US20100290901A1 - Centrifugal impeller - Google Patents

Abstract

The present relates to a centrifugal impeller. According to the invention, the centrifugal impeller includes: a base plate 11 that has a rotating shaft bracket at the center portion where a rotary shaft is fitted, and of which the surface radially formed from the rotary shaft socket is sloped downward in a straight line or at a predetermined radius of curvature to maintain an obtuse angle with respect to the rotary shaft; a plurality of blades 13 that is circumferentially arranged on the upper surface of the base plate 11; and a scroll casing 15 that is disposed on the fronts of the blades 13, has a suction hole 15′ at the center portion to suck fluid, and forms an enlarged channel 17 through which the fluid flows, between the base plate 11 and the scroll casing 15 by being sloped downward from the suction hole 15′ toward the radial end. According to the present invention, the base plate 11 of the centrifugal impeller 10 is sloped within a range of 0° to 17° of the slope angle, such that high-speed jet fluid pushed in the centrifugal direction by rotation of the rotary shaft can smoothly flow through the enlarged channel 17 between the base plate 11 and the scroll casing 15.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• The present invention relates to a centrifugal impeller, more particularly a centrifugal impeller that circumferentially discharges fluid smoothly, which is pushed by radial blades.
• 2. Description of the Related Art
• A device that transports fluid using a suction force generated by high-speed rotation is called a centrifugal air blower. The centrifugal air blower is mainly used for air movements with high pressure such as vacuum cleaners that need strong output, and fluid is sucked into the centrifugal air blower by rotating centrifugal impellers at a high speed.
• FIG. 1A and FIG. 1B are a front view and a side view, respectively, which show the structure of a centrifugal impeller according to the related art.
• Referring to the figures, the centrifugal impeller 1 includes a base plate 3 having a rotary shaft socket at the center portion, radial blades 5 circumferentially arranged on the upper surface of the base plate 3, and a scroll casing 7 disposed at the fronts of the blades 5.
• The centrifugal impeller 1 axially sucks the fluid by high-speed rotation such that the fluid obtains kinetic energy while passing through between the blades 5 circumferentially arranged on the circular base plate 3, and is radially discharged.
• Explaining the principle of the fluid supply in the centrifugal impeller 1, the fluid flowing inside by rotation of the blades 5 circumferentially arranged on the base plate 3 is pushed, in which low-pressure regions are continuously and repeatedly created, such that fluid is continuously supplied. In this operation, the fluid pushed by the centrifugal force created by the rotational force of the centrifugal impeller 1 passes through between the blades 5 and flows to an enlarged channel 9 formed between the scroll casing 7 and the base plate 3.
• However, there are problems in the related art described above.
• That is, the base plate 3 of the centrifugal impeller 1 is a horizontal plate. When the horizontal plate, the base plate 3 is perpendicular to the axis of the centrifugal impeller 1, the axis of the centrifugal impeller 1 and the motion direction of the inflow fluid make a right angle, such that the high-speed fluid that is pushed and discharged by the centrifugal force created by the rotational force of the centrifugal impeller 1 cannot smoothly flow into the enlarged channel 9.
• In particular, as it is required to reduce the size of the product, the horizontal structure of the base plate 3 makes a gap between the base plate 3 and the scroll casing 7 narrower, which increases the impact resistance of the fluid flowing at a high speed, and as a result, generates a noise and decreases the efficiency of the centrifugal impeller 1.
SUMMARY OF THE INVENTION
• The present invention is designed to overcome the above problems and it is an object of the present invention to provide a centrifugal impeller that allows a base plate to maintain an obtuse angle with respect to the rotational axis of the impeller so that fluid discharged at a high speed can smoothly pass through a passage between the base plate and a scroll casing and the volume for inlet flows can be enlarged.
• In order to achieve the objects of the present invention, a centrifugal impeller includes: a base plate that has a rotary shaft socket at the center portion where a rotary shaft is fitted, and of which the surface radially formed from the rotary shaft socket is sloped downward in a straight line or at a predetermined radius of curvature to maintain an obtuse angle with respect to the rotary shaft; a plurality of blades that is circumferentially arranged on the upper surface of the base plate; and a scroll casing that is disposed on the fronts of the blades, has a suction hole at the center portion to suck fluid, and forms an enlarged channel through which the fluid flows, between the base plate and the scroll casing by being sloped downward from the suction hole toward the radial end.
• The slope angle of the base plate is calculated by the following equations for calculating a coefficient of loss,
• $H_{\mathrm{loss}}=K\left(\frac{{\mathrm{<figure-callout\; id="2"\; label="v"\; filenames="US20100290901A1-20101118-D00003.png"\; state="\{\{state\}\}">v</figure-callout>}}^2}{2g}\right)\mathrm{and}$ $K=\left\{\begin{array}{c}0.5-0.8\theta \mathrm{for}0.0\leqq \theta \leqq 2.0\\ 0.14+0.04\theta \mathrm{for}2.0\leqq \theta \leqq 15.0\end{array}\right\}$
• [K: a coefficient of loss of flowing fluid, v: average flow rate of fluid passing through between the blades. g: acceleration of gravity, and H_loss: loss head due to enlargement of the cross section of the enlarged channel]
• The slope angle of the base plate is in a range of 0° to 17°.
• According to the present invention, since the base plate of the centrifugal impeller is sloped within a range of 0° to 17° of the slope angle, high-speed fluid pushed in the centrifugal direction by rotation of the rotary shaft can smoothly flow through the enlarged channel that is widened as compared with the related art.
• Further, since the base plate is sloped in the same direction as the scroll casing, even if the gap between the base plate and the scroll casing is decreased, as it is required to reduce the size of a product, and the axis of the impeller and the motion direction of the sucked fluid make an obtuse angle, not a right angle, the impact resistance of the fluid flowing at a high speed is reduced, thereby reducing noise and increasing the efficiency of the centrifugal impeller.
BRIEF DESCRIPTION OF THE DRAWINGS
• The above and other features and advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings in which:
• FIGS. 1A and 1B are a front view and a side view, respectively, showing the structure of a centrifugal impeller according to the related art;
• FIGS. 2A and 2B are a front view and a side view, respectively, showing a preferred embodiment of a centrifugal impeller according to the present invention;
