JP2007321643A - Centrifugal fan and air conditioner using the same - Google Patents

Abstract

An object of the present invention is to provide a centrifugal fan that suppresses noise when the pressure loss at the point of use is different from the design point and suppresses a reduction in air blowing performance, and an air conditioner using the centrifugal fan.
In a centrifugal fan according to the present invention, blades 3 are attached at a predetermined interval in the circumferential direction between a hub and a shroud arranged opposite to each other. The blade 3 has a blade shape in cross section, and the leading edge 31 is formed with a plurality of sawtooth-shaped protrusions 7 in the blade height direction, and the tip of each protrusion 7 is a blade in each protrusion 7. It is formed so as to be located at the center in the height direction and on the tangential direction of the warp line C at the front edge 31. By providing the protrusion 7 in this manner, the vertical vortex Va is generated from the leading edge 31 to the trailing edge 32 on the suction surface of the blade 3 to suppress the separation of the air current, thereby suppressing noise and improving the blowing performance. Suppresses the decline.
[Selection] Figure 5

Description

  The present invention relates to a centrifugal fan and an air conditioner using the same, and more particularly to the structure of a centrifugal fan blade.

  Regarding the blades of a centrifugal fan, in order to improve the efficiency of a conventional centrifugal fan, the cross-sectional shape thereof is made to be an airfoil. As an example of this airfoil, for example, there are those shown in FIGS. FIG. 12 is a schematic cross-sectional view of a conventionally known turbo fan 1 belonging to a centrifugal fan, and FIG. 13 is a perspective view of an impeller 2 of the turbo fan 1. In these drawings, 3 is a blade of a three-dimensional airfoil, 4 is a hub, 5 is a shroud, 6 is a bell mouth, and R is a rotation direction of the impeller. The blade shape of the blade 3 of the impeller 2 is such that the thickness of the blade 3 gradually increases from the inner peripheral side tip (the leading edge 31 of the blade 3) of the blade wheel 2 as shown in FIG. After that, it becomes thicker and gradually becomes thinner from the outer peripheral end of the impeller 2 (the trailing edge 32 of the blade 3). Further, the blade surface 3a in the rotation direction side of the blade 3 has a convex shape as a whole, and the blade surface 3b in the direction opposite to the rotation direction of the blade 3 extends in the rotation direction R from the inner peripheral side tip (front edge 31) to the vicinity of the center. On the other hand, a concave shape is formed, and a convex shape is formed from the vicinity of the center to the outer peripheral side tip (rear edge 32). Further, as shown in FIG. 13, the blade 3 has the position of the shroud 5 side coupling portion at the trailing edge 32 of the blade 3 offset by a predetermined amount in the counter-rotating direction of the impeller 2 from the position of the hub 4 side coupling portion. It is a three-dimensional blade.

FIG. 14 shows the shape of one blade element of the blade 3 and the airflow state at the design point of the turbofan 1. As shown in FIG. 14, the blade 3 having an airfoil cross-sectional shape is set so that the airflow suction direction S does not collide with the front edge 31 at the design point. That is, the airflow flowing toward the leading edge 31 smoothly flows from the leading edge 31 along the rotation direction side blade surface 3a and the rotation direction opposite blade surface 3b of the blade 3, and the rotation direction side blade surface 3a and The airflows Sa and Sb flowing along the blade surface 3b on the opposite side in the rotation direction are designed to flow from the front edge 31 toward the rear edge 32 without being substantially separated. That is, the entrance angle α and the inflow angle β are designed to be the same. The entrance angle α is an angle formed between a tangent line C1 at a leading edge of a warp line (camber line) C indicated by a one-dot chain line and a tangent line B1 at a leading edge of an inner circumferential blade line B indicated by a two-dot chain line, The inflow angle β is an angle formed between the airflow suction direction S and the tangent line B1 at the leading edge 31 of the inner circumferential blade row line B. In FIG. 14, O is the center point of the impeller 2, and Bg is the outer circumferential cascade line. Since the conventional turbofan 1 is formed in this manner, the leading edge peeling is reduced and the air blowing performance is improved as compared with a blade having a constant thickness. Examples of the turbofan 1 having a blade shape in cross section include Patent Document 1, Patent Document 2, Patent Document 3, and the like, although the blade shape is slightly different.
JP-A-5-312189 Japanese Patent Laid-Open No. 2002-364591 JP 2002-235695 A

  However, even in the case of the turbofan 1 having a blade shape in cross section as shown in FIG. 14, the use point may deviate from the design point. That is, the predicted value of the pressure loss at the point of use deviates from the actual value, or the point of use changes with the use process of the device incorporating the centrifugal fan.

