Cross flow fan, air conditioner comprising same, and method for designing cross flow fan

Abstract

Provided is a cross flow fan wherein NZ noise can be reduced by minimizing places where there are successive sections in which the difference between inter-blade pitch angles is small. In a cross flow fan (5), a plurality of blades (11) are provided at prescribed intervals in a circumferential direction around a rotation axis (O1), and when a Fourier series is expanded for inter-blade pitch angles (C), each of which is the angle formed by an imaginary line (R) connecting an outer circumference end (11a) of a blade (11) and the rotation axis (O1), and the imaginary line (R) of an adjacent blade (11), the phase difference between a second-order phase and a third-order phase is a value that does not include 0°, 90°, 180°, or 270°.

Description

Cross-flow fan, air conditioner equipped with same, and design method for cross-flow fan

[0001] The present disclosure relates to a crossflow fan, an air conditioning apparatus including the same, and a method for designing a crossflow fan.

[0002] Crossflow fans have traditionally been used as blowers in home air conditioners. A typical type of noise generated by crossflow fans is known as non-zero noise (NZ noise). One known method for reducing NZ noise is to randomly arrange the blade pitch angles of the crossflow fan (see, for example, Patent Document 1).

[0003] In Patent Document 1, attention is paid to the amplitude of each order when the arrangement of inter-blade pitch angles is expanded into a Fourier series, thereby reducing NZ sounds and low-frequency broadband noise.

[0004] Patent No. 5804044

[0005] However, in Patent Document 1, the amplitude of each order when a Fourier series is expanded is examined, but depending on the phase setting, there is a risk that a continuous area where the difference in pitch angle between adjacent blades is small may occur. If a continuous area where the difference in pitch angle between blades is small exists, there is a problem that the NZ noise reduction effect cannot be sufficiently obtained.

[0006] Furthermore, in Patent Document 1, the amplitude of each order is set to a uniformly large value. While this is effective in reducing NZ noise, it has the problem of creating locations where the inter-blade pitch angle is excessively large. This problem causes side effects such as a decrease in air volume and a decrease in blowout air velocity and backflow when the static pressure at the suction port increases due to dust accumulation on the filter.

[0007] The present disclosure has been made in consideration of the above circumstances, and aims to provide a crossflow fan that can reduce NZ noise by minimizing the number of consecutive sections with small differences in inter-blade pitch angle, an air conditioning apparatus equipped with the same, and a method for designing a crossflow fan.

[0008] Another object of the present disclosure is to provide a crossflow fan that can reduce NZ noise and avoid side effects such as a decrease in blowing air speed and the occurrence of backflow when static pressure at the intake port increases due to dust accumulation on the filter, an air conditioning apparatus equipped with the same, and a method for designing a crossflow fan.

[0009] In one embodiment of the crossflow fan of the present disclosure, a plurality of blades are arranged circumferentially around a rotation axis at a predetermined interval, and adjacent blades are spaced apart in the circumferential direction by a blade-to-blade pitch angle. When the arrangement of the blade-to-blade pitch angle in the circumferential direction is expanded into a Fourier series, the phase difference γ between the second-order phase β2 and the third-order phase β3 is a value that does not include 0°, 90°, 180°, or 270°.

[0010] An air conditioning apparatus according to one aspect of the present disclosure includes the above-described crossflow fan.

[0011] A design method for a crossflow fan according to one aspect of the present disclosure is a design method for a crossflow fan in which a plurality of blades are arranged circumferentially around a rotation axis at a predetermined interval, and adjacent blades are spaced apart in the circumferential direction by an inter-blade pitch angle, and when the circumferential arrangement of the inter-blade pitch angle is expanded into a Fourier series, the phase difference γ between the second-order phase β2 and the third-order phase β3 is a value that does not include 0°, 90°, 180°, or 270°.

[0012] The NZ noise can be reduced by minimizing the number of successive portions where the difference in inter-blade pitch angle is small.

[0013] In addition, it is possible to reduce NZ noise and avoid side effects such as a decrease in air volume and a decrease in resistance to static pressure outside the machine.

