EP0143235B2 - Axial ventilator without guide ring, especially for ventilating heat exchangers - Google Patents

Description

The invention relates to a stator-less axial fan, in particular for ventilation of heat exchangers, according to the preamble of claim 1; such an axial fan is known from DE-A-25 21 416.

In the known sound-damped axial fan with a fan unit enclosed by a housing, it is provided that the inside diameter of the housing piece, which adjoins the housing part encasing the flow-active part of the fan, to increase by about 25% by leaps and bounds; There are no special design parameters for an impeller design, a specific rounding of the downstream blade corners of the blades of the impeller, and the presence of an at least downstream protective grille in the known case.

A typical requirement for fans of the type mentioned at the outset, in particular if they are to be used for operation in conjunction with coolers, is the requirement for a certain amount of free air, i.e. a certain amount of air conveyed without a significant static pressure difference, while at the same time calling for a minimum air pressure at a certain percentage of this amount of air, e.g. B. in the case of a cooler icing or cooler or filter contamination reducing the amount of free air by 30 - 40%. Furthermore, the required amount of air should leave the fan with a speed profile that is as uniform as possible and a swirl component that is as low as possible, as a result of which flow noises on the components that are to be flowed and cooled are kept small. Furthermore, the maximum dimensions of such fans are prescribed for reasons of installation. Since the suction and pressure sides of the fans are still accessible, protective grilles must be fitted there for safety reasons, which in themselves conflict with the aforementioned requirements.

From DE-OS 2411 225 and US-PS 4173995 axial fans for use in water coolers are known, in which the fan blades are rounded at their ends and run in a housing that consists of a cylindrical part and a downstream, expanding Part exists. The housing expands steadily without jumping into a funnel, the lateral surfaces of which follow a quarter circle in the side view. Because of this housing structure, the air flow leaves the housing largely in the radial direction with deliberate use of the coander effect.
The AT-PS 240653 discloses a cooling fan also with a housing which is continuously opening towards the outflow side and is referred to as an air guide ring, in which the fan blades protrude beyond the housing on both sides. Here, too, the air flow exits the fan radially.

DE-OS 31 29 236 finally relates to the mechanical attachment of an air guide housing to an axial fan. The fan blades run in a fan ring that widens steadily towards the outlet side and radially deflects the pumped air

In contrast, it is an object of the invention to provide an axial fan designed according to the preamble of claim 1, which allows a largely axial air outlet to be reached and which allows the specific sound power level to be reduced without the need to increase or change the installation conditions, e.g. the removal of protective grids and without a deterioration in the impeller efficiency.

The object is achieved according to the invention by the teaching of claim 1. Advantageous embodiments of the invention are the subject of the dependent claims.

An axial fan is already known from DE-A-2 327125, the housing of which is provided with an extension, which begins on the outflow side either steplessly or step-wise behind the impeller or already within the impeller area; However, rounded downstream corners of the blades in cooperation with a housing that has been expanded in a certain way are neither described nor illustrated. To reduce noise, only the lowest possible speed is used.

It has been found, surprisingly, that ^G through the inventive combination of the rounding of the downstream corners of the vanes in conjunction with a sharply of enlargement of the surrounding housing contrary to Lehrbuchmeinun after derdie increasing the mean air gap between the impeller and the surrounding housing expect to a noise increase lets and also the maximum possible pressure generation (tear-off point) deteriorates with larger air gaps, nevertheless no noise increase has to be accepted.

A construction has proven to be a particularly expedient design for the entire fan housing, which is provided with an abruptly expanded diffuser housing part, which is characterized in that a total opening or diameter ratio of 1.03 ≤ D ₂ / D _A for the diffuser housing part: 9 1.25, and an entire axial length of 0.10 D _a ≤ ℓ ≤ 0.5 _D D _a vorgesenhen, where D _{a is} approximately the inside width of the fan housing in the region of the impeller, and D _{2 is} the greatest diameter of the diffuser Designated housing part.

