RU2516993C2 - Impeller of axial fan (versions) - Google Patents

Abstract

FIELD: ventilation.

SUBSTANCE: proposed impeller of an axial fan may be used in systems of thermal regulation of items in aviation and rocket engineering. The impeller comprises a hub with bases equipped with slots having width S. Tails of sheet blades with thickness s are installed in the specified slots, being connected to the bases by means of a pin joint. Inner surfaces of the tail and the slot are made in the form of sections of circular cylinder of different radii. At the same time in the first version inner surfaces of the tail and the slot are facing each other, and in the second one - external surfaces of the tail and slot are facing each other. Mathematical expressions are given for slot radius as function of the tail radius, slot and tail thickness and tail chord.

EFFECT: group of inventions is aimed at increasing reliability and manufacturability.

6 cl, 7 dwg

Description

The invention relates to fan building and can be used as part of thermal control systems for aircraft and rocket technology.

Known impeller of an axial fan containing a hub with profiled blades made at the same time with it (see RF patent No. 2133383, IPC: F04D 19/00, 1999). The disadvantage of this impeller of the axial fan is the design complexity caused by the implementation of profiled blades along with the hub.

The impeller of the axial fan, which contains a hub with bases equipped with grooves of width S, in which shanks of leaf blades of thickness s are attached to the bases by means of pin joints, is selected as a prototype (see RF patent N 2422681, IPC: F04D 19 / 02, 2011) The implementation of sheet blades significantly simplifies the design of the impeller.

The disadvantage of this impeller of the axial fan is its low reliability, which is caused by the presence of a gap in the connection between the shank of the sheet blade and the groove due to tolerances on the sheet thickness and groove width. Tolerances on the thickness of the sheet from which the blades are made are inevitable, it is also impossible to produce a groove (and it can be done either by milling or by EDM) with high accuracy, which would ensure a tight fit of the shank into the groove. With the vibrations inherent in the products of aviation, and especially space technology, the leaf blade begins to oscillate within the specified gap, which leads to an increase in the amplitude of its vibrations, and, ultimately, to the destruction of the blade caused by cyclic bending stresses. Another disadvantage of the impeller is the low adaptability, which is associated with the need to fasten the shank of each blade to the base with at least two pins - when fixing the shank of the blade with one pin, it is impossible to fix the blade in the angular direction relative to the axis of this pin.

The technical result of the claimed device is to increase reliability and manufacturability.

The specified technical result according to the first embodiment is achieved due to the fact that in the known impeller of an axial fan containing a hub with bases equipped with grooves of width S, in which shanks of sheet vanes of thickness s are attached to the bases by means of a pin connection, in contrast to the known internal the shank surface of each leaf blade is made in the form of a section of a circular cylinder of radius r with a generatrix parallel to the longitudinal axis of the leaf blade, and the inner surface each groove base is formed as a portion of a circular cylinder of radius R with a generatrix parallel to the sheet forming the inner surface of the blade shank, and the shank and the inner surface of the groove facing each other, wherein

$$R\ge \frac{r-\sqrt{r^2-L^2}-\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="00000027.png,00000030.png"\; state="\{\{state\}\}">d</figure-callout>}}{2}+\frac{{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="00000027.png,00000030.png"\; state="\{\{state\}\}">L</figure-callout>}}^2}{2\left(r-\sqrt{r^2-L^2}-d\right)},$$

where d = S-s, a L is half the width of the chord of the shank of the leaf blade on its inner surface;

The specified technical result according to the second embodiment is achieved due to the fact that in the known impeller of an axial fan containing a hub with bases equipped with grooves of width S in which shanks of sheet vanes of thickness s are attached to the bases by means of a pin connection, in contrast to the known the outer surface of the shank of each sheet blade is formed as a portion of a circular cylinder of radius r _H with a generatrix parallel to the longitudinal axis of the leaf blade, and the outer surface of the n for each base portion is formed as a circular cylinder of radius R with a generatrix parallel to the sheet forming the inner surface of the blade shank, and the shank exterior surface and a groove face each other, wherein

$$R_i\le \frac{r_i{}^{}-\sqrt{r_i^2-{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="00000027.png,00000030.png"\; state="\{\{state\}\}">L</figure-callout>}}^2}+\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="00000027.png,00000030.png"\; state="\{\{state\}\}">d</figure-callout>}}{2}+\frac{{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="00000027.png,00000030.png"\; state="\{\{state\}\}">L</figure-callout>}}^2}{2\left(r_i{}^{}-\sqrt{r_i^2-{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="00000027.png,00000030.png"\; state="\{\{state\}\}">L</figure-callout>}}^2}+d\right)},$$

where d = S-s, a L is half the width of the chord of the shank of the leaf blade on its outer surface.

