Main dimensions

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Main dimensions

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► IMPELLER | Main dimensions

The Main Dimensions menu item is used to define main dimensions of the impeller.

Details by impeller type

¢ Centrifugal/ Mixed-flow Pump/ Fan

¢ Axial Pump / Fan

¢ Centrifugal Compressor

¢ Radial-inflow Turbine

¢ Axial Turbine

Automatic calculation of impeller diameter depending on rotational speed

The automatic calculations can be easily used to determine the influence of the rotational speed on the impeller diameter, e.g. to find the required rotational speed to account for a certain limited design space.
To do this, both the Automatic parameter estimation (page Parameters) and the Automatic main dimension calculation (page Dimensions) must be activated. If you then change the Alternative speed on page Setup, the resulting impeller diameter can be checked on the Dimensions page and/ or in the Meridian diagram.

Possible warnings

Problem

Possible solutions

Automated Main dimensions are active.
Dimensions are not fixed and may adapt to input parameters.

Main dimensions are updated automatically if any input parameters are modified.

To fix the main dimensions you could uncheck the "Automatic" calculation. Then you have to manually start the calculation if required.

Automated Main dimensions are NOT active.
Dimensions are fixed, but may not reflect input parameters.

Main dimensions are not updated automatically if any input parameters are modified.

To be sure that all parameter modifications are considered you could switch to an automatic calculation by checking the "Automatic" option.

Specific speed of impeller is beyond the supported range.

The specific speed nq of the impeller is much too low or too high. The supported range is nq = 5 ... 500.

Modify specific speed defined by n, Q, Δpt in the impeller Main dimensions and/or in the Global Setup.

In some cases it may be necessary to select a different impeller type according to the specific speed.

Specific speed of impeller is beyond the recommended range.

The specific speed is lower or higher then the recommended values.

This warning is generated for

centrifugal/ mixed-flow impellers with specific speed nq < 10 or nq > 160

axial impellers with specific speed nq < 100 or nq > 400

Modify specific speed defined by n, Q, Δpt in the impeller Main dimensions and/or in the Global Setup.

In some cases it may be necessary to select a different impeller type according to the specific speed.

High pre-swirl numbers are unusual.

The impeller is the first component of the project and the inflow swirl is defined by the Global setup. With very high pre-swirl an impeller design might be impossible.

Adapt pre-swirl in the Global setup

Thermodynamic state could not be calculated for given main dimensions.
[ compressors and turbines only ]

The dimensions might be too tight for the specified mass flow and inlet conditions.

Increase the dimensions (width etc.) or change the Global setup (e.g. decrease mass flow).