JP3136737B2 - Multi-plate laminar flow fan - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-plate laminar fan, and more particularly, to a scroll shape in a multi-plate laminar fan.

[0002]

2. Description of the Related Art A multi-plate laminar flow comprising an impeller formed by stacking a large number of donut-shaped disks having suction holes in a shaft center at predetermined intervals, and a scroll casing surrounding the outer periphery of the impeller. Fans have been well known as a type of centrifugal fan, and their hydrodynamic characteristics have been studied in various ways [for example, Transactions of the Japan Society of Mechanical Engineers (B) Vol. 56, No. 524). (1990-4)].

[0003] In the above research, the influence of the number and spacing of the disks constituting the impeller and the gap of the scroll casing on the hydrodynamic characteristics has been a challenge.

[0004]

Incidentally, although the shape of the scroll casing is considered to greatly affect the fan characteristics in view of matching with the impeller, a multi-plate laminar flow fan has hitherto been used. No study has been made on a suitable scroll casing shape.

That is, in determining the shape of the scroll casing in a multi-plate laminar fan, it is determined as an extension of the scroll casing of a conventional centrifugal fan (for example, a multi-blade centrifugal fan, etc.). No consideration has been given to a scroll casing shape that takes advantage of the above characteristics.

The inventors of the present invention have conducted experiments on the effect of the angle of expansion on the fan characteristics and internal flow by making the axial width of the scroll casing constant and using a logarithmic spiral as the expansion shape of the outer wall of the scroll casing. As a result, characteristics suitable for a laminar flow fan were obtained with a small spread angle.

The present invention has been made in view of the above points, and has as its object to obtain an optimum scroll casing shape for a laminar fan by setting the spread angle of the scroll casing to a predetermined value or less. is there.

[0008]

In the present invention, as a means for solving the above-mentioned problems, as shown in the drawings, a number of donut-shaped disks 3 each having suction holes 3a, 3a,. , 3,... Are overlapped at a predetermined interval, and a multi-plate laminar flow fan composed of a scroll casing 2 enclosing the outer periphery of the impeller 1 has a spread angle θc of the scroll casing 2. , 1 to 4 °.

[0009]

According to the present invention, the following effects can be obtained by the above means.

That is, when the spread angle θc of the scroll casing 2 is set in the range of 1 to 4 °, in the low flow rate region, the fluid stays for a long time between the disks 3, 3,. As a result, the total pressure efficiency is increased, and the cross-sectional area of the flow passage in the scroll casing 2 is reduced corresponding to the low flow rate range, so that the deceleration loss when the fluid flows into the scroll casing from the outer periphery of the disk is reduced. Decrease. In addition, when the divergence angle is reduced, the circumferential distribution of the flow at the exit of the impeller 1 becomes uniform, so that the power loss is reduced.

[0011]

According to the present invention, the suction hole 3a,
A number of donut-shaped disks 3, 3
In a multi-plate laminar flow fan comprising an impeller 1 formed by superposing at predetermined intervals and a scroll casing 2 enclosing the outer periphery of the impeller 1, the spread angle θc of the scroll casing 2 is set to 1 to In the range of 4 °, the fluid stays for a long time between the discs 3, 3,.
As a result, it is possible to reduce the deceleration loss at the time of inflow due to the decrease in the cross-sectional area of the inside and the power loss by uniformizing the circumferential distribution of the flow at the exit of the impeller 1.
There is an excellent effect that the fan efficiency and the performance of the fan can be improved in the low flow rate region.

[0012]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIGS. 1 and 2, the multi-plate laminar flow fan of this embodiment includes a plurality of donut-shaped disks 3, 3,... Having suction holes 3a, 3a,. An impeller 1 that is superposed at intervals is provided with a scroll casing 2 that encloses the outer periphery of the impeller 1.

