RU2225536C2 - Centrifugal fan - Google Patents

Abstract

FIELD: power engineering. SUBSTANCE: proposed fan contains end diffuser with tongue. End edge of tongue has the form of broken line consisting of at least three straight sections. One of sections is arranged opposite to impeller at angle to impeller axis. Two remaining extreme sections adjoin housing, being parallel to impeller axis. Extreme sections are located on one straight line. EFFECT: reduced noise level, increased efficiency of centrifugal fan. 3 cl, 4 dwg

Description

 The invention relates to the field of power engineering, in particular to the design of centrifugal fans and compressors.

 Vane machines are known in which oblique tongues are used to reduce the level of aerodynamic noise.

 A known design of a centrifugal fan, consisting of a blade impeller and a housing including a spiral section, a diffuser and a tongue between them (Solomakhova TS, Chebysheva K.V. Centrifugal fans. Aerodynamic schemes and characteristics. Reference book. M .: Engineering, 1980 ) In this design, the gas flow coming out of the impeller has an inhomogeneous velocity and pressure field due to the pitch of the blades. An inhomogeneous stream interacts with the body language and causes an increased noise level at the blade frequency or a multiple thereof and is estimated by the formula: f = knz / 60 (Hz), where k = 1, 2, 3, ... is the coefficient of multiplicity; n is the number of revolutions of the impeller per minute; z is the number of impeller blades.

 It is possible to reduce the noise level due to flow heterogeneity by increasing the gap between the outer radius of the impeller and the radius of the tongue. An increase in this distance leads to a gradual decrease in the heterogeneity of the flow, and therefore, leads to a decrease in the noise level. But increasing the distance between the impeller and the tongue leads to a decrease in the efficiency of the blade machine.

 A known design of a centrifugal fan, selected as a prototype, containing an impeller with blades and a housing consisting of a spiral part, a diffuser and a tongue at the junction of the spiral part with a diffuser (G.A. Khoroshev, Yu.I. Petrov, N.F. Egorov, The noise of ship ventilation and air conditioning systems, L .: Shipbuilding, 1974, p.106, Fig. 60). Reduction of aerodynamic noise at the blade frequency and frequencies multiple to it is achieved through the use of an inclined tongue across the entire width of the spiral casing. This leads to a decrease in the intensity of the effect of the non-uniform velocity field and pressure on the surface of the tongue, as a result of which the noise from the inhomogeneity of the stream also decreases.

 The disadvantage of this design is that due to the tilt of the tongue, one part of it turns out to be more remote from the impeller and losses increase in this area, which leads to a decrease in the efficiency of the machine. In addition, the use of an inclined tongue causes an increase in its length and complicates the design of the diffuser, since the large length of the inclined tongue leads to the fact that the gap between the impeller and the tongue, variable along the length of the tongue and in some part of the tongue, can exceed the permissible limits, which leads to increase energy loss.

 The technical result of the invention is to reduce noise and increase the efficiency of a centrifugal fan.

 The specified technical result is achieved as follows. The centrifugal fan contains an impeller with blades and a housing consisting of a spiral part, a diffuser and a tongue at the transition point of the spiral part to the diffuser. According to the invention, the end edge of the tongue is in the form of a broken line consisting of at least three straight sections, one of which is located opposite the impeller at an angle to the axis of the latter. The two extreme sections adjacent to the housing are parallel to the axis of the impeller.

 The proposed shape of the end edge of the tongue allows to reduce the noise level as in the prototype, but reducing the length of the inclined part reduces the losses that accompany the prototype.

 In addition, one extreme section of the tongue edge can be connected to a section made obliquely to the axis of the impeller, and another section perpendicular to the extreme section can be made between the section made with an inclination to the axis of the impeller and the other extreme sections. This is another possible embodiment of the edge of the tongue.

 It is advisable to place the extreme sections on one straight line. This will minimize losses by ensuring the minimum equal gaps between the impeller and the extreme sections of the tongue. The same gaps will ensure minimal loss. And the noise level will be reduced by the fact that the inclined section located opposite the wheel will ensure equalization of flow velocity and pressure.

 The invention is illustrated by drawings.

 Figure 1 presents a General view of a centrifugal fan.

 In Fig.2 - view A in Fig.1.

 Figure 3 presents the shape of the edge of the tongue and its location relative to the impeller.

 Figure 4 presents another shape of the edge of the tongue.

 The centrifugal fan (FIGS. 1 and 2) consists of an impeller 1 with impellers mounted in a housing 2 with a spiral channel 3, an end diffuser 4 and a tongue 5 between them.

 Figure 3 shows the stepped tongue 5, which has two extreme sections 6, 7 parallel to the axis of the impeller 1 (figure 2), and section 8, located with an inclination to the axis of the impeller 1. The inclined section 8 is located opposite the impeller 1. The edge of the tongue 5 can be composed of four sections: two extreme - 6 and 7, section 8 and section 9, perpendicular to the extreme section 7 (figure 4). In this case, the extreme sections 6 and 7 can be located on the same line.

 When the impeller 1 rotates, air or gas enters the impeller 1, receives energy from the blades of the impeller 1 and exits into the spiral channel 3 of the casing 2 and the diffuser 4, interacting with the tongue 5. In this case, the section 8 of the edge of the tongue 5 aligns the flow velocity field, reducing aerodynamic noise. Sections 6 and 7 reduce energy loss, increasing fan efficiency. In the design of FIG. 4, when the fan is operating, energy losses will be minimal, since sections 6 and 7 are equally remote from the impeller 1 in the radial direction (i.e., parallel to the axis of the impeller 1).

 Thus, the proposed design allows to reduce noise, increase efficiency and use a more compact design of the diffuser by reducing the length of the inclined section 8 in comparison with the design of the prototype.

Claims (3)

1. A centrifugal fan, consisting of an impeller with blades, which is placed in a housing containing a spiral outlet channel and an end diffuser with a tongue between them, characterized in that the end edge of the tongue has the shape of a broken line consisting of at least three rectilinear sections, one of which is located opposite the impeller at an angle to the axis of the latter, and the two extreme sections adjacent to the housing are parallel to the axis of the impeller. 2. The centrifugal fan according to claim 1, characterized in that one extreme section is connected to a section made obliquely to the axis of the impeller, and between the section made obliquely to the axis of the impeller and another extreme section, an additional section is made perpendicular to the extreme . 3. The centrifugal fan according to claim 2, characterized in that the extreme sections are located on one straight line.

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