WO2011051002A1

WO2011051002A1 - Radial blower

Info

Publication number: WO2011051002A1
Application number: PCT/EP2010/060998
Authority: WO
Inventors: Roland Keber; Tobias Metz
Original assignee: Ebm-Papst Landshut Gmbh
Priority date: 2009-10-26
Filing date: 2010-07-29
Publication date: 2011-05-05
Also published as: NL1038334A; DE102009050684A1; NL1038334C2; EP2494212B1; EP2494212A1

Abstract

The invention relates to a radial blower (1), comprising a housing (2) and a blower wheel (3) arranged therein, around which a pressure chamber (4) is designed that increases in size in the flow direction in a substantially helical manner. A tongue (5) is arranged in the housing (2), the tongue substantially extending in the circumferential direction with the free end (5) thereof. A diffusor (6) is formed on the housing (2), the diffusor comprising a plurality of flow sections (X, Y, Z), wherein at least a first of the flow sections (X) extends inside the housing (2) and wherein the cross-sections of the flow sections (X, Y, Z) increase toward the air outlet (7) at least in some sections.

Description

centrifugal blower

Description:

The invention relates to a radial blower with a housing and an impeller arranged therein, around which a pressure space substantially spiraling in the flow direction is formed, wherein in the housing a tongue is arranged, which extends with its free end substantially in the circumferential direction and a diffuser is formed on the housing, which has a plurality of flow sections, wherein at least a first of the flow sections extends within the housing and wherein the cross sections of the flow sections increase at least in sections towards the air outlet. The fan assemblies of the present invention are often used in the heating industry as premixing blowers, usually gas and air being premixed into an ignitable mixture. The arrangement of such radial bladder in the heating technology requires that a fan is provided with extremely small space, which can be operated with high efficiency with low noise. In such radial blowers, an impeller generates a swirling flow from a center of rotation to the outside. In order to use the energy transferred in the flow as efficiently as possible, the pulse energy, which is mainly present as a twist, is converted into pressure energy. For this purpose, the swirl from the flow is deflected by means of a guide and collected the mass flow. By expanding the flow cross-section, at least part of the pulse energy can be converted back into static pressure. As a guide for example, a diffuser can be provided, which is inexpensive and can be used over a wide range especially for smaller blowers. The widening of the flow cross-section is achieved by using a spiral housing, the outer region of which widens continuously around the central fan wheel area with respect to the cross-section, so that the flow and the fan wheel can be picked up and tangentially removed at the end. In the area of the volute casing, where the wide end meets the beginning of the volute, a tongue causes the flow to "peel off." Such a tongue is disclosed, for example, in European application number 04 400 016.4 Rather, the tongue is not simply parallel to the axis of rotation, but rises from the spiral at acute angles, and the structure of the tongue also significantly affects the noise of the fan.

In radial blowers according to the prior art is disadvantageous that the diffuser is usually placed after completion of the spiral shape of the housing to provide for maximum pressure recovery. However, this is accompanied by an enlarged installation space of the radial fan. In such a design of a spiral housing with subsequent diffuser previously formed the tongue the transition to the diffuser. In this case, however, the initial cross section of the diffuser is not clearly determinable. Due to this vagueness of the diffuser is often designed too small or too large, so that not the maximum possible pressure is recovered or breaks off the flow in the diffuser. If the tongue is not formed as an extra component, as described above, but formed as a simple step, there is a risk of flow separation especially in the region following the tongue in the direction of flow. It is known from the specialist literature that the diffusers arranged in the region of the air outlet should not have a larger opening angle than 10 ° in any direction in order to reliably prevent separation of the flow. Thus, the maximum pressure recovery in a diffuser at given Spiralendquerschnitt is determined. If the dimensions of the diffuser are limited by structural or manufacturing reasons in individual directions, an optimal design of the diffuser is not possible.

In the present invention and a radial blower having the features of claim 1, a diffuser is formed such that no flow separation occurs, even if individual opening angles are greater than 10 °. This is achieved in particular by the fact that the diffuser is not connected downstream of the spiral-shaped housing, but is already at least partially formed in the interior of the spiral housing, as a result of which both an essentially loss-free flow and a low construction volume are achieved. For this purpose, the diffuser has a plurality of flow sections, preferably three of them, wherein the first flow section is still within the housing, the second flow section is in the region following the free end of the tongue in the flow direction, and the third flow section is in the upstream region of the air flow. or mixture outlet extends.

