JPS6090999A - Axial flow fan free from guide blade - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Technical Field to which the Invention Pertains] This invention relates to an axial flow fan without guide vanes, particularly for ventilation of a heat exchanger, in which the fan unit has an axial flow fan that is divided equally or unevenly around the rotor boss of the fan unit. The blade has a twisted airfoil-shaped blade arranged at a distance of 100 m, and the blade has a curvature height of the warp line on the chord, i.e., the distance between the warp f and the leading edge and the trailing edge of the blade, and the chord length t. The outside of the hole is 0.02 <'/1 < o, 1
It relates to something with a curved warp line in the range of .

[Prior art and its problems]

Such axial fans are known from prior use.

Boss ratio of this known fan (i.e. inner/outer diameter ratio Di/l)
a had a value of Di,i, > 0.4 as long as prevention of stalling or peeling and generation of high pressure were required.

The difference in the blade installation angle between the blade tip and the blade root is approximately 28
It was equal to the normal setting of 51 degrees. The ratio of the R chord length between the blade root and the blade tip was greater than 1.

Typical requirements for such a fan, especially when it is employed to operate in conjunction with a cooler, are:
3 (+-40 % reduced wind pressure in the landscape.Furthermore, the required air volume has a velocity distribution as uniform as possible and a swirl component as small as possible, in order to suppress flow noise at the object to be blown and cooled. Furthermore, for installation reasons, the maximum dimensions of the fan are specified.Furthermore, since people have access to the suction and discharge sides of the fan, there must be a A protective grid must be installed, but the protective grid itself has a detrimental effect on the above-mentioned requirements.

[Purpose of the invention]

The present invention provides an axial flow fan without guide vanes of the above type without requiring an increase or change in the dimensions of its assembly, for example, by moving the protective grid on the outflow side, and without reducing the excellent fan efficiency. , with the aim of significantly reducing sound power levels. , [Summary of the Invention] This purpose is based on this invention.

The following design parameters for the rotor of Da = Outer diameter of the four blades Di = Rotor boss diameter ta = Chord length of the airfoil at the tip of the blade li = Wing &! This is achieved by satisfying the following conditions: chord length ra of the airfoil at the root=blade attachment angle γl with respect to the circumferential direction D (rotational direction) at the blade tip=blade attachment angle with respect to the circumferential direction D (rotational direction) at the blade root.

From a technical textbook point of view, the following measures are promising for solving the above requirements: a) increasing the boss ratio Di/Da in order to achieve as uniform a velocity distribution as possible and therefore less noise generation; b) Increase in pressure coefficient; C) Increase in flow coefficient.

These three design quantities for a fan known by the average expert are interrelated, with quantities a) and C) having a similar effect, but ib) having an opposing effect.

Within the framework of the maximum built-in dimensions, the required pressure, and the required volumetric flow rate given in advance, the pressure coefficient and flow rate coefficient as design quantities are determined while keeping the circumferential speed or rotor rotation speed as low as possible for noise reasons. be done. However, the minimum compatible value of circumferential speed is the structure.

In particular, it is determined by the maximum possible value of the pressure coefficient, which depends on the rotor boss ratio DI,/I)a. In this regard, as is known, the design law holds that in order to achieve good efficiency, the smaller the value of the pressure coefficient, the larger the value of the flow coefficient.

This relationship is known from the relevant literature as the Cordile curve. Textbook “Fan” 1 by Bruno Eck
972, page 271, section 265, a modified relationship between the pressure coefficient and the flow coefficient and the dimensionless quantities of diameter number and rotational speed which are linearly related to these are known.

In relation to these dimensionless quantities, the above textbook °
A boss ratio is recommended that, in combination with good efficiency, can guarantee an optimum value. Significant deviations from this recommended value do not result in good efficiency being achieved, and in particular from the values of the boss ratio recommended in textbooks... deviations result in flow separation in the area of the boss and therefore a correspondingly high noise generation. It is said to lead to results.