• FIG. 3 is a view illustrating flow of fluid that flows through an enlarged channel according to the present invention; and
• FIG. 4 is a graph illustrating the relationship between the angle of a base plate and a coefficient of loss.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
• Hereinafter, preferred embodiments of the invention are described in detail with reference to the accompanying drawings.
• FIGS. 2A and 2B are a front view and a side view, respectively, showing a preferred embodiment of a centrifugal impeller according to the present invention, FIG. 3 is a view illustrating flow of fluid that flows through an enlarged channel according to the present invention, and FIG. 4 is a graph illustrating the relationship between the angle of a base plate and a coefficient of loss.
• Referring to the figures a centrifugal impeller 10 includes a base plate 11 having a rotary shaft socket (not shown) at the center portion, blades 13 circumferentially arranged on the upper surface of the base plate 11, and a scroll casing 15 disposed at the fronts of the blades 13.
• As shown in FIGS. 2A and 2B, the base plate 11 is a substantially circular plate, which forms the lower outer shape of the centrifugal impeller 10. The base plate 11 is sloped downward in a straight line or at a predetermined radius of curvature from the center toward the radial end to make an obtuse angle to the rotational axis (not shown) of the centrifugal impeller 10. In detail, the base plate 11 is sloped within a range of 0, which is calculated by the equations described below. The slope of the base plate 11 relatively increases the flow cross-sectional area of an enlarged channel 17, which is described below, as compared with the related art.
• Setting the slope of the base plate 11 within a range of θ is for allowing the fluid to smoothly flow through the enlarged channel 17 between the base plate 11 and the scroll casing 15, which is described below, by adjusting the slope angle of the base plate 11 such that the size of the flow cross section of the enlarged channel 17 relatively increases, as compared with the related art, even if the size of the centrifugal impeller 10 is decreased. Further, this is for reducing the impact resistance of the fluid that may be generated by the right angle made by the axial direction of the centrifugal impeller 10 and the motion direction of the fluid.
• A rotary shaft socket is formed up-down through the center portion of the base plate 11. A rotary shaft that is driven by a driving force is fitted in the rotary shaft socket.
• The blades 13 are a plurality of flat plates and circumferentially arranged between the base plate 11 and the scroll casing 15. The blades 13 push the fluid discharged at a high speed to the enlarged channel 17 while rotating with the base plate 11 and the scroll casing 15 by rotation of the rotary shaft.
• The scroll casing 15 is a part that forms the upper outer shape of the centrifugal impeller 10 and a suction hole 15′ that is communicated with the rotary shaft socket is formed at the center portion of the scroll casing 15 to suck fluid. The scroll casing 15 is a substantially circular plate corresponding to the base plate 11, which is sloped downward from the suction hole 15′ toward the radial end.
• The enlarged channel 17 is formed between the base plate 11 with the blades 13 and the scroll casing 15. The enlarged channel 17 is a passage through which the fluid sucked through the suction hole 15′ flows. The enlarged channel 17 is sloped downward with the flow cross section decreased, from the suction hole 15′ toward the radial end of the centrifugal impeller 10 by the shape of the scroll casing 15.
• It is preferable that the slope angle θ of the base plate 11 is in a range of 0° to 17° in the centrifugal impeller 10 having the above configuration. This is the optimum value calculated by the embodiment described below. When the slope angle is large, the pressure loss of the centrifugal impeller 10 increases and energy loss is generated; therefore, it is important to select an appropriate range for the slope angle θ.
• The following equation 1 is a formula for calculating a preferred range of the slope angle between the base plate 11 and the scroll casing 15.
• $\begin{array}{cc}{H}_{\mathrm{loss}}=K\left(\frac{{\mathrm{<figure-callout\; id="2"\; label="v"\; filenames="US20100290901A1-20101118-D00003.png"\; state="\{\{state\}\}">v</figure-callout>}}^2}{2g}\right)& \left(1\right)\\ K=\left\{\begin{array}{c}0.5-0.8\theta \mathrm{for}0.0\leqq \theta \leqq 2.0\\ 0.14+0.04\theta \mathrm{for}2.0\leqq \theta \leqq 15.0\end{array}\right\}& \left(2\right)\end{array}$
• where K is a coefficient of loss of flowing fluid, v is average flow rate of fluid passing through between blades, g is acceleration of gravity, and H_loss is loss head due to enlargement of the cross section of the enlarged channel. In the above equation, k is a coefficient of loss and the coefficient of loss K is a value calculated from the slope angle θ that shows the degree of enlargement of the enlarged channel.
• Equation 2 is a formula showing change of the coefficient of loss K to θ, which is defined by the result obtained by measuring the coefficient of loss with respect to fully developed turbulent flow. In particular, the angle of the base plate 11 set within the range of 0° to 17° is the optimum slope angle θ determined by a neural network, which is an optimizing method. As described above, the improved degree of the coefficient of loss K in accordance to the slope angle θ can be seen from the graph shown in FIG. 4.
• It is described hereafter in detail to obtain a range of the slope angle of the centrifugal impeller according to a preferred embodiment of the present invention.
• First, the coefficient of loss K in accordance to the angle of the base plate 11 shown in FIG. 2B is calculated from the equation 2. In this operation, the coefficient of loss K is calculated while setting the scroll casing 15 and the blades 13 with the same conditions and changing only the angle of the base plate 11.
• The coefficient of loss K is calculated by experiments using a specimen, in which the magnitude of the dynamic pressure is measured by using the difference between the total pressure and the static pressure, and then the magnitude can be determined from the measured value, as a ratio to the static pressure using the average flow rate. The change of the coefficient of loss K in accordance to the slope angle of the base plate 11 can be seen from the graph shown in FIG. 4.
• As shown in FIG. 4, it can be seen that rapid loss does not appear within the range of 0° to 17° of the angle of the base plate 11, in the coefficient of loss K.
• As described above, although the present invention is described with reference to the embodiments shown in the accompanying drawings, they are just examples and it should be understood that those skilled in the art can accomplish various changes, modifications, and other equivalent embodiments without departing from the spirit and scope of the present invention. Therefore, the spirit and scope of the present invention should be determined by the spirit described in the accompanying claims.

