JP2009541661A - Centrifugal impeller - Google Patents

Abstract

The low noise centrifugal fan impeller has a multi-honeycomb configuration comprising a number of individual radial flow channels (5) arranged in a circumferential and longitudinal array with respect to the axis of rotation. This increases the passing frequency of the blades compared to conventional impellers, and since the high frequency has low energy for a given flow output, the overall magnitude of the generated noise can be reduced. Each channel (5) extends from a respective channel inlet to a respective channel outlet that is offset in the longitudinal direction of the impeller and increases the internal dimension of the respective channel in a direction parallel to the rotational axis. As such, it helps to slow down and compress air or other media that is carried as it flows through the channel.
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Description

  The present invention relates to rotary impellers used in hydrodynamic devices for moving and / or compressing gases or liquids or other flowable materials, such as fans, blowers, propellers, pumps and compressors. The invention relates to the provision of low noise levels by such a device. Many devices of this type are in one of two main categories: axial flow devices in which the total flow direction of fluid through the impeller is approximately parallel to its axis of rotation, and in the impeller. It belongs to one of the centrifugal devices in which the entire flow direction of the fluid passing therethrough is approximately radial with respect to its axis of rotation. The latter classification is relevant to the present invention.

  The impeller is a significant noise source in such devices, and the noise from the impeller can be caused by repeated outflow of fluid from individual blades (sound noise) and turbulent passage of fluid over the blades (wide frequency band). Noise). There are clear market drives for low noise devices that exceed the requirements of current legislation. For example, low noise levels are used as an aggressive selling point for vacuum cleaners, hair dryers, cookware hoods, air conditioning units and other household appliances where the noise is dominated by aerodynamic sources. Similarly, there is a need for quieter cooling fans in compact electronic devices, particularly computers, and there is already a market for replacement fans with low noise levels and noise absorption kits. Other markets exist for low noise propulsion units for aircraft and water vehicles. The impeller according to the invention can find application in all these markets or more generally in centrifugal devices where there is a desire for low noise operation.

  In traditional bladed impellers, each individual blade compresses the amount of fluid that contributes to the overall flow through the device. The presence of a static part near the impeller, such as a centrifugal casing outlet hole, causes a split in the pressurized working fluid and whether the resulting pressure wave originates from the fluid itself or from the body of the device It can be clearly seen as one of the noises. The frequency of the noise thus caused is known as the blade passing frequency and depends on the number of impeller blades and the number of significant static features at the exit from the impeller.

  The present invention relates to a conventional vaned impeller in the form of a multi-honeycomb structure comprising a number of individual radial flow channels in which the impeller is arranged in a circumferential arrangement and a longitudinal arrangement with respect to the rotation axis of the impeller. Based on replacing. This dramatically increases the number of blades that pass through the static function and raises the frequency of the sound noise generated accordingly. For a given flow output, higher frequencies have lower energy and therefore reduce the overall magnitude of the generated noise.

  A centrifugal impeller having a structure as described above (referred to below as an impeller of the type mentioned) is disclosed and exemplified in a schematic manner in US 2004/0184914. However, the present invention seeks to provide an impeller of the above type with high hydrodynamic performance. In this regard, the efficient transfer of momentum to fluid on a rotating impeller requires an increase in effective flow area along the length of the flow channel. In the centrifugal impeller of US 2004/0184914, some increase in the effective flow area of each channel is due to the effect of the circumferential width of the channel increasing with increasing radial distance from the axis of rotation. Inherently achieved by: However, in one aspect of the invention, a further increase in the effective flow area may be achieved by configuring the flow channel to provide an increase in dimension orthogonal to the circumferential direction.