  As one of the factors that the predicted value of the use point deviates from the design point, the shape of the flow path after passing through the impeller is complicated and difficult to predict, and the state of the ventilation path around the impeller 2 is Since it is not uniform, it can be mentioned that it is difficult to match the use point and the design point all around the impeller. The latter point will be further described by taking a ceiling-embedded air conditioner as an example. In a ceiling-embedded air conditioner, an indoor heat exchanger is disposed around a turbo fan 1 that is usually a centrifugal fan. The indoor heat exchanger is annularly formed around the turbo fan 1. Rather than being arranged, they are arranged to form a square. Therefore, since the distance between the indoor heat exchanger and the turbofan 1 varies depending on the location, the in-machine resistance value varies depending on the position around the impeller 2.

  Next, the case where the use point changes with the progress of use of the apparatus incorporating the turbo fan 1 will be further described by taking an air conditioner as an example. In an air conditioner, an air filter is usually attached to an indoor air inlet. By the way, this air filter increases the ventilation resistance with the passage of time of use. Therefore, the predicted value of the point of use may be smaller or larger than the design point depending on whether the initial predicted value is in a state where there is little airflow resistance with no clogging, or the average value during use is taken. become.

  15 and 16 show a flow state diagram of the airflow in the blade shown in FIG. FIG. 15 shows the flow state when the pressure loss at the point of use of the turbofan 1 is smaller than the design point. In this case, the impeller 2 that has the inflow angle β larger than the inlet angle α and becomes a negative pressure surface. The separation vortex V1 is generated on the blade surface 3a in the direction of rotation of the blade, and the blowing performance is reduced and the noise is increased. FIG. 16 shows a flow state diagram of the air flow when the pressure loss at the use point of the turbo fan 1 is larger than the design point. In this case, the inflow angle β is smaller than the inlet angle α, and the suction surface is reduced. The separation vortex V2 is generated on the blade surface 3b opposite to the rotational direction of the impeller 2 to reduce the blowing performance and increase the noise. As shown in these figures, conventionally, when the pressure loss at the point of use of the turbofan 1 is different from the design point, the generation of the separation vortices V1 and V2 reduces the blowing performance and increases the noise.

  The present invention has been made paying attention to such problems existing in the prior art, and is a centrifugal fan that suppresses noise when the use point deviates from the design point and suppresses deterioration of the blowing performance. The purpose is to provide. Another object of the present invention is to provide a low-noise and high-performance air conditioner using such a centrifugal fan.

  The centrifugal fan according to the present invention that solves the above-described problem is one in which blades are attached at predetermined intervals in the circumferential direction between a hub and a shroud that are arranged to face each other. The blade has an airfoil cross-sectional shape, and a plurality of serrated protrusions are formed on the leading edge in the blade height direction, and the tip of each protrusion is the center of the blade height direction in each protrusion. And is substantially positioned on the tangential direction of the warp line at the front edge. With this configuration, when the air current collides with the leading edge, a vertical vortex composed of fine vortices on the left and right with the line passing through the tip from the leading edge to the trailing edge on the suction surface of the blade due to the action of the protrusion. Will occur. Then, the airflow to be separated from the blade surface by the vertical vortex is attracted to the blade surface, so that the separation of the airflow is suppressed, and the deterioration of the noise and the blowing performance is suppressed.

  In the centrifugal fan, the sawtooth-shaped protrusion may be formed in a plate shape having a predetermined thickness on the tangential direction of the warp line at the front edge. Since the plate-like object has a predetermined thickness, the structure is simplified and the manufacture is easy.

