RU2309299C2 - Centrifugal fan - Google Patents

Abstract

FIELD: fan engineering.

SUBSTANCE: centrifugal fan comprises housing that is sectional and is made of thick-walled plates oriented along the tangent to the additional spiral and bent sheet that abuts against the housing from inside through distant longitudinal ribs. The lengths of the plates and the sheet are determined from the formulae presented.

EFFECT: simplified manufacturing.

2 dwg

Description

The invention relates to centrifugal electric fans with a spiral housing.

Known centrifugal fans containing a spiral casing with an impeller located therein mounted on an electric motor shaft [1].

An electric fan is also known, which contains a welded aluminum case with a thin internal spiral plate located in the spiral grooves of the side shields of the electric fan [2] with a sound absorber providing increased sound and vibration absorption properties of the case, however, assembling and installing the spiral plate in such a case is very difficult, especially in large electric fans.

The closest (prototype) in technical essence to the proposed invention is a more technologically advanced centrifugal fan according to application 2003112564/06 [3].

The proposed centrifugal fan differs from the prototype in that in order to reduce vibration and noise indicators by improving the absorbing properties of the electric fan, the casing is made of thick-walled plates oriented tangentially to the additional process spiral and a sheet bent along the generatrix of the main working spiral. Plates provide the necessary strength properties of the casing, the sheet - the necessary shape of the casing in aerodynamic terms, and the space between the technological and working spiral filled with vibration-absorbing material - the necessary vibro-acoustic characteristic of the electric fan.

Figure 1 shows the aerodynamic diagram of the proposed centrifugal fan; figure 2 shows a possible design of a spiral casing.

The determining parameters of the proposed centrifugal fan are the disclosure of A ₁ and A _2, respectively, of the main and additional spirals (the value of A ₁ and the diameter of the wheel D _{1 are} determined by the aerodynamic calculation of the fan, the values of A ₂ and D _{2 are} determined by the requirements for vibration and noise characteristics of the fan). The main and additional spiral arcs are constructed concentrically to one quarter circles whose centers are successively moved over the tops design squares with sides a ₁ = A _1/4 and a ₂ = A _2/4. The boundaries of these arcs are at the points K ₁ , K ₃ , K ₅ , K ₇ and K ′ ₁ , K ′ ₃ , K ′ ₅ , K ′ ₇ , and the midpoints of the arcs are at the points K ₂ , K ₄ , K ₆ and K ′ ₂ , K ′ ₄ , K ′ _6, respectively. The tangent drawn through the point K _'1, K' _2, R _'3, R' _4, R _'5, R' _6, R _'7, intersect at the same angle α = 45 °, and determine the position of hull plates for additional helix.

The spiral case (Fig. 2) is made of composite rectangular flat plates 1 ... 7 fastened together, oriented through the points K ′ ₁ , K ′ ₂ , K ′ ₃ , K ′ ₄ , K ′ ₅ , K ′ ₆ , K ′ ₇ along the tangents to the contour of the additional technological spiral of a larger size, which is spaced apart from the main spiral by

Δ = A ₂ -A ₁ + (D ₂ -D ₁ ) / 2,

determined by the required thickness of sound-absorbing material, both spirals are similar, oriented coaxially and determined by the required thickness of sound-absorbing material, both spirals are similar, oriented coaxially and differ in sizes D and A, which for the main spiral are determined by the aerodynamic characteristics of the electric fan, and for the additional spiral are determined by the requirements for vibration-absorbing properties of the fan housing.

The plates 1 ... 7, fastened together by welds 8, form a supporting body, to which, from the inside through the spacing longitudinal ribs 1 ′ ... 7 ′, a curved sheet 9 forms, which forms the main working spiral. The length of the plates along the spiral is different, increasing with increasing bending radius of the portion of the technological spiral to which the plate is adjacent and is determined from the expression

L _n = 0.41 [D ₂ + (n + 1) a ₂ ],

where n = 1, 2, 3 ... is the serial number of the plate,

and ₂ is the side of the design square of the additional spiral.

