JP3411701B2 - Centrifugal blower - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a centrifugal blower having an impeller arranged in a spiral scroll casing.

[0002]

2. Description of the Related Art FIG. 2 and FIG. 3 show an example of a conventional single suction centrifugal fan. In FIG. 2, 02 is a rotary shaft that is driven to rotate by a drive source such as an electric motor, 01 is an impeller fixed to the rotary shaft 02, 04 is a spiral scroll casing, and 08 is gas in the impeller 01. Flow guide,
Reference numeral 012 is an annular space formed between the outer surface of the flow guide 08 and the scroll tongue 010.

An impeller 01 has a plurality of blades 03 fixed at equal intervals along a circumferential direction between a disc-shaped main plate 05 fixed to a rotary shaft 02 and a conical side plate 06. It becomes.

When the impeller 01 rotates during operation of this centrifugal blower, gas passes through the flow guide 08 and the impeller
After being introduced into 01 and urged by its blades 03, it flows through the vortex chamber 04a in the scroll casing 04 and is blown out from the discharge port 011.

[0005]

In the above-mentioned conventional centrifugal blower, as shown in FIG. 3 (A), the main plate 05 of the impeller 01 is orthogonal to the rotary shaft 02, and the side plate 06 is directed toward the outer periphery thereof. Since the angle θ is inclined so as to approach the main plate 05 and the curvature r of the inner surface 08a of the flow guide 08 is small,
The flow loss near the side plate 06 becomes larger than that near the main plate 05.

Therefore, when the gas flows in the impeller 01, B
-B cross section, that is, the pressure of the gas flowing near the main plate 05 is C
-C cross section, that is, higher than that of gas flowing near the side plate 06. As a result, a secondary flow B from the main plate 05 side to the side plate 06 side is generated, and this secondary flow B is theoretically generated on both the pressure surface 03b and the suction surface 03a of the blade 03.

Then, the secondary flow B flows from the main plate 05 side to the side plate 06, and then wraps around from the front edge of the blade 03 to the suction surface 03a, as shown by the white arrow in FIG. 3 (C). At negative pressure surface 03
a Peeling D occurs on the top, causing the performance of the centrifugal blower to deteriorate.

On the other hand, since the CC cross section is inclined by the angle θ with respect to the BB cross section, the mounting angle α _C (see FIG. 3C) at the leading edge of the blade 03 of the CC cross section is B. -That of section B α
_It is smaller than _B (see FIG. 3 (B)). Therefore, even if the gas flows into the main plate 05 side and the side plate 06 side at the same flow velocity, C-
The C-section has a larger incident angle than the BB-section, resulting in increased flow separation and pressure loss.

[0009]

The present invention has been invented in order to solve the above-mentioned problems, and the gist of the present invention is to fix it to a rotary shaft in a spiral scroll casing. A plurality of blades are fixed at equal intervals along the circumferential direction between orthogonal disc-shaped main plates and conical side plates inclined so as to approach the main plate toward the outer periphery. In a centrifugal blower provided with an impeller, an auxiliary blade protruding forward from a front edge of the blade is provided, and an inlet angle of the auxiliary blade is smaller than an inlet angle of the blade. is there.

Another feature is that the protruding length of the auxiliary blade is gradually reduced from the side plate toward the main plate.

[0011]

In the present invention, the incident angles of the gas with respect to the blade are almost the same on the main plate side and the side plate side, so that flow separation and pressure loss increase can be prevented.

[0012]

FIG. 1 shows an impeller of a single suction centrifugal fan according to an embodiment of the present invention.
Is a sectional view taken along the line BB of (A), and (C) is CC of (A).
It is sectional drawing which follows the line.

In FIG. 1, reference numeral 2 is a rotary shaft which is rotationally driven by a drive source such as an electric motor, 1 is an impeller, and 5 is a disk which is fixed to the rotary shaft 2 via a boss 7 and is orthogonal to the rotary shaft 2. -Shaped main plate, 6 is a conical side plate, and is inclined by an angle θ so as to approach the main plate 5 toward the outer periphery thereof.

