Patent Application
20120134794
The present invention relates to a fan and an air-conditioning apparatus provided with the fan, and, more particularly, relates to a shape of a housing, a shape of a blade (blade, hereinafter also referred to as a blade) of a cross flow fan (tangential fan, hereinafter only referred to as cross flow fan) housed in the housing, and a shape of a casing, which guides an air flow, arranged adjacent to the fan.
Typically, a cross flow fan is widely used as an air blowing mechanism of air-conditioning apparatus, and includes a housing, a cross flow fan housed in the housing, a casing, which guides an air flow, arranged on a back side of and adjacent to the cross flow fan, and a stabilizer, which stabilizes a circular vortex, arranged on a front side of and adjacent to the cross flow fan.
When the cross flow fan is used as such an air blowing mechanism of the air-conditioning apparatus, it is often the case that the housing of the cross flow fan is substantially a rectangular parallelepiped. The rectangular parallelepiped includes plural rigid sides for supporting the housing, at least one outlet side provided with an air outlet port (hereinafter also referred to as an outlet), and at least one inlet side provided with an air inlet port (hereinafter also referred to as an inlet), and the respective sides are set such that the total number of sides are 6.
In this case, since the housing will have high rigidity and will be able to hold the load in a stable manner, the side of the rectangular parallelepiped having the largest area is often used as the rigid side. It is desirable to make the air inlet port as large as possible from a viewpoint of air intake efficiency. For this reason, two sides, which are the side opposite to the rigid side having the largest area and the side that has the second largest area, are typically used as the inlet sides. Further, a lattice-like grille is usually provided to the inlet port so as to conceal the inner structure of the housing and to prevent fingers from penetrating through.
Generally, the air outlet port is provided in another side that has the second largest area, and the two sides having the smallest area are used as the rigid sides. In such a cross flow fan, air from the air inlet ports on an upper side and a front side of the housing passes through pressure loss elements such as a filter and a heat exchanger and flows into the cross flow fan; the total pressure is elevated inside the cross flow fan, and the air is blown out to a casing side. The rotation speed of the cross flow fan needs to be increased when a high air volume cannot be obtained. Accordingly, noise increases.
An invention of an air-conditioning apparatus has been disclosed in which noise is suppressed while improving fan performance by specifying the positional relation between the rear gap created by the rear guider and the front gap created by the front guider and by specifying the angle made by the horizontal line and the line connecting the rotation center of the cross flow fan and the rear gap, as well as specifying the position of the tongue portion of the front guider (see PLT 1, for example).
Additionally, an invention of a cross flow fan including plural impellers, in which plural blades are held by end plates on both sides and support plates in a middle portion, connected together has been disclosed. When an outer peripheral blade angle is Bo, an inner peripheral blade angle is Bi, the number of blades is Z, and a pitch chord ratio is T, the invention has disclosed the relationship of the outer peripheral blade angle Bo, the inner peripheral blade angle Bi, the number of blades Z, and the pitch chord ratio T of the cross flow fan in order that the cross flow fan will have high air volume and high pressure while having low noise (see PLT 2, for example).
Furthermore, an air-conditioning apparatus has been disclosed that includes a cross flow fan and a stabilizer separating the suction side passage and the discharge side passage of the cross flow fan. The stabilizer includes a tongue portion that extends towards the rotation direction of the cross flow fan in which the side of the tongue portion opposing the cross flow fan is formed so that it reduces its clearance gap with the outer circle of the cross flow fan gradually towards the rotation direction of the cross flow fan; and a protruding portion that protrudes towards the interior of the cross flow fan, that is formed at the end portion of the tongue portion such that the clearance gap between the outer circle of the cross flow fan and the tongue portion becomes smallest, and that has a substantially triangular cross-sectional shape when taken along a line perpendicular to the direction of the fan axis where the clearance gap with the cross flow fan is the smallest. The protrusion height Hs of the protruding portion from the side of the tongue portion opposing the cross flow fan is configured to be 25 to 35% of the dimension G1 of the minimum clearance gap between the outer circle of the cross flow fan and the side of the tongue portion opposing the cross flow fan, and the angle of the apical angle of the protruding portion is configured to be 50 to 75 degrees (see PTL 3, for example).
