This invention relates to a blower used, for example, for ventilation.
To achieve an improvement in efficiency in a blower, it is necessary to increase the static pressure, so that it is important that the flow in the centrifugal direction be increased in the relative flow field and that the velocity in the flow direction be reduced.
Generally speaking, in a conventional blower, to increase the flow in the centrifugal direction, it is necessary to turn the flow behind the blades into a mixed flow. In view of this, for example, JP 53-116513 A discloses a construction in which the portion of the reference line of each blade from the root to the middle portion thereof is bent at a predetermined angle of inclination in the rotating direction, and the portion of the reference line from the middle portion to the tip end portion of the blade is bent at a predetermined angle of inclination in a direction opposite to the rotating direction so that the outermost end of the reference line may be situated on the side opposite to the rotating direction with respect to the line connecting the rotation center and the above-mentioned root.
The above conventional blower is basically a so-called axial blower, in which air flows substantially along the axial direction. Thus, in its outer peripheral portion, the effect of mixed flow due to the blade profile is rather small, with the result that a sufficient increase in static pressure cannot be achieved, leading to poor ventilation efficiency, an increase in noise, etc.
This invention has been made with a view toward solving the above problems. It is an object of this invention to provide a blower in which an improvement in ventilation efficiency is achieved through an increase in static pressure, etc. and in which it is possible to achieve a reduction in noise.
This invention provides a blower including: an impeller on which a plurality of axial flow blades are arranged while mounted at circumferential intervals to an outer peripheral surface of a boss; a case surrounding the impeller; and a bell mouth cylindrically constricted so as to guide a gas into the case, in which an inner diameter of the bell mouth is smaller than an outer diameter of the impeller.
Further, this invention provides a blower including: an impeller on which a plurality of blades are arranged while mounted at circumferential intervals to an outer peripheral surface of a boss; a case surrounding the impeller; and a bell mouth cylindrically constricted so as to guide a gas into the case, in which an inner diameter of the bell mouth is smaller than an outer diameter of the impeller, and in which a portion of the blade portion situated on an outer peripheral side of the inner diameter of the bell mouth protrudes from a reduction diameter side end portion toward an expansion diameter side end portion of the bell mouth in a direction along a rotation center axis of the impeller.
Further, this invention provides a blower including a boss and a plurality of blades mounted at circumferential intervals to an outer peripheral surface of the boss, characterized in that, when the blades of the impeller are projected onto a plane perpendicular to the rotation center axis thereof, each of curves that are formed by connecting center points of arc lengths of circumferentially extending arcs formed through overlapping of concentric circles, which radially extend around an intersection point of the plane and the rotation center axis, and the projected blades, is defined as a circumferential center curve, when an angle made by a straight line connecting the intersection point and a boss-side end point of the circumferential center curve and by a straight line connecting the intersection point and an arbitrary point in the circumferential center curve is defined as a forward angle θ with a rotating direction of the blades taken as positive, and when a change ratio per unit radial length of the forward angle θ is defined as an advance ratio, each blade has, in a radial direction, a sweepforward wing portion which is on a boss side and which exhibits a positive value of the advance ratio, and a sweepback wing portion which is on an outer peripheral side of the blade and which exhibits a negative value of the advance ratio, with the arc length of each blade increasing from the boss side toward the outer peripheral side.
In the following, preferred embodiments of this invention will be described with reference to the drawings; in the following description, the components and portions of the embodiments that are the same or equivalent are indicated by the same reference numerals.
This blower is equipped with a motor shaft 20, a cylindrical boss 1 directly connected to the motor shaft 20 so as to be concentric therewith, four blades 4 mounted to the outer peripheral surface of the boss 1 circumferentially at equal intervals, a cylindrical case 19 surrounding the blades 4, and the bell mouth 8 mounted to the suction side end of the case 19 and adapted to guide air into the interior of the case 19.
The boss 1 and the four blades 4 constitute an impeller; the arrow in
In this specification, a device arranged on the flow suction side and having a curved portion smoothly guiding air flow to the impeller is called a bell mouth.
Each blade 4 is composed of a sweepforward wing portion 2 and a sweepback wing portion 3.
Here, the sweepforward wing portion 2 and the sweepback wing portion 3 will be described.
First, as shown in
It is to be assumed that, when the plane perpendicular to the rotation axis 30 is seen from the suction side, the forward angle θ in the clockwise rotating direction of each blade 4 rotating from the first straight line T is positive, and that it is negative in the rotating direction opposite thereto.
