JP6972385B2 - Centrifugal blower - Google Patents

Description

The present invention relates to a centrifugal blower provided with a scroll casing.

The centrifugal blower houses the impeller in the scroll casing. Since the centrifugal blower has a structure in which the air sucked into the scroll casing from the suction port along the axial direction of the rotating shaft of the impeller is blown out in the centrifugal direction of the rotating shaft of the impeller, an inertial force acts on the suction flow. Therefore, the airflow blown out into the scroll casing through the impeller forms a velocity distribution biased toward the bottom surface side of the scroll casing. Then, a part of the air blown into the scroll casing flows along the bottom surface and then forms a circulating flow that winds up from the main plate side of the impeller toward the tip of the blade along the inner wall surface of the scroll casing. do. This circulating flow and the airflow blown out from the impeller collide or interfere with each other, which causes a decrease in the blowing performance of the centrifugal blower and an increase in noise.

Further, in the centrifugal blower, the speed distribution of the airflow in the impeller and the scroll casing changes depending on the operating point used. For example, at the operating point on the open side where the air volume is large, the airflow blown out into the scroll casing through the impeller becomes faster, and the inertial force acts strongly on the airflow. Therefore, the airflow blown out from the impeller has a larger velocity component toward the main plate as it is closer to the suction port. Therefore, since the velocity component toward the main plate side is smaller and the velocity component in the centrifugal direction is larger toward the bottom surface side of the scroll casing, the air volume toward the centrifugal direction is larger toward the bottom surface side. In addition, the circulation flow that winds up from the main plate side of the impeller toward the tip of the blade along the inner wall surface of the scroll casing is also greatly facilitated to develop.

Patent Document 1 discloses a centrifugal blower in which a first extending portion extending from a suction port toward the main plate side of the impeller is formed so as to approach the inner circumference and the outer circumference of the impeller. In the centrifugal blower disclosed in Patent Document 1, by forming the first extension portion, a region without air flow is formed in the vicinity of the leading edge of the blade tip, and the generation of circulation flow is prevented.

Japanese Unexamined Patent Publication No. 7-293497

The centrifugal blower disclosed in Patent Document 1 prevents interference between the blade and the circulating flow at the blade tip, but the air passage is blocked by the first extension portion, so that the ventilation performance of the blade is deteriorated. In particular, when the operating point at which the blower is used is on the open side, the airflow blown into the scroll casing through the impeller becomes faster and the air volume increases. Therefore, in the centrifugal blower disclosed in Patent Document 1, the suction port is used. The formed first extension portion becomes a large air resistance, which lowers the ventilation performance and increases the noise.

Therefore, it has been desired to realize a centrifugal blower that prevents the generation of a circulating flow in the scroll casing without deteriorating the blowing performance or increasing the noise.

The present invention has been made in view of the above, and an object of the present invention is to obtain a centrifugal blower that prevents the generation of a circulating flow in the scroll casing without deteriorating the blowing performance or increasing the noise. ..

In order to solve the above-mentioned problems and achieve the object, the present invention includes a drive motor, a main plate attached to the shaft of the drive motor, and a plurality of blades arranged in an annular shape on the peripheral edge of the main plate. An impeller, a suction port facing the main plate, a bell mouth that guides the airflow toward the suction port, a scroll part that rotatably accommodates the impeller, an outlet that blows out the airflow generated by the impeller, and a blade. A scroll casing equipped with a tongue that guides the airflow generated by the car to the outlet, and a diffuser that connects the scroll and the outlet and expands the cross-sectional area of the air passage from the tongue to the outlet. Have. The bell mouth is provided with a shielding portion in which the suction downstream end closes the inner diameter side of the wing tip and blocks a part of the suction flow flowing into the scroll casing from the suction port. The shielding portion rotates the impeller starting from the first suction downstream end point, which is the intersection of the line segment connecting the shaft and the apex of the tongue and the suction downstream end when viewed along the axial direction of the shaft. Is provided in the region up to the second suction downstream end point where the angle toward the traveling direction of is the first angle. The first angle is 30 ° or more and 120 ° or less. In the region where the shielding portion is provided, the height from the upper surface of the main plate to the suction downstream end portion at the outer peripheral portion of the impeller is lower than the height of the blade. In the region ahead of the region where the shield is provided in the direction of travel of the impeller rotation, the height from the upper surface of the main plate to the suction downstream end at the outer peripheral portion of the impeller is higher than the height of the blade. ..