The fan housing is formed substantially round in addition to the spiral extension, so that, starting from the axis of the impeller, different Determine the angle of the outer peripheral housing. The angle α, the angle is determined over which the tongue extends in the circumferential direction of the fan housing. As ß the angle is determined over which extend the tongue and a first flow section of the diffuser in the circumferential direction of the housing. The angle δ is the extent of the first flow section over the outer circumference of the housing, where: δ = β - a. In a favorable embodiment, the at least one first flow section of the diffuser extends over an angle δ of at most 50 ° of the outer circumference of the housing within the housing. The helical housing encloses the impeller without the first flow section of the diffuser and without the tongue by a maximum of 310 °, ie the angle δ must be greater than 50 °. It is also advantageous if the extension of the tongue in the circumferential direction about the impeller is between α = 15 and 40 °. Failure to comply with the geometric dimensions of these areas there is a risk of flow separation, low efficiency and increased noise.

To achieve the high efficiency at low height is provided that extends the first flow section of the diffuser from the interior of the housing to a plane which is formed by the normal of the free end of the tongue perpendicular to the housing outer wall. The second flow section of the diffuser connects to the first flow section in the flow direction and preferably extends over a length between one and two thirds of the total length measured from the end of the first flow section to the air outlet. In this area, it is possible to increase the flow area from the first flow section to the second flow section so that neither flow separation nor excessive noise is exhibited.

In the present invention, the diffuser, starting from the free end of the tongue to the air outlet, by tuning the overall geometry selectively have an opening angle of about 10 °, without the cited by the literature flow separation occurs. According to one embodiment of the invention, this is achieved in that a first replacement angle of one at the end of the first flow Section formed cross-sectional area to a cross-sectional area formed at the end of the second flow section is less than 10 °. A second replacement angle of a cross-sectional area formed at the end of the second flow section to a cross-sectional area formed at the air outlet is preferably less than 7 °. The replacement angle is formed for the blower according to the invention by the following formula, A1 defining the cross-sectional area at the end of the first flow section, A2 the cross-sectional area at the end of the second flow section, D the hydraulic diameter at the end of the first flow section, and d the length of the second flow section:

As long as the tuning of the geometry is maintained based on the above-mentioned replacement angles in the respective flow sections, it is possible to ensure an overall opening angle greater than 10 ° within the diffuser without causing flow separation, but the pressure recovery is sufficiently high. In a preferred embodiment, the diffuser in the region of the third flow section, which follows the second flow section in the flow direction, may be formed as a manifold in order to minimize the required installation space. Normally, the material and space required for an additional manifold is very high, because in addition to the blower housing and the diffuser an additional component is placed, which itself must be equipped with large radii in order to exclude flow separation. It is also difficult to match extra components precisely to minimize the disadvantages mentioned. With the present invention, it is possible to integrate the manifold in the diffuser, wherein the manifold is preferably formed such that the normal of the cross section at the end of the second flow section to the normal of the cross section at the air outlet at an angle of at least 15 °, but at most 80 °. In between, any angles are possible. The cross-section of the diffuser or the bend in the region of the air outlet is formed substantially with an aspect ratio of 4: 3, wherein the housing wall extending from the tongue to the air outlet is curved in the direction of the center the cross-sectional area at the air outlet ends. The flow can thus be performed in the tongue following area, without detaching, to the air outlet at the manifold. In a favorable embodiment, the housing can be formed from a lower part and a cover, wherein the cover in the third flow section (elbow) has a ramp extending in the direction of the lower part. "Ramp" is understood to mean any form of training that extends from the cover in the direction of the lower part in such a way that the cross-section is reduced.The ramp can extend over the entire width or can be provided only in sections. when the end of the ramp in the area of the air outlet with the

Housing bottom flush.

