On page Parameters you have to put in or to modify parameters resulting from approximation functions in dependence of specific speed nq or flow rate Q (see Approximation functions).

For this purpose some specific edit fields are used.

 

 

 

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

 

 

For dS-calculation (pumps)

 

for d1 calculation (ventilator)

 

for b1 calculation (ventilator)

 

For d2-calculation

 

For b2-calculation

 

 

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

Information only

 

The casing efficiency ηc (see Global setup) is used additionally for impeller dimensioning in order to compensate the flow losses in the casing.

 

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

 

Impeller, casing and mechanical efficiency form the overall efficiency (pump/ coupling efficiency) of the stage ηSt.

When considering motor losses additionally the overall efficiency of the stage incl. motor ηSt* is defined.

 

The following summary illustrates the single efficiencies and their classification:

 

 

The obtainable overall efficiency correlates to specific speed and to the size and the type of the impeller 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 pump are available.

 

The hydraulic efficiency (or blade efficiency) describe the energy losses within the pump 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 hydraulic efficiency is the ratio between specific energy Y and the energy transmitted by the impeller blades:

 

The volumetric efficiency is a quantity for the deviation of effective flow rate Q from total flow rate inside the impeller which also includes the circulating flow within the pump casing:

(rising with impeller size)

 

The tip clearance efficiency is only relevant for unshrouded impellers. It contains losses due to the flow through the gap between blade tips and housing from the pressure to the suction side of the blades. The flow losses mainly depend on the tip clearance distance xT and decrease with rising number of blades and rising blade outlet angle β2.

 

The side friction efficiency contains losses caused by rotation of fluid between hub/ shroud and housing:

 

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

(rising with impeller size)

 

Hydraulic and volumetric efficiency as well as the tip clearance efficiency are most important for the impeller dimensioning because of their influence to and/or . Mechanical and side friction efficiency are affecting only the required driving power of the machine.

 

 

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

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