EP1998052A2 - Axial ventilator with subsequent guide vane apparatus - Google Patents

Abstract

The diffuser (1) has multiple guide blades (5) arranged in radial manner. The diffuser is arranged in flow direction of a rotor of the axial blower. The guide blades have curved inlet edge (11) and an outlet edge (13). The depth of the guide blade changes uniformly over a length of the guide blade.

Description

The invention relates to an axial fan with downstream distributor. Axial fans are used successfully in many industrial applications, such as the brick industry and the automotive industry. In order to improve the efficiency of the axial fan, it is known to arrange a diffuser behind the fan as seen in the flow direction. The diffuser serves to remove the swirl generated by the fan from the extracted air.

Conventional nozzles have simply curved vanes, which are often formed from one of a rectangular or trapezoidal sheet metal blank. Despite the downstream Leitapparats are the Efficiency and noise in these axial fans not yet optimally designed.

Furthermore, the conventional nozzles are limited to hub ratios greater than 0.4. With smaller hub ratios, the number of vanes required increases significantly in conventional nozzles, which increases the cost of construction and reduces the efficiency of the nozzle.

The invention has for its object to provide a nozzle, an axial fan with downstream nozzle and a rotary fan, comprising an axial fan and a rotatable housing, whose efficiency compared to conventional nozzles and fans is significantly improved, the noise emission is reduced and have a wide range of applications ,

This object is achieved according to the invention in a diffuser for an axial fan, wherein the diffuser comprises a plurality of substantially radially arranged vanes, wherein the diffuser is arranged in the flow direction behind an impeller of the axial fan, and wherein the vanes have an inlet edge and a trailing edge, solved in that the leading edges of the vanes are curved.

In connection with the design of the guide vanes according to the invention, the curvature is understood to mean the course of the leading edge and not the additionally existing curvature of the guide vane in the direction from the leading edge to the trailing edge. In other words, in the axial fan according to the invention, a guide blade is not made of a rectangular or trapezoidal sheet metal blank, but in a sheet metal blank for a Guide vane according to the invention, the leading edge of the sheet metal blank is already curved before bending.

It has also proved to be advantageous if the depth of the vanes changes continuously over a length of the vanes. It has proven to be particularly advantageous if a depth of the guide vanes in a range between 50% and 80% of the length of the guide vanes, preferably in a range between 60% and 80%, has a minimum. Furthermore, it has proved to be advantageous if the leading edge of the guide vanes is concavely curved.

These geometries have led to a reduction of the drive power at a constant capacity of the axial fan by about one-fifth in practically executed prototypes.

Since, of course, an interaction exists between the axial fan and the diffuser, it is not possible to define the geometry of the leading edge in the sense of a simple formula. It has therefore been found to be necessary to determine the optimum shape of the leading edge by a combination of simulation calculation and a high spatial resolution measurement of the actual flow conditions in the transition region between the axial fan and diffuser.

In a front view, the leading edge of the vane may in many cases be described by a second order polynomial, in particular a parabola, a hyperbola, an ellipse, or a combination thereof.
In many applications, a parabolic leading edge has been found to be suitable. The crest tangent of the parabolic inlet edge runs under an angle β to a radius R on a vertex S of the parabola, wherein the angle β is often in a range between 0 ° and 10 °.

If the guide vane is bent cylindrically, then the course of the leading edge results from the intersection line between said cylinder and a second-order surface, which in cross section has, for example, the shape of a parabola, a hyperbola or an ellipse.

Another advantage of the nozzle according to the invention is the reduced by its use noise emission of the axial fan. In the case of experimental installations, it was even possible to dispense with the rear silencers provided at the air outlet, which firstly improves the overall efficiency of the ventilation system and, of course, reduces the investment costs and the space requirement.

Since nowadays axial fans are usually made of sheet steel and welded construction, the costs for producing the sheet metal blanks for the guide vanes according to the invention are almost identical to the production costs of a conventional guide blade due to today's production possibilities, in particular by laser cutting.

Of course, a considerable development and research effort to determine the optimal course of the leading edge is required. However, this effort is required only during product development. In serial production, these costs can of course be transferred to the axial fans produced or the diffusers produced.

Because of the considerable savings potential of sometimes up to 20% in the drive power and the high service life of the industrially used axial fans, the costs for the distributor according to the invention often pay for themselves after a short time. Another advantage of the nozzle according to the invention is the fact that, compared to conventional nozzles, the number of vanes can be reduced. As a result, production costs are saved and the flow resistance is reduced due to the smaller number of vanes.