Claims (3)

1. A centrifugal impeller, comprising:

a base plate that has a rotary shaft socket at the center portion where a rotary shaft is fitted, and of which the surface radially from the rotary shaft socket is sloped downward in a straight line or at a predetermined radius of curvature to maintain an obtuse angle with respect to the rotary shaft;

a plurality of blades that is circumferentially arranged on the upper surface of the base plate; and

a scroll casing that is disposed on the fronts of the blades, has a suction hole at the center portion to suck fluid, and forms an enlarged channel through which the fluid flows, between the base plate and the scroll casing by being sloped downward from the suction hole toward the radial end.

2. The centrifugal impeller according to claim 1, wherein the slope angle of the base plate is calculated by the following equations for calculating a coefficient of loss,

$H_{\mathrm{loss}}=K\left(\frac{v^2}{2g}\right)\mathrm{and}$ $K=\left\{\begin{array}{c}0.5-0.8\theta \mathrm{for}0.0\leqq \theta \leqq 2.0\\ 0.14+0.04\theta \mathrm{for}2.0\leqq \theta \leqq 15.0\end{array}\right\}$

[K: a coefficient of loss of flowing fluid, v: average flow rate of fluid passing through between the blades, g: acceleration of gravity, and H_loss: loss head due to enlargement of the cross section of the enlarged channel].

3. The centrifugal impeller according to claim 2, wherein the slope angle of the base plate is in a range of 0° to 17°.

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