  Further, the sawtooth-shaped projecting portion has a shape in which the cross section in the blade thickness direction is smoothly connected from the tip of the projecting portion to the blade surface in the rotational direction of the impeller and the surface of the blade on the opposite side in the rotational direction of the impeller. It may be formed. When the sawtooth-shaped protrusion is a plate-like object having the above-mentioned predetermined thickness, since the airflow that collided with the protrusion flows along the surface of the protrusion and then collides with the front edge of the blade, Formation is reduced. In this regard, as described above, the cross-section of the sawtooth-shaped projecting portion is shaped so as to be smoothly connected from the tip of the projecting portion to the blade surface in the rotational direction of the impeller and the surface of the impeller in the reverse direction of rotation. As a result, the airflow flowing on the surface of the protruding portion smoothly flows on the surface of the blade, so that the formation of the vertical vortex is not inhibited. As a result, a vertical vortex is formed, and the vertical vortex suppresses separation of the airflow, and further suppresses noise and a decrease in blowing performance.

  In addition, the tip of the sawtooth protrusion can be formed flat or curved. In this way, since the tip portion is not sharp, the hand is less likely to be scratched or cut when the blade or impeller is handled.

  Further, the sawtooth-shaped protrusions may be formed so that the pitches and heights of the protrusions are substantially equal. In this way, peeling on the suction surface of the blade is suppressed substantially uniformly. For this reason, the fall of noise and ventilation performance can be suppressed further.

  Moreover, according to the air conditioner which concerns on this invention, since the centrifugal fan of the said structure is used, a low noise and highly efficient air conditioner can be obtained.

  According to the centrifugal fan of the present invention, on the suction surface of the blade, a vertical vortex composed of fine vortices is generated from the front end portion of the sawtooth-shaped projecting portion to the rear edge side, centering on a line passing through the front end portion. . And, this vertical vortex suppresses the separation of the air current, and suppresses the noise and the deterioration of the air blowing performance.

  Hereinafter, a centrifugal fan according to an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same parts as those of the above-mentioned conventional ones are denoted by the same reference numerals, and the description thereof is omitted.

(Embodiment 1)
First, a centrifugal fan according to Embodiment 1 and an air conditioner using the centrifugal fan will be described with reference to FIGS.

  1 is a cross-sectional view of a ceiling-embedded air conditioner using a centrifugal fan according to Embodiment 1. FIG. The ceiling-embedded air conditioner 10 shown in this figure has a main body 12 installed by being inserted into the back of the ceiling from a substantially square ceiling opening 11, and a lower surface of the main body 12 so as to cover the ceiling opening 11 from below. And a decorative panel 13 to be fixed. The main body 12 is substantially square in plan view, and the decorative panel 13 is formed in a substantially square shape that is slightly larger than the main body 12 in plan view.

  The decorative panel 13 has a substantially square indoor inlet 14 formed at the center, and an indoor outlet 15 formed at each of the four peripheral edges so as to surround the indoor inlet 14. A turbo fan 1 serving as a centrifugal fan is disposed in the central portion of the main body 12. The turbofan 1 has a lower portion as an inlet and a radially outer periphery of the impeller 2 as an outlet. And the indoor side heat exchanger 16 is provided around the blower outlet. The indoor heat exchanger 16 is arranged in an annular shape so as to form four sides that are substantially square in plan view, and a drain pan 17 is arranged below the indoor heat exchanger 16. A bell mouth 6 that forms a suction port is attached below the turbo fan 1, and an air filter 18 is disposed between the bell mouth 6 and the indoor suction port 14.

  This ceiling-embedded air conditioner 10 is connected to an outdoor unit (not shown) and is operated together with the outdoor unit to air-condition the room. During indoor air conditioning, indoor air is sucked from the indoor suction port 14 by the air blowing action of the turbo fan 1, dust is removed by the air filter 18, and then sucked into the turbo fan 1. The room air sucked into the turbofan 1 is blown out from the outer periphery of the impeller 2 toward the surrounding indoor heat exchanger 16 and is air-conditioned by the indoor heat exchanger 16. The room air conditioned by the indoor heat exchanger 16 is blown out from the four side air outlets 15 so as to air-condition the room.

