CENTRIFUGAL FAN AND HEATING DEVICE PROVIDED THEREWITH

Abstract

The present invention relates to a centrifugal fan comprising a fan housing with a radial outlet opening arranged in a radial peripheral wall thereof, a rotor arranged rotatably in the fan housing and provided close to an axial rotation axis thereof with a rotor inflow opening, wherein the fan housing is provided close to the rotation axis of the rotor with an axial inlet opening, and a tube part which extends in the fan housing from the radial outlet opening arranged in the radial peripheral wall and inward along the radial peripheral wall. The invention further relates to a heating device comprising a burner with a fuel mixture infeed opening, a centrifugal fan according to the invention, and wherein a fluid connection is provided between the fuel mixture infeed opening of the burner and the outlet opening of the centrifugal fan.

Claims

1. A centrifugal fan, comprising: a fan housing with a radial outlet opening arranged in a radial peripheral wall thereof; and a rotor arranged rotatably in the fan housing; wherein the fan housing is provided with an inlet opening, and wherein a sound-reducing tube part extends in the fan housing from the radial outlet opening of the fan housing arranged in the radial peripheral wall and extending inward along the radial peripheral wall, radially relative to the rotor along and adjacently of the rotor, whereby the outlet opening is displaced inward from the peripheral wall of the fan housing into the fan housing.

2. The centrifugal fan as claimed in claim 1, wherein the fan housing comprises a pan-like part, in which the rotor is arranged, and a cover mounted releasably on the pan-like part.

3. The centrifugal fan as claimed in claim 2, wherein the tube part extends in the fan housing from the radial outlet opening arranged in the radial peripheral wall and inward along the radial peripheral wall at a distance relative to the cover.

4. The centrifugal fan as claimed in claim 3, wherein the tube part defines, of itself and without being closed by means of the cover, in the pan-like part of the fan housing a discharge passage closed all around relative to a throughflow direction and having an entrance thereof at a distance from the radial outlet opening.

5. The centrifugal fan as claimed in claim 2, wherein a depth of the pan-like part of the fan housing substantially corresponds to a thickness of the rotor in the axial direction thereof, and the tube part extends radially relative to the rotor along and adjacently of the rotor.

6. The centrifugal fan as claimed in claim 5, wherein the tube part has a dimension in axial direction of the rotor, which dimension is at most as great as the thickness of the rotor in the same orientation.

7. The centrifugal fan as claimed in claim 5, wherein the tube part comprises a curvature corresponding to and at some distance from a periphery of the rotor.

8. The centrifugal fan as claimed in claim 1, wherein the tube part extending in the fan housing comprises a tapering part which tapers in the direction of an entrance to a discharge passage defined by the tube part, which entrance is located at a distance from the radial outlet opening.

9. The centrifugal fan as claimed in claim 8, wherein the tapering part of the tube part comprises a curved contour which substantially corresponds to the outer periphery of the rotor.

10. The centrifugal fan as claimed in claim 8, wherein the distance between the outer periphery of the rotor and the wall of the tube part facing toward the rotor lies in the range of 1-10 millimeters (mm).

11. The centrifugal fan as claimed in claim 8, wherein the tube part extending in the fan housing comprises a further tube part of substantially constant cross-section between the radial peripheral wall and the tapering part.

12. The centrifugal fan as claimed in claim 11, wherein the tube part extending in the fan housing comprises between the radial peripheral wall and the open end of the tube part at least one passage arranged in the peripheral wall of the tube part.

13. The centrifugal fan as claimed in claim 12, wherein the passage arranged in the peripheral wall of the tube part is arranged in the area between halfway along the tapering part and the radial peripheral wall.

14. The centrifugal fan as claimed in claim 12, wherein the passage arranged in the peripheral wall of the tube part is arranged in the further tube part of substantially constant cross-section.

15. The centrifugal fan as claimed in claim 12, wherein the passage arranged in the peripheral wall of the tube part is arranged in the area between halfway along the further tube part of substantially constant cross-section and the transition between the tapering part and the further tube part of substantially constant cross-section.

16. The centrifugal fan as claimed in claim 14, wherein the passage arranged in the peripheral wall of the tube part is arranged substantially adjacently of the transition between the tapering part and the further tube part of substantially constant cross-section.

17. The centrifugal fan as claimed in claim 1, wherein the inlet opening of the fan housing is axial and provided with a suction conduit for drawing in a fuel/air mixture, wherein the suction conduit extends in radial direction along the fan housing so that an indrawn fuel/air mixture is deflected close to the inlet opening from a radial flow direction to an axial flow direction.

