DE1940583A1 - Axial impeller for conveying or extracting air or gases - Google Patents

Description

Designation: Axial impeller for conveying or extracting air or Gases The invention relates to an axial impeller for conveying or suction of air or gases.

Various measures have already been taken to improve the efficiency to increase an axial impeller and reduce the noise it generates. However, all these measures are associated with the acceptance of disadvantages.

Either they require significant additional effort in tool manufacture and in production or force them to release simpler designs or cause they have a greater installation depth.

The invention is based on the object of designing a liial impeller in such a way that that without accepting the disadvantages mentioned, the efficiency is significantly increased and at the same time the noise it makes is reduced.

According to the state of the art (Dr.-Ing.Brumo Eck, Ventilatoren 1957, P. 288 ff.) There is the following between the individual sizes of the blade profile Relationship: v = z. cα. 1 = 1.0 2 #. #. K. r with z - number of blades cα - lift coefficient, 1 - profile length, # - - ratio of total pressure to dynamic Pressure, K = sin ß # # tg (ß # + #), ß # - angle of incline of the mean relative speed, 9 - Glide angle r - distance of the profile from the axis of rotation.

Proceeding from this, the stated object is according to the invention # cα # 1 is solved in that the ratio v = 2 ### # K # r in the for the whole The distance r5 from the axis of rotation, which is characteristic of the blade, has the value 0.7.

With this measure, the number of blades can be selected to be smaller, which makes a smaller sound. Second, one can use the ratio according to the invention v = 0.7 instead of v = t, O reduce the profile resistance or the slip angle # and thus increasing the efficiency of the impeller.

Another embodiment of the invention is that the size v from the value 0.7 at the distance r from which characterizes the entire blade the axis of rotation up to the distance r / ra = 1.0 approximately hyperbolically to the value r @ 0.55 decreases and, depending on the ratio ra, about up to the distance r = 0.9 r5 to the same Way to the value 0.77.

With ri / ra values up to 0.3, the variable v is advantageously in the range r = 0.9 rs up to the hub roughly parabolic, so that at r = 0.65 rs with the value 0.9 reaches the maximum and until r = 0.4 r5 falls back to the value 0.77.

With this measure one can also with smaller @ i / ra values up to reach higher pressures to the hub.

In the case of an axial vane wheel with a diameter of 355 mm designed according to the invention and n = 950 rpm, a noise is achieved by reducing the number of blades of 29 phons instead of 43 phons in a prior-art axial vane wheel same data. In another axial impeller designed according to the invention The aim is to achieve the highest possible degree of efficiency. Also with a diameter of 355 mm and n = 950 rpm resulted for = = 4 and α # = 20 as well as for the entire flight sheet characteristic distance r5 with v = 0.7 an efficiency of 90% instead of 81% an axial impeller calculated according to the prior art with the same data.

The drawings and diagrams explain the invention.

Fig. 1 and Fig. 2 show an axial impeller with 8 blades and the distances r5, ra and ri and the variable distance r in FIG for an example of the circular arc profile, the individual geometric profile sizes shown.

4 shows the function rs / ra = f (ri / ra).

Fig. 5 contains the course of cα = f () at α # = 2 ° for the circular arc profile.

Fig. 6 also shows the course of tg for the circular arc profile E as a function of α # = 10 to 30 with l / R = const. for l / R = 0.3 to 1.075 7 shows the course according to the invention for the variable v = f (r / ra).

In Fig. 1 is the distance of the profile on the hub from the axis of rotation with ri and the distance of the profile on the circumference of the impeller from the axis of rotation indicated with ra.

From Fig. 3, among other things, the following variables can be seen: γ is the pitch angle of the profile; α # is the difference between the pitch angle the profile and the pitch angle of the mean relative air speed; W #. is the mean relative air speed.

Claims (3)

P a t e n t a n's n r ü o h e 1. Axial impeller, characterized in that the z # cα # l ratio v = in the characteristic for the whole 2 ## # # K # r blade Distance, rs from the axis of rotation has the value 0.7, with z for number of blades, with ca for lift coefficient, with 1 for profile length, with # for ratio of total pressure to dynamic pressure, with K = sin ß # # tg (ß # + #), with ß # for angle of incline the mean relative speed, with # for glide angle and with r for distance of the profile from the axis of rotation. 2. Axial impeller according to claim 1, characterized in that v of the value 0.7 in the distance rs characteristic of the entire blade from the axis of rotation to the distance @ / r = 1.0 approximately hyperbolically to the ra value 0.55 drops and, depending on the ratio ri / ra, approximately up to the distance r = 0.9 rs increases in the same way to the value 0.77, with r for the distance of the profile from the axis of rotation, with ra for the largest radius of the axial vane, with rs for the distance from the axis of rotation that characterizes the entire blade, and with ri for the radius of the hub. 3. Axial impeller according to claim 1 and 2, characterized thereby, that v in the range r = 0.9 rs runs approximately parabolic to the hub, so that it at r - 0.6 rs with a value of 0.9 a maximum is reached and up again until r = 0.4 rs the value drops to 0.77.