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Unsteady Behavior and Control of Vortices in Centrifugal Compressor

Journal of Thermal Science 2014年第5期23卷 401-411页

作者： yutaka ohta Nobumichi Fujisawa Department of Applied Mechanics and Aerospace Engineering Waseda University3-4-1OkuboShinjukuTokyo169-8555Japan Graduate School of Fundamental Science and Engineering Waseda University3-4-1OkuboShinjukuTokyo169-8555Japan

Two examples of the use of vortex control to reduce noise and enhance the stable operating range of a centrifugal compressor are presented in this *** the case of high-flow operation of a centrifugal compressor with a vaned diffuser,a discrete frequency noise induced by interaction between the impeller-discharge flow and the diffuser vane,which appears most notably in the power spectra of the radiated noise,can be reduced using a tapered diffuser vane(TDV) without affecting the performance of the *** longitudinal vortices produced by leakage flow passing through the tapered portion of the diffuser vane induce secondary flow in the direction of the blade surface and prevent flow separation from the leading edge of the *** use of a TDV can effectively reduce both the discrete frequency noise generated by the interaction between the impeller-discharge flow and the diffuser surface and the broadband turbulent noise *** the case of low-flow operation,a leading-edge vortex(LEV) that forms on the shroud side of the suction surface near the leading edge of the diffuser increases significantly in size and blocks flow in the diffuser *** formation of an LEV may adversely affect the performance of the compressor and may cause the diffuser to *** a one-side tapered diffuser vane to suppress the evolution of an LEV,the stable operating range of the compressor can be increased by more than 12 percent,and the pressure-rise characteristics of the compressor can be *** results of a supplementary examination of the structure and unsteady behavior of LEVs,conducted by means of detailed numerical simulations,are also presented.

关键词： centrifugal compressor vortex control interaction tone noise noise reduction CFD DES analysis stability enhancement leading-edge vortex.

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Unsteady Behavior of Surge and Rotating Stall in an Axial Flow Compressor

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Journal of Thermal Science 2012年第4期21卷 302-310页

作者： yutaka ohta yutaka FUJITA Daisuke MORITA Department of Applied Mechanics and Aerospace Engineering Waseda University 3-4-1 Okubo Shinjuku Graduate Student Graduate School of Science and Engineering Waseda University 3-4-1 Okubo Shinjuku

Unsteady behaviors as well as unsteady cascade flow fields of a single-stage axial flow compressor were experi- mentally investigated by detail measurements of unsteady performance characteristics and casing wall pressure and internal flow velocity fluctuations. The main feature of the test compressor is a capacity tank connected di- rectly to the compressor outlet in series through slits and a concentric duplex pipe, and also jet nozzles in order to inject compressed air toward the rotor tip region. Research attention is focused on the post-stall characteristics of surge and rotating stall which occur simultaneously. When the compressor was connected to the capacity tank, surge was generated with rotating stall in accordance with the capacitance increment of whole compressor system The surge behavior changed irregularly with throttling valve installed behind the compressor, and several types of surge cycles were observed. In addition, the surge cycle changed by jet injection to the rotor tip region. The re- suits suggested that the blockages of the cascade flow which were generated by a stall cell play an important role in deciding the surge behaviors.

关键词： Axial flow compressor Surge Rotating stall Stall cell Jet injection

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Coexisting State of Surge and Rotating Stall in a Two-Stage Axial Flow Com-pressor using a Double-Phase-Locked Averaging Technique

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Journal of Thermal Science 2017年第1期26卷 38-46页

作者： Yuu SAKATA yutaka ohta Graduate school of Fundamental Science and Engineering Waseda University 3-4-10kuboShinjuku Tokyo 169-8555 Japan. Department of Applied Mechanics and Aerospace Engineering Waseda University 3-4-10kubo Shinjuku Tokyo169-8555 Japan.

The 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 identify the key factor that determines the switching phenomenon of a surge cycle. The main feature of the tested compressor is a shock tube connected in series to the compressor outlet through a diaphragm, slits, and a concentric duplex pipe: this system allows surge and rotating stall to be generated by connecting the shock tube with the compressor, or enables the compression plane wave injection. The unsteady characteristics and the internal flow velocity fluctuations were measured in detail, and the stall cell structure was averaged and visualized along the movement of the operation point under a coexisting state of surge. A coefficient of the cell scale fluctuation was calculated using the result of the averaging, and it confirmed that the processes of inner flow structure change differed from each other according to the next cycle of the surge. The result suggests that the key factor that determines the next cycle is the transformation of the internal flow structure, particularly between the stall cell and the entire circumferential stall, in both the recovering and stalling processes.