Additionally, to maximize design simplification, when implementing both the first option and the second option, the bases can be made integrally with the hub, while in the designs of axial fans with a sufficiently large sleeve ratio, at which the peripheral speeds of the points in any section of the blade are close by value, the entire leaf blade can be made with a profile that is constant along its length (both the working part of the blade located in the flow of pumped air and its shank).

Figure 1 shows an example of a specific implementation of the impeller of the axial fan, the first option, the main view; figure 2 is the same, right view; figure 3 is the same, a top view; figure 4 is a design diagram for deriving a mathematical dependence, the first option; figure 5 is an example of a specific implementation of the impeller of the axial fan, the second option, the main view; figure 6 is the same, a top view; Fig.7 is a design diagram for deriving a mathematical dependence, the second option. Figure 2 refers to both versions of the impeller of the axial fan.

The impeller of the axial fan, both in the first embodiment and in the second embodiment, contains a hub 1 with bases 2, provided with grooves 3, in which shanks 4 of leaf blades 5 are mounted, connected to the bases 2 by means of a pin connection by a pin 6. Each blade 5 there is a longitudinal axis 7. The width of each groove 3 is equal to S, and the thickness of the shank 4 of each leaf blade 5 is equal to s. When performing the impeller according to the first embodiment, the inner surface 8 of the shank 4 of each sheet blade 5 is made in the form of a section of a circular cylinder of radius r with a generatrix parallel to the longitudinal axis 7 of the sheet blade 5, and the inner surface 9 of the groove 3 of each base 2 is made in the form of a section of a circular cylinder radius R with a generatrix parallel to the forming of the inner surface 8 of the shank 4 of the leaf blade 5, the inner surfaces 8 of the shank 4 and 9 of the groove 3 are facing each other, while

$$R\ge \frac{r-\sqrt{r^2-L^2}-\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="00000027.png,00000030.png"\; state="\{\{state\}\}">d</figure-callout>}}{2}+\frac{{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="00000027.png,00000030.png"\; state="\{\{state\}\}">L</figure-callout>}}^2}{2\left(r-\sqrt{r^2-L^2}-d\right)},$$

where d = S-s, a L is half the width of the chord of the shank of the leaf blade on its inner surface.

The impeller of the axial fan operates as follows: when bringing the hub 1 into rotation from a shaft installed inside it (not shown), the leaf blades 5 create a flow of pumped gas. In this case, due to the geometric dimensions of the groove and the shank according to the geometric dependence given in the claims, the gap-free connection of the shank 4 into the groove 3 is provided — the shank 4 has three zones of linear contact with the walls of the groove 3 — one contact zone along the generatrix of the outer surface of the shank 4 in the middle of the shank and two contact zones along the generatrix of the inner surface of the shank 4 at the edges of its cross section. The gap-free connection of the shank with the groove allows you to eliminate the possibility of vibrations of the blades 5 relative to the grooves 3 and allows you to provide angular fixation of the blades 5 using only one pin 6 in each connection of the shank 4 with the groove 3. When you try to "turn" the blade in the angular direction relative to the axis of the pin 6 (for due to inertia forces, reactions of the flow of the pumped gas to the blade) there are reactions from the side of these three zones of linear contact, preventing this movement, since such a movement immediately causes elastic deformation of the shank 4 of the blade 5, preventing such movement. Thus, the pin provides the fixation of the blade in the radial direction, and these three zones of linear contact - the fixation of the blade in the angular direction. The sign “the inner surfaces of the shank and the groove facing each other” unambiguously determines their mutual position, for which the above conclusions and the design scheme are valid. Theoretically, another mutual arrangement is possible - when the inner surface of the shank and the outer surface of the groove are facing each other - the mathematical expression for him is not applicable, but such a mutual arrangement does not make practical sense, because can be provided only with a large value of d = Ss, which will greatly reduce the aerodynamic characteristics of the wheel due to the strong turbulization of the flow. For clarity, we calculate the value of R for the shank of the blade with the following parameters: s = 1 mm, L = 6 mm, S = 1 ^+0.2 mm, r = 35 mm. Substituting these values (assuming the maximum possible value for S taking into account the tolerance S = 1.2 mm, we obtain from the mathematical expression: R ≥ 56, 41 mm.

