Impeller > Main dimensions > Axial Pump / Fan

The main dimensions of a designed impeller - suction diameter dS1 and dH1 and outlet diameter dS2 and dH2 - 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 Setup and Parameters.

Individual main dimensions can be calculated separately using the button inside the value field.

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.

Neighboring components

In specific cases the dimensions of the neighboring components at inlet and/ or outlet can be used to get exactly matching geometry.

This feature is available only for explicitly uncoupled components or side-by-side impellers.

Information

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:

Work coefficient
Flow coefficient
Meridional flow coefficient
Specific diameter
Average inlet velocity
Inlet abs. circ. velocity component
Inlet relative velocity
Average outlet velocity
Outlet circ. velocity component
Outlet relative velocity
Meridional velocity ratio
Relative velocity ratio
Axial force (thrust)
NPSHR estimation	Lobanoff/ Ross see diagram below this table
	Pfleiderer with loss coefficients λc = 1.1 … 1.35, λw = (0.03) 0.1 … 0.3
	Gülich or with suction specific speed nSS = 160…280
	Stepanoff with cavitation number σ = 1.22 ∙10-3 ∙nq4/3
	Petermann with suction number Sq = (0.2) 0.4…0.6 (2.0)
	Europump

NPSHR prediction
according to
Lobanoff/ Ross

The Meridional preview is until now based on the main dimensions only.

The Cordier diagram can be used for checking the impeller diameter d2.

See Cordier.

The Velocity triangles are the result of a mid-span calculation and are based on the design point and the main dimensions.

Dimensions

Dimensions

Information