EP1503084B1 - Blower - Google Patents

Abstract

The fan arrangement (10) has a rotor with a semicircular-section circular groove near its periphery, containing radial vanes. There is a semicircular-section circular groove (14) in the fixed fan housing (12), cooperating with the groove in the rotor to make a circular-section channel. There may be a single barrier in a region (30) between the air inlet (34) and the air outlet (26). A pressure relief channel (36) runs from an intake (38) near the outlet to an outlet (40) near the inlet.

Description

The present invention relates to a blower, in particular a combustion air blower for a vehicle heater, and a method for operating such a blower.

In heaters, such as those used in vehicles, for example, as auxiliary heaters or heaters, commonly referred to as side channel blower blowers are used to feed combustion air into a burner. Such blowers have an annular conveying channel over which the conveying vanes of a conveyor wheel covering the conveyor channel in succession in the circumferential direction move sequentially in order to convey air from an inlet region to an outlet region of the conveyor channel in this manner. Due to the pressure increase occurring during the conveying process, a lower pressure prevails in the region of the inlet region of the conveying region than in the region of the outlet region. In order to avoid a flow short circuit in the blower, a so-called breaker is provided between the outlet region and the inlet region, over which the conveyor blades move with a comparatively small distance. That is, when a delivery volume of the delivery wheel formed between two circumferentially successive blades enters the region of the breaker, air of comparatively high pressure is trapped in this region. If this volume then moves further in the direction of the entry region, then, when this volume has moved beyond the interrupter, a sudden relaxation of the initially still pressurized air in this volume will occur at the entry region. This sudden relaxation Affects the structure of the spiral flow or spiral flow in the delivery channel near the inlet region and thus leads to a change in the maximum achievable delivery pressure. Furthermore, this spontaneous relaxation leads to perceptible noises, which represent a comfort impairment.

A blower according to the preamble of claim 1 is known from US-A-3,942,906. In this known fan leads out of the breaker area a branch line, which opens again downstream of the inlet opening in the annular channel. In this way, a relaxation of the trapped air volumes can occur in the breaker area. The branch line opens into the annular channel from radially outside.

DE-C-902 074 shows a fan in which leads away from the breaker area a relaxation channel, which introduces relaxing air in the interruption area in the inlet opening.

US-A-3,356,033 shows a blower in which the inlet opening into an annular channel is provided in a radially inner region of the breaker.

From US-A-3,951,567 a fan is known in which the inlet opening and the outlet opening are each arranged approximately in the radially central region of an annular channel.

From DE 44 24 629 C1, a side channel blower is known in which the inlet opening arranged downstream of the breaker area in the flow direction is elongated in the circumferential direction and arranged at the radially inner end region of the annular channel.

It is the object of the present invention to design a generic blower so that better flow conditions can be obtained. According to the invention, this object is achieved by the blower defined in claim 1.

This blower, in particular combustion air blower for a vehicle heater, comprises a blower housing, a conveyor channel formed in the blower housing, annularly extending around an axis of rotation and open on one axial side, a delivery wheel which covers and overlays the delivery duct on its axially open side on the blower housing the rotation axis is rotatably supported and has a plurality of circumferentially successive conveying blades which move upon rotation of the conveying wheel in a direction of movement over the conveying channel, an inlet region for entry of air to be conveyed into the conveying channel, an outlet region for exit from along the conveying channel conveyed air from the conveying channel, in the direction of movement of the conveying blades following the outlet region and the inlet region in advance an interruption region in which the conveying channel is interrupted in the circumferential direction, as well as a Relaxation channel arrangement, which provides a connection between the interruption area and the delivery channel.

In the blower according to the invention, the inclusion of pressurized air when crossing a breaker between the inlet region and the outlet region of the conveyor channel avoided by leading away from the interruption area a relaxation channel. In this way it is prevented that during the further movement of this volume, a sudden relaxation occurs when this comes back into the region of the inlet region. Nevertheless, since the expansion channel arrangement is still open into the delivery channel, the occurrence of considerable delivery losses is avoided, so that an impairment of the delivery efficiency or of the efficiency in the fan according to the invention does not occur.

The expansion channel arrangement has an entry area in the interruption area and has an exit area in which it is open towards the delivery channel.

