Mechanical design
AG Consultant has significant experience in the mechanical design of industrial fans in general and also in the concept of totally new products.
Success story: (with Fläkt Solyvent-Ventec / Howden Solyvent-Ventec) the development of the 2 contra-rotating axial fans of the wind-tunnel S1 of ONERA at Modane-Avrieux both aerodynamically and mechanically.
The ONERA S1MA wind tunnel has been in commercial use for the last 60 years and it is the largest sonic tunnel ever built.
It is installed in the French Alps and it is basically used for civil and military aircraft model testing.
Source: courtesy of ONERA
The heart of the wind tunnel is equipped with 2 contra-rotating fans directly driven by the Pelton turbines.
The fan diameter is 15 m (49.2 ft) with a blade length of 3.75 m (12.3 ft) and a mean chord of 1.4 m (4.6 ft).
The aerodynamic design point for the new fan blades is positioned around 9000 kg/s (20000 lbs/s).
The maximum available power is 88 MW.
The fan assembly weighs 55 tons.
Source: courtesy of ONERA
When handling such a flow 10 000 cubic meters per second, with such a power 88 000 KW, one can imagine how these elongated blades can be solicited.
That’s the reason why the original blades were daily damaged with cracks which necessitates their repair after a few hours of running.
The time spent for the studies and for manufacturing new fans (more than 10 years) is at the image of these extremely large and powerful fans.
A fatigue resistant blade design was therefore one of the main objectives.
Various options were studied before reaching a final design combining a resistant steel structure forged and machined with leading and trailing edges in carbon-epoxy composite material fixed on it.
The validation of this technology has been done on a blade prototype which has been tested in fatigue during 10 millions of cycles with the maximum expected solicitation.
This gives a guarantee of an extended infinite lifetime.
Manufacturing of such blades has also been a challenge, and particularly for BFR Meccanica (Italy) who has been able to realize the steel parts with the highest quality.
Note that the complexity of the blade shape has required its manufacturing in 2 parts, starting for each of them with a steel ingot of 11 tons reduced after machining at 420 kg for the final piece (as a result only 4% of the material used).
For the composite parts, Duqueine (France) had used his expertise in composite manufacturing for Airbus A320 to bring the best quality required.
These new fans are successfully now in operation at the ONERA wind-tunnel S1, since the end of 2018.