Next, the turbo fan 1 used for the air conditioner having the above-described configuration will be described.
As shown in the perspective view of the impeller in FIG. 2, the impeller 2 of the turbofan 1 according to the present embodiment has the blades 3 arranged at predetermined intervals in the circumferential direction between the hub 4 and the shroud 5 that are arranged to face each other. It is attached. As shown in FIG. 4, the blade 3 has a wing shape in cross section. FIG. 4 shows the blade shape of one blade element of the turbo fan 1 as in the case of FIG. 14 and also shows the flow state of the airflow when the use point and the design point coincide.

  As shown in FIG. 4, the airfoil of the turbofan 1 has the same basic shape as that shown in the above-described conventional example. However, in the blade 3 of the turbofan 1 in this embodiment, the airfoil of FIG. As shown in FIG. 3 (FIG. 3 is a side view of the blade), FIG. 4 and the like, a plurality of protrusions 7 having a sawtooth shape in the blade height direction are formed on the leading edge 31. The airfoil of the turbofan 1 is the same as that of the conventional one. In terms of design, the airflows Sa and Sb flowing along the rotation direction blade surface 3a and the rotation direction blade surface 3b are substantially separated. It is designed to flow from the front edge 31 toward the rear edge 32 without.

  The protrusions 7 are formed at the same pitch P over substantially the entire height of the front edge 31. Further, the height H of the protruding portion 7 is formed substantially the same as the pitch P. The tip of each protrusion 7 has a blade height dimension in the sawtooth-shaped protrusion 7 (that is, this dimension is the width of the protrusion 7 and corresponds to the pitch P of the protrusion 7). The position of the protrusion 7 in the blade thickness direction is substantially positioned on the tangent line C1 direction of the airfoil warp line C at the leading edge 31.

  When the turbo fan 1 is used at the design point, the airflow inflow angle β and the inlet angle α coincide with each other as shown in FIG. Therefore, the airflows Sa and Sb flowing along the rotation direction side blade surface 3 a of the impeller 2 and the rotation direction opposite side blade surface 3 b of the impeller 2 hardly cause separation from the protruding portion 7 to the rear edge 32.

  When the turbo fan 1 is used in a state where the pressure loss is lower than the design point, that is, in the air conditioner, the in-machine resistance is smaller than the design point pressure loss, or the in-machine resistance is designed depending on the location of the impeller 2. When it is smaller than the pressure loss at the point, the airflow state is as shown in FIG. That is, the airflow suction direction S collides with the front edge 31 from the opposite side of the rotation direction R of the impeller 2, and the inflow angle β becomes larger than the entrance angle α. In this case, the rotation direction side blade surface 3a of the impeller 2 becomes a negative pressure surface. However, when the airflow Sa collides with the front edge 31, the front edge 31 on the rotation direction side blade surface 3 a that is the negative pressure surface of the impeller 2, centered on the front end portion, due to the front end portion of the sawtooth-shaped protrusion 7. Longitudinal vortices Va composed of fine vortices are generated from the side to the trailing edge 32 side. Then, the vertical vortex Va draws the airflow Sa to be peeled off to the rotation direction side blade surface 3a to reduce the peeling. As a result, separation of the airflow Sa is suppressed, noise is suppressed, and deterioration of the blowing performance is suppressed.

  Further, when the turbo fan 1 is used in a state where the pressure loss is greater than the design point, that is, when the in-machine resistance is greater than the design point pressure loss in the air conditioner, or depending on the location of the impeller 2, the in-machine resistance. Is larger than the pressure loss at the design point, an airflow state as shown in FIG. 6 is obtained. That is, the airflow suction direction S collides with the front edge 31 from the rotation direction R side of the impeller 2, and the inflow angle β becomes smaller than the entrance angle α. In this case, the blade surface 3b on the opposite side in the rotational direction of the impeller 2 is a negative pressure surface. However, when the airflow Sb collides with the leading edge 31, the leading edge of the sawtooth-shaped protruding portion 7 causes the leading edge of the blade 3 on the rotation direction reverse side blade surface 3b, which is the negative pressure surface of the impeller 2, around the leading edge. A vertical vortex Vb composed of fine vortices is generated from the 31 side to the trailing edge 32 side. Then, the vertical vortex Vb draws the airflow Sb to be peeled to the blade surface 3b on the opposite side in the rotational direction to reduce the peeling. As a result, separation of the airflow Sb is suppressed, noise is suppressed, and deterioration of the blowing performance is suppressed.