For a high conveying efficiency, it is necessary or advantageous if the air conveyed in the conveying channel from the inlet region to the outlet region has a spiral or helical flow movement direction. In order not to impair this flow in the embodiment of a blower according to the invention or to support the formation of a helical or spiral flow, it is provided that the expansion channel arrangement opens radially inward into the conveying channel such that the air leaving the expansion channel arrangement in the direction of the conveying channel an air flow in the conveying channel with helical flow movement direction has a substantially tangential or secant and the flow direction of flow of the air flow rectified flow direction.

In order to be able to provide an efficient separation between the outlet region and the inlet region of the conveyor channel in order to prevent a delivery short circuit, and nevertheless to be able to provide the pressure relief desired according to the invention in a simple manner, it is further proposed that the interruption region has an interruption wall region, which the Scrape blades with low axial distance, and that the inlet region of the expansion channel arrangement comprises at least one inlet opening in the interruption Wandungsungsbereich.

In order to ensure a gradual pressure reduction upon movement of a volume of air under pressure to the interruption area, it is proposed that the at least one inlet opening have an increasing opening width in the direction of movement of the conveying blades.

Furthermore, it is possible, for example, that in the outlet region the expansion channel arrangement in the direction of movement of the conveyor blades downstream with respect to the inlet region the delivery channel opens into the delivery channel. Alternatively, it can of course also be provided that in the outlet region the expansion channel arrangement opens into the conveying channel in the region of the inlet region thereof. This also means, in particular, that the exit region can open into a channel, which then opens into the delivery channel in the entry region thereof.

The outlet region may have at least one outlet opening.

wobei

• n = Drehzahl des Förderrads,
• k = eine ungerade ganze Zahl (1, 3, 5, 7, ...)
• z = Anzahl der Förderschaufeln,
• c = Phasengeschwindigkeit der in der geförderten Luft sich ausbreitenden Wellen,
• L = Länge der Entspannungskanalanordnung.

According to a further aspect of the present invention, this provides a method for operating a blower according to the invention, in which method for operating a blower, the conveyor wheel is driven at such a speed for rotation about the axis of rotation that substantially the following relationship is fulfilled: $$\mathrm{n}\mathrm{=}\left(\mathrm{k}\mathrm{•}\mathrm{c}\right)\mathrm{:}\left(\mathrm{2}\mathrm{•}\mathrm{z}\mathrm{•}\mathrm{L}\right)\mathrm{.}$$

in which

• n = speed of the delivery wheel,
• k = an odd integer (1, 3, 5, 7, ...)
• z = number of impeller blades,
• c = phase velocity of the waves propagating in the conveyed air,
• L = length of the expansion channel arrangement.

This relationship therefore means that it is ensured by a defined setting of the speed of the feed wheel in a certain speed range or speed range that by tuning the speed to the length of the expansion channel arrangement destructive interference of the pressure fluctuations in the inlet region of the conveyor channel and the pressure fluctuations in the air, which Relaxation channel arrangement leaves in the direction of delivery channel, is generated. Upon fulfillment of this relationship, a phase shift occurs by half the wavelength of the pressure fluctuations, so that a pressure maximum in the delivery channel is compensated or approximately compensated by a pressure minimum of the air leaving the expansion channel arrangement.

Another problem with such blowers or side channel blowers is that in general their conveying capacity depends on the size, in particular the length, of the conveying channel. Due to the fact that the space available for such devices in a vehicle is limited, the fan outer dimension is correspondingly limited, so that in general the achievement of higher delivery volumes by increasing the speed of the feed wheel is accomplished. However, a higher Förderraddrehzahl leads correspondingly to a higher load of the drive motor or generally a higher load on the entire system, so that in particular in the respect to each other moving assemblies, such as grinder of the drive motor, bearings, etc., a lifetime reduction are accepted if higher production capacities are to be achieved. In addition, an increase in speed generally results in a significant increase in the noise generated in the region of such a fan, which is particularly the case in use Motor vehicles is not desired by the associated loss of comfort.

According to the invention, it can therefore be further provided that a radial dimension of the inlet opening is smaller than a radial dimension of the conveyor channel in the inlet area.

It has been found that by a defined selection of the geometry of the inlet opening, a change in the delivery characteristic of such a blower can be achieved in that at a certain pressure difference between the inlet region and the outlet region, a larger volume flow can be generated or at gleichhaltenem Volume flow a larger pressure difference can be generated without it would be necessary to increase the speed of the feed wheel.

