JPS58200097A - Axial-flow fan - Google Patents

Abstract

PURPOSE:To lower the noise level of an axial-flow fan, by reducing the relative speed of fluid flow near the top of a runner by disposing inlet guide vanes for imparting prewhirl in the direction of rotation of the runner on the upstream side of the top of runner blades. CONSTITUTION:Inlet guide vanes 5 for reducing the relative speed of fluid flow to the cascade of a runner 3 are disposed in the manner of facing the top of the runner 3 on its upstream side. The axial speed V' of fluid flow on the upstream side of the inlet guide vanes 5 is turned in the direction of rotation of the runner 3 by the inlet guide vanes 5, so that fluid is discharged in the direction shown by C'1 in the drawing. On the other hand, since the runner 3 is turned at a circumferential speed (u), the fluid flow C'1 is introduced into the runner 3 in the direction of W'1 and discharged therefrom in the direction of W'2. Similarly, the absolute speed in the direction of W'2 becomes C'2, so that the noise level is lowered.

Description

[Detailed Description of the Invention] Currently, efforts are being made to make various products quieter, and the noise level of automobile engine cooling fans and household 9-tone fans can be reduced by just 2 to 5 phons. The product value can be significantly increased.

The present invention was developed in view of the above-mentioned actual circumstances, and aims to reduce the sound generation level in axial fans used for various purposes. Corresponding to the tip of the impeller,
The present invention provides an axial flow flow characterized by the provision of an inlet guide vane that reduces the relative speed of the air flow with respect to the blade row of the impeller.

To explain a conventional example of a radiator cooling fan applied to a vehicle, Figure 1 shows the radiator (1), fan impeller (3), and engine body (4) as shown in Figure 1. The fan impeller (3) is normally rotated by the engine (4), and the air flow induced by this rotates the engine cooling system, which cools the engine cooling water in the radiator (0). At the same time, recently there are fans around the impeller (3)!
(2) is installed to prevent blade tip vortices generated at the tip of the fan's impeller (3) and improve fan efficiency and performance.

Next, regarding the action in the above-mentioned axial flow fan, if the impeller (3) shown in FIG. rRK
A straight blade row as shown is obtained, and if we now focus on the flow of air to the blade row when the impeller (3) is rotating, the absolute velocity c1 upstream of the blade row is uniform in the axial direction 1IVx For the rotating blade row, this flow Vl changes to a relative speed W1 due to the circumferential rotation speed U&C of the blade row.

This relative inflow velocity Wl is bent inwardly by the circulating flow layer (a) (synonymous with lifting force) of the arranged row during the true row ik4, and Wl
Its speed is reduced and it flows out in the direction of W2. Further, the absolute velocity of the relative outflow velocity W2 with respect to one rotary blade row becomes a swirling flow like C2.

Note that since the axial components vl and v2 of wl IW2 flow on the same circumferential surface, if the compressibility of air is ignored from the equation of continuity, v1=v2.

The above explanation was about the flow in one cross section in the impeller, but to further explain the flow in the height direction of the blade from the tip of the impeller to the root of the blade, Figure 1 (Q
The tip R1 and the average radius mRIn of the impeller (3) shown in
The blade arrangement and speed diagram of the five cross-sections of the root sR4 are shown in Figures 1 and 1. In general, in an axial fan, the radial fit horn e ray X is the free vortex flow ( It is designed under the conditions of Free Vortex Biow). That is, (A), the axial velocity is constant everywhere from the blade tip to the blade root (V in cross section 5 in the figure is constant) (B), The total pressure rise from the blade tip to the blade base is constant. This means (W:, -”Fz ) = (W, :□-W, :, )=
(W"1-W, 22) or LjtΔ0ut=U@Δ0
ua=IJrΔCur (see the illustration for the symbol).

On the other hand, since the impeller (3) is in rigid body motion, the same speed U of the impeller is large at the blade tip and small at the blade root in proportion to the radius RK. As a result, the relative speed Wl of the impeller
# Both ws increase linearly from the blade root toward the blade tip.

Regarding the noise level of the axial fan, it is generally known that the main cause of its generation is induced by the relative speed of the flow passing through the impeller, and its magnitude is approximately proportional to the fifth power of the relative speed. ing.

Now, if we compare the noise level generated per unit area between the blade tip (Rs) and the blade root for an axial fan with a boss ratio α5 (=Rr/R,), we can see that the acoustic output
) difference ΔPWL= 10 *Jog(jl!i)' ~5
0-Jog2-r 50XQ, 5=15aB In other words, in the case of a blade with a boss ratio of 0.5, according to the normal design, the acoustic output at the blade tip is 15aB (decibel) from the blade root.
It turns out that it is expensive.