A technically particularly advantageous design of the diffuser housing part is characterized in that for this housing part, a sudden expansion beginning behind the impeller with a pitch angle: 15 ° α α ₁ 60 60 ° to a diameter dimension of 1.02 D _A D D ₂₁ ≤ D ₂ and a subsequent gradual expansion with the pitch angle 0 ° <α ₂ ≤ 10 ° to the diameter dimension D _{2 is} provided. In an advantageous manner, the diffuser housing part consists of a piece of pipe widened in the area of its expansion by means of a corresponding stamp.

mit folgenden Definitionen:

• D_a = Außendurchmesser des Laufrades;
• D, = Nabendurchmesser des Laufrades;
• ℓ_a = Sehnenlänge zwischen Vorderkante und Hinterkante des Schaufelprofils im Außenschnitt;
• ℓ₁ = Sehnenlängezwischen Vorderkante und Hinterkante des Schaufelprofils im Innenschnitt;
• γ_A = Schaufeleinstellwinkel am Außenschnitt einer Schaufel gegen Umfangsrichtung D (Drehrichtung) gemessen;
• γ_l = Schaufeleinstellwinkel am Innenschnitt einer Schaufel gegen Umfangsrichtung D (Drehrichtung) gemessen.

The achievable advantages of the construction according to the invention of the surrounding fan housing in combination with the provided wing edge rounding can be further improved in the sense of the task of the present invention in that, according to one embodiment of the invention, an impeller for a statorless axial fan with a fan unit that is uniform over the circumference of the impeller hub or unevenly distributed twisted profiled blades with such a curved skeleton line that the relative amount (f / f) from the curvature height (f) of the skeleton line over the blade chord to the distance length (f) between the front and rear edge of a blade in the range: 0.02 ≤ f / ℓ ≤ 0.1, is provided, the impeller according to an embodiment of the invention being characterized by the following further construction parameters:

with the following definitions:

• D _a = outer diameter of the impeller;
• D, = hub diameter of the impeller;
• ℓ _a = chord length between the front edge and the rear edge of the blade profile in the outer cut;
• ℓ ₁ = chord length between the front edge and the rear edge of the blade profile in the internal cut;
• γ _A = blade pitch angle measured on the outer cut of a blade against circumferential direction D (direction of rotation);
• γ _l = blade pitch angle measured on the inside cut of a blade against circumferential direction D (direction of rotation).

The special construction parameters of an impeller design provided according to this configuration are also outside the guidelines recommended by the specialist literature, according to which the following applies:

• a) Verringerung des Nabenverhältnisses Di/Da zur Erzielung einer möglichst gleichmäßigen Geschwindigkeitsverteilung und damit geringen Geräuschentwicklung,
• b) Erhöhung der Druckziffer,
• c) Erhöhung der Volumenziffer.

Based on the state of the art in textbooks, the following measures promise to solve the task:

• a) Reduction of the hub ratio Di / Da in order to achieve the most uniform possible speed distribution and thus low noise,
• b) increasing the print number,
• c) Increase the volume figure.

These three design sizes for fans known to the person skilled in the art are linked to one another in such a way that sizes a) and c) act in the same sense, however, in the opposite direction to dimension size b). By specifying the maximum installation conditions and the required pressure and volume flow, the dimension sizes: pressure number and volume number are determined by trying to keep the peripheral speed or speed of the impeller as low as possible for noise reasons. However, the minimum associated value of the peripheral speed is determined by a maximum possible value for the pressure figure, which depends on the design, in particular on the hub ratio D / D _{a of} the impeller. As a rule of thumb, it is known that the greater the value of the volume figure, the smaller the value for the pressure figure, in order to achieve good efficiency. This relationship is known from the relevant literature as the Cordier curve. From the textbook 'Ventilatoren' by Bruno Eck, 1972, p.271, Fig.265, modified relationships between the pressure figure and the volume figure or the linearly dependent dimensionless sizes of the number of diameters and rapid number are known. Depending on these sizes In the textbook mentioned, a hub ratio is recommended in each case, with which an optimal value in connection with a good degree of efficiency can be guaranteed recommended values of the hub ratio, the flow in the hub area is broken off and a correspondingly higher noise level occurs.

Although the impeller design provided according to the configuration deviates from the previously mentioned or generally recommended values, it has surprisingly been shown that the fan according to the invention with the special design parameters for the blade profile while observing the required values for volume flow and maximum pressure at a certain percentage this volume flow as well as given maximum installation conditions and the lowest possible peripheral speed as well as a low hub ratio, tear-off phenomena do not occur in the impeller and the flow is closer to the state of a uniform speed change for a given volume flow than with larger, known hub ratios and that the absolute amount of this speed is lower. In addition, the blade wheel design provided according to the invention with a high work distribution in the outer area of the blade unexpectedly results in a further improvement in combination with the housing design according to the invention and the wing edge rounding with regard to the most uniform possible speed distribution with reduced peak values behind the fan and thus, despite the high delivery capacity, a further noise reduction, which in total results in a reduction from 3 to 4 dB (A).