[0014] 1. A cross-sectional view showing an indoor unit according to an embodiment of the present disclosure. 2. A perspective view showing a schematic diagram of a cross-flow fan. 3. An enlarged partial cross-sectional view showing the arrangement of the blades of a cross-flow fan. 4. A graph showing an uneven pitch arrangement of inter-blade pitch angles as a reference example. 5. An explanatory diagram of Fourier series expansion. 6. (a) is a graph showing amplitude versus order, and (b) is a graph showing phase versus order. 7. A graph showing the amount of improvement in NZ noise for second-order amplitude. 8. A graph showing the amount of improvement in NZ noise for third-order amplitude. 9. A graph showing inter-blade pitch angles when the phase difference is 180°. 10. A graph showing inter-blade pitch angles when the phase difference is 40°. 11. A graph showing the amount of improvement in NZ noise versus phase difference. 12. A graph corresponding to FIG. 11 when the same amplitude as the third order is given to fourth-order and higher amplitudes.

[0015] An embodiment of the present disclosure will be described below with reference to the drawings. Note that, in the following embodiment, a case where a wall-mounted indoor unit is used as an air conditioning device will be described as an example, but the type of air conditioning device is not limited to this.

[0016] As shown in Figure 1, the indoor unit 1 of the air conditioner is a wall-mounted room air conditioner. The indoor unit 1 is connected to an outdoor unit (not shown) by refrigerant piping. The indoor unit 1 includes a base body 2 fixed to the wall and a housing 3 fixed to the base body 2.

[0017] The housing 3 contains a cross-flow fan 5, a heat exchanger 6 arranged in a substantially lambda (Λ) shape so as to cover the cross-flow fan 5, and a filter arranged so as to cover the heat exchanger 6. Indoor air passes through the filter 7 and heat exchanger 6 in this order as shown by arrow A1, flows into the cross-flow fan 5, and is then blown out into the room through an air outlet 8. A flap 9 is provided at the outlet of the air outlet 8.

[0018] The crossflow fan 5 rotates in the direction of arrow A2 around a rotation axis O1. The rotation axis O1 extends perpendicular to the plane of the paper in FIG. 1 . The crossflow fan 5 has a plurality of blades 11 arranged circumferentially around the rotation axis O1 at predetermined intervals. Each blade 11 has approximately the same shape. As shown in FIG. 2 , the crossflow fan 5 has a cylindrical outer shape and is divided into multiple sections in the longitudinal direction by partition plates 12. The partition plates 12 are annular, not shown. Both ends of each blade 11 in the blade span direction are fixed to the partition plates 12.

[0019] 2, each blade 11 is divided into five sections in the longitudinal direction by four partition plates 12, forming a so-called five-section. The arrangement of the blades 11 in each section is the same, but adjacent sections (sections) may be connected with a phase difference (angle around the rotation axis O1).

[0020] 3 shows the arrangement of the blades 11 of the crossflow fan 5. Thirty-five blades 11 are provided in the circumferential direction. However, the number of blades 11 is not limited to this, and may be 34 or less or 36 or more.

[0021] The blades 11 are basically mounted in the same orientation (angle of attack, etc.), but differ in the spacing between adjacent blades 11 in the circumferential direction (blade pitch angle C). The blade pitch angle C is defined as the angle between an imaginary line R connecting the outer circumferential edge 11 a of a blade 11 and the rotation axis O1 and the imaginary line R of the adjacent blade 11, for example.

[0022] For convenience, the first blade 11 is designated by the reference number 11-1, and the sub-numbers of the reference number increase clockwise as 11-2, 11-3, and so on, until the reference number of the 35th blade is 11-35. The pitch number k of the inter-blade pitch angle C of the first blade 11-1 relative to the 35th blade 11-35 is 1, the pitch number k of the inter-blade pitch angle C of the second blade 11-2 relative to the first blade 11-1 is 2, and so on, with the pitch numbers k being defined as 1, 2, 3, ... in the clockwise direction.

[0023] The inter-blade pitch angles C are set to be different from one another in the circumferential direction, and the arrangement of the inter-blade pitch angles C is an uneven pitch arrangement. When the arrangement of the 35 inter-blade pitch angles C is expanded into a Fourier series, the expansion formula is as follows:

[0024] As a reference example, Fig. 4 shows an arrangement in which the inter-blade pitch angle C is random. In the figure, the horizontal axis represents the pitch number k, and the vertical axis represents the inter-blade pitch angle C [°]. The non-uniform pitch arrangement of the inter-blade pitch angle C shown in Fig. 4 can be expressed by superimposing sine waves of orders from DC (0th order) to 34th order, as shown in Fig. 5.