The following is the conclusion of the mathematical dependence for the first option. Figure 4 shows the design scheme, where point A is the middle of the chord of the inner surface of the shank, B is the extreme point of the inner surface of the shank, O and O ₁ are the centers of the inner surfaces of the groove 3 and the shank 4, respectively, point C is the tangent point of the outer surface of the shank 4 and the outer surface of the groove 3. Figure 4 shows the case when the outer surface of the shank 4 exactly touches (without clearance and interference) the outer surface of the groove 3.

Then the distance

$$O_{\mathrm{one}}C=r+s\left(\mathrm{one}\right)$$

We take the distance AC = h (the height of the upper point of the profile of the outer surface of the shank 4 above the chord of the inner surface of the shank.

$$h=O_{\mathrm{one}}C-O_{\mathrm{one}}A=r+s-\sqrt{r^2-L^2}\left(2\right)$$

- follows from the properties of a right triangle O ₁ AB.

Similarly, taking the AC - H distance (the height of the upper point of the profile of the outer surface of the groove 3 above the chord of the inner surface of the shank - in the general case, the values of H and h are not equal to each other, but Fig. 4 shows a special case of equality), we obtain from the properties of the triangle OAV :

$$H=OC-OA=R+S-\sqrt{R^2-L^2}\left(3\right)$$

it is obvious that the inequality Н ≤ h (4) is the condition for the gapless connection, i.e. the shank of the blade, resting on the edges (point B and the second, not shown in figure 4, but symmetrical to it with respect to the straight line O ₁ O) on the inner surface of the groove 3, with its outer surface resting on the outer surface of the groove 3 at point C.

Substituting in (4) the values of H and h from expressions (3) and (2), we obtain

$$R+S-\sqrt{R^2-L^2}\le r+s-\sqrt{r^2-L^2}\left(5\right)$$

Introducing the notation d = S-s, we obtain, transferring some terms of the inequality:

$$R+d-r+\sqrt{r^2-{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="00000027.png,00000030.png"\; state="\{\{state\}\}">L</figure-callout>}}^2}\le \sqrt{R^2-L^2}\left(6\right)$$

и подставим в (6):We introduce the notation $$N=r-\sqrt{r^2-L^2}-d\text{(7)}$$

and substitute in (6):

$$R-N\le \sqrt{R^2-L^2}\left(8\right)$$

Having squared both sides of the inequality and bringing similar terms, we get:

$$-2RN+{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="00000027.png,00000030.png"\; state="\{\{state\}\}">N</figure-callout>}}^2\le -L^2\left(9\right),$$

or

$$2RN\ge {\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="00000027.png,00000030.png"\; state="\{\{state\}\}">N</figure-callout>}}^2+L^2\left(10\right)$$

Since N is a positive value (in Fig. 4, this is the distance from point A to the inner surface of groove 3, measured along the straight line of the OS), then R ≥N / 2 + L ² / 2N (11), whence, substituting the value of N from (7 ), we obtain the mathematical expression given in the claims for the first embodiment.

The design of the impeller of the axial fan (second option) is basically similar to the design of the impeller of the first option. The differences are as follows: the outer surface 10 of the shank 4 of each leaf blade 5 is made in the form of a portion of a circular cylinder of radius R _H with a generatrix parallel to the longitudinal axis 7 of the leaf blade 5, and the outer surface 11 of the groove 3 of each base 2 is made in the form of a portion of a circular cylinder of radius R _H with a generatrix parallel to the forming of the outer surface 10 of the shank 4 of the leaf blade 5, the outer surfaces 10 of the shank 4 and 11 of the groove 3 are facing each other, while

$$R_i\le \frac{r_i{}^{}-\sqrt{r_i^2-{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="00000027.png,00000030.png"\; state="\{\{state\}\}">L</figure-callout>}}^2}+\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="00000027.png,00000030.png"\; state="\{\{state\}\}">d</figure-callout>}}{2}+\frac{{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="00000027.png,00000030.png"\; state="\{\{state\}\}">L</figure-callout>}}^2}{2\left(r_i-\sqrt{r_i^2-{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="00000027.png,00000030.png"\; state="\{\{state\}\}">L</figure-callout>}}^2}+d\right)},$$

where d = S-s, a L is half the width of the chord of the shank of the leaf blade on its outer surface.