In addition, it has been shown that the pressure loss at an outlet-side protective grille provided according to one embodiment is lower, which leads to a further reduction in noise as a result of lower air output and as a result of reduced flow noise.

• Fig. 1 die Seitenansicht einer in einem Ventilatorgehäuse angeordneten Ventilatoreinhelt eines leitradlosen Axialventilators,
• Fig. 2 eine stimseitige Draufsicht auf die Anordnung gemäß Fig. 1,
• Fig. 3 einen vergrößerten Teilausschnitt der Darstellung in Fig.l,
• Fig. 4 eine radiale Draufsicht auf einen Teil der als Abwicklung dargestellten Nabenoberfläche mit der Darstellung eines schaufelprofils im Innen- und im Außenschnitt.

The invention and further advantageous embodiments of the invention are explained in more detail below with reference to a schematically illustrated embodiment in the drawing; show in it:

• 1 is a side view of a fan unit arranged in a fan housing of an axial fan without stator,
• 2 is a frontal top view of the arrangement of FIG. 1,
• 3 is an enlarged partial section of the illustration in Fig.l,
• Fig. 4 is a radial plan view of a part of the hub surface shown as a development with the representation of a blade profile in the inner and outer cut.

1, 2, a fan unit consisting essentially of a drive motor M with a fan wheel LR attached to its output shaft with blades S1-S8 is arranged in a surrounding housing, which consists of a first housing part G1 directly surrounding the fan unit M, LR and a second diffuser housing part G2. A protective grille SG is attached to both the inlet and the outlet side of the housing.

According to the invention, it is provided that a second diffuser housing part G2 of abruptly enlarged clear width in the distance range of ± 0.31 _a to the downstream corners of the blades S1-S8- is connected on the outlet side to the first housing part G1 surrounding the fan unit M, LR , size 2, the chord length of the blade profile in the outer cut, and starting point of the spacing area on the impeller side starting from non-rounded corners.

In order to achieve an abrupt expansion of the housing on the one hand in terms of ventilation technology, and on the other hand to be able to produce this expansion with the least possible manufacturing outlay, according to the invention for the diffuser housing part G2, a sudden expansion behind the impeller LR in the aforementioned sense is initially with a pitch angle: 15 ° ₅ α ₁ ≤ 60 ° except for a diameter dimension: 1.02 D ₂ ≤ D ₂₁ ≤ D ₂ , which is followed by a gradual expansion with a pitch angle: 0 ° <α ₂ ≤ 10 ° to the diameter dimension D ₂ ; A diffuser housing part designed in this way is expediently produced from a tube piece initially corresponding to the diameter dimension D _A , which is widened by a stamping die having the external dimensions of the extension.

According to the invention, a total opening diameter ratio is provided for the diffuser housing part G2: 1.03 D D ₂ / D _A 1 1.25 and a total axial length: 0.10 D _A ℓ ℓ _D 0,5 0.5 D _a , where D _A denotes the inside width of the fan housing (first housing part G1) in the region of the impeller LR and D ₂ the largest diameter of the diffuser housing part G2 on its outlet side.

As can be seen in particular from FIG. 3, in the sense of a good pneumatic wheel efficiency with simultaneous high low noise in combination with the inventive expansion of the housing in the region of the diffuser housing part G2, it is provided that at least the downstream corners of the blades S1-S8 correspond to a radius of curvature of 0 , 1 ℓ _a ≤ r ≤ 0.2 ℓ _{a are} rounded off.

• D_a = Außendurchmesser des Laufrades.
• D_j = Nabendurchmesser des Laufrades;
• ℓ_a = Sehnenlänge zwischen Vorderkante und Hinterkante des Schaufelprofils im Außenschnitt;
• ℓ₁ = Sehnenlänge zwischen Vorderkante und Hinterkante des Schaufelprofils im Innenschnitt;
• _Ya = Schaufeleinstellwinkel am Außenschnitt einer Schaufel gegen Umfangsrichtung D( Drehrichtung) gemessen;
• γ_l = Schaufeleinstellwinkel am Innenschnitt einer Schaufel gegen Umfangsrichtung D (Drehrichtung) gemessen.