  In addition, when the ventilation resistance becomes large with the passage of time after the air filter 18 is used, it corresponds to the case where the above-mentioned in-machine resistance is larger than the pressure loss at the design point, and the air flow state as shown in FIG. Become. That is, the airflow suction direction S collides with the front edge 31 from the rotation direction R side of the impeller 2, and the inflow angle β becomes smaller than the entrance angle α. However, in this case as well, as in the case described above, the vertical vortex Vb is generated on the rotation direction reverse blade surface 3b, which is the suction surface of the impeller 2, and the separation of airflow is suppressed, noise is suppressed, and the air flow is reduced. A decrease in performance is suppressed.

FIG. 7 is a diagram comparing noise between the turbo fan 1 according to the present embodiment configured as described above and the conventional turbo fan 1 shown in FIGS. 12 to 16. The scale on the horizontal axis is the air volume, and one scale is 2 m ³ / min. The scale on the vertical axis is noise, and one scale is 5 dBA. Further, the noise minimum position in this figure is a use state when the design point and the use point coincide. In this minimum noise position, the separation vortices V1 and V2 are not easily generated by the action of the airfoil blades, so it is considered that the conventional fan and the fan of the present invention are not significantly different from noise. However, when the point of use is different from the design point, that is, in the state where the point of use is shifted to the left and right from the minimum noise position in FIG. 7, the air volume changes and the noise increases, and the conventional fan and the fan of the present invention. There is a noise difference between In particular, when the pressure loss is lower than the design point, the air volume increases and the noise increases, but it can be seen that the noise difference between the fan of the present invention and the conventional fan becomes significant.

The turbo fan 1 and the ceiling-embedded air conditioner 10 according to the present embodiment have the following operational effects.
(1) In the turbofan 1 according to this embodiment, the cross-sectional shape of the blade 3 is an airfoil, and a plurality of sawtooth projections 7 are formed on the leading edge 31 in the blade height direction. Each protrusion 7 is formed such that the tip thereof is the center in the blade height direction of each protrusion and is substantially positioned on the tangent line C1 of the warp C at the front edge 31. As a result, when the air current collides with the front edge 31, due to the action of the projecting portion 7, the left and right sides centering on the line passing through the front end portion of the projecting portion 7 from the front edge 31 to the rear edge 32 on the suction surface of the blade 3 are obtained. Vertical vortices Va and Vb consisting of fine vortices are generated. The air currents Sa and Sb to be separated from the surfaces 3a and 3b of the blades 3 are attracted to the surfaces 3a and 3b of the blades 3 by the vertical vortices Va and Vb. Is suppressed, and the deterioration of the blowing performance is suppressed.

(2) Since the sawtooth-shaped protrusion 7 is formed in a plate shape having a predetermined thickness on the tangent line C1 of the warp line C at the leading edge 31, the structure is simplified and the manufacture is easy.
(3) Since the pitch P and the height H of the protruding portion 7 are formed substantially equal to each other in the sawtooth-shaped protruding portion 7, peeling at the suction surface of the blade 3 is suppressed substantially uniformly. For this reason, the noise is further suppressed and the deterioration of the blowing performance is further suppressed.

  (4) Since the ceiling-embedded air conditioner 10 according to the present embodiment uses the turbo fan 1 having the above-described configuration, the low-noise and high-efficiency ceiling-embedded air conditioner 10 is obtained. Can do.

(Embodiment 2)
Next, a centrifugal fan according to Embodiment 2 will be described with reference to FIGS. FIG. 8 is a blade cross-sectional view of one blade element passing through a valley of a turbofan protrusion as a centrifugal fan according to the second embodiment, and a flow state diagram of an air flow when a use point and a design point coincide with each other It is. FIG. 9 is a comparison diagram of the flow state of the airflow in the case of the first embodiment, where (a) is an airflow flow diagram in the case of the first embodiment, and (b) is an airflow flow diagram in the case of the second embodiment. FIG. FIG. 10 is a noise comparison diagram between the turbo fan of the first embodiment and the turbo fan of the second embodiment.

