JPH071040B2 - Forward fan straightening rib structure - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a forward fan straightening rib structure used for cooling a radiator and the like.

[Problems to be Solved by Prior Art and Invention] In recent years, in automobiles, the amount of heat dissipated by a radiator tends to increase due to higher engine output, smaller engine room, etc. Higher airflow is also being promoted for Juan. In such a case, a forward fan is used in which the outer peripheral edge portion of the blade radially protruding from the boss portion is widened by protruding substantially forward in the blade rotation direction. Is lower than a general-purpose axial fan that does not project sharply forward in the rotational direction. It is said that the sharp tip protruding forward in the rotational direction has a function of suppressing the entrainment of air from the non-flow side (positive pressure surface side) of the wind flowing by fan rotation in the shroud to the upstream side (negative pressure surface side). Guessed.

However, when the forward fan is simply rotated at high speed to increase the air volume, the noise that does not cause much trouble at low speed becomes significantly louder at higher speed. This is because, as shown in FIG. 5, when the air flow passing through the radiator 4 flows through the shroud 5, a sharp tip portion is formed, so that the flow path of the air flow on the positive pressure side surface becomes long, As a result, a larger centrifugal force component is given by the high-speed rotation of the forward fan 1 and the outer peripheral edge trailing edge of the blade is
It concentrates on the X and Y parts, and this flows into the upstream side from the downstream side through the gap between the shroud inner peripheral surface and the blade outer peripheral surface, which causes the air flow at the rear end of the blade (blade body) 2. The generation of turbulence due to separation, the generation of turbulence due to air flowing from the outer peripheral end of the blade 2 to the upstream side, and the generation of turbulence during separation due to stall of the leading edge of the blade 2 are mainly mentioned. Are believed to have a significant effect on noise generation during high speed rotation. Therefore, various measures have been conventionally taken against the generation of these turbulent air flows, but in the actual situation, no sufficiently satisfactory measures have emerged as measures against high-speed rotation.

[Means for Solving Problems] The present invention was devised with the object of providing a straightening rib structure of a forward fan capable of eliminating these drawbacks in view of the above circumstances. A plurality of blade outer peripheral edges projecting from the boss portion in the radial direction are formed into an arc shape along a fan rotation locus along the inner peripheral surface of the shroud in which wind flows from the upstream side to the downstream side by fan rotation, And in the forward fan in which the outer peripheral edge portion is sharply widened forward in the rotational direction by projecting the front end portion in the rotational direction of the blade outer peripheral edge portion toward the front in the rotational direction of the fan, the blade outer peripheral edge portion One plate-shaped straightening rib is formed on the upstream blade surface so as to project, and the straightening rib is used to straighten the wind entrained from the entire outer circumference of the blade. An arc-shaped position that is substantially concentric with the blade outer peripheral edge in a position near the fan axis with respect to the rotational locus position of the sharpened protruding end of the outer peripheral edge of the Brehed, and the protrusion width extends over substantially the entire width of the blade. It is characterized in that the width is wide and the protruding height is set to be substantially equal to the distance from the outer peripheral edge of the blade to the protruding position of the flow regulating rib.

Further, according to the present invention, the turbulent airflow during high speed rotation can be effectively suppressed by this structure, and a high air flow can be achieved in a quiet state.

[Embodiment] Next, an embodiment of the present invention will be described with reference to the drawings. In the drawings, 1 is a forward-type forward fan, which is constructed by radially projecting four blades 2 from a boss portion 1a. The edge portion projects in a substantially sharp shape toward the front side in the blade rotation direction (the direction of the arrow in FIG. 1) and becomes wider toward the outer peripheral edge. The rectifying rib 3 of the present invention is provided so as to protrude from the outer peripheral edge portion of the blade that is wide. In the present invention, the following examinations 1 to 6 are performed in order to obtain the setting conditions of the rectifying rib 3 described above. I'm trying.

Here, in conducting these examinations, the forward fan actually used is as shown in FIG. 1, and specifically, the overall diameter is 300 mm, the boss portion 1a diameter is 80 mm, and the blade 2 total length is 110 mm. , The twist width X of the blade 2 is 35.5 mm, the twist center Y of the blade 2 is 16.5 mm from the front edge, and the outer peripheral edge of the blade 2 has a substantially arc shape centered on the fan axis. The standard type forward fan 1 has a sharp protruding end 2a located approximately 7 mm closer to the fan axial center from the outer peripheral edge along substantially the inner peripheral surface, and a rectifying rib 3 is provided on the standard forward fan 3 under various conditions described later. For those (study examples A to M), the number of revolutions of the forward fan 1 (rpm) to obtain the reference air volume (Q) of 1220 m ³ / h and the noise (dB) at that time
And were measured, and the results are shown in the chart. For this standard type, the 2020
rpm rpm is required, and the noise at that time is 63d
It has been previously observed by experiments that it is B.

