underwater. In this paper, describes the dev…

Transient Characteristics of Coexisting State of Surge and Rotating Stall in a Two-Stage Axial Flow Compressor Open

Yuu Sakata, Naoki NOZOE, Yutaka Ohta · 2016

Interaction between surge and rotating stall in an axial flow compressor was investigated from the viewpoint of an unsteady inner flow structure. The aim of this study was to unravel the mechanism of the interaction between the surge and r…

Optical Seafloor Observation Applying AUV Otohime Open

Shojiro Ishibashi, Hiroshi Yoshida, Makoto Sugesawa, Yutaka Ohta, Frank Fan , et al. · 2016

Stall and leading-edge vortex in a centrifugal compressor with vaned diffuser Open

Nobumichi Fujisawa, Shotaro HARA, Yutaka Ohta · 2015

The experimental and CFD analysis were conducted to investigate the relationship between stall and leading-edge vortex (LEV) in a centrifugal compressor with vaned diffuser. The LEV is distinct from the separating vortex of the diffuser le…

J1050504 Large Eddy Simulation of internal flow of a centrifugal blower with scroll Open

Yoshinobu Yamade, Taku Iwase, Yutaka Ohta, Yang Guo, Chisachi KATO · 2015

The ultimate objective of this study is to predict aeroacoustics noise radiated from a centrifugal blower. The test blower has 12 impeller blades and a vaneless diffuser with a scroll. We performed one-way coupled simulation of internal fl…

Severity of Mortality in the 2011 East Japan Giant Earthquake Age-dependency in Comparison with Past Major Earthquakes Open

Yutaka Ohta, Maki Koyama · 2015

この研究の発端は乳幼児・高令者が災害弱者と総称されている一方で、その実態が判然としないままとなっていることに疑問を持ったことにある。この疑問解消への手始めとして、いくつかの地震・津波襲来時の死者発生状況について年令区分別に詳しく調べた。その結果、主な出現パターンが4種類あることが判った。すなわち、通例のように横軸を年令軸、縦軸を死亡率とする座標上でみると、英語大文字のU字型、J字型で代表される年令依存性の高いもの2種類と、年令依存性のほとんどないFlat型のもの2種類である…

G1500401 Deep Seabed Investigation Applying Underwater Vehicles Open

Shojiro Ishibashi, Hiroshi Yoshida, Makoto Sugesawa, Yutaka Ohta, Frank Fan , et al. · 2015

JAMSTEC is now keeping a watchful eye on some global issues such as the seabed resources and energy, global warming, ocean earthquake and Tsunami. They are serious problems to us and will cause the greater damage to us in near future. In a…

1611 The Effects of Forward-Swept Blade in an Axial Flow Compressor with Inlet Distortion Open

Hiroki KASUYA, Miki Ogawa, Kengo Shimojo, Wataru Kanameda, Dai Kato , et al. · 2015

This research investigates experimentally the effect of forward-swept design on the performance of the rotor blades in a low-speed, single-stage axial-flow compressor under one-per-rev type inlet distortion. In addition to stall tests in c…

1615 The Effects of Impeller Tip Clearance on Internal Flow Characteristics in a Centrifugal Compressor Open

Miku KURODA, Sota Ikezu, Nobumichi Fujisawa, Yutaka Ohta · 2015

The CFD analysis was conducted to investigate the effect of impeller tip clearance on internal flow in a centrifugal compressor with vaned diffuser. In previous studies, the leading-edge vortex (LEV) was produced near the diffuser leading-…

J1050205 Computation of Sound from the Internal Flow in a Centrifugal Blower Open

Yang Guo, Chisachi KATO, Yoshinobu Yamade, Yutaka Ohta, Taku Iwase , et al. · 2015

The noise generated from the internal flow in a centrifugal blower was computed by computational aero-acoustics (CAA). The rotational speed of the impeller of the centrifugal blower is 3000 rpm. The sound sources were obtained by computati…

Yutaka Ohta YOU? Author Swipe