In addition to the widening of the diffuser, starting from the free end of the tongue to the greatest width, it can further be provided that the height of the diffuser in the second flow section increases substantially steadily and decreases substantially steadily in the region of the third flow section. The height reduction may be possible in an embodiment by the provision of the ramp. As the height direction while the axial direction of the impeller is defined. By reducing the cross section in the last section, an acceleration of the flow and thus an optimized inflow into the manifold is achieved.

With the given geometric dimensions, a diffuser can be provided on a radial fan that is constructed so that no flow separation occurs, even if individual areas of the diffuser or manifold have an opening angle greater than 10 °. Due to the specific design of the replacement angle in the various flow sections and by the initiation of the diffuser effect in the interior of the spiral housing and the formation of the third flow section as a manifold a small volume of construction with maximum efficiency and extremely low noise is achieved. Further features, advantages and embodiments of the invention are the subject of the following description and the schematic representation of an embodiment. Show it

1 is a plan view of a radial fan with integrated diffuser, Fig. 2 is a side sectional view of the radial fan of FIG. 1st

1 shows a radial blower 1 with a housing 2 and an impeller 3 arranged therein. The housing 2 has a substantially spiral shape, wherein in the outside area in the flow direction a pressure chamber 4 which widens substantially continuously in the circumferential direction is formed, which in the end area in FIG a formed on the housing diffuser 6 passes. The diffuser 6 has three flow sections X, Y, Z, wherein the first flow section X within the housing 2 and the third flow section Z are formed as a manifold 8. The flow cross sections of the diffuser 6 enlarge at least in sections in all sections X, Y, Z, wherein in the first and second flow section X, Y there is a substantially continuous enlargement. In the region of the end of the spiral of the housing 2 there is provided a circumferentially arranged tongue 5 whose free end 5 'forms the beginning of the spiral shape and which serves for "peeling" and subsequent application of the flow In the circumferential direction, the tongue 5 extends through the angle a, in the present case by about 30 °, measured from the free end 5 'of the tongue to one to the end of the second flow section The first flow section X of the diffuser 6 formed in the interior of the housing surrounds the circumference of the housing by the angle β, which occupies approximately 70 ° as shown in Fig. 2. In any case, however, the angle β is greater to provide the advantages of the present invention The first flow section X of the diffuser is formed outside the impeller 3 and extends inside the case up to a normal from the free end of the tongue 5 'to the housing outer wall normal over an angle δ, where: δ = ß - a, in the present case about 40 °.

Starting from the free end of the tongue 5 'up to the largest width, the diffuser 6 opens by more than 10 °, the replacement angle of the respective arranged at the end of the flow sections cross-sectional areas A1, A2, C meet the criterion that the replacement angle of A1 to A2 is less than 10 ° and from A2 to C is less than 7 °. The replacement angle is here according to the formula

where D is the hydraulic diameter at the flow inlet at the cross-sectional area A1 and d is the distance between the cross-sectional areas A1 and A2. In any case, d is to be chosen such that the third flow section Z extends at the second flow section Y for a length of one to two thirds of the total length from the cross-sectional area A1 to the exit surface C.

The tongue 5 extends from its free end 5 'tangentially to the housing wall substantially in the direction of the main axis of the diffuser 6 and then passes in the third flow section Z in a substantially parallel to the outer wall of the diffuser shape (seen in plan view). Overall, the diffuser 6 is designed so that the end cross-section does not change more than a certain amount, starting from the starting cross-section, in order to prevent separation of the flow. In this case, the third flow section Z formed as a manifold 8 at the air outlet has a substantially rectangular shape with an aspect ratio of 4: 3, wherein the housing wall extending from the tongue 5 to the air outlet 7 ends arcuately to the center of the cross-sectional area C at the air outlet 7. The along the tongue 5 and the subsequent second and third flow sections Y, Z running flow can thus be ensured over the entire length of the diffuser 6 without detachment and at the same time a high degree of pressure recovery. In Fig. 2 is a sectional view of the radial fan of Fig. 1 is shown. The housing 2 has a lower part 2 'and a lid 2 "which are fastened to one another The fan wheel 3 arranged in the interior of the housing 2 extends in a radial direction into the first and second flow sections X, Y of the diffuser 6. The Dif - Fusor 6 increases steadily in height direction h in the first and second flow section Y, Y, wherein the height h in sections in the third flow section Z by a arranged in the region of the air outlet ramp 9 on the cover 2 "is reduced. The ramp 9 is flush with the lower housing part 2 'in the region of the air outlet 7 and ensures permanent contact of the flow over the entire length of the diffuser in the vertical direction. The formed as a manifold 8 third flow section Z directs the flow by an angle τ of about 60 °, which is formed by the normal of the cross section A2 to the normal of the cross section C. However, other deflections of 90 ° and more are possible ,

