Application of a Low-Solidity Cascade Diffuser to Transonic Centrifugal Compressor

Hayami, Hiroshi; Senoo, Yasutoshi; Utsunomiya, Kenji

doi:10.1115/1.2927416

Cited by 32 publications

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“…Table 1 shows the main specifications. The basic parameters of the SVD are similar to those of an SVD69 in the literature (Hayami et al, 1990). To avoid confusion between the main vane and the small vane, the terms blade or main blade are used to refer to the main vane in this article.…”

Section: Figurementioning

confidence: 89%

“…For all operating points, the absolute flow Mach number exceeded unity at the impeller exit (Hayami et al, 1990). The surge flow rate of the VDAT was comparable only at Mt = 0.94 and Mt = 1.041.…”

Section: Comparison In the Transonic Centrifugal Compressormentioning

confidence: 90%

“…Figure 8 shows a comparison of compressor efficiency. The efficiency is normalized by the peak value, which is almost the same in the case of the SVD69 (Hayami et al, 1990). The efficiency of the VDAT is comparable only at Mt = 0.94.…”

Section: Figurementioning

confidence: 99%

“…E-mail: nakagako@ hakodate-ct.ac.jp narrow flow range. A low-solidity circular cascade diffuser was proposed so as to avoid this problem in regions of subsonic flow (Senoo et al, 1983) and transonic flow (Hayami et al, 1990). The special feature is that this type of diffuser does not have a throat.…”

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Comparison of Two Diffusers in a Transonic Centrifugal Compressor

Nakagawa

Hayami

Keimi

2003

International Journal of Rotating Machinery

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Flow mechanisms suppressing the flow separation in two diffusers, a low-solidity cascade diffuser and a vaned diffuser with additional small vanes near the inlet, were compared mainly by numerical simulation. As the superiority of the low-solidity cascade diffuser was expected, a series of experiments was conducted using a transonic centrifugal compressor with a maximum pressure ratio of 7. The performance of the compressor with the vaned diffuser was comparable to that of the low-solidity cascade diffuser only between the surge point and the design flow rate at a pressure ratio of 3.5. The maximum flow rate of the vaned diffuser was lower than that of the low-solidity cascade diffuser. At higher rotational speeds, the pressure ratio at the surge point, the efficiency, and the flow range of the low-solidity cascade diffuser exceded those of a vaned diffuser at a pressure ratio of 3.5. Keywords Compressor, Diffuser, Numerical analysis, Stall In many radial compressors, vaned diffusers are widely used to obtain high efficiency. However, this causes the problem of a Laboratory of Hitachi Industries Co., Ltd., for the execution of the numerical simulations. The authors are also grateful to Hideo Sasaki and Hidenori Hasegawa, who were graduate students while this paper was being composed, and Nobumasa Kawaguchi of Kyushu University who assisted in running the experiments.Address correspondence to Koji Nakagawa, Department of Mechanical Engineering, Hakodate National College of Technology, 14-1 Tokura-cho, Hokkaido, 042-8501, Japan. E-mail: nakagako@ hakodate-ct.ac.jp narrow flow range. A low-solidity circular cascade diffuser was proposed so as to avoid this problem in regions of subsonic flow (Senoo et al., 1983) and transonic flow (Hayami et al., 1990). The special feature is that this type of diffuser does not have a throat.Diffusers with throats, such as channel-type diffusers, are still in wide use, despite the problem of choking, because of the accumulation of data concerning them. To extend the flow range of these diffusers, modification of the vane shape is practical because of its simplicity. The V-shaped inlet (Dallenbach and Van Le, 1960) and the pipe diffuser (Morris and Kenny, 1971) are representative techniques. This V shape was effective even in subsonic cases (Yoshinaga et al., 1980). The three-dimensionally twisted vane (Jansen and Rautenberg, 1982) extended the available operation range by a factor of 2. A common feature of these diffusers is that the vane inlet matches the real flow. As a flow distortion is stronger on the shroud side than on the hub side, small vanes were added near the diffuser's vane inlet on the shroud side. This diffuser had a remarkable effect in a highsubsonic, centrifugal compressor with a pressure ratio of 2, with a suction damper (Nakagawa et al., 1995). When the damper opening was 40%, the surge flow rate decreased by 35% and the maximum head rise increased by 15%. At full damper opening, the flow range and the maximum head rise increased only a little. In addition, a...

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Section: Figurementioning

confidence: 89%

Section: Comparison In the Transonic Centrifugal Compressormentioning

confidence: 90%

Section: Figurementioning

confidence: 99%

mentioning

confidence: 99%

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Comparison of Two Diffusers in a Transonic Centrifugal Compressor

Nakagawa

Hayami

Keimi

2003

International Journal of Rotating Machinery

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“…If the impeller tip speed increases, a high pressure ratio can be achieved, but a large dynamic pressure at the impeller exit results. In such a case, a high performance diffuser, for instance, a low solidity circular cascade diffuser (LSD) is essential, which has been widely used in many centrifugal blowers [1,2,3] and compressors [4,5]. The LSD showed a high blade loading without stall even under low flow rate conditions, showing fairly high lift coefficients because the flow separation on suction surface of the LSD blade was successfully suppressed by the secondary flow formed along the side walls.…”

Section: Introductionmentioning

confidence: 99%

Control of secondary flow in a low solidity circular cascade diffuser

et al. 2012

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Kyushu University (retired)According to the previous experimental works on the low solidity circular cascade diffuser (LSD), a pressure recovery of a centrifugal blower was improved by the LSD significantly in a wide range of flow rate, and the pressure recovery was improved further by the LSD with a tandem cascade in comparison with the LSD with a single-row cascade. In the present study, the flow behavior in the LSD with the tandem cascade has been analyzed numerically by using the commercial CFD code of ANSYS-CFX12. It was shown clearly that the higher pressure recovery was achieved by applying the LSD with the tandem cascade, and the high pressure recovery is based on the high pressure rise in the vaneless space upstream of the LSD and the high blade loading of the front blade of the LSD. The high pressure recovery in the LSD could be achieved by controlling the flow separation on the suction surface of the front blade and also on that of the rear blade due to formation of the favorable secondary flow and due to increase in mass flow passing through the slit section between the front and rear blades.

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2018

Design and Analysis of Centrifugal Compressors

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Application of a Low-Solidity Cascade Diffuser to Transonic Centrifugal Compressor

Cited by 32 publications

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Comparison of Two Diffusers in a Transonic Centrifugal Compressor

Comparison of Two Diffusers in a Transonic Centrifugal Compressor

Control of secondary flow in a low solidity circular cascade diffuser

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