JPS6337516Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a mixed flow fan used in air conditioners and the like.

As this type of diagonal flow fan, the following are shown in Figs.
As shown in the figure, the peripheral wall surface 1 of the hub 1 has a truncated cone shape.
A plurality of blades 2, 2 which generate diagonal flow acceleration are provided at a.
A known compressor comprises an impeller 3 having an impeller with equal pitches and a pressure recovery device 4 consisting of a scroll for controlling the flow of air sucked in through an inlet 5 provided in the center of a front panel 4a facing the impeller 3. Reference numeral 6 denotes an outlet that protrudes tangentially from the outer circumferential surface and opens thereto.

Conventionally, in such a mixed flow fan, each blade 2 of the impeller 3, as shown in FIG.
The meridian plane shape of 2... is rectangular, and the inner diameter D ₀ of the suction port 5 is D ₁ <D ₀ <1.2D with respect to the outer diameter D ₁ of the inlet part and the outer diameter D ₂ of the outlet part of the impeller 3. It is set to a range of ₂ .

The reason for this is that this mixed flow fan is used to suck air from a free space rather than from a confined space such as a suction pipe, so if the inner diameter D ₀ of the suction port 5 is small, the suction port 5 Feather 2 behind
This is to prevent large pressure loss from occurring due to the formation of a peeling area at the tip, and
In recent air conditioners, due to energy saving trends, the heat exchanger has become larger and the internal resistance has been reduced by placing the heat exchanger in front of the fan suction port. (P _T /γ) 3/4 (where, N: rotation speed rpm, Q: air volume m ³ /
min, P _T : total pressure mmAq, γ : specific gravity Kg/m ³ ) is increasing, and in order to meet this demand, a large-diameter suction port is required to reduce pressure rise due to centrifugal force. Ru.

Furthermore, if a suction port with a large diameter is installed, the uneven flow of the air flow in the heat exchanger will be reduced, and the internal resistance will further be reduced, so a suction port with a large diameter as possible is required.

However, in the mixed flow fan of the conventional structure, when the inner diameter D ₀ of the suction port 5 is increased to the range of (D ₁ + D ₂ )/2<D ₀ <1.2D ₂ , the streamline ft′ passing through the vicinity of the inner diameter of the suction port 5 Since the blade portion 2a through which the impeller 3 passes becomes shorter, the head Ht given by the impeller 3 is given by the following formula Ht = 1/2g [(u ₂ t ² - u ₁ t ² ) + (w ₁ t ² - ₂ t ² ) + (c ₂ t ² −c ₁ t ² )] (where, g: gravitational acceleration, u: circumferential velocity, w:
Relative speed, c: absolute speed, subscript 1: blade inlet side,
Subscript 2: blade exit side) is another streamline (for example, streamline fm′ on the mean flow surface)
_The ^head _Hm ^{given by the impeller} _{3 of} ^​ _​ ^​ ], and eventually a backflow occurs from the inner diameter portion of the suction port 5, resulting in a decrease in total pressure efficiency and an increase in operating noise. The graphs indicated by solid lines X in Fig. 6a and b show the changes in the total pressure efficiency η and the specific noise Ls of the total pressure level with respect to the change in the suction port inner diameter _D0 of the conventional mixed flow fan shown in Fig. 3. This is an example.
The comparison is based on the representative internal resistance curve passing through an air volume of 20 m ³ /min and a static pressure of 4 mmAq, and the inner diameter of each suction port D ₀ (A~
This is done at the intersection with the standalone performance (shown by the solid line) corresponding to D) (see Figure 8). Here, Figure 8 shows
It is an air volume-static pressure characteristic diagram.

The present invention was devised in view of the above-mentioned problems, and includes an impeller in which a plurality of rectangular blades are installed on the peripheral wall surface of a truncated cone-shaped hub to generate diagonal flow acceleration, and the impeller. and a pressure recovery device for controlling the flow of air sucked in from the suction port _opposite to
In a mixed flow fan that is set in the range of (D ₁ + D ₂ )/2 < D ₀ < 1.2D ₂ with respect to D ₁ and outlet outer diameter D ₂ , the outer end surface of each blade has this outer diameter. In a spatial region having an imaginary substantially triangular cross section formed by the end face and the cylindrical portion of the suction port, a part of the outer edge has a slight gap in the radial direction of the impeller with respect to the inner diameter surface of the cylindrical portion of the suction port. It is characterized by a structure in which a plate-shaped bulge with a substantially triangular cross section is integrally formed along the inlet, and the heat exchanger is installed in front of the suction port, resulting in a high specific speed design with high air volume and low internal resistance. The object of the present invention is to provide a mixed flow fan that can achieve high efficiency and low operating noise when incorporated into an air conditioner or the like.

