RU2390658C2 - Centrifugal fan impeller - Google Patents

Abstract

FIELD: power industry.

SUBSTANCE: centrifugal fan impeller includes load-carrying and cover discs, profile blades installed between them and bent backwards, each of which has wing cover from the side of working surface in the area of outlet part, which is installed with confuser gap in relation to working surface of blade and having concave working surface and convex end surface. At that, inside wing cover there made is vortex chamber tangentially interconnected with confuser gap. And on its convex end surface from cylindrical cavity there made are confuser channels.

EFFECT: increasing aerodynamic loading of centrifugal fan by eliminating separated vortex formation on rear blade side of its impeller.

2 dwg

Description

The invention relates to the field of fan building, in particular to centrifugal fans with profile impeller blades curved back.

A centrifugal fan [1] is known with an impeller containing a bearing and cover disks, with vanes mounted between them and backward curved, each of which has a longitudinal protrusion located on the working surface in the area of the output part with a curved working and end surfaces. The specified impeller eliminates the disadvantage of the previously described design, i.e. increases the aerodynamic loading of the fan due to the growth of its pressure coefficient. However, the large thickness of the end face of the blade with a longitudinal protrusion causes the appearance of an intense edge trace, which leads to an increase in the angle of the lag of the flow. For this reason, the angle of exit of the flow from the impeller is substantially smaller than the angle of exit of the working surface of the longitudinal protrusion, which leads to an insufficient increase in pressure, and hence aerodynamic loading.

The closest in execution to the proposed technical solution is the impeller of a centrifugal fan [2], in which between the carrier and the cover discs there are shaped backward curved blades, each of which has a longitudinal protrusion with a curved working and convex end surfaces on the working surface in the area of the output part forming a confuser gap with a working surface, the middle line of which in the output section is parallel to the back surface of the scapula.

This design of the profile impeller blades eliminates the occurrence of a stagnant vortex zone behind the longitudinal protrusion, significantly reducing the intensity of the edge trace, which reduces the angle of the flow lag from the surfaces of the blade and the longitudinal protrusion at the exit of the impeller, thereby increasing the pressure developed by it.

However, this embodiment of the output part of the impeller blade does not provide the necessary energy of the flow passing through the confuser gap to its convex end surface, which does not significantly increase the aerodynamic loading of the centrifugal fan, since it does not provide a significant flow swirl at the exit of the impeller.

The purpose of the invention is to increase the aerodynamic loading of the impeller of a centrifugal fan by increasing the flow energy acting on the convex rear surface of the working blade in the area where tear-off vortex formation occurs.

Figure 1 shows the impeller of a centrifugal fan, a cross section; figure 2 - the blade of the impeller of a centrifugal fan.

The impeller of a centrifugal fan contains a carrier and a cover disk 1, 2, between which there are shaped, backward curved blades 3. On the output part of the blade 3 there is a longitudinal cover 4 with a vortex chamber 9. The cover 4 has a curved concave working 6 and a convex rear 7 surface. The longitudinal lining 4 is mounted with an aerodynamic confuser channel 8 to the surface of the blade with a tangential entrance to the vortex chamber 9. On the rear convex surface 7 of the lining 4 there are made confuser channels 5 connecting it to the vortex chamber 9.

When the impeller of the centrifugal fan rotates, the air flow entering the interscapular channels formed by the supporting 1, cover 2 disks and blades 3, interacting with the latter, turns in the direction of rotation of the wheel along the working surfaces of the blades 3 and their cover 4. The part of the flow, which is the control the flow, due to the pressure differential between the working 6 and the back 7 surfaces of the blade 3, enters through the confuser gap 8 in the tangential direction into the vortex chamber 9, twisting in it with a speed exceeding The rotational speed of the impeller. Due to the centrifugal force of rotation, the control flow through the confuser channels 5 enters the back surface 7 of the lid 4 of the impeller blade 3, helping to eliminate the area of tear-off vortex formation, and, as a result, a significant decrease in the lag angle of the main flow at the exit of the impeller under conditions of a significant change in the modes centrifugal fan operation. As a result of this, there is a significant increase in the aerodynamic loading of the impeller of a centrifugal fan.

According to the results of the experiments, it was found that the boundary of the zone of intensive separation of the flow is formed in the sector up to 60 ° from the inflection point of the wing 4 on its rear convex surface 7. The greatest efficiency, that is, the minimum energy consumption of the control flow to eliminate the separated vortex formation on the rear surface 7, is achieved when performing three confuser channels 5 in the range of angles: 25 ° ≥α ₁ ≥30 °; 45 ° ≥α ₂ ≥50 °; 55 ° ≥α ₃ ≥60 °. When the exit angles are less than the above values of the confuser channels α ₁ α ₂ , α _{3, the} supply of the control flow occurs in the zone on the convex rear surface 7 of the cover 4 to the point of separation of the control flow, which leads to an irrational energy consumption of the control flow. At angles greater than the indicated α ₁ α ₂ , α _{3, the} control flow acts in the region beyond the point of separation of the flow, which leads to a sharp deterioration in the efficiency of eliminating the separation vortex.

Thus, the use of such a design of the impeller blade allows eliminating tear-off vortex formation on the back side of the blade, which increases the aerodynamic loading of the impeller of a centrifugal fan, which develops a pressure that exceeds its theoretical value.

Information sources

1. Copyright certificate 1178956 (USSR), cl. F04D 29/28, publ. 1984.

2. Patent 2009379 (Russia), cl. F04D 29/28. Centrifugal fan / Makarov V.N., publ. March 15, 1994.

Claims (2)

1. The impeller of a centrifugal fan, containing the carrier and cover discs, mounted between them backward curved blades, each of which has a wing on the side of the working surface in the area of the outlet part, installed with a confuser gap relative to the working surface of the blade and having a concave working and a convex end surface, characterized in that a vortex chamber is made inside the lid, communicating tangentially with a confuser gap, and on its convex end surface is made of a cylindrical confusion channels are made in the cavity. 2. The impeller according to claim 1, characterized in that the cover is provided with three confuser channels, made in such a way that their output sections are located from the inflection point of its convex end surface in the range of angles 25 ° ≥ ₁ ≥30 °; 45 ° ≥α ₂ ≥50 °; 55 ° ≥α ₃ ≥60 °.

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