The conveying capacity of such a blower can be further improved by virtue of the fact that a circumferential dimension of the inlet opening is greater than the radial dimension of the inlet opening. That is, by designing such an opening with slot-like contour can continue to increase without increasing the speed of the feed wheel, a larger volume flow or set at the same volume flow, a higher pressure difference.

According to a particularly advantageous embodiment variant, it can be provided that a radially inner end region of the inlet opening lies in or near a radially inner end region of the conveyor channel, and / or that a radially outer end region of the inlet opening lies in or near a radially central region of the conveyor channel.

Fig. 1

den prinzipiellen Aufbau eines Seitenkanalgebläses;

Fig. 2

eine prinzipielle Axialansicht eines erfindungsgemäß ausgestalteten Seitenkanalgebläses;

Fig. 3

eine Längsschnittansicht eines gemäß den Prinzipien der Erfindung aufgebauten Seitenkanalgebläses;

Fig. 4

in den Darstellungen a) bis d) verschiedene Formgebungen von Eintrittsöffnungen einer Entspannungskanalanordnung;

Fig. 5

in den Darstellungen a) und b) verschiedene Formen von Austrittsöffnungen einer Entspannungskanalanordnung;

Fig. 6

eine der Fig. 2 entsprechende Ansicht einer alternativen Ausgestaltungsart eines erfindungsgemäßen Gebläses;

Fig. 7

eine Teil-Längsschnittansicht eines erfindungsgemäßen Gebläses;

Fig. 8

eine der Darstellung der Fig. 6 entsprechende Axialansicht des in Fig. 7 gezeigten Gebläses;

Fig. 9

ein Kennliniendiagramm, das den Zusammenhang zwischen dem Volumenstrom durch den Förderkanal und der zwischen dem Eingangsbereich und dem Ausgangsbereich erreichbaren Druckdifferenz veranschaulicht.

The present invention will be described below in detail with reference to the accompanying drawings with reference to preferred embodiments. It shows:

Fig. 1

the basic structure of a side channel blower;

Fig. 2

a schematic axial view of an inventively designed side channel blower;

Fig. 3

a longitudinal sectional view of a constructed according to the principles of the invention side channel blower;

Fig. 4

in the representations a) to d) different shapes of inlet openings of a relaxation channel arrangement;

Fig. 5

in the representations a) and b) different forms of outlet openings of a relaxation channel arrangement;

Fig. 6

a view corresponding to Figure 2 of an alternative embodiment of a blower according to the invention.

Fig. 7

a partial longitudinal sectional view of a blower according to the invention;

Fig. 8

a corresponding to the representation of Figure 6 axial view of the fan shown in Figure 7;

Fig. 9

a characteristic diagram illustrating the relationship between the flow rate through the delivery channel and the achievable between the input range and the output pressure difference.

First, with reference to FIG. 1, a blower 10 which can be used in vehicle heaters and generally referred to as a side channel blower will be described. The side channel blower 10 comprises a blower housing 12, in which a conveying channel 14, which is arranged concentrically with respect to a rotation axis A and extends in an annular manner around the rotation axis A, is formed. The delivery channel 14, which may for example have a circular segment-like cross-sectional contour, is axially open on one side and is covered there by a delivery wheel generally designated 16. The conveyor wheel 16 is driven by a drive motor, not shown, for rotation about the axis of rotation A and is positioned with respect to the blower housing 12 so that it lies with its side facing the conveyor channel 14 at a short distance above the blower housing 12 and the conveyor channel 14 and thus with a Förderradschale 18 substantially closes the conveyor channel 14 tight. The Förderradschale 18 has in the conveyor channel 14 covering area thereof a shape, the essentially also corresponds to the shape of the conveyor channel, is thus also formed for example with circular or circular segment-like cross-sectional contour and carries in this contour a plurality of circumferentially successively arranged conveyor blades 20. Upon rotation of the conveyor wheel 16 in a direction R, the conveyor blades move 20th also in this direction R above the conveying channel 14, so that in the conveying channel 14 or in the volume range of the conveying wheel 16 existing air is conveyed in a conveying direction F, which essentially corresponds to the direction of movement R of the conveying wheel 16 and the conveying blades 20. This air to be conveyed passes into the region of the conveying channel 14 via an inlet region 20 which is only generally recognizable in FIG. 1 and which, for example in the region of the conveying channel 14, comprises an inlet opening which is not recognizable any further. The air conveyed away from the inlet region 22 in the conveying direction F then moves in the direction of an outlet region 24. In this outlet region 24, an outlet opening 26 is provided, via which the air leaving the conveying channel 14 passes into an outlet channel 28 and from there, for example, into the combustion chamber of a vehicle heater.