Hereinafter, a mixed flow fan according to an embodiment of the present invention will be described with reference to FIGS. 4 and 5.

FIG. 4 shows a scroll-equipped mixed flow fan which is the first embodiment of the present invention, and since its basic structure has already been described in FIGS. 1 and 2, the same parts will be the same. Reference numerals are given and detailed explanations are omitted. That is, this mixed flow fan includes an impeller 3, which is made up of a plurality of rectangular blades 2, 2, etc., planted at equal pitches on the circumferential wall surface 1a of a truncated conical hub 1, for generating diagonal flow acceleration. The pressure recovery device 4 is composed of a scroll that controls the flow of air sucked in from a suction port 5 facing the impeller 3, and the inner diameter D ₀ of the suction port 5 is equal to the inlet portion of the impeller 3. The outer diameter D ₁ and the outlet outer diameter D ₂ are set in the range of (D ₁ +D ₂ )/2<D ₀ <1.2D ₂ .

Therefore, in the outer end surface 2b of each of the blades 2, in a spatial region having an imaginary substantially triangular cross section formed by the outer end surface 2b and the cylindrical portion of the suction port 5,
A plate-shaped bulge 7 having a substantially triangular cross section is integrally formed, and a part of the outer edge thereof extends in the radial direction of the impeller 3 with a slight gap S between them and the inner diameter surface of the cylindrical portion of the suction port 5. ing. The gap S may be such that the tips of the bulging portions 7, 7, . . . of the blades 2, 2, .

Further, the bulging portion 7 is formed so as not to protrude from the outer end surface of the suction port 5.

Next, to explain the operation of the mixed flow fan of the first embodiment shown in the figure, the air W sucked in from the suction port 5 is accelerated by the blades 2, 2, etc. as the impeller 3 rotates, and then The flow is controlled in a pressure recovery device 4 made of a scroll and is blown out from an outlet 6.

At this time, the blade portion 2a through which the streamline ft passing close to the inner diameter surface of the suction port 5 passes is larger than that of the conventional example shown in FIG. 3 by the amount by which the bulge 7 is formed. Therefore, the change in relative velocity on the two surfaces of each blade occurs smoothly, the loss is reduced, and the slip ratio ν H = νH∞ (where H: number of blades) is expressed by the following formula. The theoretical total pressure head in a finite case (H∞: theoretical total pressure head in the case of an infinite number of blades) increases in proportion to the length of the blade portion 2a, and even if the suction port 5 is enlarged, backflow occurs. In addition, due to the increase in the effective blade action surface due to the presence of the bulging portion 7, in Fig. 8, a comparison of the fan unit performance at each suction port inner diameter D ₀ (A to D) (dotted line: conventional example, solid line As shown in Embodiment 2), the performance has been improved and the operating range has been expanded (in Fig. 8, the x mark indicates the backflow limit, and backflow occurs when the air volume is smaller than this point).

The reason why backflow is less likely to occur when the slip ratio ν is large is clear from the following equation.

As shown in Fig. 7, the head H' = 1/2g [(u ₂ t ² - u ₁ t ² ) + (w ₁ t ² - w ₂ t ² ) + c ₂ due to the conventional streamline ft' t ² −c ₁ t ² )] and the head H = 1/2g [(u ₂ t ² −u ₁ t ² ) + (w ₁ t ² −w ₂ t ² ) + (c ₂ t ² −c ₁ t ² )], then w ₁ t≒w ₁ t′ C ₁ t≒c ₁ t′ w ₂ t＜w ₂ t′ c ₂ t＜c ₂ t′, so H This is clear from the fact that ′<H.

In addition, the graph shown by the dotted line Y in FIGS. 6a and b is
Specific noise of total pressure efficiency η and total pressure level with respect to changes in suction port inner diameter D ₀ of the mixed flow fan shown in Figure 4
This shows an example of changes in L _SA . The comparison is made at the intersection of the representative in-machine resistance curve passing through an air volume of 20 m ³ /min and a static pressure of 4 mmAq and the individual performance (shown as a solid line) corresponding to each suction port inner diameter D ₀ (A to D) ( (See Figure 8). According to this, in the range of (D ₁ + D ₂ )/2 < D ₀ < 1.2D ₂ , the mixed flow fan of the present invention significantly improves the total pressure efficiency η compared to the conventional example, and also has low noise. As a result, it is possible to supply a fan with a wider operating range that is compatible with air conditioners with high air volume, low static pressure, and high specific speed design.

Next, FIG. 5 shows a mixed flow fan with a radius transition type diffuser, which is a second embodiment of the present invention. In this case, as the pressure recovery device 4, a radial transition type diff user is employed which blows out air from an air outlet 6 that opens in all radial directions. Moreover, in this embodiment, the inner diameter D ₀ of the suction port 5 is set to D ₁ +D ₂ /2<D ₀ with respect to the outer diameter D ₂ of the outlet portion of the impeller 3, and D ₂ <D ₀ <1.2D. It is set to a range of ₂ .