The centrifugal blower according to the present invention has an effect that the generation of a circulating flow in the scroll casing can be prevented without deteriorating the blowing performance or increasing the noise.

Perspective view of the centrifugal blower according to the first embodiment of the present invention. Top view of the centrifugal blower according to the first embodiment Cross-sectional view in a plane passing through the rotation axis of the impeller of the centrifugal blower according to the first embodiment. Cross-sectional view of the centrifugal blower according to the first embodiment in a plane perpendicular to the rotation axis of the impeller of the impeller. The figure which shows the wind speed distribution result in the height direction of the blade by the fluid analysis for designing the shield part of the centrifugal blower which concerns on Embodiment 1. The figure which shows the wind speed distribution result in the rotation direction of an impeller by the fluid analysis for designing the shield part of the centrifugal blower which concerns on Embodiment 1. The figure which shows the enlarged angle of the scroll casing of the centrifugal blower which concerns on Embodiment 1. The figure which shows the shape of the suction port of the centrifugal blower which concerns on Embodiment 1. The figure which shows the modification of the centrifugal blower which concerns on Embodiment 1. The figure which shows the shape of the shielding part of the centrifugal blower which concerns on Embodiment 1. The figure which shows the relationship between the size of the shielding part of the centrifugal blower which concerns on Embodiment 1 and the improvement amount of a fan efficiency. The figure which shows the relationship between the static pressure efficiency and the air volume of the centrifugal blower which concerns on Embodiment 1. The figure which shows the relationship between the suction noise and the air volume of the centrifugal blower which concerns on Embodiment 1.

Hereinafter, the centrifugal blower according to the embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment.

Embodiment 1.
FIG. 1 is a perspective view of the centrifugal blower according to the first embodiment of the present invention. FIG. 2 is a plan view of the centrifugal blower according to the first embodiment. FIG. 3 is a cross-sectional view taken along a plane passing through the rotation axis of the impeller of the centrifugal blower according to the first embodiment. FIG. 3 shows a cross section along line III-III in FIG. FIG. 4 is a cross-sectional view taken along the plane perpendicular to the rotation axis of the impeller of the centrifugal blower according to the first embodiment. FIG. 4 shows a cross section along the IV-IV line in FIG. The centrifugal blower 1 according to the first embodiment has a drive motor 2, an impeller 3, and a scroll casing 4. The impeller 3 includes a main plate 5 attached to the shaft 2a of the drive motor 2, a plurality of blades 6 arranged in an annular shape on the peripheral edge of the main plate 5, and an annular reinforcing ring 7 attached to the outer periphery of the blade 6. And have. The impeller 3 rotates about the shaft 2a. When viewed along the axial direction of the shaft 2a, the rotation center O of the impeller 3 is located on the shaft 2a.

The scroll casing 4 is generated by a suction port 9 facing the main plate 5, a bell mouth 8 that guides an air flow toward the suction port 9, a scroll portion 41 that rotatably accommodates the impeller 3, and an impeller 3. The outlet 10 that blows out the airflow, the tongue portion 11 that guides the airflow generated by the impeller 3 to the outlet 10, the scroll portion 41, and the outlet 10 are connected, and the wind is blown from the tongue portion 11 toward the outlet 10. It is equipped with a diffuse 12 that expands the road cross-sectional area. The bell mouth 8 includes a shielding portion 13 that closes the inner diameter side of the wing tip 6a to block a part of the suction flow.