The present invention was developed focusing on the fact that the relative speed of the blade tips in an axial flow fan governs the noise level as described above, and as shown in FIG. Upper fiK: By providing an inlet guide vane that gives a pre-turn in the rotational direction, the relative speed near the tip of the impeller can be lowered and the free vortex
ex Flow).

A practical example of the present invention is a cooling fan KK for a radiator in an automobile, which is composed of a radiator (11, a fan casing (2), a fan impeller (3), and an engine body (4) as shown in AJ). ; and the impeller (3
) is characterized by the installation of an inlet guide vane (5) corresponding to the tip of the impeller in the upper fill to reduce the relative speed of the flow to the blade row of the impeller.

As shown in the figure, the inlet guide vanes (5) are provided over a range Dn from 0.7 to 0.8 times the diameter Do of the fan casing (2) to the diameter Do of the fan casing (2). The blade arrangement and speed diagram of the front end of the impeller (R1 cross section) shown in Figure 2 @, and the final $% (D n part) of the inlet guide vane (5) shown in Figure 2 (Q). It is represented by a blade arrangement and a speed diagram (in Figure 2, various quantities in the speed diagram are shown with °), and the fan in the actual example is the same as that shown in Figure 1. The following can be said about the various quantities in the same cross section in the conventional example shown in FIG. 1 and the practical example of the present invention shown in FIG.

(1), v=v'=constant (2), each radius [O16 (W''-W7)=(vi11
! Vi'1)=constant(3), ri on each radius,=(J'now, Fig. 2(6
), the axial flow velocity V in front of the inlet guide vane (5) is bent in the rotational direction by the inlet guide vane (5) row, and the direction of C; leaks to. On the other hand, since the impeller (3) is moving at ti circumferential speed U, the consideration of C1 is Wl with respect to the impeller base (3).
The flow will flow in the direction of and the wave will crest in the direction of Wj, and the same! The absolute velocity of /CWI becomes Q/.

As a result, at the tip of the impeller (Ri cross section), bacteria 1
Comparing the conventional example shown in the figure with the practical example of the present invention shown in FIG. 2, it is found that Wl>W'1 and w2>w'.

In addition, the population guide vane (:5) is not located in the actual case. In the cross section, as shown in Figure 2 (Q), the inlet guide vanes (5) do no work because the target blades are arranged in the axial direction, and the flow is wl = w' w, = w'2, which is 1%. Ru.

That is, Ri, Rm-Rrll# in the case of the second alJK
The velocity diagram of 10 is shown in Figure 2 + DI, and the 1st
Figure (Impeller IC in the range of at-Rn compared to the case shown in the ladle)
Since it has a pre-rotation function in the direction of rotation, the relative speed at the tip of the impeller is 4.
,Sakunau, :'l Now, if the relative inflow velocity at the tip of the impeller in the Honjime example is made 80% of the conventional one, the difference in acoustic output in this part is, that is, a 5 decile reduction in sound. The effect is better.

As described above, in the practical embodiment of the present invention, the entrance guide vanes have a significant sound reduction effect, and the commercial value can be greatly improved. In addition,
In the practical example described above, a cooling fan for a radiator in an automobile was described, but the present invention #4 can be applied to axial flow fans used in various types of equipment.

Although the present invention 4 has been described above with reference to actual examples, the present invention is of course not limited to these 5 examples, and may be modified in various designs without departing from the spirit of the present invention. 5 things.

[Brief explanation of the drawing]

Figure 1 (Al is a mechanical diagram of a conventional radiator cooling fan,
The first bulge is shown in Figure 1 (Nno 1-1 view, Figure 1 (O is the first
Figure (partial enlarged view of a, Figure 1)
Work! R□□1□5□engineering 2. . , □゛Speed diagram, Figure 1 (The eyes are straight blade row diagrams in five radial cross sections of the impeller, Figure 1 (The scoop is Figure 1 (Speed diagram in uniform, Figure 2)
Figure TAI is a mechanical diagram of an engine cooling fan which is an example of the present invention.
Figure 2 ta+ is a linear blade row diagram and velocity diagram in a cross section with the same radius Rn (Dn); 1: Radiator 2: Fan casing 5 = impeller 4: Engine body 5: Inlet guide vane Sub-agents: 4 patent attorneys, 1 outsider: 2 people

Claims (1)

[Claims] An axial flow fan characterized in that an inlet guide vane is installed corresponding to the tip of the impeller at the upper ft@ of the impeller to reduce the relative speed of the flow to the blade row of the same impeller. fan.