In
Each blade 4, composed of the sweepforward wing portion 2 and the sweepback wing portion 3, increases in arc length dimension from the boss 1 side toward the outer peripheral side portion 7. Further, the arcuate shape of the boundary portion 5 between the sweepforward wing portion 2 and the sweepback wing portion 3 substantially coincides with the arcuate shape at a radial position of the blade 4. The advance ratio, which is a change per unit radial length in the forward angle θ of this blade 4, is zero at the position of the intersection point C of the boundary portion 5 and the circumferential center curve 6; the blade portion on the outer diameter (outer peripheral) side of this point C is the sweepback wing portion 3, where the advance ratio θ is negative, and the portion thereof on the inner diameter (boss) side of this intersection point C is the sweepforward wing portion 2, where the advance ratio is positive.
In this specification, the blade 4, constructed as described above, is referred to as a composite blade, and a blade as used in an ordinary axial blower is referred to as an axial flow blade. As described in detail below, in the composite blade, the sweepforward wing portion 2 functions mainly as an axial blower, and the sweepback wing portion 3 functions mainly as a centrifugal blower.
As shown in
Further, as shown in
Further, as shown in
As a result, the curved surface of the impeller on the pressure surface side is inclined toward the discharge side and toward the outer peripheral side, making it possible to generate a flow directed radially outwards and to achieve an increase in static pressure.
While in the example shown in
Further, in the sweepforward wing portion 2, which is in the region on the inner peripheral side of the diameter D1 of the bell mouth 8, this blade 4 exhibits a circumferential sectional configuration (sectional configuration obtained by cutting the blade 4 perpendicularly to the rotation axis 30) that is similar to that of a blade of an axial blower (axial flow blade), and generates a flow along the rotation center axis 30 as indicated by the arrow of
Due to this construction, it is possible to realize a blower providing both the high static pressure characteristic of a centrifugal blower and the large air capacity characteristic of an axial blower.
When a large air capacity is to be achieved, the blower constructed as described above is in the state as shown in
In contrast, when a small air capacity is to be obtained, the blower is in the state as shown in
In this way, each blade 4 has, in the radial direction, the sweepforward wing portion 2 situated on the boss 1 side and exhibiting a positive advance ratio value, and the sweepback wing portion 3 situated on the outer peripheral side of the blade 4 and exhibiting a negative advance ratio value. Further, the arc length of each blade 4 increases from the boss 1 side toward the outer peripheral side. Thus, the arc length of the blade increases in the radial direction toward the outer peripheral side, so that the blade area along the flow increases in the blade outer peripheral portion, and there is a substantial increase in blade radius with respect to the flow, with the result that there is an increase in static pressure due to centrifugal force, making it possible to increase the work-load of the blade.
Further, in each circumferential center curve 6 of the sweepforward wing portion 2, the angle of inclination of a tangent to the circumferential center curve 6 gradually increases to a large degree in the rotating direction as transition is effected from the boss 1 side toward the boundary portion 5 side, with the rotation axis serving as a reference; further, as transition is effected from the boundary portion 5 side toward the outer peripheral side, the angle of inclination of the tangent to the circumferential center curve 6 increases gradually to a large degree to the opposite side with respect to the rotating direction.
As a result, in the sweepforward wing portion 2, the same flow as in an axial blower is obtained, which means the blower operates as an axial blower. On the outer peripheral side of this blade 4, the advance ratio is reduced to a negative value so as to attain substantial coincidence with the flow, and the portion corresponding to the sweepback wing portion 3 resembles a blade of a centrifugal blower, which means the blower operates as a centrifugal blower.
Thus, in the blower of this embodiment, it is possible to provide the functions of both an axial blower and a centrifugal blower; further, it is possible to adapt the blade profile to two flow fields: the flow field spreading in the radial direction similar to that in a centrifugal blower generated due to the installation of the bell mouth and to the flow field similar to that in an axial blower flowing parallel to the rotation center axis, thereby making it possible to suppress an increase in noise due to disturbance.
Further, in each circumferential center curve 6 of the sweepforward wing portion 2, the angle of inclination of a tangent to the circumferential center curve 6 gradually increases to a large degree in the gas discharge side as the circumferential center curve 6 extends from the boss 1 side toward the boundary portion 5 side, with the rotation axis serving as a reference; further, the circumferential center curve 6 extends from the boundary portion 5 side toward the outer peripheral side, the angle of inclination of the tangent to the circumferential center curve 6 increases gradually to a large degree to the gas suction side. Accordingly, the curved surface of the impeller is inclined toward the outer peripheral side, making it possible to generate a flow directed radially outwards and to achieve an increase in static pressure.