Between the inlet region 22 and the outlet region 24 there is an interruption region 30. This interruption region 30, which is essentially radially extending and thus configured in the manner of a sector of a circle, interrupts the delivery channel 14 in the circumferential direction, so that a flow or delivery short circuit in the delivery channel 14 is avoided. In particular, the interruption region 30 comprises a wall 32 which closes off the outlet opening 26 in the axial direction, in particular on that axial side on which the delivery channel 14 is open. The positioning of this interrupt wall 32 is such that the conveyor wheel 16 with its conveying blades 20 when passing over the interruption area 30 with only a very small distance over this wall 32 moves away.

Since the pressure in the air rises when conveying air from the inlet region 22 to the outlet region 24 and thus the maximum pressure is reached in the region of the outlet region 24, when an air volume trapped between two circumferentially immediately following conveying blades 20 becomes moved over the wall 32, this volume enclosed and basically maintained due to the small distance between the conveyor blades 20 and the wall 32 of this pressure also. If the conveying blade 20, which runs ahead in the direction of movement R, then moves out of the region of the wall 32 into the region of the inlet region 20, a spontaneous pressure release would occur, which on the one hand adversely affects the flow characteristics in the inlet region 20 or in the entire conveying channel 14, in particular the Construction of a spiral or spiral flow affected, on the other hand leads to pressure fluctuations and pulsations, which also affect the operating characteristics and can lead to audible noise.

To counteract this problem, the present invention provides for measures which have been described in detail below with reference to FIGS. 2 to 6. Fig. 2 shows first in an axial view simplifies the above-described fan housing 1 2 with the conveyor channel formed therein 14. It can be seen the inlet region 22 with the inlet opening 34, the interruption area 30 with the swept by the conveying blades 20 at a small distance wall 32 and the As already indicated above, in the inlet region 22 in the region of the conveying channel 14 entering or sucked there air is conveyed in the conveying direction F toward the outlet region 24, wherein by interaction of the conveying channel 14 with the feed wheel 16th the illustrated in Fig. 3 spiral or spiral flow S is constructed. 2 shows a relaxation channel 36. This expansion channel 36 extends from the interruption region 30 into the delivery channel 14, and Although in an upstream region, so for example, one of the inlet opening 34 and the inlet region 22 nearby area. An inlet opening 38 of the expansion channel 36 is provided in the wall 32, and the expansion channel 36 leads from this inlet opening 38 to an outlet opening 40 which is located in the embodiment of FIG. 2 in the conveying direction F shortly after the inlet opening 34 of the conveying channel 14.

By means of this expansion channel 36 it is achieved that the above-mentioned volume of air formed or enclosed between two conveying blades 20 which follow one another directly in the direction of movement R can gradually relax when passing over the interruption region 30 via the expansion channel 36 to the conveying channel 14, so that, even before this volume returns to the inlet region 22, a significantly reduced pressure is present and the above-mentioned pulsations do not occur. Nevertheless, the relaxation in the direction of the delivery channel 14 ensures that delivery losses are largely avoided and thus the delivery efficiency and the efficiency of such a blower 10 can be significantly improved.

According to a further advantageous aspect, which is illustrated more clearly in FIG. 3, in the fan 10 according to the invention the expansion channel 36 is guided or the outlet opening 40 is positioned such that the direction of relaxation E in the discharge channel 36 flows through or exits Air supports the spiral or helical flow built up in the delivery channel 14 or supports the structure of this helical flow. It can be seen in FIG. 3 that the expansion channel 36 is positioned such that the air leaving it is guided essentially tangentially or secantially to the spiral or spiral flow with essentially the same flow direction and thus mixed or connected with this spiral flow that the helical flow is not impaired but rather supported. This also results in a significant increase in the efficiency result. In particular, this can be achieved by virtue of the fact that the air entering the region of the delivery channel 14 in the direction E has the same flow direction or flow component there as the spiral or helical flow present in this region.