The impeller 1 has a donut shape with respect to an end plate 6 fixed to a connecting plate 5 pivotally attached to a shaft end of a rotary shaft 4 connected to a drive source (not shown) (not shown). The discs 3, 3,... Are fixed via connecting members 7, 7,. In this embodiment, the suction holes 3a, 3a,... In the donut-shaped disks 3, 3,.

In this embodiment, a suction nozzle 8 is provided on the suction side of the scroll casing 2 for an experiment to be described later.

The spread shape of the scroll casing 2 is formed using a logarithmic spiral given by the following equation.

R = r ₂ · exp (θ, tan θc) where r ₂ is the distance between the tongue 2b of the scroll casing 2 and the rotation axis O, θ is the angle radian from the tongue 2b, θc is the scroll The spread angle (°) of the casing 2, r: the distance between the inner wall of the scroll casing 2 and the rotation axis O at an angle θ from the tongue 2 b.

In the multi-plate laminar flow fan, the fluid F sucked from the suction nozzle 8 is supplied to the impeller 1
Are sucked from the suction holes 3a, 3a,... Between the donut-shaped disks 3, 3,... Due to the viscosity of the fluid and the centrifugal force, from the outer peripheral edge of the donut-shaped disks 3, 3,. 2 and is swirled through the fluid passage in the scroll casing 2 to be blown out from the discharge port 2a.

In the following, the case where the spread angle θc of the scroll casing 2 is variously changed (that is, θc =
The performance characteristics of the fan at 1 °, 2 °, 4 °, 6 ° and 8 °) and the flow state at the impeller outlet are considered. The various conditions at this time were as follows.

That is, the impeller rotation speed N = 1800 rpm, the disk outer diameter D ₂ = 380 mm, the disk thickness δ = 1.5 mm, the disk interval δd = 1.6 mm, the number of disks Z = 15, the scroll casing Width = 73mm, inner diameter of disk is D ₁ = 1 at entrance
It is 70 mm and is reduced linearly at an angle of θs = 32 ° in the axial direction.

The number of revolutions was measured by an electromagnetic pickup and the driving torque T was measured by a torque detector. The flow state at the outlet of the impeller was measured by using a spherical pitot tube.

The data arrangement was performed based on the following equation.

Pressure coefficient ψ = 2Pts / ρU ₀ ² (1) Flow coefficient φ = Q / (2πr ₂ bδdU ₀ ) (2) Power coefficient λ = L / (πρbδdr ₂ U ₀ ) (3) Total pressure efficiency η = ρgQPts / ωT = ψφ / λ (4) where U ₀ is the outer peripheral speed of the donut-shaped disk 3, Pts is the total pressure of the fan in the measuring tube, Q is the flow rate, L is the shaft power, ρ is the air density, ω Is a rotational angular velocity, g is a gravitational acceleration, and b is a coefficient.

The performance characteristics of the fan based on the above experimental results are as shown in FIG.

That is, as the spread angle θc of the scroll casing 2 is reduced, the maximum total pressure efficiency ηmax and the pressure coefficient ψ are increased, and the efficiency is greatly increased particularly in a low flow rate region. This means that the spread angle θ of the scroll casing 2 is
When c is small, the cross-sectional area of the flow passage in the scroll casing 2 is small, so that the fluid stays between the donut-shaped disks 3, 3,... The trajectory of the fluid sucked from the 3a side becomes longer, indicating that the absolute speed increases due to the shearing force generated by the disks 3, 3,... And the static pressure increases as the relative speed decreases. Figure 1
In the graph, the dotted line x indicates the trajectory of the fluid at the spread angle θc = 1 ° at a low flow rate, and the dashed line y indicates the trajectory of the fluid at the spread angle θc = 1 ° in the large flow rate region.

Then, in order to make it easier to understand the effect of the change in the spread angle θc of the scroll casing 2 on the fan efficiency η, the maximum efficiency in FIG. 3 was plotted, and a curve as shown in FIG. 4 was obtained.

According to this, the spread angle θc is 1 °-
High fan efficiency η in the range of 4 °, θc> 4
°, the fan efficiency decreases.
From this, it is desirable that the optimum range of the spread angle θc of the scroll casing 2 in the laminar flow fan be θc = 1 to 4 °.