However, all of the above-mentioned conventional fans are inventions based on a case in which the inlet area is made to be as large as possible. In these conventional fans, when the width of the air inlet port provided at the top side and front side of the housing is A, the diameter of the cross flow fan is D, and the size factor δ of the cross fan is defined as δ=A/D, then the width A of the air inlet port provided at the top side and front side of the housing is sufficiently wide against the diameter D of the cross flow fan and the size factor δ of the cross fan is typically about 3 to 4. Accordingly, stable air can be supplied without occurrence of excessive negative pressure and drift in the air inlet port while air flows into the cross flow fan.
The aesthetic appearance of the front side of the housing has a large influence on consumers. Accordingly, there has been a strong demand for a configuration with no inlet on the front side. Further, there has also been a strong demand for the miniaturization of the product and hence, it is necessary to make the size factor δ of the cross flow fan small.
In such a case, when the inlet is narrowed while having the same configuration as that of the conventional fan as described above, excessively large negative pressure or drift is generated when air flows into the cross flow fan, and thus the flow is changed. The angle between the blade of the cross flow fan and the flow direction becomes large, and, as a result, momentum transfer efficiency of the blade to the fluid reduces, the fan performance is hindered, as well as the increase in pressure fluctuation and noise. Further, as the result of narrowing the inlet port, air pushed out from the blade of the cross flow fan drifts to the inlet port side, and, hence, the flow in a cross section of the cross flow fan becomes unstable, whereby the air flow impinges on the normal direction of the surface of the casing and loss is increased. The invention provides a fan disposed with a cross flow fan that can overcome the above drawbacks, and a cross flow fan with high air volume and high pressure as well as low noise even when an air inlet port is narrow.
The invention is made to overcome the above-mentioned drawbacks, and an object thereof is to provide a fan that is capable of suppressing noise as well as increasing fan performance even with a fan with a narrow air inlet port such that δ=A/D is 2 or less (where the width of the air inlet port is A, the diameter of the cross flow fan is D, and the size factor δ of the cross fan is defined as δ=A/D) by specifying an outer peripheral blade inflow angle that influences the air intake efficiency of the blade of the cross flow fan.
An fan according to the invention includes: a housing including an inlet port and an outlet port; a cross flow fan disposed in the housing; a casing arranged on a back side of the cross flow fan, the casing constituting a part of the outlet port; and a stabilizer arranged on a front side of the cross flow fan, the stabilizer opposing the casing and constituting a part of the outlet port, in which, where A is a maximum inlet width of the inlet port in a direction substantially orthogonal to a rotation axis of the cross flow fan, D is a diameter of the cross flow fan, β is an outer peripheral blade inflow angle,
β=(A/D)γ(radian),
in which A/D≦2 and 0.4≧γ≧0.3 is defined.
According to the invention, a fan that is capable of suppressing noise as well as increasing fan performance even when the air inlet port is narrow can be obtained.
Next, embodiments of the invention will be explained with reference to the drawings. In the drawings described hereinafter, identical or similar parts will be given same or similar reference numerals. It should be noted that the drawings are schematic, and ratios of dimensions and the like are different from the actual ones. Accordingly, specific sizes and the like should be determined by referring to the descriptions below. Further, it is needless to say that the dimensional relationships and ratios between the drawings may differ in some portions.
A cross flow fan 2 having a plurality of blades oriented in the fan rotation direction is arranged inside the housing 1, and heat exchangers 3 that are arranged in an inverted V-shape are provided in an air flow on the inlet side of the cross flow fan 2. The heat exchangers 3 control temperature of air sucked from the outside into the cross flow fan 2 through gaps of an inlet grille 5, which is provided in the air inlet port 4, and a filter 6. The casing 7 enlarges as it approaches the bottom panel 1d and is positioned on substantially the rear side and downstream of the cross flow fan 2. The casing 7 constitutes an outlet side passage leading to the outlet port 8 to send out air that has been heat exchanged in the heat exchangers 3 to the room. A stabilizer 9 is positioned adjacent to and facing the front side and substantially the bottom portion of the cross flow fan 2, and separates the inlet side passage and the outlet side passage of the cross flow fan 2. Symbol A indicates a maximum inlet width of the inlet port 4 in the direction substantially orthogonal to the rotation axis of the cross flow fan 2, and symbol D indicates a diameter of the fan.