As shown in FIGS. 3 and 4, the shielding portion 13 includes a line segment connecting the shaft 2a and the apex of the tongue portion 11 and the suction downstream end portion 8a of the bell mouth 8 when viewed from the axial direction of the shaft 2a. Starting from the first suction downstream end point A located at the intersection, the angle toward the traveling direction of the rotation of the impeller 3 is provided in the region up to the angle θ. That is, the shielding portion 13 is formed from the first suction downstream end point A to the second suction downstream end point B advanced by an angle θ which is the first angle in the rotation direction of the impeller 3. In the region where the shielding portion 13 is provided, the height Hr from the upper surface 5a of the main plate 5 to the suction downstream end 8a of the bell mouth 8 at the outer peripheral portion of the impeller 3 becomes lower than the total height Hb of the blade 6. There is. Since the shielding portion 13 is not formed in the region on the downstream side extending in the rotation direction from the second suction downstream end point B, the suction downstream end portion of the bell mouth 8 is formed from the upper surface 5a of the main plate 5 on the outer peripheral portion of the impeller 3. The height Hr up to 8a is higher than the total height Hb.

The air sucked from the suction port 9 passes through the impeller 3 and is blown out into the scroll casing 4. Since the inertial force acts on the airflow, the airflow passing through the impeller 3 forms a velocity distribution biased toward the main plate 5. A part of the air blown from the impeller 3 into the scroll casing 4 forms an air flow that winds up from the main plate 5 side toward the stip 6a along the side wall surface 4a of the scroll casing 4, and eventually the stip 6a. It becomes a circulation flow U that reaches the vicinity. If the circulating flow U and the airflow blown out from the impeller 3 collide or interfere with each other in the scroll casing 4, it causes a decrease in the blowing performance of the centrifugal blower 1 and an increase in noise. The circulation flow U is generated by the air flow blown out from the impeller 3, but it takes a certain amount of time for the circulation flow U to reach the vicinity of the blade tip 6a in the scroll casing 4.

The centrifugal blower 1 according to the first embodiment performs fluid analysis of the airflow inside the centrifugal blower not provided with the shielding portion 13, obtains the velocity distribution of the airflow near the outer periphery of the impeller, and shields based on this velocity distribution. The part 13 is designed. The size of the impeller used for the fluid analysis is 180 mm in diameter and 100 mm in height of the blade, and the impeller rotates under the conditions of the impeller ^{rotation speed of 800 times / minute and the operating air volume of 8 m 3 / min.} The radial velocity at a position 95 mm from the center was determined.

FIG. 5 is a diagram showing the result of wind speed distribution in the height direction of the blade by fluid analysis for designing the shielding portion of the centrifugal blower according to the first embodiment. FIG. 6 is a diagram showing the result of wind speed distribution in the rotation direction of the impeller by fluid analysis for designing the shielding portion of the centrifugal blower according to the first embodiment. As shown in FIGS. 5 and 6, the velocity distribution of the airflow blown from the impeller in the centrifugal blower without the shielding portion 13 changes depending on the rotational position in the scroll casing and the height position of the blade. .. Here, when the total height of the blades of the impeller is Hb'and the angle in the rotation direction of the impeller is the angle θ'starting from the straight line connecting the center of rotation of the impeller and the apex of the tongue, the angle θ. In the region where the angle θ is 120 ° or less from the tongue where ‘ The speed v2 in the central portion of the wing is a positive value. This indicates that the circulating flow U generated in the scroll casing does not reach the vicinity of the blade tip, and the airflow blown out from the impeller is not obstructed by the circulating flow U.