关键词： Axial flow compressor, Rotating stall, Surge, Double-phase-locked measurement, Compression wave.

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Coexisting Phenomena of Surge and Rotating Stall in an Axial Flow Compressor

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Journal of Thermal Science 2013年第6期22卷 547-554页

作者： Takuya ABE Hiroaki MITSUI yutaka ohta Graduate Student Graduate School of Science and EngineeringWaseda University Department of Applied Mechanics and Aerospace Engineering Waseda University

The unsteady inner flow structure of a single-stage axial flow compressor under the coexisting conditions of surge and rotating stall was experimentally investigated via detailed measurements of the unsteady characteristics and the internal flow velocity fluctuations. The main relevant feature of the tested compressor is a shock tube with a capacity tank connected in series to the compressor outlet through slits and a concentric duplex pipe: surge and rotating stall can both be generated by connecting the shock tube. Research attention is focused on the unsteady behavior of a rotating stall during the surge cycle. The size of the rotating stall cell during the recovery process of an irregular surge cycle was experimentally determined by the circumferential flow velocity fluctuations ahead of the rotor blade. The results suggested that the size of the rotating stall cell at the switching point of the performance curve between large and small cycles is considered to be the key parameter in determining the following surge cycle. In addition, the surge cycle is largely influenced by the unsteady behavior of the rotating stall cell.

关键词： Axial flow compressor Surge Rotating stall Coexisting state of surge and rotating stall

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Behavior of Vaneless Diffuser Stall in a Centrifugal Compressor

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Journal of Thermal Science 2022年第1期31卷 3-12页

作者： AGARI Yuki YAMAO Yoshifumi FUJISAWA Nobumichi ohta yutaka Department of Applied Mechanics and Aerospace Engineering Waseda UniversityTokyo 169-8555Japan

The rotating stall in a centrifugal compressor with a vaneless diffuser was investigated both experimentally and numerically with focus on the effect of the internal flow field within the impeller on the diffuser *** numerical analysis,the boundary layer separation at the impeller outlet was found to play an important role in the expansion and rotation processes of the diffuser *** particular,the expanded boundary layer separation near the hub side at the outlet of the main blade(M.B.)suction surface passage was considered to be the main cause of the expansion and rotation processes.A longitudinal vortex existed at the throat of the ***,and the mass flow rate in the *** was significantly reduced by the blockage *** addition,the longitudinal vortex induced the rolling up flow near the hub side at the impeller ***,the boundary layer separation expanded.

关键词： centrifugal compressor vaneless diffuser pressure and velocity measurement CFD rotating stall

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Effects of Diffuser Vane Geometry on Interaction Noise Generated from a Centrifugal Compressor

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Journal of Thermal Science 2005年第4期14卷 321-328页

作者： yutaka ohta Naho TAKEHARA Yasuhiko OKUTSU Eisuke OUTA Department of Mechanical Engineering Waseda University 3-4-1 Okubo ShinjukuTokyo 169-8555Japan

The characteristics of interaction tone noise radiated from a centrifugal compressor with a vaned diffuser are discussed by experiments, including visualization techniques using the oil-film method. Research attention is paid to the leading edge geometries of the diffuser vanes that are deeply related to the generation mechanism of the interaction tone noise. The compressor-radiated noise can be reduced by several decibels by setting some clearances in both the hub and shroud surfaces of the diffuser wall along with some decline in the pressure-rise coefficient. Since the decline turned out to be caused by the flow impingement and also by the secondary flow within the diffuser passages, several new types of diffuser vane geometries which do not detract from both the performance and noise level are developed and utilized for the experiments. The presented diffuser vane geometries will offer a few basic guidelines for the diffuser vane design.

关键词： centrifugal compressor vaned diffuser interaction noise noise reduction.

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Unsteady Flow Field under Surge and Rotating Stall in a Three-stage Axial Flow Compressor

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Journal of Thermal Science 2011年第1期20卷 6-12页

作者： Takayuki HARA Daisuke MORITA yutaka ohta Eisuke OUTA Graduate Student Graduate school of Science and EngineeringWaseda University3-4-1 OkuboShinjukuTokyo 169-8555Japan Department of Applied Mechanics and Aerospace Engineering Waseda University3-4-1 OkuboShinjukuTokyo 169-8555Japan

The unsteady flow structure between rotor blade-to-blade passages in a three-stage axial flow compressor is experimentally investigated by detailed measurements of unsteady performance characteristics,casing wall pressure fluctuations and their wavelet *** main feature of the test compressor is a capacity tank facility connected in series to the compressor outlet in order to supply compression and/or expansion waves from downstream of the *** attention is focused on the post-stall characteristics of the surge and rotating stall which occur *** influence of the compressor operating point on the unsteady performance curve shows that the surge cycle changes irregularly depending on the steady-state resistance characteristics,and the results of the wavelet analyses of the wall pressure fluctuations suggest that the surge cycle may selectively be determined by the rotating stall cell structure within the rotor cascade.