A plurality of blades 3 are arranged at equal intervals along the circumferential direction, and both ends thereof are fixed to the inner surface 5a of the main plate 5 and the inner surface 6a of the side plate 6. Auxiliary wings 14 projecting forward are fixed to the front edges 3c of these wings 3.

As shown in FIG. 1 (B), the tangent line Y at the leading edge 3c of the blade 3 of the circle R, whose center is the auxiliary blade 14 and is in contact with the leading edge 3c of the blade 3 about the rotational axis 2a of the impeller 1. The angle between
The incident angle β of the auxiliary blade 14 is slightly smaller than the incident angle α of the blade 3 (5 to 5
15 °) is set to be small.

The chord length l of the auxiliary blade 14 is at least 10% or more of the chord length L of the blade 3, and the distance between the adjacent blades 3 due to the installation of the auxiliary blade 14 causes a decrease in the flow rate. The pitch is set to 40% or less of the blade pitch P (= Rφ) so as not to be narrow. Further, since the auxiliary wing 14 does not need to be installed near the main plate 5, the chord length l thereof is configured to become smaller as it approaches the main plate 5, as shown in FIGS. 1 (A) and 1 (C). .

However, when the gas flows toward the main plate 5 and the side plate 6 at the same flow velocity, since the inner surface 6a of the side plate 6 is inclined, the incident angle on the side plate 6 side is larger than that on the main plate 5 side. Become.

However, since the auxiliary blade 14 having an incident angle β smaller than the incident angle α of the blade 3 is provided near the side plate 6,
The incident angles of the main plate 5 side and the side plate 6 side are substantially the same, and flow separation and increase in pressure loss due to the non-uniform incident angle as in the conventional case can be prevented.

The case where the present invention is applied to the single-suction type centrifugal blower has been described above, but it goes without saying that the present invention can be applied to a double-suction type blower.

[0020]

According to the present invention, since the auxiliary blade protruding forward from the leading edge of the blade is provided and the entrance angle of this auxiliary blade is smaller than the entrance angle of the blade, the incident angle to the blade is closer to the main plate and the side plate. Therefore, flow separation and increase in pressure loss can be prevented.

[Brief description of drawings]

1 shows an embodiment of the present invention, (A) is a sectional view taken along the axis of the impeller, (B) is a sectional view taken along the line BB of (A), FIG.
(C) is a sectional view taken along the line CC of (A).

FIG. 2 shows an example of a conventional single suction centrifugal fan, (A)
3B is a cross-sectional view taken along the line AA of (B), (B) is a cross-sectional view taken along the line BB of (A), and (C) is an external perspective view of the impeller.

FIG. 3 shows an impeller of a conventional single-suction centrifugal fan,
(A) is a sectional view taken along the axial center, (B) is a sectional view taken along line BB of (A), and (C) is a sectional view taken along line CC of (A).

[Explanation of symbols]

1 impeller 2 rotation axes 3 wings 3a suction side 3b Pressure side 5 Main plate 6 side plate 14 Aileron

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Bibliography Sho 60-107399 (JP, U) Rikai Hei 1-66500 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F04D 29/30 F04D 29/28 F04D 29/42

Claims (2)

(57) [Claims] 1. Between a disc-shaped main plate which is fixed to a rotary shaft in a spiral scroll casing and which is orthogonal to the rotary shaft, and a conical side plate which is inclined so as to approach the main plate toward the outer periphery. In a centrifugal blower comprising an impeller having a plurality of blades fixed at equal intervals along the circumferential direction thereof, an auxiliary blade protruding forward from the front edge of the blade is provided. A centrifugal blower, wherein the blade inlet angle is smaller than the blade inlet angle. 2. The centrifugal blower according to claim 1, wherein the protruding length of the auxiliary blade is gradually reduced from the side plate toward the main plate.