It is also possible with the nozzle according to the invention to cover hub ratios up to 0.3, which is not possible with conventional downstream nozzles or at least not with reasonable economic effort.

The advantages according to the invention can also be realized by means of an axial fan with a downstream distributor, the distributor having guide vanes with the claimed geometry according to the invention.

The same applies to a rotary fan comprising an axial fan and a rotatably mounted housing, wherein at least one air outlet opening is provided on the housing, wherein the nozzle has the inventive shape of the guide vanes.

Further advantages and advantageous embodiments of the invention are the following drawings, the description and the claims removable. All of the features disclosed in the drawing, the description and the claims can be essential to the invention both individually and in any combination with one another.

drawings

Figur 1

eine Ansicht von vorne auf ein Ausführungsbeispiel eines erfindungsgemäßen Leitapparats;

Figur 2

das Ausführungsbeispiel gemäß Figur 1 in verschiedenen Ansichten,

Figur 3

einen Drehlüfter mit Axiallüfter und erfindungsgemäßem Leitapparat in einer Seitenansicht und

Figur 4

ein weiteres Ausführungsbeispiel eines erfindungsgemäßen Axiallüfters.

Figur 4

ein Diagramm, welches die Druckerhöhung in Abhängigkeit der Durchflusszahl zeigt und

Figur 5

ein Diagramm, welches den Wirkungsgrad in Abhängigkeit der Durchflusszahl zeigt.

In the drawing show:

FIG. 1

a front view of an embodiment of a nozzle according to the invention;

FIG. 2

the embodiment according to FIG. 1 in different views,

FIG. 3

a rotary fan with axial fan and inventive nozzle in a side view and

FIG. 4

a further embodiment of an axial fan according to the invention.

FIG. 4

a diagram showing the pressure increase as a function of the flow rate and

FIG. 5

a diagram showing the efficiency as a function of the flow rate.

Description of the embodiments

FIG. 1 shows a front view of an embodiment of a nozzle according to the invention 1. The nozzle 1 comprises mounting flanges 3, of which in FIG. 1 only one is visible, and a plurality of guide vanes 5, of which only one has been provided with the reference numeral 5 for reasons of clarity. The vanes 5 extend from a hub 7 with a diameter D _i to the flanges 3 with the diameter D _a . The hub 7 is at the in FIG. 1 illustrated embodiment designed as a pipe section. Likewise, as is out FIGS. 2b and c results, between the flanges 3, an outer tube section 9 is provided.

In the embodiment according to FIG. 2 the distributor 1 is designed as a welded construction. This means that the guide vanes 5 are welded at their first end to the hub 7 and at its second end to the pipe section 9. Of course, the invention is not limited to weldments or certain materials.

The vanes 5 each have an entry edge 11 and an exit edge 13. A length coordinate L begins at the hub 7 and ends at the pipe section 9. The longitudinal coordinate L extends in the radial direction and begins at an inner diameter D _i . A depth T of the vanes 5 extends in the tangential direction.

In the geometry of the guide vanes 5 according to the invention, the leading edge 11 is curved. The trailing edge 13 is in the embodiment according to FIG. 1 just. This means that a depth T (r) of the guide vanes 5 depends on the radius R. Starting from a maximum depth at the root of the vane 5, where it is welded to the hub 7, the depth T of the vane 5 decreases steadily until a minimum depth T _{min is} reached. Subsequently, the depth T rises again to the tip of the guide blade 5 "where it is welded to the outer pipe section 9.

zu berechnen.It has proven advantageous in prototypes performed when the minimum depth T _{min of} the vanes is in a range between 50% and 85% of the length L of the vanes, more preferably in a range between 60% and 80%, of the length of the vanes lies. In this case, the total length L of the guide vanes 5 is according to the formula $$\mathrm{L}\mathrm{=}\mathrm{½}\mathrm{\cdot }\left({\mathrm{D}}_{\mathrm{a}}\mathrm{-}{\mathrm{D}}_{\mathrm{i}}\right)$$

to calculate.