If the divergence angle θc is large, the flow passage cross-sectional area of the scroll casing 2 becomes large, so that the flow velocity in the scroll casing 2 becomes small, and the deceleration loss when flowing into the scroll casing 2 becomes large. When the spread angle θc is small, the scroll casing 2
Since the cross-sectional area of the flow path becomes small, the flow velocity increases, and the deceleration loss at the time of flowing into the scroll casing 2 decreases. This also greatly contributes to the improvement of the fan performance.

Next, in considering the flow state at the outlet of the impeller 1, FIG. 5 shows the circumferential distribution of the static pressure on the wall surface of the impeller outlet when the maximum efficiency is exhibited at each spread angle θc. .

According to this, when the spread angle θc is large, the nonuniformity is large, and as the spread angle θc decreases, the static pressure value increases and the uniformity in the circumferential direction is improved. I understand. This tendency is particularly remarkable when θc = 1 ° or 2 °.

Further, as shown in FIG.
Becomes smaller, the power coefficient λ also becomes smaller. However, as described above, in the scroll casing 2 having a small divergence angle θc, the flow around the impeller 1 is uniform and the flow is non-uniform. It is presumed that the power loss is smaller than in the case where the spread angle θc flowing three-dimensionally is large.

The reduction of the power coefficient λ as described above greatly contributes to the improvement of the fan efficiency.

As described above, in the multi-plate laminar flow fan, at low flow rate conditions, the exit flow angle a of the impeller 1 is extremely small and the flow velocity is large, so that the spread angle θc
When the scroll casing 2 having a large diameter is used, the deceleration loss at the time of inflow of the scroll casing becomes large, the obtained static pressure rise becomes small, and a drift occurs in the flow in the scroll casing 2, and the circumferential distribution becomes non-uniform. However, when the scroll casing 2 having a small divergence angle θc is used, the deceleration loss at the time of inflow of the scroll casing is reduced and the resulting static pressure rise is large, and the circumferential distribution of the flow in the scroll casing 2 is increased. Becomes uniform, so that the efficiency is increased.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a multi-plate laminar flow fan in which a spread angle of a scroll casing is changed.

FIG. 2 is a half vertical sectional view showing an example of a multi-plate laminar flow fan.

FIG. 3 shows the performance characteristics of a fan in a multi-plate laminar flow fan using scroll casings having different divergence angles (ie,
FIG. 4 is a characteristic diagram showing changes in a pressure coefficient, a total pressure efficiency, and a power coefficient with respect to a flow coefficient.

FIG. 4 is a characteristic diagram showing a change in maximum fan efficiency with respect to a spread angle in a multi-plate laminar flow fan using scroll casings having different spread angles.

FIG. 5 is a characteristic diagram showing a change in a pressure coefficient with respect to an angle radian from a scroll casing tongue in a multi-plate laminar flow fan using scroll casings having different spread angles.

[Explanation of symbols]

1 is an impeller, 2 is a scroll casing, 2a is a discharge port, 2b is a tongue, 3 is a donut-shaped disk, 3a is a suction hole,
Is the rotation axis, r ₂ is the distance between the scroll casing tongue 2b and the rotation axis O, θ is the angle radian from the scroll casing tongue 2b, θc is the spread angle of the scroll casing 2, and r is the scroll casing tongue 2b. And the distance between the inner wall of the scroll casing 2 and the rotation axis O at an angle of θ from.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F04D 17/08 F04D 29/28 F04D 29/66

Claims (1)

(57) [Claims] 1. An impeller (1) comprising a plurality of donut-shaped disks (3), (3) having suction holes (3a), (3a),. ) And a scroll casing (2) enclosing the outer periphery of the impeller (1), wherein the scroll casing is
The multi-plate laminar flow fan characterized in that the spread angle (θc) of (2) is set in the range of 1 to 4 °.