The matters examined are described below.

<Study 1 (Study of Protruding Surface of Rectifying Rib)> Here, it will be examined whether the rectifying rib 3 should be provided on the downstream side or the upstream side of the blade 2. The forward fan 1 of each study example used here is an arc-shaped position of a concentric circle with respect to the outer peripheral edge of the blade 2 of the standard type, and at a position of 10 mm from the outer peripheral edge toward the fan axis.
The height (maximum height) of the central portion was 10 mm, and the rectifying ribs 3 were formed so that the shape of the upper edge was set to be substantially the same as the curvature of the outer peripheral portion of the blade 2. And this straightening rib 3
Provided on the upstream side (study example A), on the downstream side (study example B), and on both sides (study example C)
For each of the above, the number of rotations required to obtain the reference air volume and the noise at that time were measured, and the results are shown in the chart. According to this, it is recognized that the noise when obtaining the reference air volume in any of the studied examples is lower than that of the standard type, but especially the one provided only on the upstream side and both sides This tendency is remarkable in the case where the rectifying rib 3 is provided at least on the upstream side.

<Study 2 (Study of Number of Rectifying Ribs)> Next, the number of rectifying ribs 3 will be examined. This is the same as the blade 2 of Examining Example A described above at a position displaced by 10 mm from the axial center side. The same measurement was performed using the other two rectifying ribs 3 provided for convenience (study example D), and the results are shown in the chart. According to this, the straightening rib 3
In the case of two sheets, it is necessary to rotate at high speed in order to obtain the reference air volume, and therefore it is not efficient to increase the number of the rectifying ribs 3, and the noise is the same as in the study example A. It's a little worse, but it's admitted to be better than the standard one. Therefore, it can be said that the number of the rectifying ribs 3 is preferably one as in Study Example A.

<Study 3 (Study of protrusion angle of straightening rib)> Here, what angle the straightening rib 3 is provided with respect to the outer peripheral edge of the blade 2 will be examined.
Therefore, the rib angle of the straightening rib 3 with respect to the outer peripheral edge is such that the front end matches the outer peripheral edge of the blade 2 (study example E) and the rear end matches the outer circumferential end of the blade 2 (study example F).
The same conditions as in Study Example A were examined except that they were respectively inclined with respect to the outer peripheral edge, and the measurement results are shown in the chart. According to this, the noises of Study Examples E and F are similar to those of the standard type in terms of noise, and as a result, the rib angle with respect to the outer peripheral edge of the rectifying rib 3 is the same as that of Study Example A. It can be said that it is preferable to be parallel to and substantially concentric.

<Study 4 (Study of Height of Rectifying Rib)> Next, in examining the protruding height of the rectifying rib 3, only the rib height of the rectifying rib 3 is lower than that of the study example A of 10 mm. Measurements were made for a thickness of 5 mm (Study Example G) and a height of 15 mm (Study Example H), and the results are shown in the chart. According to this, the rib height of 10 mm in Examination Example A is the lowest noise, and it is recognized that the noise is increased when the rib height is larger or smaller than that. It can be said that the height is preferably substantially the same as the distance from the outer peripheral edge of the blade 2.

<Study 5 (Study of Protruding Positions of Rectifying Ribs)> Here, it is examined how much the rectifying ribs 3 should project from the outer peripheral edge of the blade 2. Therefore, only the protruding position of the flow straightening rib 3 is protruded to the blade outer peripheral end position (that is, 0 mm position from the outer peripheral edge) (Study Example I), and the position 5 mm from the outer peripheral edge to the fan shaft core side (the sharp protruding end 2).
As the one projecting at a position close to the side opposite to the fan axis direction with respect to the rotation locus of a) (Study Example J), and the one projecting at the same position on the 15 mm fan shaft center (Study Example K) , Only the protruding position was set to be different from that in Study Example A, these were measured, and the results are shown in the chart. According to this, in the case of Study Example I, almost no noise reduction was observed,
It is recognized that the lowest value is shown in Study Example A,
From this, it can be said that it is preferable that the protruding position of the rectifying rib 3 is closer to the fan axis center than the rotational locus position of the sharpened protruding end in the outer peripheral edge of the blade, and is closer to the rotational locus of the protruding end 2a. .

<Study Example 6 (Study of Shape of Rectifying Rib)> Here, what shape of the rectifying rib 3 is the best will be examined. Therefore, the rectifying rib 3 of the examination example A
Is a wedge shape in which a portion on the front side in the rotation direction of the forward fan 1 is cut out, and the cutout position is set to approximately 1/3 of the rib width of the rectifying rib 3 (study example L), rear end portion The above (measurement example M) was measured, and the results are shown in the chart. According to this, the rib shape of Study Example A is the best for noise, and it is recognized that the noise increases as the front end portion is cut out. Therefore, the upper end edge shape of the straightening rib 3 is It can be said that the shape closer to the outer peripheral edge shape of 2 is more effective in reducing noise.