[0025] However, the amplitudes α of the 18th to 34th orders are as follows: α18 = α17, α19 = α16 ... α34 = α1 Furthermore, the phases β of the 18th to 34th orders are as follows: β18 = -β17, β19 = -β16 ... β34 = -β1 In other words, once the amplitudes α and phases β of the 1st to 17th orders are determined, the uneven pitch arrangement is uniquely determined. Therefore, the amplitudes α and phases β of the 18th to 34th orders will be omitted hereafter.

[0026] 6 shows the results of Fourier series expansion of the non-uniform pitch arrangement of FIG. 4. (a) shows the distribution of amplitude α with respect to order m, and (b) shows the distribution of phase β with respect to order m.

[0027] In this embodiment, when the inter-blade pitch angle C is expanded into a Fourier series, the second-order amplitude α2 is set to be 0.2° or more and 0.4° or less, and the third-order amplitude α3 is set to be 50% or less of the second-order amplitude α2. The fourth-order and higher amplitudes α may be 0.

[0028] Furthermore, the phase difference γ (= β3 - β2) between the second-order phase β2 and the third-order phase β3 is a value that does not include 0°, 90°, 180°, and 270°. Preferably, the phase difference γ is set to satisfy the following formula: 90n+10° or more and 90(n+1)-10° or less, or -{90(n+1)-10}° or more and -(90n+10)° or less (n is an integer of 0 or more).

[0029] The fourth or higher order phase β is set to an arbitrary value.

[0030] The reasons for setting the amplitude α and phase difference γ as described above will be explained below. <Second-order amplitude α2> Fig. 7 shows the results of a numerical simulation of the improvement in NZ sound with respect to the second-order amplitude α2. In the figure, the horizontal axis represents the second-order amplitude α2 [°], and the vertical axis represents the improvement in NZ sound [dB]. Regarding NZ sound, a 1NZ sound was examined.

[0031] As can be seen from the figure, the amount of improvement is greatest when the second-order amplitude α2 is around 0.3°, and significant improvement is observed when the second-order amplitude α2 is between 0.2° and 0.4°.

[0032] <Third-order amplitude α3> Fig. 8 shows the results of a numerical simulation of the amount of improvement in NZ noise with respect to the third-order amplitude α3 when 0.3°, which has the greatest effect of reducing NZ noise in Fig. 7, is used as the second-order amplitude α2. In the figure, the horizontal axis represents the third-order amplitude α3 [°], and the vertical axis represents the amount of improvement in NZ noise [dB]. Regarding NZ noise, 1 NZ noise was investigated.

[0033] As can be seen from the figure, the amplitude of 0.3°, which is the same as that of the second order, has the greatest effect in reducing NZ noise. However, if the same amplitude as the second order is used for the third order, there will be locations where the inter-blade pitch angle C is excessively large, which may result in side effects such as reduced air volume and reduced resistance to external static pressure. Therefore, it is preferable to use an amplitude α3 for the third order that is smaller than the amplitude α2 for the second order.

[0034] 8, it can be seen that the NZ noise reduction effect is achieved when the amplitude α3 is 10% to 50% of the second-order amplitude α2. Therefore, the third-order amplitude α3 is set to 10% to 50% of the second-order amplitude α2.

[0035] <Phase difference γ> The phase difference γ between the second-order phase β2 and the third-order phase β3 was examined. Figures 9 and 10 show the results of numerical simulations in which the second-order amplitude α2 is 0.3° and the third-order amplitude α3 is 0.14° (50% of α2). In each figure, the horizontal axis represents the pitch number k, and the vertical axis represents the inter-blade pitch angle C.

[0036] Figure 9 shows the calculation results when the phase difference γ is 180°. As can be seen from the figure, the inter-blade pitch angle C is approximately constant in the section where the pitch number k is 1 to 4 and in the section where it is 33 to 35. If there are consecutive sections like this where the difference between adjacent inter-blade pitch angles C is small, it is not possible to expect a sufficient effect in reducing NZ noise. Similar results were also obtained when the phase difference γ was 0°, 90°, and 270°.

[0037] Figure 10 shows the calculation results when the phase difference γ is 40°. As can be seen from the figure, there are no consecutive locations where the difference in the pitch angle C between adjacent blades is small. This makes it possible to eliminate the factors that reduce the NZ noise.