Therefore, the bulge 7 integrally formed on the outer end of the blade 2
is formed over the entire length of the outer end surface 2b of the blade 2.

In this case, the total pressure efficiency η and the specific noise L _SA at the total pressure level are as shown by the dashed line Z in Fig. 6a and b.
Compared to a scroll, the internal pressure loss is smaller, which further improves the performance, and this mixed flow fan exhibits good performance, especially at the point of use in a high specific speed design with high air volume and low static pressure.

In addition, in the case of this embodiment, even if the inner diameter D ₀ of the suction port 5 is slightly larger than the outer diameter D ₂ of the outlet part of the impeller 3,
There is no backflow, resulting in high efficiency and low operating noise, and since the blades 2 do not come into contact with the suction port 5 during assembly, the impeller 3 can be easily assembled.

Next, the effects of the mixed flow fan of the present invention will be described.

According to the present invention, there is provided an impeller 3 in which a plurality of rectangular blades 2, 2, . and a pressure recovery device 4 that controls the flow of air sucked in from the opposing suction ports 5, and the inner diameter _D0 of the cylindrical portion of the suction port 5 is equal to the outer diameter D1 of the inlet portion and the outer diameter _D2 of the outlet portion of the impeller _3. In a mixed flow fan set in the range of (D ₁ +D ₂ )/2<D ₀ <1.2D ₂ , the outer end surfaces 2b, 2b... of each of the blades 2, 2...
In a spatial region having a virtual triangular cross section formed by the outer end surface 2b and the cylindrical portion of the suction port 5, a part of the outer edge is located at a radius of the impeller 3 relative to the inner diameter surface of the cylindrical portion of the suction port 5. Since the plate-shaped bulges 7 with a substantially triangular cross section extending along the direction with a slight gap S are formed integrally with each other, even if the inner diameter D ₀ of the suction port 5 is made as large as possible, the suction air flow is This has the practical effect of being able to provide a mixed flow fan with high efficiency and low noise at a high specific speed design point with high air volume and low static pressure.

Note that, as in the second embodiment, the inner diameter D ₀ of the suction port 5
is set in the range D ₂ <D ₀ <1.2D ₂ with respect to the outer diameter D ₂ of the outlet part of the impeller 3, and the bulge 7 is formed over the entire length of the outer end surface 2b of each blade 2. This has the advantage that the total pressure efficiency η can be further improved and the impeller 3 can be easily assembled.

[Brief explanation of the drawing]

Fig. 1 is a front view of a general mixed flow fan, Fig. 2 is a sectional view taken along the - line in Fig. 1, Fig. 3 is an explanatory diagram of air flow near the suction port of the conventional example, and Fig. 4 is a diagram of the present invention. A cross-sectional view of essential parts explaining the air flow near the suction port of the mixed flow fan according to the first embodiment, FIG. 5 is a longitudinal cross-sectional view of the mixed flow fan according to the second embodiment of the present invention, and FIG. A graph showing the characteristics of the total pressure efficiency η with respect to the size of the inner diameter D ₀ for the conventional example, the first example, and the second example. FIG. 8 is an air volume-static pressure characteristic diagram comparing the conventional example and the first embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Hub, 1a...Hub peripheral wall surface, 2...Blade, 2b...Blade outer end surface, 3...Impeller, 4...
Pressure recovery device, 5... Suction port, 7... Swelling part,
D ₀ ... Inner diameter of the suction port, D ₁ ... Outer diameter of the inlet of the impeller,
D ₂ ... Outer diameter of the impeller outlet, S ... Gap.

Claims (1)

[Claims for Utility Model Registration] An impeller 3 comprising a plurality of rectangular blades 2, 2, . It has a pressure recovery device 4 that controls the flow of air sucked in from the suction port 5 facing the wheel 3, and the inner diameter _D0 of the cylindrical portion of the suction port 5 is equal to the outer diameter D1 of the inlet portion and the outlet portion of the impeller ₃ . In a mixed flow fan set in the range of (D ₁ + _{D 2 )} /2<D ₀ <1.2D ₂ with respect to the outer diameter D 2, the outer end surfaces 2b, 2b... of each of the blades 2, 2... teeth,
In a spatial region having a virtual triangular cross section formed by the outer end surface 2b and the cylindrical portion of the suction port 5, a part of the outer edge is located at a radius of the impeller 3 relative to the inner diameter surface of the cylindrical portion of the suction port 5. Plate-like bulges 7, 7 with a substantially triangular cross section along the direction with a slight gap S therebetween...
A mixed flow fan characterized by being integrally formed with.