The 1° parameter set according to the present invention as set forth in claim 1 deviates from the design conditions recommended by specialized books. Nevertheless, the fan according to the invention has the advantage that, while ensuring the required values for the volumetric flow rate and the maximum pressure at a defined % partial volume sweep, also for the given maximum installed dimensions and the smallest possible circumferential speed. When the boss ratio is small, stalling or separation occurs in the rotor C, and the flow is closer to a uniform velocity distribution state at a given volumetric flow rate than when the boss ratio is larger, and the absolute value of this velocity is Contrary to expectations, it has been found that there is an advantage in that the value is small.

Furthermore, the pressure loss in the protective grid on the outflow side is small, so that the ventilation power consumed in this location is reduced and the flow noise is reduced, resulting in a further reduction in fan noise.

In order to further reduce the noise while guaranteeing the required data of the fan unit, a second diffuser casing part is provided in contact with the outlet side of the first casing part which directly surrounds the fan unit, and this diffuser casing part The inner diameter of the blade starts to increase rapidly within a distance range of ±0.3ta from the outflow side corner of the blade, and preferably 0.1ta<r<0.312. It is advantageous to round the curve using the radius of curvature.

West German Patent Publication No. 2! No. 12141G discloses a low-noise axial flow fan with a fan unit surrounded by a casing. Although the internal diameter has increased sharply by about 25%, special design parameters for the rotor design and the rounding of the blade corners and the presence of a protective grid at least on the outflow side are missing.

Due to the selection of the above-mentioned rotor geometry which, for the fan according to the invention, has a high distribution of work in the area of the rotor's periphery, and especially in combination with the said casing structure and the rounding of the corners of the blades, a peak value at the rear of the fan is obtained. It is possible to obtain a significant improvement in the speed distribution in that the speed distribution is reduced and to have a uniform speed distribution, and a large noise reduction effect in which the noise can be reduced by 3 to 4 dB (Al). This is contrary to the textbook view, according to which an increase in the average clearance between the rotor and the surrounding casing would itself lead to an increase in the noise level.Furthermore, in general, the maximum possible developed pressure (stall point ) is thought to decrease if the air gap between the rotor and casing is large.

A rational design method for a full fan casing with a rapidly expanding diffuser casing section is to reduce the total opening ratio, or diameter ratio D, to the diffuser casing section.
2/DA is 1-03 < L) 2/I) A < L 25
and the total axial length tD is 0.10 DA < 1
．． Designs characterized by D<0.5 DA have given good results.

The structure of the diffuser casing that is particularly advantageous in manufacturing is such that the partial force of the diffuser casing is 5u<α1×LiO'
1.02 DA (: D21
(: a rapid expansion that begins after the rotor reaches a diameter D21, which is Dz, followed by 0° and α2<10°
The diameter D2 is gradually expanded with an inclination angle α2. In this case, it is advantageous for the diffuser housing part to consist of a tube which has been expanded in the area of its widening by means of a suitable stamping die.

[Embodiments of the invention]

Next, the present invention will be described in detail with reference to drawings showing embodiments of an axial flow fan based on the present invention.

In Figs. 1 and 2, a fan unit consisting mainly of a drive motor M and a seven rotor LR having blades 181-88 fixed on its output shaft is arranged in a casing surrounding it. , this casing is 7 ununi,
)M, is assembled from a casing part Gl of MEI directly surrounding LR and a second diffuser casing part G2. Protective gratings SG are fixed to the inlet and outlet sides of the casing, respectively.

In this embodiment of the invention, Fanyuni, ToM.

A second casing portion G1 directly surrounding the LR is in contact with the first casing portion G1.
A diffuser casing portion G2 is provided, and the inner diameter of this diffuser portion begins to increase rapidly within a distance range of ±0.31a from the outflow side corner of the vane 5l-88. where ta is the chord length of the blade airfoil, and the starting point of the range starts from the unrounded corner of the rotor.

