Whether water slides, surfing facilities or wave pools - there are no limits to the attractions in water parks and fun pools. They are becoming ever higher, faster and more exciting. This results in new requirements for the design and technical system components of water attractions. While structural components are already designed precisely for the respective water attraction, pump technology is still lagging far behind in this area.
Radial pumps are used for the standard pool water circuit in swimming pools. For water attractions, however, where large volumes of water have to be pumped at low delivery heads (the difference in height of the water to be overcome), radial pumps reach their limits. Radial pumps convey the water out of the impeller perpendicular to the pump shaft. Impellers of centrifugal pumps must therefore perform a high specific pumping work to build up the required pressure. For flow rates that are 5 to 10 times greater, it is no longer possible to design the impellers in this way. Axial pumps are therefore used instead for large flow rates. With axial-flow pumps, the water is conveyed parallel to the pump shaft (horizontally), i.e. the water is not deflected. Compared to radial pumps, these pumps have lower specific pumping work, but can pump larger flow rates due to the larger flow cross-section of the axial impeller.
However, the axial-flow pumps available are designed for a completely different range of applications, such as sewage treatment plants for pumping waste water or flood pumping stations. This is why, for example, the blade geometry and the surface quality are designed for the blockage-free transportation of solids, which is not necessary in the area of clean water. Conveying solids requires, for example, a thickening of the blade profile. This in turn leads to a higher drag coefficient and increasing outflow losses at the trailing edge of the impeller blade (see chapter 1.4). Furthermore, the available axial-flow pumps are optimized for discrete operating points, as they always run at constant operating points, for example once in sewage treatment plants and once in flood pumping stations. For this reason, the pitch angles of the vane profiles of the current axial pumps are selected in such a way that there is a shock-free flow to the vane for each of these discrete operating points in the best-point flow rate of the axial pump. With the current axial pumps, there are therefore only a few fixed selection options with regard to the angle of attack (β_S). With other best-point flow rates and therefore other angles of attack, as occur with water attractions, this limited selection of angles of attack must still be used and the next best angle setting (e.g. β_S=13°, 17°, 21°) must be selected. This leads to high impact losses.
The high flow loss due to the thickening of the blade profile, the unsuitable angle of attack and the resulting poor efficiency lead to an immensely high, unnecessary energy consumption of the axial pumps in water attractions. In the approx. 2,000 water parks around the world alone (each with an average of 5 pumps), the unused energy saving potential amounts to around 262,800,000 kWh per year.
The project, which is co-financed by the European Union, aims to prevent this unnecessary energy consumption in the future by developing a new type of axial pump that is specially designed for water attractions. Flow losses are to be minimized by developing a new impeller blade geometry including a new manufacturing concept with surface finishing by coating the pump components in contact with the medium. In addition, an innovative algorithm is being developed with which, for the first time, the optimum angle of attack of the impeller blades for each individual operating point of the pump can be calculated precisely (e.g. 13.7°), thus achieving maximum efficiency. A parametric model (impeller blades and guide vanes) is being developed so that the negative mold can be produced automatically using the 3D sand printing process. In addition, an energy-efficient motor (efficiency class IE5) is used, the dimensions of which are designed in such a way that it causes as few losses as possible in the flow channel and at the same time achieves maximum power density. By developing a new type of periphery for the motor, it can also be safely mounted horizontally in the piping (these pumps are normally mounted vertically in a pipe). With these developments for the new axial-flow pump, the energy consumption per pump can be reduced by at least 3 % (approx. 26,280 kWh) and by costs of approx. 8,000 € per pump within one year (at an electricity price of 0.30 € / kWh) compared to the most energy-efficient pump currently available from KSB (see chapter 3.3).
published on 27.01.2025, Herborner Pumpentechnik GmbH & Co KG