JPS62186145A - Ventilation fan - Google Patents

Abstract

PURPOSE:To provide a ventilation fan of a large resistance against an external air flow speed in which an unstable static pressure-air flow quantity curve is removed and any extraordinary sound is prevented by radially providing a plurality of guide vanes inclined in the turning direction of an axial flow type impeller on the suction side of a bell mouth positioned at the outer peripheral portion of the impeller. CONSTITUTION:When an impeller 2 is rotated by a motor 1, indoor air is sucked up from a space between an ornamental panel 3 and a suction bell mouth 4. Upon this occasion, since a plurality of guide vanes 9 in each of which the inner diameter side is bent in the rotating direction of the impeller 2 shown by arrow 10, are attached between the ornamental panel 3 and the suction bell mouth 4, indoor air which has been sucked up pre-rotates to the rotational direction of the impeller 2 and flows into the impeller 2. Therefore, even at the same quantity of air flow, an angle of attack alphaA of a blade 2b toward a section 6 in the rotational direction largely decreases as compared with an angle of attack alphaB when there is no pre-rotation. Because the angle of attack alphaA decreases, an exfoliation starting air flow quantity decreases, and the outer peripheral portion of the blade 2b has larger pre-rotation and smaller angle of attack alphaA, the exfoliation does not occur in the full area at the same time, and hence a convex type function curve is not formed but the closing static pressure rises up.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to an axial-flow impeller ventilation fan for indoor ventilation in general industrial applications.

Conventional technology Conventionally, this type of ventilation fan often rotates in the opposite direction to blow air indoors when the wind speed outside is strong, and the closing static pressure drops significantly, especially in structures with a panel attached to the front of the indoor side. Even outside wind with a wind speed of about 4 m/s can reverse the flow and bring outside air into the room, so there was a need for a means to prevent it.

For this reason, in the conventional ventilation fan with a panel, as shown in FIG. A decorative panel 3 is provided on the suction side of the impeller 2, and a shutter 7 is installed on the outlet side so as to be opened by the blown airflow.
An intake port 6 was provided between the two. This creates a diagonal flow of suction airflow and increases the closing static pressure, resulting in a wind speed of 6
The impeller 2 is prevented from rotating in the opposite direction if the outside wind is up to about am/s.

Problems to be Solved by the Invention In the conventional ventilation fan described above, the static pressure-air volume curve is convex, as shown by the broken line in FIG. In this case, the introduction of outside air suddenly starts and moves back and forth on the performance curve from near point A to near point B and vice versa, resulting in a problem of generating a dry and harsh abnormal sound.

The present invention has been made in consideration of the above-mentioned conventional problems, and aims to provide a ventilation fan that eliminates the unstable static pressure-air volume curve, prevents abnormal noise, and has a high external wind speed.

Means for Solving the Problem In order to solve this problem, the present invention provides a bell mouth provided at the outer periphery of an axial flow type impeller, which is arranged radially on the suction side of the bell mouth in the rotating direction of the impeller. It is equipped with a plurality of guide vanes that are slanted.

Effect: With this configuration, the air sucked in from the suction side is pre-rotated in the direction of rotation of the impeller by multiple guide vanes, and then enters the impeller, stabilizing the static pressure air volume curve and This results in an increase in static pressure.

EXAMPLE Hereinafter, an example of the present invention will be described based on FIGS. 1 to 3. The same parts as in the conventional example are given the same numbers, and detailed explanation will be omitted. In the figure, reference numeral 8 denotes a box-shaped main frame with openings on both sides, and inside thereof is an axial-flow type impeller 2 in which a plurality of blades 2b are formed radially around the outer circumference of a hub 2a directly connected to the electric motor 1. A suction pel mouth 4 without a cylindrical portion is provided on the outer periphery of the impeller 2, and eight guide vanes 9 whose inner diameter side is bent in the rotational direction of the impeller 2 are arranged radially on the suction side at equal intervals. The decorative panel 3 is fixed in contact with the leading end of the guide vane 9, and the length of the guide vane 9 is determined so as to provide a space between the suction bell mouth 4 and the decorative panel 3 necessary for passage of the suction airflow. It is. A shutter 7 is provided on the outlet side of the main body frame 8 and is opened by the airflow.

In the above configuration, when the impeller 2 is rotated by the electric motor 1, indoor air is sucked from between the decorative panel 3 and the suction perme mouth 4. At this time, the suction permouth 4 is provided with a plurality of guide vanes 9, the inner diameter of which is bent in the rotational direction of the impeller 2, as indicated by the arrow 1°, between the suction panel 3 and the decorative panel 3, so that the suctioned indoor air is It pre-turns in the rotational direction of the impeller 2 and flows into the impeller 2. Therefore, as shown in Fig. 3, even with the same air volume, the angle of attack (angle formed by the inflow angle WA and the mounting angle β) to the rotation direction cross section 6 of the vane blade 2b.
αA is greatly reduced compared to the angle of attack αB when there is no pre-turn. The convexity of the performance curve is caused by the angle of attack αA being separated by the angle of attack (1
oO~120) and the separation angle of attack is simultaneously reached in the entire area from the knob 2a of the vane blade 2b to the outer periphery. One thing is to add a pre-turn.
As shown in Fig. 3, the angle of attack αA decreases and the amount of air at which separation starts decreases. Another reason is that the pre-swivel of the outer circumference of the vane blade 2b is large and the angle of attack αA is small, so separation does not occur simultaneously in the entire area. Therefore, there is no convex performance curve, and the closing static pressure increases.

Fig. 6 shows a comparison of the static pressure air volume curves of the conventional example and the present invention. According to this, the convex phenomenon is eliminated and the closing static pressure is o.
, 86IIMAq to 2.411ffA9, the maximum static pressure has improved from 1.4ffA to 2.4ffA9, and the external wind pressure resistance has improved from 5.7m/S to 7.6m/S. The relationship between static pressure and external wind speed is expressed by the following formula. Static pressure = 1.2/1
9.6 Xo, 7 X (wind speed) 2 However, 0.7 is the wind pressure coefficient.

Effects of the Invention As described above, according to the present invention, the suction airflow enters the impeller after pre-turning in the direction of rotation of the impeller, so even if there is resistance on the suction side, the static pressure landscape curve does not have an unstable shape. Therefore, there is no abnormal noise, and the external wind speed can be improved by 50%.

[Brief explanation of drawings]

Fig. 1 is a side sectional view showing a ventilation fan according to an embodiment of the present invention, Fig. 2 is a front view showing the same ventilation fan, Fig. 3 is a comparison diagram of the angle of attack between the present invention and a conventional example, and Fig. 4 is a FIG. 5, a side sectional view showing a conventional ventilation fan, is a comparison diagram of performance curves of the present invention and a conventional example. 2... Impeller, 4... Suction pel mouth, 9... Guide vane. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure Par-°”41 4--- a, moxibustion ν8

Claims (1)

[Claims] A ventilation fan including a plurality of guide vanes radially inclined in the rotational direction of the impeller on the suction side of a bell mouth provided on the outer periphery of an axial flow type impeller.