In one embodiment of the diffuser casing G2 according to the invention, the rotor L) After that, first 1 with an inclination angle αl of 15° and 6m<6C°.
．． 02 DA A rapid expansion reaching the diameter D21 where <D21 < Dz, followed by a 0° angle α2<10
A gradual widening reaches the diameter D2 with an inclination angle α2 of .degree. Such a diffuser casing section may first be fabricated from a tube of equal diameter diameter and then expanded by means of a die having the dimensions of the enlarged section.

According to a different embodiment of the invention, the total opening ratio or diameter ratio D2/D for the portion of the diffuser casing is
A is 1.03 < Dz/DA = 1.25, and the total axial length tD is 0. IOD person <tn <0.5 DA. Here, DA is rotor 1. Dz is the inner diameter of the fan casing (first casing portion) in the range R, and Dz is the maximum diameter on the outlet side of the diffuser casing G2.

As shown in Fig. 3, in order to obtain good fan efficiency and good low noise performance, the diffuser casing G2
In combination with the enlargement of the casing according to the invention in the range of , the outflow corners of the vanes 5l-88 are rounded with a radius of curvature r such that 0.1t2<r<0.3ta.

In combination with the design parameters regarding the fan casing and the outflow corners of the blades, the configuration of the fan rotor according to the invention requires screws arranged equally or unequally over the circumference of the rotor boss of the fan unit, as mentioned in the introduction. The ratio of the curvature height of the curvature line of chord-H, that is, the curvature f, to the distance between the leading edge and the trailing edge of the two blades, that is, the chord length, is 0.02<'/7 For an axial flow fan without guide vanes with a warp line in the range of <0.1, the rotation direction, air blowing direction, tip and root are determined according to the partially exploded view of boss N in Figure 4. The tombs marked on the wing diagram with cross-sections shown are located within the following range.

0.25 <”/1) a<0.35 70°<ri　<so.

35°<rI-ta×50°0.7<ti/la<1 where Da-rotor outer diameter Di = rotor boss diameter 1, = airfoil chord length Ai at blade tip = = blade root length R chord length γ3 of the airfoil here=blade mounting angle B with respect to the circumferential direction D (rotational direction) at the blade tip=blade mounting angle with respect to the circumferential direction D (rotational direction) at the blade root.

Using the above design parameters, all of the blade airfoils can be determined based on conventional calculation methods for blower and fan airfoil blades. In addition, in this case, it should be based on the blade over-paragraph relationship that is normally used and recommended in the case of axial flow rotor crotch pulling.

〔Effect of the invention〕

The rotor of the axial fan according to the invention has design parameters that deviate from the values recommended in existing technical literature. Nevertheless, by keeping the circumferential speed and boss ratio small while satisfying the requirements for external dimensions, pressure requirements for open air volume and partial air volume, and the installation of protective grids at the casing entrance and exit, it is possible to uniformly It was found that a wind speed distribution with a small wind speed distribution and a small absolute wind speed value were obtained, and that no stall occurred in the rotor in the required partial scenery.

The adoption of such rotor design parameters, especially in combination with the enlarged structure of the diffuser casing and the rounding of the blade corners, reduces the noise level by 3 to 4 d.
B (AJ can be lowered.

Furthermore, the reduction in pressure loss across the protective grid on the outflow side
The reduction in ventilation power and flow noise results in further noise reduction.

