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On page Parameters one has to put in or to modify parameters resulting from approximation functions in dependence on specific speed nq (see Approximation functions).

For details of how to handle the parameter edit fields please see Edit fields with empirical functions.


Parameter and efficiency values can be handled manually or can be switched to automatic update by the checkbox on top of the page. Then the default values are used always, even after design point modifications (see Global setup).

If the automatic mode is not selected the current default values can be specified by one of the following options:

globally by the button on top of the page

regionally by the default button within the Parameters or Efficiency region

individually by the default button within the input field when selected


The panel Parameters allows defining alternative parameters in each case for the calculation of the following impeller diameters:



dS1, dH1

dS2, dH2



For dS1-calculation

Work coefficient ψ

dimensionless expression for the specific energy:

Specific diameter δ

according to Cordier diagram (see Dimensions)


For dH1 calculation

Diameter ratio dH1/dS1


For dS2/dH2-calculation

Meridional velocity ratio cm2/cm1

strictly axialdH2 = dH1 and dS2 = dS1
const. hubdH2 = dH1
const. middM2 = dM1
const. shroud dS2 = dS1



In panel Efficiency you have to specify several efficiencies. You have to distinguish between design relevant efficiencies and efficiencies used for information only:

Design relevant

hydraulic efficiency ηh

Information only

mechanical efficiency ηm

The losses resulting in energy dissipation from the fluid form the internal efficiency.

Internal and mechanical efficiency form the overall efficiency (coupling efficiency) of the stage ηSt.

PQ: Runner power

PD: Power output (coupling)


The following summary illustrates the single efficiencies and their classification:



Relevant for impeller design




additional hydraulic

yes: for energy transmission






no: for overall information only

The obtainable overall efficiency correlates to specific speed and to the size and the type of the runner as well as to special design features like bypass installations and auxiliary aggregates. Efficiencies calculated by approximation functions are representing the theoretical reachable values and they should be corrected by the user if more information about the impeller or the whole turbine are available.

The hydraulic efficiency (or blade efficiency) describe the energy losses within the turbine caused by friction and vorticity. Friction losses mainly originate from shear stresses in boundary layers. Vorticity losses are caused by turbulence and on the other hand by changes of flow cross section and flow direction which may lead to secondary flow, flow separation, wake behind blades etc.

The mechanical efficiency mainly includes the friction losses in bearings and seals:

Hydraulic and volumetric efficiency are most important for the runner dimensioning because of their influence on and/or . The mechanical efficiency is affecting only the actual output power of the machine.


In the right area of the register Parameter you can find again some calculated values for information:


Actual power output

Power loss

Internal efficiency

Stage efficiency