  Thus, in one aspect, the invention is an impeller of the type described above, wherein at least a plurality of channels extend from each channel inlet to a respective channel outlet that is offset from each inlet in the longitudinal direction of the impeller, and It is comprised so that the internal dimension of each channel may increase in the direction parallel to the rotational axis of the impeller. The flow channel is also configured to collectively define a dish-shaped inlet array in which the inlet of the flow channel surrounds the axis of rotation, the radius of the array from the main inlet to one end of the impeller It decreases with increasing distance in the longitudinal direction to the impeller.

  The arrangement of the flow channels of the impeller according to the invention is preferably in the form of a series of circumferential rows of such channels arranged along the impeller, each such channel being adjacent to one another. It is offset in the circumferential direction from the channel of the row. This circumferential offset reduces the number of channels passing through the same static function at any moment and reduces the generation of individual sounds and further breaks up the fluid flow that distributes noise over a wide range of frequencies. To do. In a preferred embodiment of the invention, the flow channel is a continuous mosaic with a cross-sectional shape based on a hexagon (or a truncated hexagon in the case of a row of channels at each end of the impeller). This flow channel provides an inherently strong structural form with high area efficiency for fluid flow, allows a natural offset for the adjacent row of channels, and a flat radial surface for acting on the fluid And is more efficient in terms of structure weight and flow area than circular or elliptical channels. This flow channel is not an essential feature of the present invention, but other cross-sectional configurations may be employed if desired. For example, a square-based channel configuration provides slightly higher area efficiency at the expense of some structural strength for a given wall thickness and is therefore more suitable for low load applications.

  The number of flow channels in each circumferential row is preferably the same, and is preferably a prime number that reduces the harmonic formation of the pass frequencies of the noise spectrum vanes.

  These and other features of the present invention will be specifically described by way of example with reference to the accompanying drawings.

  With reference to FIGS. 1 and 2, the impeller shown therein is for a centrifugal air fan or blower as incorporated into a vacuum cleaner, hair dryer or similar device. The impeller consists of a substantially annular structure with one end in the longitudinal direction bounded by a disk 1 having a central opening 2 which constitutes the main air inlet to the device and the other end closed by a disk 3, the disk being in use blades Extending inwardly in the form of a streamlined body 4 adapted to fit on the spindle of an associated motor (not shown) for rotating the car. A number of air radial flow channels 5 extend through the impeller and, when rotated, pass through the opening 2 and along the channel 5 are directed to associated conventional vortex chambers (when required) ( Induces an air flow into (not shown).

  In particular, in the illustrated embodiment, there are a total of 44 channels 5 arranged in an array of four circumferential rows side by side, each row comprising 11 channels arranged along the impeller. The individual channels have a substantially hexagonal cross section, the end rows bounded by the discs 2 and 3 are truncated on five sides, and the center of each row channel is from the next row channel. As shown in the figure, a mosaic is formed so that the half width of the channel is shifted in the circumferential direction.

  In addition, the centerlines of channel 5 are not each in a single radial plane, but in particular, as shown in FIG. It is spread from the inlet end in the longitudinal direction of the impeller so that it can be moved to the center. By this means, a useful increase in the effective cross-sectional area for the flow in each channel can be achieved along the length of the channel, in addition that the channel is out of the impeller axis. Naturally occurs by the circumferential expansion of the channel as it extends in the direction, thus assisting in the deceleration and compression of the air as it flows through the channel. This feature of the channel shape is more easily understood by the simplified representation of FIG. 3, where the dimensions of each channel 5 in a direction parallel to the axis of rotation of the impeller, ie the dimensions a and at the typical channel inlet and outlet in FIG. It can be seen that the “axial thickness” illustrated by b increases along the length of each channel.

  Also, as shown in FIGS. 1 and 2, the inlet end of the channel 5 is widened toward the main inlet 2, and the radius of the channel inlet ring of each circumferential row is reduced for successive rows from the main inlet 2, As a result, the channel inlet collectively defines a dish-shaped array surrounding the body 4. In combination with the contoured central body 4, this shape allows the air flow from the axial direction into which the air flow enters the inlet 2 to the radial direction through which the air flow passes through the channel 5 while maintaining the desired flow area ratio. Help smooth the transition. At the boundary, each channel is widened to the extent that these individual inlets lie in the plane of the opening 2 and acts as an axial impeller at the inlet end of the channel and further at the transition to the centrifugal impeller along the channel. It becomes a hybrid form of the device.