  The turbo fan 1 according to the second embodiment is obtained by changing the shape of the sawtooth protrusion 7 in the turbo fan 1 according to the first embodiment. That is, in the turbofan 1 according to the second embodiment, as shown in FIG. 8, the sawtooth-shaped protrusion 71 has a tip portion of each protrusion 71, as in the protrusion 7 of the first embodiment. The protrusion 71 is formed so as to be positioned substantially at the center in the blade height direction and on the tangential direction of the warp C at the leading edge 31. In addition, the sawtooth-shaped projecting portion 71 has a smooth cross section in the blade thickness direction from the tip of the projecting portion 71 to the rotation direction side blade surface 3a of the impeller 2 and the rotation direction reverse side blade surface 3b of the impeller 2. It is formed in the shape to be connected. The turbofan 1 according to the second embodiment is the same as the first embodiment except that the sawtooth-shaped protrusion 71 is different from the sawtooth-shaped protrusion 7 in the first embodiment as described above.

  Since the turbo fan 1 according to Embodiment 2 is configured as described above, the following effects can be achieved. In the case of the first embodiment, since the protrusion 7 is a plate-like object having a predetermined thickness, the air currents Sa and Sb that collide with the protrusion 7 are formed on the surface of the protrusion 7 as shown in FIG. After flowing along, it collides with the leading edge 31 of the blade 3. For this reason, it is considered that the formation of the vertical vortices Va and Vb (not shown) to be generated by the protrusions 7 is reduced. On the other hand, in the case of the second embodiment, the cross section of the projecting portion 71 is from the tip end portion of the projecting portion 71 to the rotation direction side blade surface 3a of the impeller 2 and the rotation direction reverse side blade surface 3b of the impeller 2. Since the connection is made smoothly, the airflows Sa and Sb flowing on the surface of the protrusion 71 flow smoothly on the surface of the blade 3. For this reason, vertical vortices Va and Vb (not shown) formed on the left and right of the protrusion 71 grow from the front edge 31 toward the rear edge 32, and the separation of the airflow is suppressed by the vertical vortices Va and Vb. It is considered that the airflow is further suppressed and the deterioration of the air blowing performance is further suppressed.

  FIG. 10 is a view similar to FIG. 7, and here, the first embodiment and the second embodiment are compared. As in the case of FIG. 7, the noise lowest point position is a case where the use point and the design point coincide. As shown in this figure, when the pressure loss at the point of use deviates from the design point, that is, at the left and right positions of the noise lowest point position in FIG. 10, the turbo fan 1 of the second embodiment is replaced with the turbo of the first embodiment. The noise is smaller than that of the fan 1.

(Embodiment 3)
Next, the turbo fan 1 according to Embodiment 3 will be described with reference to FIG. FIG. 11 is a side view of the blade 3 corresponding to FIG. As shown in FIG. 11, the turbofan 1 according to the third embodiment has a serrated projection 72 formed on the leading edge 31 of the blade 3 and a tip 72 a of the projection 72 is flattened. The other points are the same as those of the first embodiment. Since the turbo fan 1 according to Embodiment 3 is configured as described above, there is convenience in that the hand 3 is less likely to be scratched or cut when the blade 3 or the impeller 2 is handled.

(Modification)
(1) In each embodiment, the blade 3 has a two-dimensional configuration in which the position of the shroud 5 side coupling portion and the position of the hub 4 side coupling portion at the trailing edge 32 of the blade 3 are the same with respect to the rotation direction of the blade 3. It is good also as a feather.

  (2) In the second embodiment, the tip portion of the sawtooth-shaped protrusion 71 may be formed flat as in the third embodiment. Moreover, in Embodiment 1 and Embodiment 3, you may form the front-end | tip part of the sawtooth-shaped protrusion parts 7 and 72 in the shape of a curved surface. In this manner, when the tip portions of the saw-toothed projecting portions 7 and 72 are formed in a curved surface shape, it is less likely to be scratched or cut.

