EP0143235B1 - 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 connects to the housing part encasing the flow-active part of the fan, is increased 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. with a freezer volume reduced due to cooler icing or cooler or filter contamination 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 subjected to flow and to be cooled remain 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.

It is therefore an object of the present invention, starting from a stator-free fan of the type mentioned without the need to enlarge or change the installation conditions, such as. B. removing outflow Schu _t zgittern and without deterioration of the efficiency of the impeller to be able to significantly reduce the specific sound power level.

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-2 327 125, 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 surprisingly been found that the combination according to the invention of the rounding of the downstream corners of the blades in connection with an abruptly expanded surrounding housing contradicts the textbook opinion that the increase in the average air gap between the impeller and the surrounding housing expects a noise level increase lets and also the maximum possible pressure generation (tear-off point) is deteriorated with larger air gaps, nevertheless no noise increase has to be accepted.

A construction has proven to be a particularly expedient construction design for the entire fan housing, which is provided with an abruptly expanded diffuser housing part, which is characterized in that an overall opening or diameter ratio of 1.03, <D _{2 /} D for the diffuser housing part _a <1.25 and a total axial length of 0.10 D _{a <1 D} ≤ 0.5 D _a is provided, 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 embodiment 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 ₁ ≤ 60 ° to a diameter of 1.02 D _A <D ₂₁ <D ₂ and a subsequent gradual expansion with the pitch angle: 0 ° ≤ a 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 extension by means of a corresponding stamp.

mit folgenden Definitionen:

• D_e = Außendurchmesser des Laufrades;
• D_i - Nabendurchmesser des Laufrades;
• I_a = Sehnenlänge zwischen Vorderkante und Hinterkante des Schaufelprofils im Außenschnitt;
• 1, - Sehnenlänge zwischen Vorderkante und Hinterkante des Schaufelprofils im Innenschnitt;
• _YA-Schaufeleinstellwinkel am Außenschnitt einer Schaufel gegen Umfangsrichtung D (Drehrichtung) gemessen;
• γ_i=Schaufeleinstellwinkel am Innenschnitt einer Schaufel gegen Umfangsrichtung D (Drehrichtung) gemessen.

The achievable advantages of the construction of the surrounding fan housing according to the invention 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 or over the circumference of the impeller hub of a fan unit . twisted profiled blades with an arched skeleton line arranged in an unevenly distributed manner such that the relative amount (f / 1) from the curvature height (f) of the skeleton line over the blade chord to the distance length (1) between the front and rear edge of a blade in the range: 0.02 <f / 1 _< 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 _e = outer diameter of the impeller;
• D _i - hub diameter of the impeller;
• I _a = chord length between the front edge and the rear edge of the blade profile in the outer cut;
• 1, - chord length between front edge and rear edge of the blade profile in the inner cut;
• _YA - blade setting angle measured on the outer cut of a blade against circumferential direction D (direction of rotation);
• γ _i = blade setting angle measured on the inside cut of a blade against circumferential direction D (direction of rotation).

• Ausgehend vom lehrbuchmäßigen Stand der Technik sind zur Lösung der gestellten Aufgabe folgende Maßnahmen erfolgversprechend:
  • a) Verringerung des Nabenverhältnisses D_;/D_e zur Erzielung einer möglichst gleichmäßigen Geschwindigkeitsverteilung und damit geringen Geräuschentwicklung,
  • b) Erhöhung der Druckziffer,
  • c) Erhöhung der Volumenziffer.

The special design 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:

• Based on the state of the art in textbooks, the following measures promise to solve the task:
  • a) Reduction of the hub ratio D _{; /} D _{e 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 opposition 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. The minimum associated value of the peripheral speed is, however, determined by a maximum possible value for the pressure figure, which is dependent on the design, in particular on the hub ratio D _{i /} 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 number and the volume number or the linearly dependent dimensionless quantities of the number of diameters and rapid number are known. Depending on these sizes, a hub ratio is recommended in the textbook mentioned, with which an optimal value in connection with a good efficiency can be guaranteed. A significant deviation from the recommended values should mean that a good degree of efficiency cannot be achieved and, in particular, that when the values of the hub ratio recommended in the textbook are undershot, 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 and given the maximum installation conditions and the lowest possible circumferential speed and a low hub ratio, tear phenomena in the impeller do not occur and the flow is closer to the state of a uniform speed distribution 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 in an unexpected manner in combination with the housing design according to the invention and wing edge rounding results in a further improvement with regard to the most uniform possible speed distribution with reduced peak values behind the fan and thus, despite the high conveying capacity, a further noise reduction, which is a total Allows a reduction of 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 stirnseitige Draufsicht auf die Anordnung gemäß Fig. 1,
• Fig. 3 einen vergrößerten Teilausschnitt der Darstellung in Fig.1,
• Fig. 4 eine radiale Draufsicht auf einen Teil der als Abwicklung dargestellten Nabenoberfläche mit der

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 front plan view of the arrangement of FIG. 1,
• 3 shows an enlarged partial section of the illustration in FIG. 1,
• 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 one embodiment of the invention, it is provided that on the outlet side of the first housing part G1 directly surrounding the fan unit M, LR, there is a second diffuser housing part G2 of a suddenly enlarged clear width in the distance range from ± 0.3 1 ₈ to the downstream corners of the blades S1-S8-, with size 1, the chord length of the blade profile in the outer cut, and starting point of the distance area on the impeller side starting from non-rounded corners.