As illustrated in
In
In
In the fractional factorial design based on the design of experiments, an experimental method using orthogonal arrays, in which only the factors that have significant effects are sampled by uniformly changing the multiple factors in the experiment corresponding to the full factorial design, will be conducted. The reliability of the optimum value obtained by the fractional factorial design will be confirmed by analysis of variance and by conducting an F test, and accordingly will be statistically supported by the level of significance. In Embodiment 1 of the invention, the shape factors contributing to the efficiency of the air flow path and the blade was estimated in 4374 ways by conducting 18 experiments analyzing 8 factors based on L18 orthogonal arrays. With the above method, it has been confirmed that the optimum value of γ is in a range of 0.4≧γ≧0.3. The level of significance was verified to be 1% or less with the F test, and thus it has been confirmed that the optimum value is statistically significant at 99%.
In the conventional art, γ is, typically, 0.28 or less in view of preventing the momentum transfer efficiency to the fluid from dropping, which is caused by the acute angle between the blade of the fan and the flow of air. That is, when (A/D) takes a value close to the minimum value 1, β is 0.28 or less when γ is 0.28 or less. β is 16.1 degrees or less. When the outer peripheral blade inflow angle β is less than 20, the transfer of momentum by the blade to the fluid remarkably drops, and it will be necessary to increase the rotation speed. Hence, a fan is not configured to have γ that is 0.28 or less.
Further, it is when β is an extremely large value or (A/D) is an extremely small value, when γ is 0.43 or more. Suppose (A/D) takes the maximum value 2, then β is 0.86 radian or more when γ is 0.43 or more, and accordingly the outer peripheral blade inflow angle β is 49.3 degrees or more. In this case, the angle of the blade of the fan against the air flow is acute, and the momentum transfer efficiency to the fluid drops.
In contrast, when (A/D) takes the minimum value and supposing (A/D)=1, then the inlet width A and the fan diameter D will be the same. In general, the width of an air flow path of a fluid machinery is desirably constant to prevent loss caused by contraction flow or expansion flow. From this aspect, it is desirable that an inlet width A is half the length of the circumference, in which A=π (circular constant≈3.14)×D, that is, (A/D)=π. Since the loss caused by the contraction flow or the expansion flow increases in proportion to the flow velocity to the power of 2, when (A/D)=1, then the loss will be π to the power of 2 (9.87 times) compared to a case in which the air flow path is constant. Thus, it will be difficult to function as a machine. Accordingly, there is generally no fan in which γ is 0.43 or more.
In the fan shown in Embodiment 1 of the invention in which the air inlet port 4 is narrow such that δ=A/D is 2 or less, by setting the outer peripheral blade inflow angle β of the blade 10 of the cross flow fan 2 within a preferable range, the angle between the blade 10 of the cross flow fan 2 and the air flow in its flow direction can be optimized. Accordingly, the momentum transfer efficiency of the blade 10 to the fluid and the fan performance are enhanced, and, as a result, the input energy can be suppressed and, consequently, noise and vibration can be reduced. Although in Embodiment 1 of the invention, description has been made with respect to an air-conditioning apparatus, substantially the same effects can be obtained with other apparatus with a fan mechanism with no heat exchanger or a filter.
In the above Embodiment 1, a configuration of a fan has been disclosed in which generation of noise is suppressed while increasing fan performance when the air inlet port is narrow by specifying the range of the outer peripheral blade inflow angle β. In Embodiment 2 of the invention, the configuration of the fan will be specified by a function r(θ) that is defined based on a distance and angle from a rotation center of a cross flow fan, where θ is an angle from a starting portion of a curve of an enlarged air flow path of a casing.