In the case of the invention, the following values for minimum depth T _{min of} the guide vanes 5 have proven to be optimal: Hub ratio D _i / D _a Minimum vane depth T _min in percent of the depth T (D _i ) on the inner diameter D _i 0.315 75% 0.35 70% 0.45 75%

The concrete design of the concave curvature of the leading edge 11 naturally depends on the dimensions of the distributor, the blading of the axial fan, not shown, as well as the position of the optimum efficiency in the curve. Also, the downstream ones can Components, such as a diffuser or a housing of a rotary fan, have an influence on the flow behavior of the distributor 1 according to the invention. Therefore, it is not possible to specify the geometry of the curvature of the leading edge 11 of the guide vanes 5 according to the invention in the sense of a simple formula. Rather, a combination of measurements and simulation calculations is required in order to determine the optimum design of the leading edge 11 for specific axial fans.

To a good approximation, the course of the curved part of the leading edge 11 in the front view ( FIG. 1 ) are approximated by a parabola. In this case, a vertex S is at the location where the depth T of the vane 5 is minimal (T _R = T _min ). A vertex tangent ST of the parabola encloses an angle β with a radius R of the vertex S. This angle β may be different from zero. In some applications, an angle β between 0 ° and 10 °, more preferably between 4 ° and 7 °, has been found to be advantageous. A focal point of the parabola has been provided with the reference symbol F.

In FIG. 2a is the view according to FIG. 1 shown a little scaled down. Also, not all references have been taken for the sake of clarity.

FIG. 2b shows a sectional view taken along the line AA through the nozzle according to the invention, while in the Figure 2c an isometric view of the embodiment of a nozzle according to the invention is shown. The flow direction is indicated by a plurality of arrows 15.

From the FIG. 2b is good to see that the vanes 5 are simply curved in the region of the leading edge 11, wherein the guide vanes 5 extend in the region of the trailing edge 5 parallel to the longitudinal axis of the nozzle 1 and thus the air flowing through the nozzle or the flowing through the nozzle 1 gaseous Medium flows virtually swirl-free from the nozzle 1. It has proven to be particularly advantageous if the guide vanes 5 are curved in the region of the leading edge 11 in the form of a cylinder.

In FIG. 3 is a side view of a equipped with a nozzle 1 according to the invention rotary fan 17 is shown.

The flow direction of the air is again indicated by arrows 15. The rotary fan 17 includes an axial fan 19, a nozzle 1 according to the invention and a housing 21. In the axial fan 19, an impeller 23 is arranged, which is rotated by a drive shaft 25 in rotation. The axial fan 19 may be a conventional axial fan. At the in FIG. 3 illustrated embodiment, an inventive nozzle 1 is arranged with vanes 5 in the housing 21 and secured thereto.

The housing 21 of the rotary fan is frusto-conical and has a plurality of baffles 27. For reasons of clarity, not all baffles are provided with reference numerals.

The baffles 27 cause that the air conveyed by the axial fan 19 or its impeller 23 is blown out horizontally. The housing 21 is in its in FIG. 3 rotatably supported at the bottom and rotates during operation slowly about its longitudinal axis or is during the Operating slowly pivoted about its longitudinal axis. Together with the housing 21, the Nachleitapparat 5 and the housing of the axial fan 19 rotate.
The warehouse is in FIG. 3 provided with the reference numeral 29. As a result of the rotation of the housing 21, the outlet direction of the air changes continuously, so that the entire surrounding area of the rotary fan is supplied with dry air, as required, for example, in the manufacture of bricks.

Also at the in FIG. 3 illustrated application in which the diffuser 1 according to the invention is integrated in a rotary fan 17, the advantages of the nozzle 1 according to the invention can be achieved because the air flows into the housing 21 almost twist-free. As a result, all baffles 27 are supplied with almost spin-free dry air and it turns over the entire length of the housing 21, a nearly constant exit velocity of the air from the outlet openings 27 a. As a result, a very uniform dry result is achieved and also the performance of the axial fan 19 can be significantly reduced. Because of the improved drying result due to the nozzle 1 according to the invention, the throughput can be increased by the drying device in which the rotary fan 17 according to the invention are arranged, or it can be achieved with less energy use, the same drying performance.

• ψ_tot: Druckzahl total
• ψ_fa: Druckzahl frei ausblasend / statisch

In FIG. 4 the pressure number ψ is plotted against the flow rate φ. Where:

• ψ _dead : total pressure
• ψ _fa : pressure freely blowing / static

In this case, the characteristic of an axial fan equipped with a Nachleitapparat 1 according to the invention is shown as a solid line, while the characteristic of a equipped with a conventional Nachleitapparat 1 axial fan is shown as a dashed line.

