EP3139046B1 - Electric centrifugal blower - Google Patents

Description

• The present invention relates to an electric centrifugal blower, in particular a volute for an electric blower able to optimize the air suction efficiency.
• In fact, with reference to new regulations, each blower is classified in the respective energetic efficiency class on the base of the Fluid Dynamic Efficiency (FDE) parameter calculated in the Best Efficiency Point (BEP). In particular, IEC 61591 provides for the terms and types of instruments for the execution of tests to verify the performance of the electric blower. Its overall efficiency descends from the aerodynamic efficiency, that is from the handling of air flow defined by the measured values of the static pressure and the volumetric flow rate of the blower volute, and from the electromechanical efficiency of the motor.
• In order to improve the electric blower efficiency, studies were carried out oriented to the optimization of the suction process and, more generally, to the air flow analysis to improve the aerodynamic aspects of the aspirated air flow by acting on the volute of the electric blower.
• US 2006/204382 A1 discloses an electric centrifugal blower comprising an impeller having an orthogonal rotation axis coincident with the z axis of a coordinate system. The impeller is within a blower volute that has a discharge mouth parallel to a plane passing through the orthogonal rotation axis and perpendicular to the xy-plane, wherein that said blower volute has a baffle in the vicinity of the end cross-section of said discharge mouth.
• US 2009/114206 A1 discloses an air distribution blower housing for an air handler. The blower housing utilizes a volute outer wall having an exponentially increasing expansion angle in the direction of air flow through the blower housing, so that the volute has a logarithmic shape.
• So, in general, an object of the invention is to identify the best conformation of an aspirating blower volute, able to optimize the suction process of electric centrifugal blowers.
• In particular, an object of the invention is to really enhance the air suction aerodynamic process of electric centrifugal blowers in suction hoods, which represent the final product into which such electric centrifugal blowers are assembled.
• The mentioned and other objects are achieved by an electric centrifugal blower as defined in the enclosed claims.
• The blower volute has an outer radius R1 at an angle of 172.66 grades in the xy-plane, an outer radius R2 at an angle of 256.02 grades in the xy-plane, an outer radius R3 at an angle of 372.34 grades in the xy-plane, the ratios of said radii R1, R2, R3 to the diameter D1 of the impeller being R1/D1 = 0.79 ± 5%, R2/D1= 0.70 ± 5% and R3/D1 = 0.57 ± 5%, respectively.
• From the above it should be understood that the present invention, which aims to optimize the air suction process, refers exclusively to the shape of the electric blower volute.
• The advantages arising from the shape and size of the electric blower volute have been highlighted by a comparison of the electric blower aerodynamic performance according to the present invention with those resulting from the use of the same electric motor assembled in other volutes of electric blowers available on the market. In this way it was possible to study and analyse separately the different configurations of the blower volute by identifying the correct improvements to be made to optimize the aerodynamic efficiency of the entire casing.
• The present invention will be now described, for an illustrative but not limitative example, with reference to the accompanying drawings, in which:
• Figure 1 is a perspective view of an electric blower of the prior art without cover;
• Figure 2 is a perspective view of an electric blower according to the present invention without cover;
• Figure 3 is a plan view of the interior of the electric blower in Figure 2; and
• Figure 4 is a view similar to that of Figure 3 that represents the geometry of the blower volute.
• First referring to Figure 1, which is a perspective view of an electric blower 1 of the prior art shown without cover, for convenience of illustration, a blower volute generally indicated as 2 and an impeller generally indicated as 3 can be seen.
• The blower volute 2 has a discharge mouth 4. Shown in Figure 2 is a perspective view of an electric blower 10 according to the present invention without cover. By using the same numbers in Figure 1 to indicate identical parts, the blower volute 10 is indicated as 20, the impeller as 3 and the discharge mouth as 4. The discharge mouth 4 of the electric blower 10 has an end cross-section 5 as shown in Figure 3. The electric blower 10 according to the present invention has a baffle 6 in the vicinity of the end cross-section 5 of the discharge mouth 4.
• In order to define the other design features of the electric blower volute according to the present invention, the impeller 3 has a z orthogonal rotation axis coincident with the z axis of an xyz coordinate system, whose xy-plane is represented in Figure 4, which is a view similar to that of Figure 3. Shown in Figure 4 are the points P1, P2, P3, P4, which represent the curvature centre of tracts of the blower volute 20 with relative radii R1, R2, R3, R4, used for the construction of the blower volute spiral.
• In an embodiment, the diameter D1 of the impeller of the electric blower 10 is 147 mm as calculated at the ends of the blades of the impeller itself, having the point P0 (0; 0) as centre of the circumference.
• For the calculation of the blower volute spiral the three different external geometric radii above mentioned were taken into consideration, applied in the points which have as coordinates the following values expressed in mm:
• Radius R1 = 116 applied at the point P1 (15.2; 8.8)
• Radius R2 = 103 applied at the point P2 (2.2; 9.3)
• Radius R3 = 84.5 applied at the point P3 (-2.2; -8.6)
• The outer radius R1 is measured at an angle of 172.66 grades in the xy-plane, the outer radius R2 at an angle of 256.02 grades in the same plane, the outer radius R3 at an angle of 372.34 grades.
• In order to make independent such radii from the sizes of the blower volute, the ratios of these radii R1, R2, R3 to the impeller diameter D1 are claimed. These ratios are, respectively: $$\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="imgf0001.png"\; state="\{\{state\}\}">R</figure-callout>}1/\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="imgf0001.png"\; state="\{\{state\}\}">D</figure-callout>}1=0.79\pm 5\%\mathrm{\hspace{0.17em}},$$