In the region where the angle θ'is more than 120 ° and 250 ° or less, the velocity v2 at the center of the blade is a positive value, but the velocity v1 at the tip side is a negative value. This indicates that the circulating flow U reaches the vicinity of the wing tip and the airflow blown out from the impeller is obstructed. The velocity v1 on the tip side in the region where the angle θ'is more than 120 ° and 250 ° or less is a negative value from the impeller to the scroll casing in the region where the angle θ'is more than 0 ° and 120 ° or less. This is a result of the fact that a part of the airflow blown out to the circulation flow U was involved. In the region where the angle θ'is more than 250 ° and less than 360 °, both the velocity v1 on the wing tip side and the velocity v2 at the center of the wing are positive values. This is because the side wall surface of the scroll casing is separated from the impeller, and the airflow blown out from the impeller passes through the diffuser to the outlet before it becomes a circulating flow U and reaches the vicinity of the wing tip. , It is shown that the airflow blown out from the impeller is not obstructed by the circulating flow U.

The centrifugal blower 1 according to the first embodiment has an angle along the rotation direction of the impeller 3 from the first suction downstream end point A to the second suction downstream end point B based on the above fluid analysis result. By setting θ to 30 ° or more and 120 °, the circulation flow U reaching the blade tip 6a is reduced in the region where the angle θ exceeds 120 ° and is 250 ° or less, and the velocity v1 is prevented from decreasing.

As described above, in the centrifugal blower 1 according to the first embodiment, the shielding portion 13 closes the inner diameter side of the blade tip 6a to block a part of the suction flow, so that the centrifugal blower 1 is blown out from the impeller 3 into the scroll casing 4. It weakens the airflow and reduces the development of the circulating flow U generated in the scroll casing 4. Therefore, the airflow blown out from the impeller 3 can easily pass through the scroll casing 4 without being obstructed by the circulation flow U, and the blowing performance of the centrifugal blower 1 can be improved. Further, the centrifugal blower 1 according to the first embodiment can reduce the collision and interference between the airflow blown from the impeller 3 and the circulation flow U in the scroll casing 4, so that noise can be reduced.

At first glance, the shielding portion 13 blocking the wing tip 6a to block a part of the suction flow seems to reduce the blowing performance of the centrifugal blower 1. However, as shown in FIGS. 5 and 6, the air blown into the scroll casing from the impeller of the centrifugal blower not provided with the shielding portion 13 becomes faster on the downstream side where the angle θ'is large, and the air volume increases. This is because the air passage cross-sectional area of the scroll casing gradually expands, which makes it easier for air to flow. Therefore, the centrifugal blower 1 according to the first embodiment also enhances the blowing performance of the entire centrifugal blower 1 by improving the blowing characteristics in the region where the angle θ is large.

As described above, in the centrifugal blower 1 according to the first embodiment, the development of the circulation flow U is reduced on the downstream side traveling in the rotational direction from the second suction downstream end point B, so that the centrifugal blower 1 is blown out from the impeller 3. The air flow easily passes through the scroll casing 4 without being obstructed by the circulating flow U. Therefore, by further widening the air passage around the wing 6 to make the wing 6 easier to function, the synergistic effect of the wing 6 becoming easier to function and the air passage expanding, and the blowing performance of the centrifugal blower 1 Can be further enhanced.

FIG. 7 is a diagram showing an enlarged angle of the scroll casing of the centrifugal blower according to the first embodiment. The enlargement angle of the scroll casing 4 is defined by an angle formed by the outer diameter of the impeller 3 and the side wall surface 4a of the scroll casing 4 when they are developed in a plane. As shown in FIG. 7, the angle θ on the downstream side advanced in the rotational direction from the enlarged angle α1 of the scroll casing 4 in the region where the angle θ advanced in the rotational direction from the apex of the tongue 11 is 120 ° or less is The magnified angle α2 of the scroll casing 4 is larger in the region of more than 120 ° and 250 ° or less. By doing so, the distance from the rotation center O of the impeller 3 to the side wall surface 4a of the scroll casing 4 is longer than in the case where the enlargement angle of the scroll casing 4 is constant at the enlargement angle α, and the distance inside the scroll casing 4 is extended. The cross-sectional area of the air passage will be expanded. Therefore, the air sucked from the suction port 9 passes through the impeller 3 and is easily blown out into the scroll casing 4, and further improvement of the ventilation performance can be realized. Further, by keeping the magnifying angle α1 smaller than the magnifying angle α, it is possible to improve the blowing performance of the centrifugal blower 1 while suppressing the entire scroll casing 4 from becoming large.