Further, by mounting the bell mouth 8 to the air suction side of the case 19, the nozzle size of the blower on the suction side is equal to the diameter D1 of the bell mouth 8, and the suction area is reduced. In the sweepforward wing portion 2, which is in the region where the flow field is in the same condition as in an axial blower and where the diameter of the blade 4 is smaller than the diameter D1 of the bell mouth 8, the suction side diameter of the impeller is equal to the diameter D1 of the bell mouth 8, and the flow is the same as that in an axial blower for both large and small air capacity, so that the blower operates as an axial blower.
In contrast, in the sweepback wing portion 3, which is in the region where the flow field constitutes a flow directed outwards in the radial direction and where the nozzle size of the blade 4 is larger than the diameter D1 of the bell mouth 8, the advance ratio is, as described with reference to
Thus, this blower is endowed with the functions of both an axial blower and a centrifugal blower, and an increase in total pressure (Euler head) due to centrifugal force is to be expected, thus making it possible to achieve an increase in static pressure.
It can be seen from this diagram that when the profile of the blade 4 is such that the ratio ranges from 80% to 130%, it is possible to achieve a marked reduction in blower noise from approximately 3.0 (dBA) to approximately 4.7 (dBA); with a ratio of 105%, the specific noise level is reduced by 4.7 (dBA) at maximum. When the ratio ranges from 100% to 110%, the specific noise level is reduced by 4.5 (dBA) or more, thus providing an especially marked noise reduction effect. Further, as can be seen from this diagram, at the ratio of 147%, the specific noise level is zero; in this condition, the bell mouth 8 does not contribute to a reduction in specific noise level, and the effect obtained is the same as that obtained when there is no bell mouth 8.
It can be seen from this diagram that a remarkable effect of achieving a reduction in the noise of the blower can be obtained in the advance ratio ranging from −2.0 (°/mm) to −2.9 (°/mm) and that the specific noise level is reduced by approximately 11 [dBA] at maximum at an advance ratio of −2.2.
Further, as shown in
Further, when, instead of causing a portion 4A of the blade portion to protrude, the space into which the portion 4A of the blade portion is to protrude is filled by, for example, increasing the thickness of the bell mouth, the reduction diameter side end portion and the circular vortex move toward the suction side, and the effective blade area decreases, resulting in an increase in noise and an increase in input.
In view of this, when, as shown in
Thus, it is possible to control both the circular vortex generated between the reduction diameter side end portion 8B and the expansion diameter side end portion 8C of the bell mouth 8 through rotation of the impeller, and the leakage flow from between the reduction diameter side end portion 8B of the bell mouth 8 and the impeller, so that it is possible to achieve high static pressure and large air capacity, thereby making it possible to achieve an enhancement in efficiency and a reduction in noise.
It is to be noted that this invention is not restricted to the use of an impeller having a composite blade as described above; it is also possible, as in the case of the above composite blade, to achieve an improvement in ventilation efficiency and a reduction in noise in a blower equipped with an ordinary axial blade or a centrifugal blade, a case surrounding the impeller, and a bell mouth cylindrically constricted so as to guide gas into the case, which is constructed such that the inner diameter of the bell mouth is smaller than the outer diameter of the impeller, due to the fact that a portion of the blade portion situated on the outer peripheral side of the inner diameter of the bell mouth protrudes from the reduction diameter side end portion toward the expansion diameter side end portion in the direction along the rotation center axis of the impeller.
In the above-described Embodiment 1, a case was shown in which the boundary portion 5 constituting the boundary between the sweepforward wing portion 2 and the sweepback wing portion 3 substantially coincides with the inner diameter of the bell mouth 8.
In contrast, in this embodiment, as shown in
The blade profile of the blade 4 (impeller) on the inner peripheral side of the boundary portion 5 between the sweepforward wing portion 2 and the sweepback wing portion 3 is that of the sweepforward wing portion 2, and, in the region on the inner peripheral side of the inner diameter D1′ of the bell mouth 8, the blower operates as an axial blower, so that it provides a large air capacity characteristic. Further, the blade profile of the blade 4 (impeller) on the inner peripheral side of the boundary portion 5 is that of the sweepforward wing portion 2, and, in the region on the outer peripheral side of the inner diameter D1′ of the bell mouth 8, constriction is effected by the bell mouth 8, so that a flow expands radially outwards, making it possible to achieve an increase in static pressure due to centrifugal force.
