<< Click to Display Table of Contents >>

Navigation:  Impeller > Main dimensions > Axial Pump / Fan >


Previous pageReturn to chapter overviewNext page

The main dimensions 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 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.


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:

Flow properties at:
- impeller inlet
- impeller outlet

static pressure p
total pressure pt
volume flow Q
mass flow
swirl s

Velocity triangles at:
- impeller inlet
- impeller outlet

velocities u, cm, cm*, cu, c, wu, w
flow angles α, β

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)

Reynolds number

with d1 = highest diameter at inlet

with b1 = width at inlet

with d2 = highest diameter at outlet

with b2 = width at outlet

NPSHR estimation
(Pumps only)

(Available at inlet)

Available head level distance to vaporization at impeller inlet (pv = fluid vapor pressure)

Lobanoff/ Ross

see diagram below this table


with loss coefficients
λc = 1.1 … 1.35, λw = (0.03) 0.1 … 0.3



with suction specific speed nSS = 160…280


with cavitation number σ = 1.22 ∙10-3 ∙nq4/3


with suction number Sq = (0.2) 0.4…0.6 (2.0)


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.