In Fig. 4, various possibilities of shaping the inlet opening 38 of the expansion channel 36 are shown in the illustrations a) to d). It can be seen in Fig. 4a), the circular shape shown in Fig. 2 while in Fig. 4b) an elongated, however, however, rounded in the longitudinal ends shape is present. In Fig. 4c), a triangular shape is present, wherein in the direction of movement R, as well as in the two previously described shapes, the width B, ie the dimension transverse to the direction of movement R, increases. In FIG. 4d), a shaping with a plurality of triangular opening segments is shown, whereby in each of these segments and thus also in the combination of the segments, the total width or effective width B in the direction of movement R increases. This increase in the width B of the inlet opening 38 results in an optimized expansion behavior when the air volume trapped between two immediately successive conveyor blades 20 moves into the region of the inlet opening 38.

In Fig. 5, two possible shapes of the outlet opening 40 are shown, wherein the Fig. 5a) again represents the circular shape, while in Fig. 5b), the elongated in the direction of movement R shape is present. This shaping can be adapted to the requirement to support the helical flow or its structure optimized.

A modified embodiment of the blower 10 according to the invention is shown in FIG. It can be seen, however, that the expansion channel 36 with its outlet opening 40 in the inlet region 22 of the conveyor channel 14 is open where the inlet opening 34 is positioned. In other words, the air leaving the expansion channel 36 via the outlet opening 40 thereof enters into the delivery channel 14 in the region of the inlet opening 34, together with the air sucked in from the outside.

Dabei entspricht die Zahl k einer ungeraden ganzen Zahl, da destruktive Interferenz nicht nur bei einer Verschiebung von λ/2, sondern beispielsweise auch bei einer Verschiebung von 3λ/2,5λ/2 usw. erlangt wird.Another possibility to ensure that the occurrence of pressure pulsations as far as possible in the blower according to the invention is the tuning of the length of the expansion channel 36 to the frequency or the wavelength of these pressure pulsations. If, for example, the delivery wheel 20 rotates at a certain speed n, then forcibly a pressure fluctuation with the frequency f = n · z will occur. Here, z is the number of conveying blades 20 on the feed wheel 16 again. From this pulsation frequency f thus determined, the wavelength can be determined as λ = c / f via the relationship with the phase velocity c of the waves propagating in the gaseous medium air. If, by means of a corresponding length dimension of the expansion channel, a phase shift of the pulsations transported via the expansion channel 36 with respect to the pulsations generated in the conveyor channel 14 by λ / 2 occurs, destructive interference and thus a marked reduction in the delivery channel 14 occur pulsations. In order to be able to obtain this destructive interference, there is generally the following relationship between the rotational speed n of the delivery wheel 20 and the length L of the expansion channel 36: $$\mathrm{n}\mathrm{=}\left(\mathrm{k}\mathrm{•}\mathrm{c}\right)\mathrm{:}\left(\mathrm{2}\mathrm{•}\mathrm{z}\mathrm{•}\mathrm{L}\right)\mathrm{,}$$

In this case, the number k corresponds to an odd integer, since destructive interference is obtained not only with a shift of λ / 2, but also, for example, with a shift of 3λ / 2.5λ / 2 and so on.

This has the consequence that at one time by the structural design of the blower 10 predetermined length L of the expansion channel 36 during operation of the fan 10, the speed n of the feed wheel 20 is preferably set so that it is in the range of speed n, as they are made of the preceding equation taking into account the quantities L and z, which are the only constructive quantities. It goes without saying that it is also possible to work with other speeds for adjusting the delivery rate, which deviates from the speed optimized with regard to the reduction in pulsation. Basically, but taking into account the preceding context, the blower 10 can be constructively designed so that when the combustion air required for a normal heating operation, the feed wheel 16 can be operated at the optimized speed.

It will be understood that various changes may be made to the blower of the invention without, however, departing from the spirit of the present invention. Thus, of course, a plurality of expansion channels 36 may be provided, so that a relaxation channel arrangement so not only the shown in the figures single expansion channel 36, but for example, two, three or four such expansion channels 36 may then, for example, at different areas to the delivery channel 14 out are open or whose inlet openings 38 are also positioned in different areas of the interruption area 30. Furthermore, it goes without saying that the delivery channel 36 or, if appropriate, the plurality of delivery channels 36 can be integrated into the latter by appropriate design of the fan housing 12 or can be created by providing separate, hose-like connections. Also the leadership or

Shaping these expansion channels can be optimized to achieve a gradual pressure relief, for example, it is possible to provide an undulating shaping or to hold a throttle point.

