DE2225599A1 - IMPELLER FOR A FAN - Google Patents

Description

May 19, 1972 Schi-Bo

Annex to the patent and
Utility model registration

ROBERT BOSCH HAUSGERÄTE GMBH, Giengen, Robert-Bosch-Strasse

Impeller for a fan

The invention relates to an impeller for a fan, in particular for an axial fan of an air conditioner, with a Hub and several more or less radially directed away from it paddle-shaped, twisted flights! whose cross section in the flow direction between a front and a rear end portion by a convex and a concavely curved profile line is delimited.

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In a known impeller of this type, the cross-section of the impeller blades is designed as an airfoil profile arranged symmetrically on both sides of a circular segment-shaped center line, so that the concave profile line (arched into the profile) is less arched in the acceleration range of the flow than in the deceleration range of the flow _; (DT-PS 679 517). With such a blade cross-section, the flow breaks away from the surface of the wing blade even with a relatively little increased counterpressure. Pies results in a high level of noise and a reduced flow rate of the impeller.

The invention is based on the object of an impeller create that is easy and economical to manufacture and that only relatively weakly even with increased counter pressure © © # » noise developed.

This is achieved according to the invention by & aS one of the two profile lines is designed as an arc of a circle.

An advantageous further development of the subject of the discovery results from the fact that the concave profile line is an arc of a circle is with a radius of

2 sin

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In it is

1 the length of the blade cross-section,

ß .. the angle between the vector of the circumferential speed (ü ~) and the relative velocity vector (w-) at the Point of entry of the flow into the impeller and

ß "the angle between the vector of the circumferential speed (u) and the relative velocity vector (w «) at the Point of exit of the flow from the impeller.

Another advantage is that each of the at the convex running profile line of the blade cross-section Tangents in a delay area of the flow adjacent to the rear end section of the blade cross section with the Vector of the peripheral speed an angle of

^{= ß}

includes, where

ß the angle between the vector of the peripheral speed (u) and the vector of the relative flow velocity (w) at the point of contact of tangent and profile line and

an angle in the range from 3 to 10 °, preferably from 6 represents.

In the drawing is an embodiment of the subject the invention shows an impeller of an axial fan,

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Show it: ,

1 shows a partial view of an impeller in the axial direction, FIG. 2 shows a cross section along the line II-II in " FIGS

3 shows a graphic representation of the on a blade cross section of a wing blade along the line III-III Velocity vectors appearing in FIG.

With 10 an impeller is referred to, with a cup-shaped hub 11, and seven radially away from her wing blades 12, which sit with their wing root 13 on the circumference of the hub 11 and point away with their wing tip 14 from the hub 11 .. The hub 11 has a Bore 15 for connecting the impeller 10 to a shaft, not shown, of a drive motor. Each of the wing blades 12 has aerofoil-shaped blade cross-sections 16 running in the circumferential direction of the hub, which are delimited in the flow direction between a front and a rear end section 17 and 18 by a convex profile line 19 (curved outwards from the profile) and a concave profile line 20 are. Each of the blade cross-sections 16 includes an angle B _{00 with} a tangent 21 adjacent to its front end section 17 and rear end section 18, assigned to the profile line 20 and a vector of the circumferential speed ΰ directed against the direction of rotation of the impeller 10, which extends from the wing tip 14 to

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Wing root 13 becomes continuously larger, whereby the Blade blades 12 are twisted in itself. The concavely curved profile lines 20 are an arc of a circle with a radius

R = -

2 sin - ^ ₅ ---

formed, where 1 is the length of the blade cross-section 16 and ß- or ß "the angle between the vector of the circumferential speed ΰ and the vector of the relative flow speed W-. or L at the point of entry or exit of the flow. The vector of the relative flow velocity w is determined in its direction and in its size at each point of the impeller by vector addition of the respective absolute flow velocity c ~ and the circumferential speed ü ~ increasing from the wing root 13 to the wing tip 14 and closes with the vector of the circumferential speed ΰ "in each case an angle β. The length of a blade cross-section 16 and the associated angle R ₀₀ are mutually dependent (Bruno Eck, Ventilatoren, Springer-Verlag 1962, pp. 217-219, 268-269).

Between the wing blades 12, the flowing medium is in one of the front end sections 17 of the blade cross-section adjacent region 22, which extends over approximately half the profile length, is accelerated and in a subsequent region Area 23 delayed. The convex, arched profile line 19

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is built up in the acceleration area 22 by superimposing the concavely arched, circular arc-shaped profile line 20 with an airfoil profile known per se (Göttingen profile 624). In order to delay the tearing off of the flow, the convexly curved profile line 19 in the delay area 23 of the flow, deviating from the Göttingen profile 624, is curved in such a way that each of the tangents lying on the profile line 19 forms an angle β = β + with the vector of the circumferential speed ΰ r · includes, where T represents an angle of 6.

- 7 -

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Claims (4)

Expectations ί IJ impeller for a fan, especially one Axial fan of an air conditioning unit, with a hub and several hydrofoil-shaped, approximately radially directed away from it, twisted wing blades, the cross section of which in the direction of flow between a forward one and a rear end portion is delimited by a convex and a concavely curved profile line, thereby characterized in that at least one of the two profile lines (19, 20) is designed as a circular arc. 2. Impeller according to claim 1, characterized in that the concave profile line (20) of the blade cross section (16) Arc is. 3. Impeller according to claim 1 and 2, characterized in that the circular arc with a radius of R = 2 sin is formed, wherein 1 the length of the blade cross-section (16), B ₁ the angle between the vector of the circumferential speed koit (ü ") and the vector of the relative speed (W-) at the point of entry of the flow into the wing 309849 / 023S rad (10) and ß_ der.winkel between the vector of the circumferential speed (u) and the vector of the relative velocity (w “) at the point of exit of the flow represents the impeller (10). 4. Impeller according to claim 3, characterized in that each the tangent lying on the convex profile line (19) of the blade cross-section (16) in one of the rear End section (18) of the blade cross-section (16) adjacent delay area (23) of the flow with the vector of the circumferential speed an angle of ß ₃ - ß + γ includes, where ß the angle between the vector of the peripheral speed (U) and the vector of the relative flow velocity (w) at the point of contact between the tangent and the profile line (19) and Y "represents an angle in the range from 3 to 10, preferably 6. i. ι 309849/0236 Blank page