Comparative Rotating Stall and Surge Characteristic of a Centrifugal Compressor with Three Different Types of Diffusers PDF Download

Author: Abraham Engeda
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Category :
Languages : en
Pages : 0

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Presented at the International Gas Turbine & Aeroengine Congress & Exhibition, Orlando, FL, Jun 2 - Jun 5, 1997.

Author:
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ISBN:
Category : Mechanical engineering
Languages : en
Pages : 562

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Author:
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Category : Mechanical engineering
Languages : en
Pages : 566

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Author: R. C. Pampreen
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Category : Technology & Engineering
Languages : en
Pages : 532

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High efficiency axial and centrifugal compressors are important in fields as diverse as aircraft engines, superchargers and turbochargers, process and refrigeration compressors. Compressors must achieve high efficiency in blade rows in diffusing flow fields. Of equal and sometimes greater importance is the range os stable operation of the compressor. Blade row stall characteristics determine the limit os stable operation. Blading can stall uniformly with symmetric flow breakdown or asymmetrically in rotating stall, wich propagates around the periphery of the blade row. Depending on aerodynamic conditions, surge may occur instead of, in concert with, or subsequent to blade row stall. The transient breakdown and recovery of aerodynamic loading not only limits compressor performance but also leads to mechanical failures caused by the vibrational loads imposed on the blades. There is no need to know what initiates these performance limits so that surge and stall margins can be optimized and control strategies can be planned. the first step toward understanding is to be knowledgeable about he physical processes occurring during surge and stall. This will permit the designer to anticipate variable geometry needs such as variable inlet guide vanes, variable statuors, and bleed port strategies. Theoritical treatment is far from being well established, however, there are many approaches discussed in the literature. This book is a unique reference to the subject matter. Physical descriptions of the phenomena are given, test results are presented, and analytical studies are discussed. There has been much written about the experimental investigations and theoretical treatments related to surge and stall. To assist those who would pursue advancements in furthering ou knowledge of surge and stall, it seemed appropriate to have a resource that contains a compendium of information on this subject. That is the purpose of this book. [Source : d'après la 4e de couverture].

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Category : Compressors
Languages : en
Pages : 198

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Author: P. Frigne
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Category :
Languages : en
Pages : 17

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A comparative experimental investigation of the unstable operating modes of a centrifugal compressor is made. Hot wire measurements, in two different compressor configurations, allowed to distinguish between the different unsteady flow pattern. Impeller and/or diffuser rotating stall has been observed, depending on the flow conditions. The measured relative rotational speed of this perturbation is cross-checked with other experimental data and it is shown that the rotational speed is strongly dependent on the type of rotating stall. The diffuser absolute inlet flow angle at the onset of diffuser rotating stall agrees well with the value predicted by an existing stability criterion.

Author: P. C. Tramm
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Category : Centrifugal pumps
Languages : en
Pages : 226

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Author: Jonathan Neil Everitt
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Category :
Languages : en
Pages : 158

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In compression systems the range of stable operating is limited by rotating stall and/or surge. Two distinct types of stall precursors can be observed prior to these phenomena: the development of long-wavelength modal waves or a short-wavelength, three-dimensional ow breakdown which is typically known as a "spike". The cause of the latter is not well understood; in axial machines it has been suggested that over-tip spillage ow has a significant role, but spikes can also occur in shrouded vaned diffusers of centrifugal compressors, where these flows are not present, suggesting an alternative mechanism may be at play. Unsteady Reynold's Averaged Navier-Stokes simulations are performed for an isolated vaned radial diffusers from a highly loaded centrifugal compressor. Key to their success is the definition of pitchwise "mixed out" averaged inlet conditions derived from the impeller exit flow field from separate single passage stage calculations. This guarantees the relevant flow features are carried into the diffuser model, particularly the spanwise profile of flow angle and total pressure. It is shown that the isolated diffuser model compares well with experimental data and time-averaged, unsteady, full wheel simulations. The stability of the flow is tested via numerical forced response experiments whereby the inlet conditions are perturbed by a total pressure forcing small in temporal and spatial extent. An unstable rotating stall precursor is observed at low diffuser inlet corrected flow, due to the spanwise non-uniform flow angle and total pressure at the diffuser inlet. The radial pressure gradient imposed by the highly swirling bulk flow leads to flow angles in excess of 90 in the shroud endwall flow. This results in shroud-side separation at the diffuser vane leading edge and a region of recirculating ow in the vaneless space. Vorticity shed from the diffuser vane leading edge convects back to the vaneless space and joins the vortical structures within the recirculating flow. This is suggested to lead to spike stall inception.

Author:
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Category : Power resources
Languages : en
Pages : 912

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Author: Massachusetts Institute of Technology. Gas Turbine Laboratory
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Category :
Languages : en
Pages : 263

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