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Dimensions |
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Dimensions |
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On page Dimensions, panel Shaft/ hub, the required shaft diameter is computed and the hub diameter is determined by the user.
The main dimensions of a designed impeller - suction diameter dS, impeller diameter d2, outlet width b2 - can be seen on Main dimensions panel. They can be recomputed by pressing the Calculate-button. The computation is based on "Euler's Equation of Turbomachinery", on the continuity equation and the relations for the velocity triangles as well as on the parameters and parameter ratios given in the tab sheets Design Point and Parameters.
You may accept the proposed values or you can modify them slightly, e.g. to meet a certain normalized diameter.
In case the checkbox Automatic is activated a new calculation will accomplished after any change of parameter. Then the manual alteration of the main dimensions is not possible.
Regarding the impeller size one should try to attain d2 values as low as possible. But there is a limit for a specified task: lower impeller diameters are leading to higher blade loading - up to blade angles β2 which may not be suitable anymore.
A specific problem exists for ventilator impellers. If the suction diameter dS is calculated by diameter ratio d1/d2, then the hub has to be planar, i.e. hub diameter dN = 0. Otherwise the empirical correlations are invalid. If the user defines a dN value deviating from 0, a warning symbol points to this problem. The solution is to select a different parameter for the calculation of the suction diameter dS (see Parameters).
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You can select a value for the diameters dS from standard specifications. For that purpose you have to press the button
The small dialog gives you the possibility to select a diameter from several standard specifications. If material, standard name and pressure range are selected the lower panel shows all diameters of the chosen standard. One diameter is highlighted as a proposal. Nominal diameter, outside diameter and wall thickness for the marked entry is displayed. Using of
At File location the name of the file containing the diameters is shown. The file is originally called Diameter.cftdi and is located in the installation directory of CFturbo. Modifications of the list will be saved if the user is leaving the dialog window by clicking the OK-button. In case there are no write permissions the user can choose another directory to save the file. Renaming of files is possible by Save as- functionality. By clicking the Open-button a previously saved file can be opened.
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In the right panel of any tab sheet an information panel is situated, which holds the computed variables in accordance to the actual state of design, the resulting Meridional section as well as the Cordier-Diagramm with the location of the best point. These three sections can be chosen by the appropriate soft buttons in the heading.
In the Value section the following variables are displayed for information which result from calculated or determined main dimensions:
Pressure coefficient |
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Average inlet velocity |
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Average inlet velocity (net) |
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Average outlet velocity |
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Average outlet velocity (net) |
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NPSH value |
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Outlet width ratio |
b2/d2 |
Meridional deceleration |
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Estimated axial force |
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The Meridional section is based on the until now designed min dimensions.
The Cordier diagram is based on an intensive empirical analysis of proved turbomachinery using extensive experimental data.
Page url: http://www.cfturbo.com/fileadmin/content/manual/en/index.html?md_dimensions_pumpvent.html
right beside the input field.
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buttons additional standard specifications and user defined diameters can be added or existing parameters can be removed from the list.
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