• η_tot: Wirkungsgrad total
• η_fa: Wirkungsgrad frei ausblasend / statisch

In FIG. 5 the efficiency η is plotted against the flow rate φ. Where:

• η _dead : total efficiency
• η _fa : Efficiency free blowing / static

Also in FIG. 5 is the characteristic of an equipped with a Nachleitapparat 1 axial fan according to the invention shown as a solid line, while the characteristic of a equipped with a conventional Nachleitapparat 1 axial fan is shown as a dashed line.

The pressure factor ψ _tot and the efficiency η _tot are based on the total pipe outlet area and were determined with a pressure-side equalizing pipe with a length of 2 x pipe diameter.

The flow rate φ was determined according to the following equation: $$\mathrm{\phi }\mathrm{=}\mathrm{4}\mathrm{\cdot }{\mathrm{V}}^{\mathrm{°}}\mathrm{/}\left({\mathrm{<figure-callout\; id="3"\; label="D"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">D</figure-callout>}}^{\mathrm{3}}\mathrm{\cdot }{\mathrm{\Pi }}^{\mathrm{2}}\mathrm{\cdot }\mathrm{n}\right)$$

The pressure number ψ was determined according to the following equation: $$\mathrm{\psi }\mathrm{=}\mathrm{2}\mathrm{\cdot }\mathrm{Ap}\mathrm{/}\left(\mathrm{\rho }\mathrm{\cdot }{\mathrm{D}}^{\mathrm{2}}\mathrm{\cdot }{\mathrm{\Pi }}^{\mathrm{2}}\mathrm{\cdot }{\mathrm{n}}^{\mathrm{2}}\right)$$

• V°: Volumenstrom [m³/s]
• Δp: Druckerhöhung [Pa]
• ρ: Dichte [kg/m³]
• D: Schaufelraddurchmesser [m]
• n: Drehzahl [1/s]

With:

• V °: volumetric flow [m ³ / s]
• Δp: pressure increase [Pa]
• ρ: density [kg / m ³ ]
• D: paddle wheel diameter [m]
• n: speed [1 / s]

From the comparison of in FIGS. 4 and 5 the characteristics shown are the main advantages of Nachleitapparats invention 1 clear.

Claims (12)

A nozzle for an axial fan (19), wherein the nozzle (1) comprises a plurality of substantially radially arranged guide vanes (5), wherein the nozzle (1) in the flow direction behind an impeller (23) of the axial fan (19) is arranged, wherein the guide vanes (5) have an entry edge (11) and an exit edge (13), characterized in that the entry edges (11) are curved. The nozzle of claim 1, characterized in that a depth (T) of the vanes (5) continuously changes over a length (L) of the vanes (5). A nozzle according to claim 1 or 2, characterized in that a depth (T) of the guide vanes (5) in a range between 50% and 85% of the length (L) of the guide vanes (t), more preferably in a range between 60% and 80%, a minimum (T _min ). Guide device according to one of the preceding claims, characterized in that the leading edge (11) of the guide vanes (5) is concavely curved. Guide apparatus according to one of the preceding claims, characterized in that the leading edge (11) at least partially in a view from the front by a polynomial, curve second order, in particular a parabola, a hyperbola and / or an ellipse, can be approximated. Guide apparatus according to claim 5, characterized in that in the vertex (S) of the parabolic portion of the leading edge (11) a depth (T) of the guide vanes (5) is minimal (T = T _min ). Guide apparatus according to claim 5 or 6, characterized in that a vertex tangent (ST) and a radius (R) to the apex (S) of the parabolic portion of the leading edge (11) include an angle (β) between 0 ° and 10 °. Guide device according to one of the preceding claims, characterized in that the number of guide vanes (5) as a function of the outer diameter (D _a ) is in a range which is calculated according to the following equation: $${\mathrm{n}}_{\mathrm{vane}}\mathrm{=}\mathrm{C}\mathrm{\cdot }{\mathrm{D}}_{\mathrm{a}}\mathrm{/}\mathrm{L}$$

With: c: Constant for the respective impeller type Da: outer diameter diffuser L: total length of the diffuser Axial fan with a downstream diffuser (1), characterized in that the diffuser is a diffuser (1) according to one of the preceding claims. Axial fan with a downstream diffuser, characterized in that the axial fan (19) has a hub ratio (D _i / D _a ) of 0.3 or greater. Rotary fan comprising an axial fan (19) and a rotatably mounted housing (21), wherein on the housing (21) at least one air outlet opening (27) is provided, characterized in that the axial fan (19) is followed by a diffuser (1) according to one of claims 1 to 8. Rotary fan according to claim 11, characterized in that the housing (21) is frusto-conical.

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