In contrast, the blade profile of the blade 4 (impeller) on the outer peripheral side of the boundary portion 5 between the sweepforward wing portion 2 and the sweepback wing portion 3 is that of the sweepback wing portion 3, so that the blower operates as a centrifugal blower. Thus, substantial coincidence with the meridional flow expanding in the centrifugal direction is effected, so that the load thereon decreases, and the ventilation efficiency is enhanced. Thus, it is desirable for the boundary portion 5 of the blade 4 (impeller) between the sweepforward wing portion 2 and the sweepback wing portion 3 to be on the outer peripheral side of the inner diameter D1′ of the bell mouth 8. In view of this, it is desirable for the inner diameter D1′ of the bell mouth 8 to be on the boss 1 side with respect to the radial position of the boundary portion 5 of the blade 4 (impeller) between the sweepforward wing portion 2 and the sweepback wing portion 3.
The minimum noise point of an axial blower is on the open side, and the minimum noise point of a centrifugal blower is on the high static pressure side. Thus, by varying the proportion of the sweepforward wing portion 2 and the sweepback wing portion 3, and the inner diameter dimension of the bell mouth 8 according to the requisite operating point, the three-dimensional flow field generated in the impeller (blade 4) is varied, and it is possible to control the flow difference due to the operating point through the inner diameter D1′ of the bell mouth 8. For example, when the inner diameter D1′ of the bell mouth 8 is reduced, the region where the flow expands radially outwards is enlarged, resulting in a flow state simulating the flow on the high static pressure side of the impeller. In contrast, when the inner diameter D1′ of the bell mouth 8 is increased, the region where the flow expands radially outwards is diminished, and the blade region which is on the boss 1 side of the inner diameter D1′ of the bell mouth 8 and which operates as an axial blower is enlarged, resulting in a flow state simulating the flow on the low static pressure side.
As described above, in this embodiment, the boundary portion 5 constituting the boundary between the sweepforward wing portion 2 and the sweepback wing portion 3 is situated on the outer peripheral side of the inner diameter of the bell mouth 8, so that, by varying the inner diameter D1′ of the bell mouth 8, the three-dimensional flow field generated in the impeller (blades 4) is varied, making it possible to control the flow difference due to the operating point through the inner diameter D1′ of the bell mouth 8.
It is to be noted that, as described with reference to Embodiments 1 and 2, this invention is not restricted to the case in which the relationship between the diameter D3 of the boundary portion 5 which constitutes the boundary between the sweepforward wing portion 2 and the sweepback wing portion 3, and the inner diameter D1′ of the bell mouth 8 is as follows: D1′<D3; as long as the inner diameter D1′ of the bell mouth is smaller than the outer diameter D4 of the blade, it is possible to realize a radial outward flow, making it possible to achieve an increase in static pressure through the flow expanding in the radial direction.
As shown, for example, in
That is, the gas flow when the inner diameter D1′ of the bell mouth 8 is smaller than the outer diameter D4 of the axial flow impeller is throttled by the bell mouth when it flows into the impeller on the suction side of the impeller, and gradually expands radially outwards from the bell mouth toward the discharge side.
In the axial flow impeller (axial flow blade 40), in the region on the inner peripheral side of the inner diameter D1′ of the bell mouth 8, the blower operates as an axial blower, so that it provides a large air capacity characteristic. In contrast, in the axial flow impeller (axial flow blade 40), in the region on the outer peripheral side of the inner diameter D1′ of the bell mouth 8, constriction is effected by the bell mouth, so that the flow expands radially outwards, making it possible to achieve an increase in static pressure by centrifugal force.
Thus, when the inner diameter D1′ of the bell mouth 8 is diminished, the region where the flow expands radially outwards is enlarged, resulting in a flow state simulating the flow on the high static pressure side of the axial flow impeller. In contrast, when the inner diameter D1′ of the bell mouth 8 is increased, the region where the flow expands radially outwards is diminished, and the blade region which is on the boss 1 side of the inner diameter D1′ of the bell mouth 8 and which operates as an axial blower is enlarged, resulting in a flow state simulating the flow on the low static pressure side.
Thus, by varying the inner diameter D1′ of the bell mouth 8 within the range of the outer diameter of the axial flow impeller, the three-dimensional flow field generated in the axial flow impeller is varied, making it possible to control the flow field through the magnitude of the inner diameter D1′ of the bell mouth 8 as a flow difference due to the operating point.