Furthermore, in combination with the aforementioned construction parameters of the fan housing and the downstream corners of the blades with reference to the partial development of the hub N according to FIG. 4 with the reference values entered there for the direction of rotation D, the air flow direction L and a blade shown in the outer and inner cut an impeller construction according to the invention is characterized by the following construction parameters:

• D _a = outer diameter of the impeller.
• D _j = hub diameter of the impeller;
• ℓ _a = chord length between the front edge and the rear edge of the blade profile in the outer cut;
• ℓ ₁ = chord length between front edge and rear edge of the blade profile in the internal cut;
• _Ya = blade pitch angle measured on the outer cut of a blade against circumferential direction D (direction of rotation);
• γ _l = blade pitch angle measured on the inside cut of a blade against circumferential direction D (direction of rotation).

With the aforementioned construction parameters, the entire blade profile can be determined on the basis of the usual calculation methods for profiled blades of compressors and fans; the overlap ratios customary and recommended for the construction of axial impellers are to be used as a basis.

Claims (6)

1. Axial fan without guide ring, particularly for the ventilation of heat exchangers, having a first housing part which directly surrounds a fan unit, and a second diffusor housing part directly adjoining on the outflow side and having an abruptly increased internal width, characterised in that at least the downstream comers at the outer edge of the vanes (S1-S8) of the fan unit (M; LR) are rounded (radius of curvature r), and in that the beginning of the abruptly increased internal width of the diffusor housing part (G2) is located at a distance in the region of ± 0.3 I_a from the point of intersection of the prolongation of the rear edge of the vane, on the one hand, and the vane chord, on the other hand, in the region of the downstream corners of the vanes (S1-S8) of the impeller (LR), where the diffusor housing part has an abrupt widening, starting after the impeller (LR), having an angle of divergence of 15° 5 a₁ ≤ 60° up to a diameter dimension of 1.02 D_A ≤ D₂₁ ≤ D₂ and an adjoining gradual widening having an angle of divergence of 0° < α₂ ≤10° to the diameter dimension D₂, with a total opening ratio or diameter ratio of 1.03 ≤ D₂/D_A ≤1.25 and an overall axial length of 0.10 D_A ≤ I_D ≤ 0.5 D_A, where l_a is the chord length of the vane profile at the outer section, D_A is the internal width of the first housing part (G1) and D₂, is the largest diameter of the diffuser housing part (G2).

2. Axial fan without guide ring according to Claim 1, characterised in that the diffusor housing part ( G2) consists of a tubular element which has been expanded in the region of its widening by means of a expanded in the region of its widening by means of a corresponding press die.

3. Axial fan without guide ring according to Claim 1 or 2, characterised in that the first housing part (G1) and the diffusor housing part (G2) together form an integral tubular element.

4. Axial fan without guide ring according to one of Claims 1 to 3, characterised in that the diffusor housing part (G2) is provided on the outflow side with a protective screen (SG).

5. Axial fan without guide ring according to Claim 1, characterised in that the downstream corners of the vanes (S1-S8) are rounded according to a radius of curvature of 0.1 · l_a ≤ r ≤ 0.3 l_a.

6. Axial fan without guide ring having twisted, profiled vanes which are arranged so as to be uniformly or non-uniformly distributed around the periphery of the impeller hub of a fan unit, the mean camber line of a vane being curved in such a way that the ratio (f/l) of height of curvature (f) of the mean camber line relative to the vane chord to the spacing length (I) between the front and rear edges of a vane is in the range of 0.02 5 f/l ≤ 0.1, according to one of Claims 1 to 5, characterised by the following design parameters of the fan unit impeller:

with the following definitions:

D_a = external diameter of the impeller,

D_l = hub diameter of the impeller,

l_a = chord length between the front and rear edges of the vane profile at the outer section;

I_l = chord length between the front and rear edges of the vane profile at the inner section;

ya = vane adjustment angle at the outer section of a vane, measured in the peripheral direction D (direction of rotation);

yi =vane adjustment angle atthe innersection of a vane, measured in the peripheral direction D (direction of rotation).

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