FIG. 8 is a diagram showing the shape of the suction port of the centrifugal blower according to the first embodiment. As shown in FIG. 8, the distance L2 between the third suction downstream end point C located axially symmetric with the second suction downstream end point B with respect to the rotation center O of the impeller 3 and the rotation center O of the impeller 3 is , The distance L1 between the rotation center O of the impeller 3 and the second suction downstream end point B is longer. That is, when viewed along the axial direction of the shaft 2a, the distance L2 between the third suction downstream end point C located on the opposite side of the second suction downstream end point B across the shaft 2a and the shaft 2a is the second. The distance between the suction downstream end point B of 2 and the shaft 2a is longer than the distance L1. By doing so, the opening area of the suction port 9 is expanded, the average wind speed of the suction flow is lowered, the air passage pressure loss is reduced, and the air easily flows in the impeller 3, so that the ventilation performance is further improved. Can be done.

FIG. 9 is a diagram showing a modified example of the centrifugal blower according to the first embodiment. As shown in FIG. 9, the impeller 3 may be formed so that the inner diameter of the blade increases from the intermediate portion of the blade 6 toward the tip 6a, or both the inner diameter of the blade and the outer diameter of the blade increase. In the example shown in FIG. 9, the blade inner diameter increases from DI1 to DI2 and the blade outer diameter increases from DO1 to DO2 from the intermediate portion of the blade 6 toward the blade tip 6a. By doing so, the gap between the shielding portion 13 and the wing 6 is widened, so that the shielding portion 13 can be easily designed. Further, since the opening area of the suction port 9 can be further expanded according to the inner diameter of the blade, the average wind speed of the suction flow is lowered to reduce the air passage pressure loss, and the airflow is easily passed through the impeller 3 to further blow air. Performance can be improved. Further, the ventilation performance can be improved as the shape of the blade 6 changes.

FIG. 10 is a diagram showing the shape of the shielding portion of the centrifugal blower according to the first embodiment. As shown in FIG. 10, a plurality of shielding portions 13a, 13b, 13c may be provided in order to block a part of the suction flow flowing into the scroll casing 4 from the suction port 9. In particular, when the centrifugal blower 1 is mounted in the housing of a device such as an air conditioner and used, the suction flow is locally accelerated. Therefore, by individually adjusting the shape and size of the shielding portion 13, the shape and size of the shielding portion 13 can be adjusted. It can be expected to effectively block a part of the suction flow and improve the ventilation performance. Although FIG. 10 shows a structure in which three shielding portions 13 are provided, the plurality of shielding portions 13 may be two or four or more.

FIG. 11 is a diagram showing the relationship between the size of the shielding portion of the centrifugal blower according to the first embodiment and the amount of improvement in fan efficiency. The size of the shielding portion 13 is the central angle of the shielding portion 13 formed by the first suction downstream end point A, the shaft 2a, and the second suction downstream end point B in a plane perpendicular to the axial direction of the shaft 2a. It is represented by AOB. As shown in FIG. 11, from the relationship between the size of the shielding portion 13 and the improvement amount Δη of the fan efficiency η of the centrifugal blower 1, the central angle ∠AOB of the shielding portion 13 is 30 ° ≤ ∠AOB ≤ 120 °. By forming the shielding portion 13 so as to be, the fan efficiency η can be improved by 0.5 points or more. Similarly, if the shielding portion 13 is formed so that 60 ° <∠AOB <110 °, the fan efficiency η can be improved by 1 point or more. The fan efficiency η of the centrifugal blower 1 is calculated by calculating η = PQ / 60W based on the static pressure P [Pa], the air volume Q [m ³ / min], and the shaft output W [W]. bottom.