关键词： Axial flow compressor Surge Rotating stall Stall cell Wavelet analysis.

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Stall Inception Process and Prospects for Active Hub-Flap Control in Three-Stage Axial Flow Compressor

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Journal of Thermal Science 2008年第4期17卷 324-330页

作者： Tomoya OKADA Atsushi KAWAJIRI yutaka ohta Eisuke OUTA Graduate school of Science and Engineering Waseda University Department of Applied Mechanics and Aerospace Engineering Waseda University

The possibility to apply the active hub-flap control method, which is a proven rotating stall control method for a single-stage compressor, to a 3-stage axial compressor is experimentally discussed, where complex rotating stall inception processes are observed. The research compressor is a 3-stage one and could change the stagger angle settings for rotor blades and stator vanes. Sixteen rotor blade/stator vane configuration patterns were tested by changing stagger angle for the stator vanes. By measurement of surface-pressure fluctuation, stall inception proc- esses are investigated and the measured pressure fluctuation data is used as a predictive signal for rotating stall. The experimental results show that the stall detection system applied to active hub-flap control in a single-stage compressor could be usefully applied to that in a 3-stage compressor with a more complex stall inception process.

关键词： axial flow compressor rotating stall active stall control stall inception stall precursor.

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Noise Reduction and Surge Margin Improvement Using Tapered Diffuser Vane in a Centrifugal Compressor

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Journal of Thermal Science 2010年第1期19卷 21-25页

作者： Takashi Goto Eri Ohmoto yutaka ohta Eisuke Outa Department of Applied Mechanics and Aerospace Engineering Waseda University Graduate Student Graduate School of Applied Mechanical EngineeringWaseda University

Improvement of surge margin and reduction of interaction tone noise radiated from a centrifugal compressor with a vaned diffuser is discussed from experiments and CFD *** types of one-side tapered diffuser vanes,which are shroud-and hub-side tapered vanes,were used in the *** height of the leading edge of the tapered vanes varied from 100% to 10%.Both types of tapered vanes are effective for the reduction of the interaction tone noise radiated from the compressor,because of the smaller interaction area between impeller-discharge flow and diffuser vane ***,the hub-side tapered diffuser vane suppresses the evolution of the leading-edge vortex,which causes reverse-flow in the diffuser ***,the hub-side tapered diffuser vane,which has an optimized diffuser leading edge shape,can improve the compressor pressure-rise characteristics at low-flow operation and can enlarge the surge margin.

关键词： Centrifugal compressor tapered diffuser vane interaction tone noise CFD

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Design and Prototyping of Micro Centrifugal Compressor

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Journal of Thermal Science 2003年第1期12卷 33-37页

作者： Shimpei Mizuki Gaku Minorikawa Toshiyuki Hirano Yuichiro Asaga Naoki Yamaguchi yutaka ohta Eisuke Outa 1. Department of Mechanical Engineering Hosei University 7-2Department of Mechanical Engineering Hosei University 7-2Department of Mechanical Engineering Hosei University 7-2Department of Mechanical Engineering Hosei University 7-2Department of Mechanical Engineering Waseda University 4-1Department of Mechanical Engineering Waseda University 4-1 Department of Mechanical Engineering Hosei University 7-2 Kajinocho 3 chome Koganei-shi Tokyo 184-8584JapanKajinocho 3 chome Koganei-shi Tokyo 184-8584JapanKajinocho 3 chome Koganei-shi Tokyo 184-8584Japan Kajinocho 3 chome Koganei-shi Tokyo 184-8584JapanKajinocho 3 chome Koganei-shi Tokyo 184-8584Japan Ohkubo 3 chome Shinjuku-ku Tokyo 169-8555JapanOhkubo 3 chome Shinjuku-ku Tokyo 169-8555Japan

In order to establish the design methodology of ultra micro centrifugal compressor,wich is the most important component of ultra micro gas turbine unit,a 10 times of the final target size model was designed,prototyped and *** problems to be solved for downsizing were examined and 2-dimensional impeller was chosen as the first model due to its *** conventional 1D prediction *** and the inverse design were *** prototyped compressor was driven by using a turbocharger and the performance characteristics were measured.

关键词：离心式压缩机设计性能

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