Another aspect of the invention will be described below with reference to FIGS. 7-9. A further variant of a blower 10 is shown in FIGS. 7 and 8, in which, although not the previously described expansion channel or a corresponding arrangement is provided, but in the area of the inlet opening 34 is provided by special design measures that a Such blower 10 has a further improved operating characteristic. It should be expressly understood that the aspects described below with reference to FIGS. 7-9 can of course be combined with the previously described aspects. In particular, already mentioned FIG. 6 shows a variant in which the inlet opening 34 essentially satisfies the conditions for the geometry of the inlet opening explained below.

It can be seen in particular in Figs. 7 and 8, that the inlet opening 34 is dimensioned so that, unlike, for example, in the embodiment of FIG. 2, not the entire radial region of the conveying channel 14 from its radially inner dimension r _i to its radially outer dimension r _a covered. Rather, in the radial direction, the inlet opening 34 is dimensioned so that its radially inner end portion 40 substantially coincides with the radially inner end portion 42 of the conveyor channel 14 and is positioned there, while its radially outer end portion 44 approximately with the radially central portion 46 of the conveyor channel 14 matches or lies there. That is, in this embodiment variant, the inlet opening 34 covers only the radially inner half portion of the conveying channel 14, while a corresponding overlap in the radially outer half portion is not present.

Furthermore, the inlet opening 34 is dimensioned such that its circumferential extent L _{S is} greater than its radial extent B _S. With a correspondingly long configuration in the circumferential direction, therefore, a curved slot-like contour results. Also, the recognizable in Fig. 6 substantially elliptical configuration can be used here.

The transition from a substantially circular inlet opening 34, which moreover covers approximately the entire radial region of the conveying channel 14, to the geometry shown in FIGS. 7 and 8 and also with an elongated contour in the circumferential direction and positioning in the radially inner region of the Delivery channel 14, a subsequently explained with reference also to FIG. 9 change in the delivery and operating characteristics of such a blower 10 is obtained.

It can be seen in Fig. 9, first on the basis of the rectilinear curve or line a in a blower according to FIG. 2 generally existing relationship between the flow rate V _S (ie per unit time the conveyor fan 10 passing through volume of the medium to be delivered) and the between the inlet region 22 and the outlet region 24 constructed pressure difference .DELTA.P. In the transition to a geometry, as shown for example in FIGS. 7 and 8, this characteristic, as can be seen with reference to the line b, becomes flatter. That is, while it takes the maximum achievable flow rate V _S from a value V to a value V _{Smaxa Smaxb} to, while the maximum pressure P _maxb compared to the attainable at the line a maximum pressure P _maxa decreases. The curves or lines a and b intersect at a volume flow V _Smin . In the direction of larger volume flows V _S , the curve b lies over the curve a, while in the direction of smaller volume flows V _S , the curve a lies above the curve b.

The consequence of this characteristic shift is that, when working with a volume flow above the volume flow V _Smin , in which in the 7 and 8, the pressure difference ΔP achievable at a given volume flow V _{S is} significantly higher, while at a given pressure difference ΔP a significantly higher volume flow can be achieved or, as can be seen, the maximum achievable volume flow increases, all of this always below the specification As can be ensured by the operating requirements and in particular by the design of such a blower 10 that in normal operation of this blower 10 always works in the volume flow range above the flow rate V _Smin , can through the In FIGS. 6-8, the configuration or position of the inlet opening 34 shown, a substantially more efficient operation of the fan 10 can be ensured. That is, at a given speed significantly more volume of the medium to be conveyed through the blower 10 or at a given volume throughput or volumetric flow V _S , the speed can be reduced at the transition to the special geometry of the inlet opening 34. The consequence of this, in turn, is that on the one hand the noise impairment is reduced and on the other hand the mechanical load on the blower, in particular the storage or grinding areas, is reduced.

All the above-mentioned aspects can be achieved in the blower 10 shown in FIGS. 7 and 8 and also in FIG. 6, without the total circumferential length of the delivery channel 14 being increased with a corresponding increase in the outer circumference of the blower 10.