For example, in the case of use at an operating point on the low static pressure side, the inner diameter D1′ of the bell mouth 8 is enlarged, and in the case of use on the high static pressure side, the inner diameter D1′ of the bell mouth 8 is diminished.
In this way, by controlling the magnitude of the inner diameter D1′ of the bell mouth 8, it is possible to control the operating point, and it is possible to use the impeller at the target operating point, so that it is possible to achieve a reduction in noise and an improvement in efficiency.
As described above, by making the inner diameter of the bell mouth smaller than the outer diameter of the axial flow impeller, it is possible to realize a radial outward flow, making it possible to achieve an increase in static pressure by the flow expanding in the radial direction.
Further, since the bell mouth guiding air flow is arranged on the suction side of the axial blower (axial flow impeller), there is the effect of making the distribution of the suction flow irrespective of the mounting condition of the axial flow impeller, so that it is possible to reduce the disturbance flowing into the axial flow impeller and to achieve a reduction in noise.
As can be seen from
As can be seen from
From the results of
The air course in which the impeller is arranged differs depending on the mounting condition; in some cases, there arises a difference in suction flow velocity in the circumferential direction of the rotation center axis 30 of the impeller on the impeller suction side. In such cases, the inner face of the constricting portion from the expansion diameter side end portion to the reduction diameter side end portion of the bell mouth 8 is formed as a curved surface spaced apart from the rotation center axis 30 of the impeller by an uneven distance, and, in the portion where the flow velocity is high, the curvature of the inner face of the constricting portion of the bell mouth is made larger than in the other portions, whereby the disturbance generated by separation on the bell mouth is reduced, making it possible to prevent an increase in noise. Further, the uneven distribution of the flow velocity on the suction side generated by the circumferentially uneven construction of the air course is smoothened, making it possible to reduce the rotation noise due the unevenness in the flow velocity on the suction side.
As shown in
As shown in
While the construction shown in
While in the above-described embodiments four blades are mounted to the boss, the number of blades is of course not restricted thereto; this invention is applicable to a case where a plurality of blades are mounted.
Further, this blower is not restricted to a blower for ventilation; it is naturally also applicable to a blower for cooling the heat exchanger, for example, of an automobile, a refrigerator, or an air conditioner.
Further, what is blown is not restricted to air; any gas will serve the purpose.
As described above, in the blower of the present invention, the inner diameter of the bell mouth is smaller than the outer diameter of the axial flow impeller, so that the flow is turned into a mixed flow and an increase in static pressure is achieved due to centrifugal force; thus, it is possible to achieve an improvement in ventilation efficiency and to generate a flow field where the flow in the vicinity of the blade surface is matched with the blade, thereby making it possible to achieve a reduction in noise.
Further, the inner diameter of the bell mouth is smaller than the outer diameter of the impeller, and a portion of the blade portion situated on the outer peripheral side of the inner diameter of the bell mouth protrudes from the reduction diameter side end portion toward the expansion diameter side end portion of the bell mouth in the direction along the rotation center axis of the impeller, so that it is possible to control both the circular vortex, which is generated between the reduction diameter side end portion and the expansion diameter side end portion of the bell mouth through the rotation of the impeller, and the leakage flow from between the reduction diameter side end portion of the bell mouth and the impeller, whereby it is possible to achieve an increase in static pressure and an increase in air capacity, thereby making it possible to achieve an improvement in ventilation efficiency and a reduction in noise.
Further, the blade is equipped with the sweepforward wing portion which is on the boss side and which exhibits a positive advance ratio value in the radial direction and the sweepback wing portion which is on the outer peripheral side and which exhibits a negative advance ratio value, with the arc length of the blade increasing from the boss side toward the outer peripheral side, so that it is possible to achieve an improvement in ventilation efficiency through an increase in static pressure and to achieve a reduction in noise.
Number | Date | Country | Kind |
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2003-173867 | Jun 2003 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2004/008839 | 6/17/2004 | WO | 00 | 1/21/2005 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2004/113732 | 12/29/2004 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
4927328 | Scoates et al. | May 1990 | A |
5273400 | Amr | Dec 1993 | A |
5551841 | Kamada | Sep 1996 | A |
Number | Date | Country |
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53-116513 | Oct 1978 | JP |
63-36697 | Mar 1988 | JP |
2-207197 | Aug 1990 | JP |
9-68199 | Mar 1997 | JP |
2002022210 | Jan 2002 | JP |
Number | Date | Country | |
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20050260075 A1 | Nov 2005 | US |