18. The centrifugal fan as claimed in claim 17, wherein the suction conduit comprises a mixing part which is in fluid connection with a fuel feed conduit and which is further in fluid connection with an air supply.

19. The centrifugal fan as claimed in claim 18, wherein the fuel feed conduit is an inner conduit arranged inside the fluid connection to the air supply.

20. The centrifugal fan as claimed in claim 18, wherein the fluid connection to the air supply comprises an open connection to the environment.

21. The centrifugal fan as claimed in claim 18, wherein the mixing part is provided with a venturi.

22. A heatng device, comprising: a burner with a fuel mixture infeed opening; and a centrifugal fan according as claimed in claim 1; wherein a fluid connection is provided between the fuel mixture infeed opening of the burner and the outlet opening of the centrifugal fan.

Description

[0039] Preferred embodiments of the present invention are further elucidated in the following description with reference to the drawing, in which:

[0040] FIG. 1 is a cut-away perspective view of a heating device comprising a centrifugal fan according to the invention;

[0041] FIGS. 2A and 2B are perspective views of the centrifugal fan of FIG. 1;

[0042] FIGS. 3A and 3B are perspective views according to FIG. 2A, wherein the suction conduit is cut away and FIG. 3B shows an exploded view;

[0043] FIG. 4 is a perspective and partially cut-away view of the suction conduit of the centrifugal fan;

[0044] FIG. 5 is a schematic view of the suction conduit of the centrifugal fan;

[0045] FIG. 6 is a perspective view of the fan housing with a rotor arranged therein and tube part according to the invention provided therein; and

[0046] FIG. 7 is a perspective view according to FIG. 6 wherein the rotor is omitted.

[0047] Heating device 1 in FIG. 1 comprises a housing 2 in which a burner 4 is arranged. Burner 4 is provided via a pressure conduit 6 with a fuel/air mixture which is drawn in by a centrifugal fan 24 via a suction conduit 10. Provided in suction conduit 10 is a mixing chamber 12 in which air drawn in by a fluid connection 14 is mixed with fuel drawn in by a fuel feed conduit 16 from a gas block 18. Centrifugal fan 24 is driven by a motor 8.

[0048] Centrifugal fan 24 comprises a fan housing 26 closable with a cover and having a radial outlet opening 30 arranged in a radial peripheral wall 28 thereof. In the shown embodiment the radial outlet opening 30 runs in an approximately tangential direction to a coupling part 32 to which pressure conduit 6 is connectable (FIGS. 2A and 2B).

[0049] A rotor 34 is arranged rotatably in fan housing 26. Rotor 34 is provided close to an axial rotation axis 36 thereof with a rotor inflow opening 38. Fan housing 26 is provided close to rotation axis 36 of rotor 34 with an axial inlet opening 40.

[0050] When rotor 34 is driven rotatably in fan housing 26 by motor 8, the revolving rotor 34 exerts a centrifugal force on the fluid present close to rotor inflow opening 38. This fluid is hereby moved in radial direction outward in the direction of radial peripheral wall 28 of fan housing 26. Because the fluid flows away from rotor inflow opening 38, an underpressure is created there which ensures that centrifugal fan 24 draws in fresh fluid via axial inlet opening 40 of fan housing 26. A suction conduit 10 extending radially along fan housing 26 is connected to axial inlet opening 40. The substantially right-angled deflection of the fuel/air mixture at the transition from suction conduit 10 to axial inlet opening 40 of fan housing 26 has a favourable effect on the thermoacoustic behaviour, wherein this measure contributes toward the sound reduction obtained by a tube part 42 to be further elucidated below and extending in fan housing 26 from radial outlet opening 30 arranged in radial peripheral wall 28 and inward along radial peripheral wall 28.

[0051] The fluid moved radially outward by rotor 34 is compressed to some extent and, due to the overpressure and the velocity imparted by rotor 34, will flow away via radial outlet opening 30 out of fan housing 26 in the direction of burner 4 of heating device 1, such as via the pressure conduit 6 shown in FIG. 1 which is connectable to coupling part 32. Centrifugal fan 24 in this way provides for a continuous flow of fluid via axial inlet opening 40 to radial outlet opening 30.

[0052] As shown in FIGS. 3A and 3B, suction conduit 10 comprises a mixing part 12 which is in fluid connection with fuel feed conduit 16 and further has a fluid connection 14 to an air supply. Fuel and air are mixed in mixing part 12 to form a fuel/air mixture which is guided further from mixing part 12 through suction conduit 10 to axial inlet opening 40 of fan housing 26.