FIG. 12 is a diagram showing the relationship between the static pressure efficiency and the air volume of the centrifugal blower according to the first embodiment. The centrifugal blower 1 according to the first embodiment has a maximum static pressure efficiency improvement of 1.5 points as compared with the centrifugal blower not provided with the shielding portion 13. FIG. 13 is a diagram showing the relationship between the suction noise of the centrifugal blower according to the first embodiment and the air volume. The centrifugal blower 1 according to the first embodiment has a maximum noise reduction effect of -1 dB with respect to the centrifugal blower not provided with the shielding portion 13.

The centrifugal blower 1 according to the first embodiment is provided with a shielding portion 13 in a region from the first suction downstream end point A to the second suction downstream end point B in a state of being viewed along the axial direction of the shaft 2a. Therefore, it is possible to prevent the generation of the circulation flow U in the scroll casing 4 without deteriorating the ventilation performance or increasing the noise.

The configuration shown in the above-described embodiment shows an example of the content of the present invention, can be combined with another known technique, and is one of the configurations as long as it does not deviate from the gist of the present invention. It is also possible to omit or change the part.

1 Centrifugal blower, 2 Drive motor, 2a shaft, 3 Impeller, 4 Scroll casing, 4a Side wall surface, 5 Main plate, 5a Top surface, 6 wings, 6a Wing tip, 7 Reinforcing ring, 8 Bellmouth, 8a Suction downstream end, 9 suction port, 10 outlet, 11 tongue, 12 diffuse, 13, 13a, 13b, 13c shield, 41 scroll.

Claims (5)

With the drive motor
An impeller having a main plate attached to the shaft of the drive motor and a plurality of blades arranged in an annular shape on the peripheral edge of the main plate.
A suction port facing the main plate, a bell mouth that guides the airflow toward the suction port, a scroll portion that rotatably accommodates the impeller, an air outlet that blows out the airflow generated by the impeller, and the above. A tongue portion that guides the airflow generated by the impeller to the outlet, and a diffuse that connects the scroll portion and the outlet and expands the cross-sectional area of the air passage from the tongue portion toward the outlet. With a scroll casing and
The bell mouth is provided with a shielding portion in which the suction downstream end closes the inner diameter side of the wing tip of the wing to block a part of the suction flow flowing into the scroll casing from the suction port.
The shielding portion starts from a first suction downstream end point which is an intersection of a line segment connecting the shaft and the apex of the tongue portion and the suction downstream end portion when viewed along the axial direction of the shaft. , The angle toward the traveling direction of the rotation of the impeller is provided in the region up to the second suction downstream end point, which is the first angle.
The first angle is 30 ° or more and 120 ° or less.
In the region where the shielding portion is provided, the height from the upper surface of the main plate to the suction downstream end portion at the outer peripheral portion of the impeller is lower than the height of the blade.
In the region ahead of the region where the shielding portion is provided in the traveling direction of rotation of the impeller, the height from the upper surface of the main plate to the suction downstream end portion at the outer peripheral portion of the impeller is the height. rather than higher than the height of the wing,
The blade inner diameter and blade outer diameter of the blade are constant between the main plate and the intermediate portion in the height direction, and the blade inner diameter and blade outer diameter increase from the intermediate portion toward the blade tip. A centrifugal blower featuring. The magnified angle of the scroll casing in the region where the shield is provided is the magnified angle of the scroll casing in the region ahead of the region where the shield is provided in the traveling direction of rotation of the impeller. The centrifugal blower according to claim 1, wherein the centrifugal blower is smaller than the above. The distance between the shaft and the third suction downstream end point located on the opposite side of the second suction downstream end point across the shaft when viewed along the axial direction of the shaft is the second suction downstream end point. The centrifugal blower according to claim 1 or 2, wherein the length is longer than the distance between the downstream end point and the shaft. The centrifugal blower according to any one of claims 1 to 3 , wherein the shielding portion is provided at a position higher than the center in the height direction of the blade. The centrifugal blower according to any one of claims 1 to 4, wherein the shielding portion is provided at a position higher than a position where the inner diameter of the blade of the blade starts to increase.

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