In
That is, the enlarged area ratio τ is obtained as a ratio between an integral value of the function r(θ) for a region between the enlarged air flow path start angle θ1 and the angle θ2, which is an angle with respect to the direction extending from the center of rotation of the cross flow fan 2 perpendicular to the direction of the air inlet port with an angle θ from the start portion, and an integral value of a sector portion of the circle. In general, the enlarged area ratio τ is expressed by enlarged area ratio τ=(exp(2×ι×θ2)−exp(2×ι×θ1))/(2×ι×(θ2−θ1)). Particularly, when θ is =90 degrees, the enlarged area ratio τ is expressed by enlarged area ratio τ=(exp(2×ι×π/2)−exp(2×ι×0))/(2×ι×π/2).
Here, in the technical field of fluid machinery, the function r(θ) is a function which determines the shape of a general air flow path referred to as a logarithmic spiral. The function r(θ) is a function induced from the equation of continuity assuming that the flow is uncompressed and is without any loss and from the equation of flow line which is induced from the nature of the constant flow angle of the enlarged air flow path in solving the law of conservation of an angular momentum.
In order to guide the air flow in the casing 7 and to favorably convert dynamic pressure into static pressure, it is necessary to change the degree of enlargement of the curve using the value of ι. However, the curve, which is induced from the formula, is solved based on the assumption that the flow is uncompressed without any loss. Thus, the flow line does not completely agree with the flow of the fluid machinery because, in practice, there will be a loss. Accordingly, a straight line may be partially provided. In the fan of Embodiment 2 of the invention, the shape of the casing 7 is not specified by r(θ) but is specified by an enlarged area ratio of the air flow path which is of primary importance to the character of the enlarged air flow path.
In
In the fractional factorial design based on the design of experiments, an experimental method using orthogonal arrays, in which only the factors that have significant effects are sampled by uniformly changing the multiple factors in the experiment corresponding to the full factorial design, will be conducted. The reliability of the optimum value obtained by the fractional factorial design will be confirmed by analysis of variance and by conducting an F test, and accordingly will be statistically supported by the level of significance. In Embodiment 2 of the invention, the shape factors contributing to the efficiency of the air flow path and the casing was estimated in 4374 ways by conducting 18 experiments analyzing 8 factors based on L18 orthogonal arrays. With the above method, it has been confirmed that the optimum value of ι to induce τ is in a range of 0.21≧ι≧0.23. The level of significance was verified to be 1% or less with the F test, and thus it has been confirmed that the optimum value is statistically significant at 99%.
Based on the above result ι, the range of the enlarged area ratio ι that increases the fanning efficiency has been compared in percentage based on the fractional factorial design of the design of experiments. In the conventional art, since ι is about 0.2 or 0.3, τ is 1.39 or 1.66, and only about 60% of the efficiency of the fan of Embodiment 2 is obtained. On the other hand, by setting the enlarged area ratio ι to a range of 1.416≧τ≧1.466 for the fan of Embodiment 2, greater fanning efficiency is obtained compared with conventional fans. The rotation speed can be lower for obtaining the same air volume, and as a result, noise can be reduced.
In the above-mentioned Embodiment, the explanation has been made by focusing on the case where the curve of the casing 7 is a logarithmic spiral. However, the enlargement ratio of the air flow path is fundamentally important, and the curve may not be limited to the logarithmic spiral and may include a straight line section. In the range from the enlarged start point of the air flow path to 90 degrees therefrom, the preferable range of the enlarged area ratio t against the diameter D of the cross flow fan will be analyzed.
A casing enlargement curve can be set at a preferable range with the configuration of the fan of Embodiment 2 according to the invention. Hence, loss caused by the air flow, which has been discharged from the blades of the cross flow fan, impinging the wall of the casing can be averted, and the momentum of the fluid transferred by the cross flow fan is not lost. The fan performance is accordingly improved and, as a result, the input energy can be suppressed, reducing noise and vibration. Although in Embodiment 2 of the invention, description has been made with respect to an air-conditioning apparatus provided with a fan, the same effect will be present with a fan with no heat exchanger or a filter.
1. housing; 1a front panel; 1b rear panel; 1c upper panel; 1d bottom panel; 1e left side panel; 1f right side panel; 2 cross flow fan; 3 heat exchanger; 4 inlet port; 5 grille; 6 filter; 7 casing; 8 outlet port; 9 stabilizer; 10 blade; 10a blade outer side; 10b blade inner side.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/004088 | 8/25/2009 | WO | 00 | 2/1/2012 |