[Brief explanation of drawings]

FIG. 1 is a side view of the axial fan, showing an embodiment of the axial fan without guide vanes according to the present invention arranged in a fan casing, and FIG. 2 is a side view of the axial fan shown in FIG. 1. Fig. 3 is a partially enlarged view of Fig. 1, and Fig. 4 is a partially developed boss showing the tip and root airfoils of the axial flow 7-ang blade shown in Fig. 1. Figure. In the drawing, 14 is the rotor, M is the electric motor, LR and M are the fan unit, Gl is the first casing part, G2 is the second diffuser casing part, Sq is the protection grid, and 5l-88 is the blade. , L is the ventilation direction, D is the direction of rotation, N is the boss, Da is the outer diameter of the rotor, Di is the outer diameter of the boss, H is the inner diameter of the casing in the range of the rotor,
D2 is the maximum diameter of the diffuser casing part, D21
is the maximum diameter of the rapid expansion, G1 is the inclination angle of the rapid enlargement, G2 is the inclination angle of the gradual expansion, r is the rounding radius of the outflow corner of the blade, f is the curvature of the airfoil, and ta is the inclination angle of the gradual expansion. The chord length at the tip of the blade, Ll is the chord length at the root ζ of the blade, γ
8 is the blade attachment angle with respect to the rotational direction at the blade tip, r
i is the mounting angle of the blade relative to the rotational direction at the blade root.

Claims (1)

[Claims] l) A fan unit comprising twisted airfoil-shaped blades arranged equally or unequally around the rotor boss of the fan unit;
This blade has a ratio f4 of the curved height of the warp line on the chord, that is, the warp f, and the distance between the leading edge and the trailing edge of the blade, or the chord length t, in the range of 0.02≦'/l<0.1. For those with a certain curved warp line, (the following design parameters for the rotor of the fan unit are in the following range: 0.25 <Di/1) a < o, a 570° < rl
<80゜35゜γl-γ3゜50゜0.7゜tgin3〔3〈1 where Da = rotor outer diameter Lli = rotor boss diameter ta two-blade chord length of airfoil at tip ti = blade root An axis without guide vanes, characterized in that the chord length ra of the airfoil in the blade tip is the blade-attached angle ri in the circumferential direction (rotational direction) at the blade tip=the blade attachment angle in the circumferential direction (rotational direction) at the blade root flow fan. 2. The fan according to claim 1, further comprising an attached casing that surrounds at least the fan unit, and a second disc that is in contact with the outlet side of the first casing portion that directly surrounds the fan unit. A trickle fan without guide vanes, characterized in that a 7-user casing section is provided, the inner diameter of this diffuser casing section begins to increase sharply in a distance range of ±0.3 ta from the outflow corner of the vanes. 3) The fan according to claim 2, without guide vanes, characterized in that the outflow side corners of the vanes are rounded with a radius of curvature r, where o, lta < r, 3ta. Axial fan. 4) Scope of claims! In the fan described in item s2 or item 3, the total aperture ratio, that is, the diameter ratio Dη with respect to the casing portion is 05<, D2/DA<1.25, where DA=rotor Axial fan without guide vanes, characterized in that the inner diameter D2 of the first casing part in the range=maximum diameter of the dephasor casing part. 5) The fan according to any one of claims 2 to 4, characterized in that the total axial length tD of the diffuser casing portion is 0, 10 DA < 7D < Q, 51) A. Axial flow fan without guide vanes. 6) In the fan according to any one of claims 2 to 5, the diffuser casing portion has an inclination angle α1 of 15° and α1<60° of 1.0°.
2 a sudden widening starting after the rotor (,, LR) reaching the diameter D21 with DA <, D21 <D2;
An axial flow fan without guide vanes, characterized in that this is followed by a slowly expanding portion that reaches a diameter D2 with an inclination angle α2 of 0° and α2<100. 7) A fan according to any one of claims 2 to 6, characterized in that the diffuser casing part consists of a tube whose enlarged area is expanded by a suitable die. Axial fan without blades. 8) In the fan according to any one of claims 2 to 7, the first casing part and the diffuser casing part are both formed from one pipe. Axial fan without guide vanes. 9) In the fan according to any one of claims 2 to 8, the shaft m7 has no guide vanes, characterized in that a protective grid is provided on the outflow side of the diffuser casing part.