In order on the one hand to achieve a sudden expansion of the housing in a technologically advantageous manner and on the other hand to be able to produce this expansion with the least possible manufacturing effort, a sudden expansion behind the impeller LR in the aforementioned sense is initially carried out with an embodiment of the invention for the diffuser housing part G2 Pitch angle: 15 ° ≤ α ₁ ≤ 60 ° except for a diameter dimension: 0.4 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 connects; 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 a further embodiment of the invention, the total opening diameter ratio for the diffuser housing part G2 is: 1.03 ≤ D _A / D ₂ ≤ 1.25 and the total axial length is 0.10 D _A <1 _D 0,5 0.5 D _a provided, 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 air 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 1 _a ≤ r ≤ 0.2 1 _{a are} rounded off.

• D_a=Außendurchmesser des Laufrades.
• D_i = Nabendurchmesser des Laufrades;
• 1_a = Sehnenlänge zwischen Vorderkante und Hinterkante des Schaufelprofils im Außenschnitt;
• 1_i ― Sehnenlänge zwischen Vorderkante und Hinterkante des Schaufelprofils im Innenschnitt;
• γ_a = Schaufeleinstellwinkel am Außenschnitt einer Schaufel gegen Umfangsrichtung D (Drehrichtung) gemessen;
• γ_i - 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 _i = hub diameter of the impeller;
• 1 _a = chord length between the front edge and the rear edge of the blade profile in the outer cut;
• 1 _i - 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 _i - 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 (9)

1. An axial ventilator without guide ring, particularly but not exclusively for ventilating heat exchangers, comprising a first housing part which directly surrounds a ventilator unit, and a second diffuser-housing part connected at the outflow end and of abruptly increased internal width, characterised in that at least the downstream corners at the outer edge of the vanes (S1 - S8) of the ventilator unit (M; LR) are rounded (radius of curvature r) and the beginning of the abruptly increased internal width of the diffuser housing part (G2) is located at a distance in the region of ± 0.3 1, 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 1a is the chord length of the vane profile in the outer section.

2. An axial ventilator without guide ring as claimed in Claim 1, characterised in that the downstream corners of the vanes (S1 S8) are rounded to correspond with a radius of curvature: 0.1 1_,a ≤r≤ 0.3 1g.

3. An axial ventilator without guide ring as claimed in Claim 1 or 2, characterised in that an overall opening ratio, or diameter ratio, of 1.03 < D₂/D_A < 1.25, is provided for the diffuser housing part (G2), where D_A corresponds to the internal width of the ventilator housing (first housing part G1) in the region of the impeller (LR) and D₂ is the maximum diameter of the diffuser housing part (G2).

4. An axial ventilator without guide ring as claimed in one of Claims 1 - 3, characterised in that an overall axial length of 0.10 D_A < 1_D < 0.5 D_A is provided for the diffuser housing part (G2), where D_A corresponds to the internal width of the ventilator housing (first housing part G1) in the region of the impeller (LR).

5. An axial ventilator without guide ring as claimed in one of Claims 1 - 4, characterised in that for the diffuser housing part (G2), an abrupt widening is provided starting after the impeller (LR), with an angle of divergence: 15° ≤ α₁ ≤ 60° to a diameter of 0.04 D_A≤ D₂₁ ≤ D₂ and a subsequent gradual increase in width with an angle of divergence: 0° ≤α₂≤ 10° to a diameter D₂.

6. An axial ventilator without guide ring as claimed in one of Claims 1 - 5, characterised in that the diffuser housing part (G2) consists of a tubular element which is caused to bulge in the region of its widened portion by means of a corresponding press die.

7. An axial ventilator without guide ring as claimed in one of Claims 1 - 6, characterised in that the first housing part (G1) and the diffuser housing part (G2) together form an integral tubular member.

8. An axial ventilator without guide ring as claimed in one of Claims 1 - 7, characterised in that at the outflow end, the diffuser housing part (G2) is provided with a protective screen (SG).

9. An axial ventilator without guide ring, comprising twisted, profiled vanes which are arranged so as to be uniformly or non-uniformly distributed around the periphery of the impeller hub of a ventilator unit, the mean camber line of a vane being curved in such manner that the ratio (f/1) of height of curvature (f) of the mean camber line relative to the vane chord to the spacing length (1) between the front and rear edges of a vane is in the range of 0.02 ≤ f/1 ≤ 0.1 as claimed in one of Claims 1 - 8, characterised by the following constructional parameters for the impeller of the ventilator unit:

with the following definitions:

D_a=outer diameter of the impeller;

D_i=hub diameter of the impeller;

1_a= chord length between front and rear edges of the vane profile at the outer section;

1_i=chord length between front and rear edges of the vane profile at the inner section;

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

γ_i=vane adjustment angle at the inner section of a vane, measured in the peripheral direction D (direction of rotation).

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