Claims (11)

1. A fan, in particular a combustion air fan for a vehicle heating appliance, comprising:

   - a fan housing (12);

   - a conveying duct (14) which is formed in the fan housing (12), extends annularly around an axis of rotation (A) and is open on one axial side;

   - an impeller (16) which is provided on the fan housing (12) overlapping the conveying duct (14) on its axially open side and is mounted rotatably about the axis of rotation (A) and has a plurality of impeller blades (20) which are arranged consecutively in a peripheral direction and which upon rotation of the impeller (16) move in a direction of movement (R) over the conveying duct (14),

   - an inlet zone (22) for the inlet of air to be conveyed into the conveying duct (14),

   - an outlet zone (24) for the outlet of air conveyed along the conveying duct (14) from the conveying duct (14),

   - in the direction of movement (R) of the impeller blades (20) following the outlet zone (24) and preceding the inlet zone (22) an interrupted zone (30) in which the conveying duct (14) is interrupted in a peripheral direction,

   - an expansion duct arrangement (36) which provides a connection between the interrupted zone (30) and the conveying duct (14), wherein the expansion duct arrangement (36) has an inlet zone (38) in the interrupted zone (30) and has an outlet zone (40), in which it is open towards the conveying duct (14),

   characterised in that the expansion duct arrangement (36) discharges radially inwards into the conveying duct (14) in such a way that the air leaving the expansion duct arrangement (36) in the direction of the conveying duct (14) has, in relation to an air stream (S) in the conveying duct (14) with a helical direction of flow movement, a flow direction (E) which is substantially tangential or secantial and which is equidirectional to the direction of flow movement of air stream.
2. A fan according to Claim 1, characterised in that the interrupted zone (30) has an interruption wall zone (32) over which the impeller blades (20) pass at a small axial distance, and in that the inlet zone (38) of the expansion duct arrangement (36) comprises at least one inlet opening (38) in the interruption wall zone (32).
3. A filter fan according to Claim 2, characterised in that the at least one inlet opening (38) has an opening width (B) increasing in the direction of movement (R) of the impeller blades (20).
4. A fan according to any one of Claims 1 to 3,
   characterised in that in the outlet zone (40) the expansion duct arrangement (36) discharges into the conveying duct (14) in the direction of movement (R) of the impeller blades (20) downstream with respect to the inlet zone (22) of the conveying duct (14).
5. A fan according to any one of Claims 1 to 3,
   characterised in that in the outlet zone (40) the expansion duct arrangement (36) discharges into the conveying duct (14) in the vicinity of the inlet zone (22) thereof.
6. A fan according to any one of Claims 1 to 5,
   characterised in that the outlet zone (40) has at least one outlet opening (40).
7. A fan according to any one of Claims 1 to 6,
   characterised in that one radial dimension (L_s) of the inlet opening (34) is smaller than a radial dimension (L_k) of the conveying duct (14) in the inlet zone (22).
8. A fan according to Claim 7, characterised in that one peripheral dimension (L_s) of the inlet opening (34) is larger than the radial dimension (B_s) of the inlet opening (34).
9. A fan according to Claim 7 or 8, characterised in that a radially inner end zone (40) of the inlet opening (34) is situated in or near a radially inner end zone (42) of the conveying duct (14).
10. A fan according to any one of Claims 7 to 9,
    characterised in that a radially outer end zone (44) of the inlet opening (34) is situated in or near a radially central zone (46) of the conveying duct (14).
11. A method of operating a fan (10) according to any one of the preceding Claims, in which method the impeller (16) is driven at such a speed of rotation so as to rotate about the axis of rotation (A) that the essentially the following relationship is satisfied: $$\mathrm{n}\mathrm{=}\left(\mathrm{k}\mathrm{•}\mathrm{c}\right)\mathrm{:}\left(\mathrm{2}\mathrm{•}\mathrm{z}\mathrm{•}\mathrm{L}\right)\mathrm{,}$$

    

    
    wherein

    n = speed of rotation of the impeller (16),

    k = an uneven whole number (1,3,5,7,...)

    z = number of impeller blades (20),

    c = phase velocity of the waves being propagated in the conveyed air,

    L = length of the expansion duct arrangement (36).

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