  

  $$\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="imgf0001.png"\; state="\{\{state\}\}">R</figure-callout>}2/\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="imgf0001.png"\; state="\{\{state\}\}">D</figure-callout>}1=0.70\pm 5\%\mathrm{\hspace{0.17em}},$$

  

  and $$\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">R</figure-callout>}3/\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="imgf0001.png"\; state="\{\{state\}\}">D</figure-callout>}1=0.57\pm 5\%\mathrm{\hspace{0.17em}},$$

  

  said blower volute 20 has an outer radius R1 at an angle of 172.66 grades in the xy-plane, an outer radius R2 at an angle of 256.02 grades in the xy-plane, an outer radius R3 at an angle of 372.34 grades in the xy-plane, the ratios of said radii R1, R2, R3 to the diameter D1 of the impeller being R1/D1 = 0.79 ± 5%, R2/D1 = 0.70 ± 5%, and R3/D1 = 0.57 ± 5%, respectively.

Claims (2)

1. An electric centrifugal blower (10) comprising an impeller (3) having an orthogonal rotation z axis coincident with the z axis of an xyz coordinate system, the impeller (3) having a diameter D1 and being within a blower volute (20) that has a discharge mouth (4) parallel to a plane passing through the z axis and perpendicular to the xy-plane, wherein the x-axis passes through the rotation z-axis and is perpendicular to the discharge mouth, said blower volute (20) having a baffle (6) in the vicinity of the end cross-section (5) of said discharge mouth (4), said blower volute being characterised in that it is constructed from a plurality of tracts with relative radii R1, R2, R3, wherein R1 is the outer radius of the said blower volute (20) at an angle of 172.66 grades in the xy-plane, R2 is the outer radius of the said blower volute (20) at an angle of 256.02 grades in the xy-plane, R3 is the outer radius of the said blower volute (20) at an angle of 372.34 grades in the xy-plane, the relationships of said radii R1, R2, R3 to the diameter D1 of the impeller being respectively R1/D1 = 0.79 ± 5%, R2/D1= 0.70 ± 5% and R3/D1 = 0.57 ± 5%.
2. The electric centrifugal blower (10) according to claim 1, wherein said outer radius R1 at an angle of 172.66 grades in the xy-plane has the point P1 (15.2; 8.8) as its centre and a length of 116 mm, said outer radius R2 at an angle of 256.02 grades in the xy-plane has the point P2 (2.2; 9.3) as its centre and a length of 103 mm, and said outer radius R3 at an angle of 372.34 grades in the xy-plane has the point P3 (-2.2; -8.6) as its centre and a length of 84.5 mm.

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