[0038] FIG. 11 shows the amount of improvement in NZ sound versus phase difference γ. In the figure, the horizontal axis represents phase difference γ [°], and the vertical axis represents the amount of improvement in NZ sound (1 NZ sound) [dB]. As shown in the figure, when the range of phase difference γ was examined to be between 130° and 230°, it was found that the amount of improvement in NZ sound was smallest when the phase difference γ was 180°. Furthermore, in the range other than 180±10°, a reduction effect of 1 NZ sound of approximately 0.1 dB or more can be obtained. This can be said to be similar in terms of periodicity for 0°, 90°, and 270°. Therefore, the following ranges of phase difference γ are preferable: between 90n+10° and 90(n+1)-10°, or between -{90(n+1)-10}° and -(90n+10)°.

[0039] The effects of the present embodiment described above are as follows: When the arrangement of the inter-blade pitch angles is expanded into a Fourier series, the phase difference γ between the second-order phase β2 and the third-order phase β3 is set to a value that does not include 0°, 90°, 180°, or 270°, thereby minimizing the number of consecutive portions where the difference between adjacent inter-blade pitch angles C is small. This makes it possible to reduce NZ noise.

[0040] By setting the phase difference γ to be equal to or greater than 90n+10° and equal to or less than 90(n+1)-10°, or equal to or greater than -{90(n+1)-10}° and equal to or less than -(90n+10)°, it is possible to minimize the number of consecutive portions where the difference in the inter-blade pitch angle C is small, thereby reducing the NZ noise.

[0041] A low-noise crossflow fan can be achieved by appropriately setting the secondary amplitude α2 and the tertiary amplitude α3, which have a large NZ noise reduction effect. Specifically, α2 is set to 0.2° or more and 0.4° or less. However, setting α2 and α3 equal to each other has the side effect of creating locations where the blade pitch angle C is large. In contrast, by setting α3 to 10% or more and 50% or less of α2, the locations where the blade pitch angle C is large can be reduced, and a decrease in airflow and a decrease in resistance to external static pressure can be avoided as much as possible.

[0042] In this embodiment, it is preferable to make the primary amplitude small to avoid an increase in fan unbalance vibration, for example, an amplitude of 0 or close to 0 is used.

[0043] Furthermore, this embodiment can be modified as follows: In the above-described embodiment, the fourth and higher order amplitudes α are each set to 0, but they may be set to 10% to 50% of the second order amplitude α2.

[0044] Fig. 12 shows the results of a numerical simulation in which the amplitude α of each of the fourth to seventeenth orders is set to the same value (0.14°) as the third-order amplitude α3. This figure uses the same horizontal and vertical axes as Fig. 11, and the same values ​​as Fig. 11 are plotted with black circles. As can be seen from this figure, by giving the fourth to seventeenth orders an amplitude similar to the third-order amplitude α3, a greater effect of reducing NZ noise can be obtained than in the case of Fig. 11. Note that the same value as in the above-mentioned embodiment is used for the phase difference γ.

[0045] The cross flow fan, the air conditioner including the same, and the method of designing the cross flow fan described in each of the embodiments described above can be understood, for example, as follows.

[0046] In a crossflow fan (5) according to a first aspect of the present disclosure, a plurality of blades (11) are arranged around a rotation axis (O1) at predetermined intervals in the circumferential direction, adjacent blades are spaced apart in the circumferential direction by an inter-blade pitch angle (C), and when the arrangement of the inter-blade pitch angle in the circumferential direction is expanded into a Fourier series, the phase difference γ between a second-order phase β2 and a third-order phase β3 is a value that does not include 0°, 90°, 180°, or 270°.

[0047] When the arrangement of the inter-blade pitch angles is expanded into a Fourier series, the phase difference γ between the second-order phase β2 and the third-order phase β3 is set to a value that does not include 0°, 90°, 180°, or 270°, thereby minimizing the number of consecutive portions where the difference in the adjacent inter-blade pitch angles is small, thereby reducing the NZ noise.

[0048] In the crossflow fan according to the second aspect of the present disclosure, in the first aspect, the phase difference γ is set to be equal to or greater than 90n+10 [°] and equal to or less than 90(n+1)-10 [°], or equal to or greater than -{90(n+1)-10} [°] and equal to or less than -(90n+10) [°] (n is an integer equal to or greater than 0).

