Ziehl-Abegg talks to CCN about the use of bionics in fan development.
Fan manufacturer Ziehl-Abegg is once again applying knowledge gained from nature to reach peak efficiency in fan development.
The idea for this new latest generation of radial fans comes from the humpback whale and enables energy savings of up to 10 per cent.
Ziehl-Abegg board chair, Peter Fenkl, said the company's engineers are at the forefront of bionics and remain leaders in fan technology.
He said Ziehl-Abegg delivers peak efficiency in excess of 70 per cent in its radial fans.
“Every approach must therefore be used to optimise this. The angle at which the airflow meets the fan blade depends on the flow volume,” Fenkl said.
“The whale has to overcome similar challenges when swimming in the sea: the movement of the fins causes the angle to constantly change.
If its pectoral fins were to be at too steep an angle to the counter-flow this would produce a lot of turbulence as the water passes over them.
The technical manager for ventilation systems at Ziehl-Abegg, Dr Walter Angelis, said the characteristic features of excessive turbulence are high flow losses and noise.
“Over millennia the humpback whale has optimised the design of its fins. For example, the leading edge of the whale’s fins contains golf ball sized bumps (technical term is tubercles),” Angelis said.
“With its long pectoral fins, a whale weighing 25 to 30 tonnes can therefore swim very quickly and with great agility.
“We have recreated this on the leading edge of the fan blade and implemented it as an undulating profile.”
The flow engineers have also taken a close look at the whale’s rear fin, the “fluke”. The v-shaped contour of the rear section of the wing delays potential flow breaks – enabling the fan to be used for numerous different pressure ranges.
Overall, evolution has optimised the flow efficiency of the humpback whale in such a way that makes it a very good and agile swimmer despite its body size.
Without this evolution its long journeys through the world's oceans without taking in food would not be possible. The latest generation of radial fans at Ziehl-Abegg in sizes starting from 710 mm, is now benefitting from this knowledge gained in the field of bionics. The product name ZAbluefin is borrowed from the English.
“We have also fitted a torsion to the fan blade,” Angelis said.
“This creates an optimum angle of flow over the entire span. It’s not just the jagged trailing edges that make the impeller run quieter. The undulating design of the blade surfaces reduces the noise level.”
The experts at Ziehl-Abegg have spent about two years on the new centrifugal impeller for air-handling units and industrial ventilation. A bionic profile has proven very effective in terms of efficiency and low-noise.
With the bionic profile blades, unlike currently commercially available hollow profiled blades, there are no gaps into which dirt or condensation can penetrate, leading not only to corrosion but also creating an imbalance.
The steel is therefore pressed into a corrugated shape using a 600-tonne press.
“This gives us additional strength and enables us to optimise the weight,” Angelis said. “Less weight protects the bearings in the motor.”
The new radial impeller possesses characteristics from two completely different approaches to the field of bionics: both in terms of aerodynamics (ornithology) as well as hydrodynamics (marine biology).
For example, the trailing edges of the ventilator blades recreate the flight of an owl. “As the quietest bird of prey, the owl has already been used by us as a model for a number of designs,” he said.
The serrated trailing edges on fans have since become one of Ziehl-Abegg’s trademarks. On the new fan however the edges have been slightly modified and softened.