RU2525037C1 - Centrifugal fan impeller - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: centrifugal fan impeller comprises a supporting disk and a covering disk, set in-between profiled blades folded backwards, each of which is fitted by a vane attachment set on the working surface side in the outlet part zone with a converging gap in respect to the working surface of the blade and having concave working surface and convex end face surface and a swirl chamber communicating tangentially with the converging gap, on its convex end face surface. Outlet converging channels are provided from the swirl chamber, and inlet converging channels are provided to the swirl chamber entering it tangentially from the concave working surface of the vane attachment.

EFFECT: use of invention allows for significant increase of the aerodynamic load of a centrifugal fan.

2 cl, 2 dwg

Description

The invention relates to the field of fan building, in particular to the impellers of centrifugal fans with backward-curved profile blades.

A centrifugal fan is known [Patent 2009379 (Russia), cl. F04D 29/28. Centrifugal fan / Makarov V.N., publ. March 15, 1994] with an impeller containing between the main and the cover discs 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 outlet, forming a confuser gap with the working surface, the middle line of which in the outlet section parallel to the back surface of the scapula.

This design of the backward-curved impeller profile vanes 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 surface 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 backward-curved impeller blades does not provide the necessary energy for the control flow passing through the confuser gap to its convex end surface, that is, it does not significantly increase the flow swirl energy at the exit of the impeller, which significantly limits the growth of aerodynamic loading, that is, the developed pressure of a centrifugal fan.

The closest to the implementation of the proposed technical solution is the impeller of a centrifugal fan [Patent 20390658 (Russia), cl. F04D 29/28. The impeller of a centrifugal fan / Makarov N.V., Belov S.V., Fomin V.I. et al., publ. October 10, 2009.], containing the carrier and cover discs, between which the profile vanes are bent backward, on the output part of which there is a longitudinal lining with a vortex chamber having a concave working and convex rear surface and installed with a confuser gap to the surface of the blade with a tangential entrance into the vortex chamber, and from the rear convex surface of the napkin, confuser channels are made connecting it to the vortex chamber.

This embodiment of the lining of backward-curved impeller blades increases the swirling energy of the control flow in the vortex chamber, which, due to the centrifugal force of rotation, enters the back surface of the impeller blade lining, contributing to a more effective elimination of the area of separation vortex formation and, as a result, a substantial decrease in the lag angle of the main flow at the exit of the impeller in conditions of a significant change in the operating modes of the centrifugal fan. As a result of this, the aerodynamic loading of the impeller of the centrifugal fan increases.

However, this embodiment of the output part of the backward-curved blade of the impeller does not fully provide an increase in the energy of the control flow swirling in the vortex chamber, and also does not improve the structure of the main flow on the working concave surface of the napkin, which does not significantly increase the aerodynamic loading of the centrifugal fan, since it does not provide a significant increase in the pressure drop between the working and solid surfaces of the blade.

The objective of the invention is to increase the aerodynamic loading of the impeller of a centrifugal fan by increasing the kinetic energy of the control flow swirling in the vortex chamber, and its effect on the main flow not only on the convex end surface of the blade lining, but also on its concave working surface.

This task is achieved by the fact that in the proposed impeller of a centrifugal fan, containing the carrier and the cover discs, profile blades are installed between them backward curved, each of which has liners on the side of the working surface to the outlet part area, installed with a confuser gap with respect to the working surface vanes having a concave working and convex end surfaces and a vortex chamber communicating tangentially with a confuser gap to its convex end surface from a vortex the chambers are made exhaust discharge channels. From the concave working surface of the lining into the vortex chamber, inlet confuser channels are made with a tangential entrance to it.

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 1 and a cover 2 disks, between which there are shaped backward curved blades 3. On the outlet of the blade 3 there is a longitudinal cover 4 with a swirl chamber 5. The longitudinal cover 4 has a concave working 6, a convex rear surface 7 and is installed with confuser gap 8 to the surface of the blades, having a tangential entrance 9 into the vortex chamber 5.

Outlet channels 10 are made from the vortex chamber 5 of the cover 4 onto its end convex surface 7. Inlet confuser channels 11 with a tangential entrance 12 are made to the concave working surface 6 of the cover 4 into the vortex chamber 5. 13 - the output edge of the wing, that is, the transition region of the convex end 7 of the surface into a concave working surface 6 of the wing 4.

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 difference between the working 6 and the back 7 surfaces of the wing 4 of the blade 3 through the tangential inlet 9 of the confuser gap 8, flows in the tangential direction into the vortex chamber 5, closed chivayas therein with a speed exceeding the speed of rotation of the impeller. Due to the excess pressure on the working concave surface 6 of the cover 4 with respect to the pressure in the vortex chamber 5, part of the flow from the interscapular channel through the inlet confuser channels 11 through the tangential inlets 12 enters tangentially, i.e. tangentially, into the vortex chamber 5, further increasing the rotation energy control flow.

Due to the centrifugal rotation force, the high-energy control flow through the confuser channels 10 enters the rear 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, significantly reducing the lag angle of the main flow at the exit of the impeller under conditions of significant change centrifugal fan operating modes. As a result of this, there is a significant increase in the aerodynamic loading of the impeller of a centrifugal fan.

In addition, the suction of a part of the flow from the interscapular channel on the working concave surface of the wing 4 through inlet confuser channels 11 leads to a decrease in the flow rate on the working surface of the wing 4 of the blade 3, contributing to an increase in pressure on it due to the Magnus effect, i.e. an increase in the pressure drop between the working 6 and the back 7 of the lining 4 of the blade 3, which increases the aerodynamic loading of the impeller of a centrifugal fan.

The total effect of decreasing the angle of lag of the main flow at the exit of the impeller and increasing the pressure drop between the working 6 and back 7 surfaces of the wing 4 of the blade 3 due to the suction of part of the main flow from the working surface 6 of the wing 4 leads to a significant increase in the aerodynamic loading of the impeller.

According to the results of the experiments, it was found that the greatest efficiency, that is, the maximum increase in aerodynamic loading due to an increase in the pressure drop when a part of the main stream is sucked from the working surface 6 of the wing 4 is achieved when the entrance to one of the inlet channels 11 is located on the output edge 13 of the wing 4, then there is in the area of transition of the convex end surface 7 to the concave working surface 6 of the cover 4.

Thus, the use of this design of the impeller blades allows you to effectively eliminate the tear-off vortex formation on the back side of the blade and increase the pressure drop between its working and back surfaces, which increases the aerodynamic loading of the impeller of a centrifugal fan.

Claims (2)

1. The impeller of a centrifugal fan, containing the carrier and the cover discs, the profile blades installed between them, backward curved blades, on each of which a cover with a concave working and convex end face is installed on the side of the working surface in the area of the outlet part with a confuser gap with respect to the working surface of the blade surfaces having a vortex chamber communicating tangentially with a confuser gap, and exhaust confuser channels are made from the vortex chamber onto its convex end surface, scheesya in that the concave working surface of the swirl chamber nakrylka made convergent inlets with tangential entry into it. 2. The impeller according to claim 1, characterized in that one of the inlet confuser channels is made from the exit edge of the lining into the vortex chamber.

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