The impeller of the axial fan (second option) works as follows: when bringing the hub 1 into rotation from a shaft installed inside it (not shown), the leaf blades 5 create a flow of pumped gas. In this case, due to the geometric dimensions of the groove and the shank according to the geometric dependence given in the claims, the gap-free connection of the shank 4 into the groove 3 is provided — the shank 4 has three zones of linear contact with the walls of the groove 3 — one contact zone along the generatrix of the inner surface of the shank 4 in the middle of the shank and two contact zones along the generatrix of the outer surface of the shank 4 along the edges of its cross section. The gap-free connection of the shank with the groove eliminates the possibility of vibrations of the blades 5 relative to the grooves 3, and allows for the angular fixing of the blade 5 using only one pin 6 in each connection of the shank 4 with the groove 3. When trying to “turn” the blade in the angular direction relative to the axis of the pin 6 ( due to inertia forces, the reaction of the pumped gas flow to the blade), reactions occur from the side of these three linear contact zones, preventing this movement, since such a movement immediately causes elastic deformation of the shank 4 of the blade 5, impeding such movement. Thus, the pin provides the fixation of the blade in the radial direction, and these three zones of linear contact - the fixation of the blade in the angular direction. The sign “the outer surfaces of the shank and the groove facing each other” unambiguously determines their mutual position, for which the above conclusions and the design scheme are valid. Theoretically, another mutual arrangement is possible - when the inner surface of the shank and the outer surface of the groove are facing each other - the mathematical expression for him is not applicable, but such a mutual arrangement does not make practical sense, because can be ensured only with a large value of d = S-s, which will greatly reduce the aerodynamic characteristics of the wheel due to the strong turbulization of the flow.

Below is the conclusion of the mathematical dependence for the second option. Figure 7 shows the design scheme, where point D is the middle of the chord of the outer surface of the shank, E is the extreme point of the outer surface of the shank, Q and Q ₁ are the centers of the outer surfaces of the groove 3 and the shank 4, respectively, point F is the point of contact of the inner surface of the shank 4 and the inner surface of the groove 3. Figure 7 shows the case when the inner surface of the shank 4 exactly touches (without clearance and interference) the inner surface of the groove 3.

Then the distance Q ₁ F = r _H - s (12)

We take the distance FD = z (the distance from the center of the profile of the inner surface of the shank 4 to the chord of the outer surface of the shank

- следует из свойств прямоугольного треугольника Q₁ED. $$z=Q_{\mathrm{one}}D-Q_{\mathrm{one}}F=\sqrt{r_i{}^2-L^2}-r_H+s\left(13\right)$$

- follows from the properties of a right triangle Q ₁ ED.

Similarly, taking the distance DF - Z (the distance from the center profile of the inner surface of the groove 3 to the chord of the outer surface of the shank in the general case, the values of Z and z are not equal to each other, but Fig. 7 shows a special case of equality), we obtain from the properties of the triangle QED:

Очевидно, что условием беззазорного соединения будет неравенство Z ≤ z (15), т.е. хвостовик лопатки, опираясь краями (точка Е и вторая, не показанная на фиг.7, но симметричная ей относительно прямой Q₁Q) на наружную поверхность паза 3, своей внутренней поверхностью опирается на внутреннюю поверхность паза 3 в точке F. $$Z=FG-DG=FG-\left(QG-QD\right)=S-(R_H-\sqrt{R_i{}^2-L^2})=S-R_H+\sqrt{R_i{}^2-L^2}\left(\mathrm{fourteen}\right)$$

Obviously, the condition for a gapless connection is the inequality Z ≤ z (15), i.e. the shank of the blade, resting on the edges (point E and the second, not shown in Fig. 7, but symmetrical to it with respect to the straight line Q ₁ Q) on the outer surface of the groove 3, with its inner surface rests on the inner surface of the groove 3 at point F.

Substituting in (15) the values of Z and z from expressions (14) and (13), we obtain

$$S-R_H+\sqrt{R_i{}^2-{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="00000027.png,00000030.png"\; state="\{\{state\}\}">L</figure-callout>}}^2}\le \sqrt{r_i{}^2-L^2}-r_H+s\left(16\right)$$

Introducing the notation dSs, we obtain, transferring some terms of the inequality: $$$$

$$\sqrt{R_i{}^2-{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="00000027.png,00000030.png"\; state="\{\{state\}\}">L</figure-callout>}}^2}\le R_H-d-r_H+\sqrt{r_i{}^2-L^2}\left(17\right)$$

(18) и подставим в (17):We introduce the notation $$M=d+r_H-\sqrt{r_i{}^2-L^2}$$

(18) and substitute in (17):

$$R_H-M\ge \sqrt{R_i^2-L^2}\left(19\right)$$

Having squared both sides of the inequality and bringing similar terms, we get:

,или $$-2R_{H}M+{\mathrm{<figure-callout\; id="2"\; label="M"\; filenames="00000027.png,00000030.png"\; state="\{\{state\}\}">M</figure-callout>}}^2\ge -L^2\left(\mathrm{twenty}\right)$$

,or

$$2R_{H}M\le {\mathrm{<figure-callout\; id="2"\; label="M"\; filenames="00000027.png,00000030.png"\; state="\{\{state\}\}">M</figure-callout>}}^2+L^2\left(21\right)$$

Since M is a positive value (in Fig. 4, this is the distance DG), then

$$R_H\le M/2+{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="00000027.png,00000030.png"\; state="\{\{state\}\}">L</figure-callout>}}^2/2M\left(22\right)$$

whence, substituting the value of M from (18), we obtain the mathematical expression given in the claims for the second embodiment.

In the given examples of a specific design of the impeller, both in the first embodiment and in the second embodiment, the bases are made in one piece with the hub in the form of milled protrusions on the inside of the hub. However, it is also possible to fasten the blades to a rotary (as in the prototype) base, therefore, in the independent claims, a generalizing attribute “base” is given, which can be either an element of the hub or a separate part installed in it. Also in the examples of specific performance, the case is given when the entire leaf blade is made with a profile that is constant along its length. However, the claimed invention can be used in the case of different sections of the shank and the working part of the scapula. The above mathematical expressions impose an exact limit on one side only - the minimum value of the radius of the inner surface of the groove for the first option, and the maximum value of the radius of the outer surface of the groove for the second option. The specific value of these radii is determined by conventional design methods, for example, on the basis of the criterion so that when the shanks are installed in the grooves, the deformation of the shanks would remain elastic.

The use of the invention significantly increases the reliability of the impeller, because the gap-free connection of the shank with the groove allows you to eliminate the possibility of vibrations of the blades 5 relative to the grooves 3. Also increases the manufacturability of the impeller by ensuring the fixation of the blades using only one pin. These advantages allow us to recommend the claimed technical solution for use in aviation and space technology products.

Literature

1. RF patent No. 2133383, IPC: F04D 19/00, 1999

2. RF patent N 2422681, IPC: F04D 19/02, 2011 (prototype).

Claims (6)

1. The impeller of the axial fan, comprising a hub with bases equipped with grooves of width S, in which shanks of leaf blades of thickness s are attached to the bases by means of a pin connection, characterized in that the inner surface of the shank of each leaf blade is made in the form of a section of a circular cylinder of radius r with a generatrix parallel to the longitudinal axis of the leaf blade, and the inner surface of the groove of each base is made in the form of a section of a circular cylinder of radius R with a generatrix, steam allelic generatrix of the inner surface of the shank of the leaf blade, and the inner surface of the shank and groove facing each other, while
$$R\ge \frac{r-\sqrt{r^2-L^2}-d}{2}+\frac{L^2}{2\left(r-\sqrt{r^2-L^2}-d\right)},$$

where d = Ss, a L is half the width of the chord of the shank of the leaf blade on its inner surface. 2. The impeller of the axial fan according to claim 1, characterized in that the base is made in one piece with the hub. 3. The impeller of the axial fan according to claim 1, characterized in that the entire sheet blade is made with a profile that is constant along its length. 4. The impeller of the axial fan, containing a hub with bases equipped with grooves of width S, in which shanks of sheet vanes of thickness s are installed, attached to the bases by means of a pin connection, characterized in that the outer surface of the shank of each sheet blade is made in the form of a section of a circular cylinder of radius r _n with a generatrix parallel to the longitudinal axis of the leaf blade, and the outer surface of the groove of each base is made in the form of a section of a circular cylinder of radius R _n with a generatrix, a pair the llelic generatrix of the outer surface of the shank of the leaf blade, and the outer surfaces of the shank and the groove face each other, while
$$R_i\le \frac{r_i-\sqrt{r_i{}^2-L^2}+d}{2}+\frac{L^2}{2\left(r_i-\sqrt{r_i{}^2-L^2}+d\right)},$$

where d = Ss, a L is half the width of the chord of the shank of the leaf blade on its outer surface. 5. The impeller of the axial fan according to claim 4, characterized in that the base is made in one piece with the hub. 6. The impeller of the axial fan according to claim 4, characterized in that the entire sheet blade is made with a profile that is constant along its length.

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