And considering from the results of each of the above-described studies 1 to 6, it is clear that the rectifying rib 3 of Study Example A has an excellent property, as in the present invention. The rib 3 is provided on the upstream surface so that the protruding position is near the fan shaft center side with respect to the rotational locus position of the sharpened protruding end 2a of the blade outer peripheral edge portion and the blade outer peripheral edge. With respect to the arcuate position that is approximately the same depth as the above, the projection width is wide across the entire width of the blade, and the projection height is approximately equal to the distance from the outer peripheral edge of the blade to the straightening rib projection position. A noise reduction is clearly recognized in the set ones.

[Operation] As described above, in the forward fan provided with the long sharp tip 2a protruding forward in the rotation direction of the blade 2, the air entrainment from the downstream side to the upstream side is suppressed at low speed rotation. During high speed rotation, a large centrifugal force component is given to the air flow on the downstream side and concentrates on the outer peripheral edge trailing edge of the blade, which passes through the gap between the shroud inner peripheral surface and the blade outer peripheral edge to the downstream side. Try to flow into the upstream.

However, the straightening ribs 3 set on the blade 2 are set.
In the configuration in which the upstream side air flow generated by the sharpened tip 2a is caught between the straightening rib 3, the upstream outer end surface of the blade 2 and the shroud inner peripheral surface. The concentrated eddy current is maintained as it is to the blade trailing edge side, and the concentrated eddy current on the upstream outer peripheral edge receives the centrifugal force component and concentrates from the downstream side to the upstream side. It functions as a partition wall for the air flow to be flowed in to prevent the flow-in. As a result, even during high-speed rotation, it is presumed that the generation of turbulence is suppressed by blocking the flow of air from the downstream side of the blade 2 over the outer peripheral edge to the upstream side. The fact that the generation of turbulence is suppressed has also been confirmed in a wind tunnel experiment (tuft method), and it can be presumed that the present invention is theoretically correct.

Judging from further investigations 4 and 5, the ratio of the diameter of the forward fan 1 to the position of the straightening rib 3 protruding from the outer peripheral edge of the blade and the height of the straightening rib 3 is 30. On the other hand, it can be judged that the closer the ratio is to 1, the more preferable, and it can be said that such a condition is particularly desirable.

[Effects] In short, since the present invention is configured as described above, the presence of the rectifying ribs prevents the air flow from flowing from the downstream side to the upstream side during high speed rotation in the forward fan. Due to the function of the partition wall of the concentrated eddy current generated on the upstream side, it will be done over the entire width of the blade outer peripheral edge portion, and as a result, the air inflow prevention effect is effective even at high speed rotation. To work,
The occurrence of turbulence due to the inflow of air from the downstream side to the upstream side at the blade outer peripheral edge portion at the time of high speed rotation can be suppressed as much as possible, and the generation of noise can be effectively reduced.
Therefore, in the forward fan, even if the high air flow that has been recently demanded is measured, it can be made quiet with less noise.

[Brief description of drawings]

The drawings show an embodiment of a straightening rib structure of a forward fan according to the present invention, in which FIG. 1 is a front view of a main part of the forward fan, and FIG. 2 is a sectional view taken along line XY in FIG. FIG. 3 is a cross-sectional view of the blade portion, FIG. 4 is a chart showing measurement results, and FIGS. 5 (A), (B), and (C) are operation explanatory views showing the mechanism of noise generation. In the figure, 1 is a forward fan, 2 is a blade, and 3 is a straightening rib.

Claims (2)

[Claims] 1. An outer peripheral edge of a plurality of blades projecting radially from a boss is made to follow a fan rotation locus along an inner peripheral surface of a shroud in which wind flows from upstream to downstream by fan rotation. In a forward fan in which the outer peripheral edge portion is abruptly widened forward in the rotational direction by projecting the front end portion in the rotational direction of the blade outer peripheral edge portion toward the front in the rotational direction of the fan, and making the outer peripheral edge portion abruptly wider toward the front side in the rotational direction. A plate-shaped straightening rib is formed to project on the upstream blade surface in the outer peripheral edge of the blade, and the straightening rib is used to straighten the wind caught from the entire outer peripheral circle of the blade. The position is an arcuate position that is a position near the fan axis with respect to the rotational locus position of the sharpened protruding end of the outer peripheral edge of the Brehed and is substantially concentric with the outer peripheral edge of the blade, and the protrusion width is approximately the blade width. Rectifying rib structure forward Juan is wider across the width, further protrusion height, characterized in that it set is allowed to be substantially equal to the distance from the blade outer peripheral edge up to the commutation rib protruding position. 2. The distance from the blade outer peripheral edge of the straightening rib to the projecting position and the projecting height from the blade surface are set to be approximately 30: 1 with respect to the diameter of the advancing fan. The rectifying rib structure of the forward fan according to claim 1, wherein