The sheet 9 is brought into the rail 10 as far as it will go, its other end part is flanged 11 and fixed by the rail 12. The length of the sheet 9 from the beginning of plate 1 (point B) to the end of plate 7 (point C) is determined from the expression

L _l = 2.77 (D ₁ + 5a ₁ ),

where a ₁ is the side of the design square of the main spiral.

The curved part of the sheet is preloaded due to its own elastic forces to the spacing ribs of the body plates. In this case, the supporting contact points give the curved sheet a spiral shape. For ease of attachment to the body of the injection pipeline 13 and the outer surface 14 of rails 12 and 10 are located on the same plane as the surface plate 15 1. The rail 10 has the shape of "language" ordering air circulation, its surface facing the wheel, is framed radius R ₁ = 0.5D ₁ + 0.5a ₁ .

The sizes of the radii of the spirals R ₁ , R ₂ , R ₃ , R ₄ and R ′ ₁ , R ′ ₂ , R ′ ₃ , R ′ _{4 are} determined from the expressions

R _n = 0.5 (D ₁ -a ₁ ) + na ₁ ,

R ′ _n = 0.5 (D ₂ -a ₂ ) + na ₂ ,

where n = 1, 2, 3 ... is the ordinal number of the radius.

The space between the plates and the sheet is filled with vibration-absorbing material 16, for example, foam rubber, polyurethane foam, materials based on composite.

When the fan is operating, the necessary strength, aerodynamic and sound-absorbing properties of the casing are provided. Due to the prefabricated housing design, its manufacturing technology is simplified, because the basis of the power part is made up of plates of simple configuration, and the forming part consists of one sheet. The power part of the housing can be manufactured, for example, by welding plates previously laid outside the technological mandrel in the form of a necessary technological spiral. To obtain a spiral shape of the sheet, it is enough to bend it to contact with the spacing ribs of the body plates and fix the end sections with rails.

The prefabricated housing design expands the choice of materials. So, for example, the sheet can be made of dust-resistant material, and the vibration-absorbing material can be granular, foamy, porous or composite.

To improve the maintainability of the fan, the rails can be removable so that the worn sheet and vibration-absorbing material can be replaced.

Literature

1. Centrifugal fan. Certificate for utility model of the Russian Federation No. 15918, Bull. No. 32, 2000.

2. Bratkovsky O.A., Tsekhmestryuk G.S., Anufriev V.V., Sudov V.B. A new series of radial AC electric fans // Electronic and electromechanical systems and devices. Sat scientific works of SPC "Polyus". Tomsk, 2001. S.217-220.

3. The decision to grant a patent for the invention of 09/14/04 on the application 2003112564/06, cl. IPC ⁷ F04D 17/08. Centrifugal fan / Podlevsky N.I., Khitruk B.S., Garganeev B.P., Abdrakhmanova T.B.

Claims (1)

A centrifugal fan containing a composite spiral casing of thick thick-walled outer plates and an inner thin-walled sheet, curved in a spiral, resting on the plates, characterized in that, in order to improve vibration and noise performance by increasing the absorption properties of the electric fan casing, these plates are provided with spacing longitudinal ribs and are oriented along tangent to an additional spiral, the geometrical parameters of which are the opening of A ₂ and the diameter D ₂ , exceed the parameters of the main spiral in magnitude - disclosure A ₁ and the diameter of the fan wheel D ₁ by Δ = A ₂ -A ₁ + (D ₂ -D ₁ ) / 2, determined by the required thickness of the sound-absorbing material, and the length of the body plates is determined from the expression L _n -0.41 [D ₂ + (n + 1) a ₂ ], where n = 1, 2, 3 ... - serial number of the plate; and ₂ is the side of the design square of the additional spiral.

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