The invention relates to a high-pressure fan which comprises an electric motor provided with a shaft that goes through it; blade wheels which are mainly made of a carbon fibre-based composite material, arranged on both sides of the electric motor and mounted directly on the shaft of the electric motor; fan housings surrounding the blade wheels; and an intermediate channel which connects a pressure opening of one fan housing to a suction opening of the other fan housing, the intermediate channel being integrated into the base structure of the high-pressure fan and located substantially below the electric motor and the blade wheels mounted to it.
This type of compact high-pressure fan except for the intermediate channel structure integrated to the base structure is known from FI patent 101564. When the blade wheels are made of a mainly carbon fibre-based composite material, the weight of the blade wheel is considerably reduced in comparison with the conventional steel and aluminium blade wheels. In spite of this, it has been possible to design the blade wheels at least as strong as when using the conventional materials. Due to the light weight of the blade wheels, they also do not require separate bearings and the bearings of the electric motor suffice. Due to the light weight of the rotating parts and the possibility to use smaller slide bearings instead of roller bearings, it has also been possible to raise considerably the rotation rate of the fan. The first critical rotation rate of the high-pressure fan is at the same time also at a higher level than that of the conventional solutions, which facilitates the use of rotating control in the entire area of operation, the control being easy to implement by means of a frequency converter.
The two series-connected steps of the high-pressure fan, i.e. the entities formed by each blade wheel and fan housing, are in this solution according to FI patent 101564 connected to each other by means of an intermediate channel running over the entire fan structure.
Even though this known high-pressure fan structure provides the significant advantages listed above, problems are still caused by said intermediate channel that requires a lot of space and causes vibration especially at high rotation rates.
An intermediate channel structure integrated to the base structure is in turn known from SU invention report 1710849.