Working machine

Technical Field

The present invention relates to a working machine, for example a fan, a blower and a compressor.

Prior Art

Axial fans are known coupled to heat exchangers for optimising the heat exchange. A particular type of fans provides for the use of a propeller downstream of which a bladed stator is positioned. This allows the rotational component of the air flow at the outlet from the fan to be reduced, increasing the axial component. This translates into an increase in static pressure downstream of the stator and therefore an increase in the fan head. The stator therefore allows part of the rotational kinetic energy at the outlet from the blade of the propeller to be recovered which would otherwise, through the development of turbulence, get lost in the environment (all this happening with the same power absorbed by the motor activating the propeller).

Object of the invention

The aim of the present invention is to propose a working machine that allows the efficiency thereof to be optimised.

In particular, the object of the present invention is to provide a working machine that allows aeraulic losses to be reduced.

The stated technical task and specified objects are substantially achieved by a working machine comprising the technical features disclosed in one or more of the appended claims.

Brief description of the drawings

Further characteristics and advantages of the present invention will become more apparent from the following indicative and therefore non-limiting description of a working machine as illustrated in the appended drawings, in which:

- figure 1 shows a perspective view of a working machine according to the present invention;

- figure 2 shows a view according to a circumferential section of a portion of the working machine;

- figure 3 shows a detail of figure 1 ;

- figure 4 shows a component of figure 1.

Detailed description of preferred embodiments of the invention

In the accompanying figures reference number 1 denotes a working machine that transfers energy to a processed fluid. This happens to the detriment of the mechanical work of a drive shaft of the machine. Such working machine 1 may be a fan, a blower or a compressor. Preferably, such working machine is axial, but in a particular solution it could also be a centrifuge; such types of working machines are well known in the technical sector and therefore will not be described further. The working machine 1 can be advantageously used in the aeraulic field. An application example could be the ventilation of rooms or the improvement of the heat exchange with an element to be cooled. Appropriately the working machine 1 comprises a bladed rotor 2 (also known as a propeller in the technical sector). It is rotatable about an axis 20 of rotation. Appropriately the working machine 1 comprises a central hub 21 to which the blade elements 22 are constrained. Such blade elements 22 are distributed circumferentially around the hub 21. They extend radially away from the hub 21. The hub 21 is keyed onto a drive shaft (activated directly or indirectly by an electric or thermal motor). The rotor 2 is crossed by the working gas (typically air). In the case of an axial working machine there is no rear support plate for supporting the blade elements 22 orthogonal to the axis 20 of rotation.

The blade elements 22 are advantageously airfoil-shaped.

The working machine 1 further comprises a stator 3 placed downstream of the rotor 2 (with respect to the movement flow of the gas, typically air). Such stator 3 faces the rotor 2. In particular the stator 3 is coaxial to the rotor 2. The stator 3 is fixed and during use is not rotatable about the axis 20 of rotation. Appropriately the stator 3 comprises a plurality of blades 30. The blades 30 are distributed along a circular crown.

Advantageously, the working machine 1 comprises vortex generators 4 applied to the blades 30 of the stator 3. The vortex generators 4 allow the separation of the boundary layer from the blades 30 to be delayed. Consequently, it is possible to use larger keying angles (angle A between the chord of the blades 30 and the axis 20 of rotation in figure 2) without incurring stall conditions. The boundary layer is a very thin layer in which the gaseous current is close to the blade. The separation (or detachment) of the boundary layer takes place as the latter is braked by the viscosity of the air external to the boundary layer. With the separation of the boundary layer vortices are generated that are no longer limited within the boundary layer, but start to affect a larger area around the surface. In this situation the vortex generators 4 have the task of transferring the amount of motion from the outside to the inside of the boundary layer.

Vortex generators 4 are well known elements as such and are used in different technological sectors (e.g. wings of aircrafts).

The presence of vortex generators 4 on the blades 30 of the stator 3 is important and more advantageous than their position on the rotor 2. In fact, their use in such context thanks to a larger keying angle A allows the axial dimensions of the working machine 1 to be reduced (as can be seen in figure 2, if the angle A increases the axial dimensions are reduced). A similar argument cannot be repeated for the rotor 2 as in that case the keying angle of the blades of the rotor 2 is imposed by fluid dynamic conditions and by the rotation speed of the rotor 2.

The vortex generators 4 comprise profiles 40 that extend transversally away from the blades 30. Appropriately the profiles 40 extend alongside each other.

Appropriately the profiles 40 are located on a surface of the blades 30 facing towards the rotor 2.

The profiles 40 are on suction faces 31 of the blades 30.

In particular, the vortex generators 4 or more precisely the profiles 40 are fin-shaped 41 . The profiles 40 can have, for example, a triangular or rectangular or trapezoidal extension. They define a blade. They can be straight or curved.

Appropriately the fins 31 have a minimum height of 60 millimetres and an extension along the axis 20 of rotation of the rotor 2 less than 100 millimetres.

Preferably, the profiles 40 have a ramp 42 and a subsequent step 43; the ramp 42 facilitates the lifting of the boundary layer and the step 43 determines the fall onto the blade 30 facilitating the re-attachment of the boundary layer. It is therefore appropriate for at least a part of the profiles 40 to be at an area in which the separation of the boundary layer has occurred as this facilitates the reattachment thereof.

In the preferred solution, from two to five vortex generators 4 are preferably applied to each of the blades 30 of the stator 3.

The blades 30 extend from a common base 300; the vortex generators 4 are placed at a radial distance from the base 300 that is preferably greater than 30% of the radial extension of the blades 30.

In fact, the detachment of the boundary layer is more likely to take place at a distance from the base 300. The base 300 is advantageously keyed onto a bearing of the shaft that places the rotor 2 in rotation.

Appropriately the rotor 3 may be of the modular type. In particular, it can comprise modular blades applicable to the base 300. The stator 3 can possibly comprise modular blades 30 constituted by the assembly of various radial portions.

In a particular solution not illustrated, there may appropriately be vortex generators present also along the blade elements 22 of the hub 21 . The blade elements 22 preferably have an airfoil profile. Also in this case the blade elements 22 are placed at the suction face of the blade elements 22. The present invention achieves important advantages.

In fact, it allows the efficiency of the working machine 1 to be optimised or however, with the same efficiency, allows the axial dimensions to be reduced.

The invention as it is conceived is susceptible to numerous modifications and variations, all falling within the scope of the inventive concept characterising it. Furthermore, all the details can be replaced with other technically equivalent elements. In practice, all the materials used, as well as the dimensions, can be any according to requirements.