The invention is not limited in its execution to the embodiment shown above. Rather, a number of variants are conceivable, which make use of the illustrated solution even with fundamentally different embodiments and are also within the scope of the invention. For example, it is possible to form the housing in one piece or to adapt the flow guide within the diffuser not by the outer wall itself, but by additionally introduced means for changing the cross section.

* * * * *

Claims

claims

1. Radial fan (1) with a housing (2) and an impeller (3) arranged therein, around which a pressure space (4), which increases in a substantially spiral-shaped manner in the flow direction, is formed,

wherein in the housing (2) a tongue (5) is arranged, which extends with its free end (5 ') substantially in the circumferential direction, and

a diffuser (6) having a plurality of flow sections (X, Y, Z) is formed on the housing (2), at least a first of the flow sections (X) extending within the housing (2), and wherein the cross sections of the flow sections (X, Y, Z) to the air outlet (7) toward at least partially enlarge.

2. Radial fan according to claim 1, characterized in that the at least one first flow section (X) of the diffuser (6) extends over an angle (δ) of at most 50 degrees of the outer circumference of the housing within the housing.

3. Radial fan according to one of the preceding claims, characterized in that the first flow section (X) extends to a plane which is formed by the normal of the free end (5 ') of the tongue (5) perpendicular to the housing outer wall.

4. Radial blower according to one of the preceding claims, characterized in that the second flow section (A2) adjoins the first flow section (A) in the flow direction and over a length between one and two thirds, from the end of the first flow section (X) until the Air outlet (7) measured total length extends.

5. Radial fan according to one of the preceding claims, characterized in that the diffuser (6), starting from the free end (5 ') of the tongue (5) opens to the air outlet (7) out by at least 10 degrees.

6. Radial fan according to at least one of the preceding claims, characterized in that a first replacement angle (μ) at the end of the first flow section (X) formed cross-sectional area (A) to a at the end of the second flow section (Y) formed cross-sectional area (A2) smaller 10 DEG is.

7. Radial fan according to at least one of the preceding claims, characterized in that a second (μ ') replacement angle formed at the end of the second flow section (Y) cross-sectional area (A2) to a at the air outlet (7) formed cross-sectional area (C) less than 7 degrees is.

8. Radial fan according to one of the preceding claims, characterized in that the tongue (5) extends over at least 15 to at most 40 degrees of the outer circumference of the impeller (3).

9. Radial fan according to at least one of the preceding claims, characterized in that the diffuser (6) in the region of the third flow section (Z) as a manifold (8) is formed.

10. Radial fan according to the previous claim, characterized in that the manifold (8) is formed such that the normal of the cross section (B) to the normal of the cross section (C) has an angle of at least 15 degrees.

1 1. A radial blower according to at least one of the preceding claims, characterized in that the cross section (C) at the air outlet (7) is substantially rectangular with an aspect ratio of 4: 3 formed, which from the tongue (5) to the air outlet ( 7) towards the center of the cross-sectional area (C) at the air outlet (7) towards the end.

12. Radial fan according to at least one of the preceding claims, characterized in that the housing (2) from a lower part (2 ') and a lid (2 ") is formed, wherein the lid (2") in the third flow section (Z) a has in the direction of the lower part (2 ') extending ramp (9).

13. Radial fan according to one of the preceding claims, characterized in that the height (h) of the diffuser (6) in the second flow section (Y) increases substantially steadily.

14. Radial fan according to one of the preceding two claims, characterized in that the height (h) of the diffuser (6) decreases substantially steadily in the third flow section (Z) and the ramp (9) substantially flush with the housing lower part (2 ') in the area of the air outlet (7) closes.

15. Radial fan according to at least one of the preceding claims, characterized in that the replacement angle is formed in each case by the formula