[0053] In the shown embodiment fuel feed conduit 16 is an inner conduit which is arranged inside the fluid connection 14 to the air supply. Fluid connection 14 with the air supply is here an open connection to the environment.

[0054] Mixing part 12 is provided with a venturi 20 which provides an additional suctioning effect. Just as suction conduit 10 in which it is arranged, venturi 20 is oriented in radial direction, i.e. substantially transversely of the flow through axial inlet opening 40 (see among others FIGS. 4 and 5).

[0055] Centrifugal fan 24 has a tube part 42 which extends in fan housing 26 from radial outlet opening 30 arranged in radial peripheral wall 28 and inward along radial peripheral wall 28 (FIGS. 6 and 7). The outlet opening is in fact hereby displaced inward from radial peripheral wall 28 of fan housing 26 into fan housing 26.

[0056] In the shown embodiment tube part 42 has, extending inward from radial peripheral wall 28 of the fan housing, first a part 46 of a substantially constant cross-section which transposes into a tapering part 44. Fuel/air mixture leaving fan housing 26 follows the reverse path and enters tube part 42 via the open outer end 50. Tapering part 44 then widens in downstream direction, whereby a pressure drop occurs in the main flow through tube part 42 flowing through opening 50 before the main flow reaches the part 46 of substantially constant cross-section.

[0057] Close to the transition between tapering part 44 and the part 46 of substantially constant cross-section a passage 52 is arranged in the wall of tube part 42. Because of this passage 52 an additional flow of fuel/air mixture moved radially outward by rotor 34 will occur in tube part 42 which enters into an interaction with the main flow already flowing there. It has been found experimentally that this is favourable in preventing thermoacoustic sound effects. As a result of the interaction which occurs a favourable thermoacoustic effect results which substantially wholly suppresses the undesired humming sound.

[0058] It is advantageous for passage 52 to be arranged close to the transition between tapering part 44 and the part 46 of substantially constant cross-section because the fuel/air mixture has the opportunity between rotor 34 and wall 48 of tapering part 44 to build up pressure.

[0059] In order on the one hand to enhance this pressure buildup of fuel/air mixture upstream of passage 52 and on the other enable a maximum flow rate of the main flow through tube part 42 the tapering part 44 is embodied with a curvature corresponding to the outer periphery of rotor 34.

[0060] Fan housing 26 comprises a pan-like part 41 in which rotor 34 is arranged, and a cover as in FIGS. 4 and 5 mounted releasably on the pan-like part. Tube part 42 extends in fan housing 26 in tangential direction from radial outlet opening 30 arranged in radial peripheral wall 28 and inward along radial peripheral wall 28 at a distance relative to the cover. Tube part 42 closes all around, even without the cover on pan-like part 41. The centrifugal fan is such here that tube part 42 defines, of itself and without being closed by means of the cover of FIGS. 4 and 5, in pan-like part 41 of fan housing 26 a discharge passage closed all around and having an entrance 50 as in FIG. 6 at a distance from radial outlet opening 30.

[0061] In this embodiment with a pan-like part 41 and a cover as in FIGS. 4 and 5 the centrifugal fan according to the present disclosure is such that a depth of pan-like part 41 of fan housing 26 substantially corresponds to a thickness of rotor 34 in the axial direction thereof. Tube part 42 extends radially relative to rotor 34 along and adjacently of rotor 34 so as to define a substantially tangentially oriented passage. The centrifugal fan is further such here that tube part 42 has a dimension in axial direction of rotor 34 which is at most as great as the thickness of rotor 34 in the same orientation. The tube part is centered here at a height or thickness of rotor 34 whereby swirling airflows are minimized in height or thickness direction of the rotor. A compact configuration can thus be realized which, by means of the optionally also realized lengthening of the discharge passage to open outer end 50, brings about a drastic reduction in noise when compared to the single radial outlet opening 30.

[0062] Tube part 42 further comprises a curvature 44 corresponding to and at some distance from a periphery of rotor 34.

[0063] Although it shows a preferred embodiment of the invention, the above described embodiment is intended only to illustrate the present invention and not in any way to limit the specification of the invention. When measures in the claims are followed by reference numerals, such reference numerals serve only to contribute toward understanding of the claims, but are in no way limitative of the scope of protection. The rights described are defined by the following claims, within the scope of which many modifications can be envisaged.