  The channel 5 also has a curved component that improves the compression of air in the circumferential direction.

  FIG. 4 shows the noise spectrum obtained from a conventional vacuum cleaner with the original centrifugal impeller (conventional design with seven blades having a diameter of 90 mm) as a solid line, and the impeller is shown in FIGS. FIG. 6 is a graph showing a noise spectrum obtained from the same electric appliance when it is replaced with one of the same diameter according to the design shown in FIG. In each case, the vacuum cleaner was placed on the floor and operated, and measurements were taken with a sound level meter located 1 meter above the appliance and 1 meter in front of the appliance. By comparing the results, the impeller according to the present invention eliminated a number of individual peaks in the conventional spectrum and achieved a reduction in amplitude over virtually all of the frequency range to which the human ear is most sensitive. I understand that.

  Although a preferred embodiment of a rotating impeller has been described above and illustrated in the accompanying drawings, many design variations, such as flow channels, are possible so that many variations can meet specific needs and applications without departing from the scope of the present invention. It will be appreciated by those skilled in the art that this may be done with respect to the number, size, and hydrodynamic form.

1 is a perspective view of a preferred embodiment of a centrifugal fan impeller according to the present invention. FIG. It is an axial direction sectional view which passes along the impeller of FIG. FIG. 3 is a simplified schematic diagram illustrating an increase in “axial thickness” of the flow channel of the impeller of FIGS. 1 and 2. Figure 3 shows a comparative noise spectrum measured for a conventional vacuum cleaner with the original impeller and with the impeller according to the present invention.

Claims (11)

Comprising a number of individual radial flow channels arranged in a circumferential arrangement and a longitudinal arrangement with respect to the rotational axis of the impeller;
At least a plurality of the channels extend from the respective channel inlets to respective channel outlets that are offset from the respective inlets in the longitudinal direction of the impeller and in parallel to the rotational axis of the impeller. Configured to increase the internal dimensions of the channel,
A centrifugal impeller characterized by that.   The flow channel is configured to collectively define a dish-shaped inlet array in which these inlets surround a rotational axis, the radius of the array from the main inlet to the impeller at one end of the impeller The impeller according to claim 1, wherein the impeller decreases with increasing distance in the longitudinal direction.   3. A contoured body disposed about an axis of rotation within the dish-shaped inlet array, wherein the radius of the body increases with increasing distance from the main inlet in the longitudinal direction of the impeller. The impeller described in 1.   The impeller of claim 1, wherein the flow channels are configured to collectively define an inlet array whose inlets are located in a substantially radial plane with respect to an axis of rotation.   The impeller according to any of claims 1 to 4, wherein at least the plurality of flow channels have a substantially hexagonal cross section.   The impeller according to any one of claims 1 to 4, wherein at least the plurality of flow channels have a substantially rectangular cross section.   The array of flow channels is in the form of a series of circumferential rows of such channels arranged along the impeller, wherein each such row of the channels is the channel of the adjacent such row. The impeller according to any one of claims 1 to 6, wherein the impeller is biased in the circumferential direction from the center.   6. The claim as added to claim 5, wherein there are at least three such rows and at least those flow channels of these rows that are not the longitudinal ends of the array are of approximately hexagonal cross section. 7. The impeller according to 7.   The arrangement of flow channels is in the form of a series of circumferential rows of such channels arranged along the impeller, wherein the number of channels in each such row is the same number. The impeller according to any one of 8.   The impeller according to claim 9, wherein the number is a prime number.   A hydrodynamic device incorporated in the impeller according to claim 1.

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