(3) Although the turbo fan 1 is used in the first to third embodiments as an example of the centrifugal fan, a radial fan including airfoil blades may be used.
(4) As in the case of the first embodiment, the turbo fan 1 according to the second and third embodiments is incorporated into the ceiling-embedded air conditioner 10 to reduce noise and improve performance. The ceiling-embedded air conditioner 10 can be provided. Further, the air conditioner is not limited to the above-described ceiling-embedded air conditioner 10, and other types of air conditioners, for example, a ceiling-suspended air conditioner and a wall-mounted air conditioner are appropriately used. It can be applied to air conditioners.

It is sectional drawing of the air conditioner using the turbo fan which concerns on Embodiment 1 of this invention. It is a perspective view of the impeller of the turbofan. It is a side view of the blade of the turbofan. It is the figure which showed the cross-sectional shape in the 1 blade | wing element of the blade of the turbofan, and the flow state of the airflow in case the pressure loss of the use point of the turbofan is the same as a design point. It is the figure which showed the flow state of the airflow in case the pressure loss of the use point of the turbofan is smaller than a design point. It is the figure which showed the flow state of the airflow in case the pressure loss of the use point of the turbofan is larger than a design point. It is a noise comparison figure of the turbo fan and the conventional turbo fan. It is the figure which showed the cross-sectional shape in the 1 blade | wing element of the blade | wing of the turbo fan which concerns on Embodiment 2 of this invention, and the flow state of the airflow in case the pressure loss of the use point of the turbo fan is the same as a design point. It is a comparison figure of the air current flow state in the turbo fan and the turbo fan which concerns on Embodiment 1, (a) is a thing in the case of Embodiment 1, (b) is a thing in the case of Embodiment 2. It is. 2 is a noise comparison diagram between the turbo fan and the turbo fan according to Embodiment 1. FIG. It is a side view of the blade | wing of the turbo fan which concerns on Embodiment 3 of this invention. It is sectional drawing of the conventional turbofan. It is a perspective view of the impeller of the turbofan. It is the figure which showed the cross-sectional shape in the 1 blade | wing element of the blade of the turbofan, and the flow state of the airflow in case the pressure loss of the use point of the turbofan is the same as a design point. It is the figure which showed the flow state of the airflow in case the pressure loss of the use point of the turbofan is smaller than a design point. It is the figure which showed the flow state of the airflow in case the pressure loss of the use point of the turbofan is larger than a design point.

Explanation of symbols

  C: Warp line, C1: Tangent line, P: Pitch of protrusion, H: Height of protrusion, 2 ... Impeller, 3 ... Blade, 3a ... Rotation side blade surface of impeller, 3b ... Rotation of impeller Reverse direction blade surface, 4 ... hub, 5 ... shroud, 31 ... front edge, 7, 71, 72 ... protrusion, 72a ... tip, 10 ... ceiling-embedded air conditioner.

Claims (6)

  Centrifugal fan in which blades are attached at predetermined intervals in the circumferential direction between a hub and a shroud arranged opposite to each other, and this blade has a blade shape in cross section, and a sawtooth shape in the blade height direction at the leading edge Are formed such that the tip of each protrusion is positioned at the center in the blade height direction of each protrusion and substantially on the tangential direction of the warp line at the leading edge. Centrifugal fan characterized by   2. The centrifugal fan according to claim 1, wherein the sawtooth-shaped protrusion is formed in a plate shape having a predetermined thickness on the tangential direction of the warp line at the front edge.   The sawtooth-shaped projecting portion is formed such that the cross section in the blade thickness direction is smoothly connected from the tip of the projecting portion to the blade surface in the rotating direction side of the impeller and the surface of the blade on the opposite side in the rotating direction of the impeller. The centrifugal fan according to claim 1, wherein the centrifugal fan is provided.   4. The centrifugal fan according to claim 2, wherein the serrated protrusion has a tip or a curved surface. 5.   The centrifugal fan according to any one of claims 1 to 4, wherein the sawtooth-shaped protruding portion is formed so that a pitch and a height of the protruding portion are substantially equal.   An air conditioner using the centrifugal fan according to any one of claims 1 to 5.

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