[0049] By setting the phase difference γ to be equal to or greater than 90n+10° and equal to or less than 90(n+1)-10°, or equal to or greater than -{90(n+1)-10}° and equal to or less than -(90n+10)°, it is possible to minimize the number of consecutive portions where the difference in inter-blade pitch angle is small, thereby reducing NZ noise.

[0050] In the crossflow fan according to the third aspect of the present disclosure, when the Fourier series expansion is performed in the first or second aspect, the second-order amplitude α2 is set to be 0.2° or more and 0.4° or less, and the third-order amplitude α3 is set to be 50% or less of α2.

[0051] A low-noise crossflow fan can be achieved by appropriately setting the secondary amplitude α2 and the tertiary amplitude α3, which have a large NZ noise reduction effect. Specifically, α2 is set to 0.2° or more and 0.4° or less. However, setting α2 and α3 equal to each other has the side effect of creating locations where the inter-blade pitch angle is large. In contrast, by setting α3 to 10% or more and 50% or less of α2, the locations where the inter-blade pitch angle is large can be reduced, and a decrease in airflow and a decrease in resistance to external static pressure can be avoided as much as possible.

[0052] In a crossflow fan according to a fourth aspect of the present disclosure, in the third aspect, when the Fourier series expansion is performed, the amplitudes of fourth and higher orders are set to be 10% to 50% of α2.

[0053] For the fourth and higher amplitudes, the NZ noise can be further reduced by setting the amplitude to 10% to 50% of α2.

[0054] An air conditioning apparatus according to a first aspect of the present disclosure includes the cross flow fan according to any one of the first to fourth aspects.

[0055] A design method for a crossflow fan according to a first aspect of the present disclosure is a design method for a crossflow fan in which a plurality of blades are arranged circumferentially around a rotation axis at a predetermined interval, and adjacent blades are spaced apart in the circumferential direction by an inter-blade pitch angle, and when a Fourier series expansion is performed on the circumferential arrangement of the inter-blade pitch angle, the phase difference γ between the second-order phase β2 and the third-order phase β3 is a value that does not include 0°, 90°, 180°, or 270°.

[0056] REFERENCE SIGNS LIST 1 Indoor unit (air conditioner) 2 Base body 3 Housing 5 Cross flow fan 6 Heat exchanger 7 Filter 8 Air outlet 9 Flap 11 Blade 12 Partition plate O1 Rotation axis C Blade pitch angle k Pitch number R Virtual line α Amplitude β Phase γ Phase difference

Claims

1. A crossflow fan having a plurality of blades arranged circumferentially around a rotation axis at a predetermined interval, wherein adjacent blades are spaced apart in the circumferential direction by a blade-to-blade pitch angle, and wherein, when the arrangement of the blade-to-blade pitch angle in the circumferential direction is expanded into a Fourier series, the phase difference γ between the second-order phase β2 and the third-order phase β3 is a value that does not include 0°, 90°, 180°, or 270°.

2. A crossflow fan according to claim 1, wherein the phase difference γ is equal to or greater than 90n+10° and equal to or less than 90(n+1)-10°, or equal to or greater than -{90(n+1)-10}° and equal to or less than -(90n+10)° (n is an integer equal to or greater than 0).

3. A crossflow fan according to claim 1 or 2, wherein, when the Fourier series is expanded, the second-order amplitude α2 is set to be equal to or greater than 0.2° and equal to or less than 0.4°, and the third-order amplitude α3 is set to be equal to or greater than 10% and equal to or less than 50% of α2.

4. A crossflow fan according to claim 3, wherein, when the Fourier series is expanded, the amplitudes of the fourth and higher orders are 50% or less of α2.

5. An air conditioner equipped with the crossflow fan according to claim 1.

6. A design method for a crossflow fan in which a plurality of blades are arranged circumferentially around a rotation axis at predetermined intervals, and adjacent blades are spaced apart in the circumferential direction by an inter-blade pitch angle, wherein, when the arrangement of the inter-blade pitch angle in the circumferential direction is expanded into a Fourier series, the phase difference γ between the second-order phase β2 and the third-order phase β3 is a value that does not include 0°, 90°, 180°, or 270°.

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